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FFMPEG-FILTERS(1)					     FFMPEG-FILTERS(1)

NAME
       ffmpeg-filters - FFmpeg filters

DESCRIPTION
       This document describes filters, sources, and sinks provided by the
       libavfilter library.

FILTERING INTRODUCTION
       Filtering in FFmpeg is enabled through the libavfilter library.

       In libavfilter, a filter can have multiple inputs and multiple outputs.
       To illustrate the sorts of things that are possible, we consider the
       following filtergraph.

			       [main]
	       input --> split ---------------------> overlay --> output
			   |				 ^
			   |[tmp]		   [flip]|
			   +-----> crop --> vflip -------+

       This filtergraph splits the input stream in two streams, sends one
       stream through the crop filter and the vflip filter before merging it
       back with the other stream by overlaying it on top. You can use the
       following command to achieve this:

	       ffmpeg -i INPUT -vf "split [main][tmp]; [tmp] crop=iw:ih/2:0:0, vflip [flip]; [main][flip] overlay=0:H/2" OUTPUT

       The result will be that in output the top half of the video is mirrored
       onto the bottom half.

       Filters in the same linear chain are separated by commas, and distinct
       linear chains of filters are separated by semicolons. In our example,
       crop,vflip are in one linear chain, split and overlay are separately in
       another. The points where the linear chains join are labelled by names
       enclosed in square brackets. In the example, the split filter generates
       two outputs that are associated to the labels [main] and [tmp].

       The stream sent to the second output of split, labelled as [tmp], is
       processed through the crop filter, which crops away the lower half part
       of the video, and then vertically flipped. The overlay filter takes in
       input the first unchanged output of the split filter (which was
       labelled as [main]), and overlay on its lower half the output generated
       by the crop,vflip filterchain.

       Some filters take in input a list of parameters: they are specified
       after the filter name and an equal sign, and are separated from each
       other by a colon.

       There exist so-called source filters that do not have an audio/video
       input, and sink filters that will not have audio/video output.

GRAPH
       The graph2dot program included in the FFmpeg tools directory can be
       used to parse a filtergraph description and issue a corresponding
       textual representation in the dot language.

       Invoke the command:

	       graph2dot -h

       to see how to use graph2dot.

       You can then pass the dot description to the dot program (from the
       graphviz suite of programs) and obtain a graphical representation of
       the filtergraph.

       For example the sequence of commands:

	       echo <GRAPH_DESCRIPTION> | \
	       tools/graph2dot -o graph.tmp && \
	       dot -Tpng graph.tmp -o graph.png && \
	       display graph.png

       can be used to create and display an image representing the graph
       described by the GRAPH_DESCRIPTION string. Note that this string must
       be a complete self-contained graph, with its inputs and outputs
       explicitly defined.  For example if your command line is of the form:

	       ffmpeg -i infile -vf scale=640:360 outfile

       your GRAPH_DESCRIPTION string will need to be of the form:

	       nullsrc,scale=640:360,nullsink

       you may also need to set the nullsrc parameters and add a format filter
       in order to simulate a specific input file.

FILTERGRAPH DESCRIPTION
       A filtergraph is a directed graph of connected filters. It can contain
       cycles, and there can be multiple links between a pair of filters. Each
       link has one input pad on one side connecting it to one filter from
       which it takes its input, and one output pad on the other side
       connecting it to the one filter accepting its output.

       Each filter in a filtergraph is an instance of a filter class
       registered in the application, which defines the features and the
       number of input and output pads of the filter.

       A filter with no input pads is called a "source", a filter with no
       output pads is called a "sink".

   Filtergraph syntax
       A filtergraph can be represented using a textual representation, which
       is recognized by the -filter/-vf and -filter_complex options in ffmpeg
       and -vf in ffplay, and by the
       "avfilter_graph_parse()"/"avfilter_graph_parse2()" function defined in
       libavfilter/avfilter.h.

       A filterchain consists of a sequence of connected filters, each one
       connected to the previous one in the sequence. A filterchain is
       represented by a list of ","-separated filter descriptions.

       A filtergraph consists of a sequence of filterchains. A sequence of
       filterchains is represented by a list of ";"-separated filterchain
       descriptions.

       A filter is represented by a string of the form:
       [in_link_1]...[in_link_N]filter_name=arguments[out_link_1]...[out_link_M]

       filter_name is the name of the filter class of which the described
       filter is an instance of, and has to be the name of one of the filter
       classes registered in the program.  The name of the filter class is
       optionally followed by a string "=arguments".

       arguments is a string which contains the parameters used to initialize
       the filter instance. It may have one of the following forms:

       ·   A ':'-separated list of key=value pairs.

       ·   A ':'-separated list of value. In this case, the keys are assumed
	   to be the option names in the order they are declared. E.g. the
	   "fade" filter declares three options in this order -- type,
	   start_frame and nb_frames. Then the parameter list in:0:30 means
	   that the value in is assigned to the option type, 0 to start_frame
	   and 30 to nb_frames.

       ·   A ':'-separated list of mixed direct value and long key=value
	   pairs. The direct value must precede the key=value pairs, and
	   follow the same constraints order of the previous point. The
	   following key=value pairs can be set in any preferred order.

       If the option value itself is a list of items (e.g. the "format" filter
       takes a list of pixel formats), the items in the list are usually
       separated by '|'.

       The list of arguments can be quoted using the character "'" as initial
       and ending mark, and the character '\' for escaping the characters
       within the quoted text; otherwise the argument string is considered
       terminated when the next special character (belonging to the set
       "[]=;,") is encountered.

       The name and arguments of the filter are optionally preceded and
       followed by a list of link labels.  A link label allows to name a link
       and associate it to a filter output or input pad. The preceding labels
       in_link_1 ... in_link_N, are associated to the filter input pads, the
       following labels out_link_1 ... out_link_M, are associated to the
       output pads.

       When two link labels with the same name are found in the filtergraph, a
       link between the corresponding input and output pad is created.

       If an output pad is not labelled, it is linked by default to the first
       unlabelled input pad of the next filter in the filterchain.  For
       example in the filterchain:

	       nullsrc, split[L1], [L2]overlay, nullsink

       the split filter instance has two output pads, and the overlay filter
       instance two input pads. The first output pad of split is labelled
       "L1", the first input pad of overlay is labelled "L2", and the second
       output pad of split is linked to the second input pad of overlay, which
       are both unlabelled.

       In a complete filterchain all the unlabelled filter input and output
       pads must be connected. A filtergraph is considered valid if all the
       filter input and output pads of all the filterchains are connected.

       Libavfilter will automatically insert scale filters where format
       conversion is required. It is possible to specify swscale flags for
       those automatically inserted scalers by prepending "sws_flags=flags;"
       to the filtergraph description.

       Follows a BNF description for the filtergraph syntax:

	       <NAME>		  ::= sequence of alphanumeric characters and '_'
	       <LINKLABEL>	  ::= "[" <NAME> "]"
	       <LINKLABELS>	  ::= <LINKLABEL> [<LINKLABELS>]
	       <FILTER_ARGUMENTS> ::= sequence of chars (eventually quoted)
	       <FILTER>		  ::= [<LINKLABELS>] <NAME> ["=" <FILTER_ARGUMENTS>] [<LINKLABELS>]
	       <FILTERCHAIN>	  ::= <FILTER> [,<FILTERCHAIN>]
	       <FILTERGRAPH>	  ::= [sws_flags=<flags>;] <FILTERCHAIN> [;<FILTERGRAPH>]

   Notes on filtergraph escaping
       Some filter arguments require the use of special characters, typically
       ":" to separate key=value pairs in a named options list. In this case
       the user should perform a first level escaping when specifying the
       filter arguments. For example, consider the following literal string to
       be embedded in the drawtext filter arguments:

	       this is a 'string': may contain one, or more, special characters

       Since ":" is special for the filter arguments syntax, it needs to be
       escaped, so you get:

	       text=this is a \'string\'\: may contain one, or more, special characters

       A second level of escaping is required when embedding the filter
       arguments in a filtergraph description, in order to escape all the
       filtergraph special characters. Thus the example above becomes:

	       drawtext=text=this is a \\\'string\\\'\\: may contain one\, or more\, special characters

       Finally an additional level of escaping may be needed when writing the
       filtergraph description in a shell command, which depends on the
       escaping rules of the adopted shell. For example, assuming that "\" is
       special and needs to be escaped with another "\", the previous string
       will finally result in:

	       -vf "drawtext=text=this is a \\\\\\'string\\\\\\'\\\\: may contain one\\, or more\\, special characters"

       Sometimes, it might be more convenient to employ quoting in place of
       escaping. For example the string:

	       Caesar: tu quoque, Brute, fili mi

       Can be quoted in the filter arguments as:

	       text='Caesar: tu quoque, Brute, fili mi'

       And finally inserted in a filtergraph like:

	       drawtext=text=\'Caesar: tu quoque\, Brute\, fili mi\'

       See the ``Quoting and escaping'' section in the ffmpeg-utils manual for
       more information about the escaping and quoting rules adopted by
       FFmpeg.

TIMELINE EDITING
       Some filters support a generic enable option. For the filters
       supporting timeline editing, this option can be set to an expression
       which is evaluated before sending a frame to the filter. If the
       evaluation is non-zero, the filter will be enabled, otherwise the frame
       will be sent unchanged to the next filter in the filtergraph.

       The expression accepts the following values:

       t   timestamp expressed in seconds, NAN if the input timestamp is
	   unknown

       n   sequential number of the input frame, starting from 0

       pos the position in the file of the input frame, NAN if unknown

       Additionally, these filters support an enable command that can be used
       to re-define the expression.

       Like any other filtering option, the enable option follows the same
       rules.

       For example, to enable a blur filter (smartblur) from 10 seconds to 3
       minutes, and a curves filter starting at 3 seconds:

	       smartblur = enable='between(t,10,3*60)',
	       curves	 = enable='gte(t,3)' : preset=cross_process

AUDIO FILTERS
       When you configure your FFmpeg build, you can disable any of the
       existing filters using "--disable-filters".  The configure output will
       show the audio filters included in your build.

       Below is a description of the currently available audio filters.

   aconvert
       Convert the input audio format to the specified formats.

       This filter is deprecated. Use aformat instead.

       The filter accepts a string of the form:
       "sample_format:channel_layout".

       sample_format specifies the sample format, and can be a string or the
       corresponding numeric value defined in libavutil/samplefmt.h. Use 'p'
       suffix for a planar sample format.

       channel_layout specifies the channel layout, and can be a string or the
       corresponding number value defined in libavutil/channel_layout.h.

       The special parameter "auto", signifies that the filter will
       automatically select the output format depending on the output filter.

       Examples

       ·   Convert input to float, planar, stereo:

		   aconvert=fltp:stereo

       ·   Convert input to unsigned 8-bit, automatically select out channel
	   layout:

		   aconvert=u8:auto

   adelay
       Delay one or more audio channels.

       Samples in delayed channel are filled with silence.

       The filter accepts the following option:

       delays
	   Set list of delays in milliseconds for each channel separated by
	   '|'.	 At least one delay greater than 0 should be provided.	Unused
	   delays will be silently ignored. If number of given delays is
	   smaller than number of channels all remaining channels will not be
	   delayed.

       Examples

       ·   Delay first channel by 1.5 seconds, the third channel by 0.5
	   seconds and leave the second channel (and any other channels that
	   may be present) unchanged.

		   adelay=1500:0:500

   aecho
       Apply echoing to the input audio.

       Echoes are reflected sound and can occur naturally amongst mountains
       (and sometimes large buildings) when talking or shouting; digital echo
       effects emulate this behaviour and are often used to help fill out the
       sound of a single instrument or vocal. The time difference between the
       original signal and the reflection is the "delay", and the loudness of
       the reflected signal is the "decay".  Multiple echoes can have
       different delays and decays.

       A description of the accepted parameters follows.

       in_gain
	   Set input gain of reflected signal. Default is 0.6.

       out_gain
	   Set output gain of reflected signal. Default is 0.3.

       delays
	   Set list of time intervals in milliseconds between original signal
	   and reflections separated by '|'. Allowed range for each "delay" is
	   "(0 - 90000.0]".  Default is 1000.

       decays
	   Set list of loudnesses of reflected signals separated by '|'.
	   Allowed range for each "decay" is "(0 - 1.0]".  Default is 0.5.

       Examples

       ·   Make it sound as if there are twice as many instruments as are
	   actually playing:

		   aecho=0.8:0.88:60:0.4

       ·   If delay is very short, then it sound like a (metallic) robot
	   playing music:

		   aecho=0.8:0.88:6:0.4

       ·   A longer delay will sound like an open air concert in the
	   mountains:

		   aecho=0.8:0.9:1000:0.3

       ·   Same as above but with one more mountain:

		   aecho=0.8:0.9:1000|1800:0.3|0.25

   afade
       Apply fade-in/out effect to input audio.

       A description of the accepted parameters follows.

       type, t
	   Specify the effect type, can be either "in" for fade-in, or "out"
	   for a fade-out effect. Default is "in".

       start_sample, ss
	   Specify the number of the start sample for starting to apply the
	   fade effect. Default is 0.

       nb_samples, ns
	   Specify the number of samples for which the fade effect has to
	   last. At the end of the fade-in effect the output audio will have
	   the same volume as the input audio, at the end of the fade-out
	   transition the output audio will be silence. Default is 44100.

       start_time, st
	   Specify time for starting to apply the fade effect. Default is 0.
	   The accepted syntax is:

		   [-]HH[:MM[:SS[.m...]]]
		   [-]S+[.m...]

	   See also the function "av_parse_time()".  If set this option is
	   used instead of start_sample one.

       duration, d
	   Specify the duration for which the fade effect has to last. Default
	   is 0.  The accepted syntax is:

		   [-]HH[:MM[:SS[.m...]]]
		   [-]S+[.m...]

	   See also the function "av_parse_time()".  At the end of the fade-in
	   effect the output audio will have the same volume as the input
	   audio, at the end of the fade-out transition the output audio will
	   be silence.	If set this option is used instead of nb_samples one.

       curve
	   Set curve for fade transition.

	   It accepts the following values:

	   tri select triangular, linear slope (default)

	   qsin
	       select quarter of sine wave

	   hsin
	       select half of sine wave

	   esin
	       select exponential sine wave

	   log select logarithmic

	   par select inverted parabola

	   qua select quadratic

	   cub select cubic

	   squ select square root

	   cbr select cubic root

       Examples

       ·   Fade in first 15 seconds of audio:

		   afade=t=in:ss=0:d=15

       ·   Fade out last 25 seconds of a 900 seconds audio:

		   afade=t=out:st=875:d=25

   aformat
       Set output format constraints for the input audio. The framework will
       negotiate the most appropriate format to minimize conversions.

       The filter accepts the following named parameters:

       sample_fmts
	   A '|'-separated list of requested sample formats.

       sample_rates
	   A '|'-separated list of requested sample rates.

       channel_layouts
	   A '|'-separated list of requested channel layouts.

	   See the Channel Layout section in the ffmpeg-utils(1) manual for
	   the required syntax.

       If a parameter is omitted, all values are allowed.

       For example to force the output to either unsigned 8-bit or signed
       16-bit stereo:

	       aformat=sample_fmts=u8|s16:channel_layouts=stereo

   allpass
       Apply a two-pole all-pass filter with central frequency (in Hz)
       frequency, and filter-width width.  An all-pass filter changes the
       audio's frequency to phase relationship without changing its frequency
       to amplitude relationship.

       The filter accepts the following options:

       frequency, f
	   Set frequency in Hz.

       width_type
	   Set method to specify band-width of filter.

	   h   Hz

	   q   Q-Factor

	   o   octave

	   s   slope

       width, w
	   Specify the band-width of a filter in width_type units.

   amerge
       Merge two or more audio streams into a single multi-channel stream.

       The filter accepts the following options:

       inputs
	   Set the number of inputs. Default is 2.

       If the channel layouts of the inputs are disjoint, and therefore
       compatible, the channel layout of the output will be set accordingly
       and the channels will be reordered as necessary. If the channel layouts
       of the inputs are not disjoint, the output will have all the channels
       of the first input then all the channels of the second input, in that
       order, and the channel layout of the output will be the default value
       corresponding to the total number of channels.

       For example, if the first input is in 2.1 (FL+FR+LF) and the second
       input is FC+BL+BR, then the output will be in 5.1, with the channels in
       the following order: a1, a2, b1, a3, b2, b3 (a1 is the first channel of
       the first input, b1 is the first channel of the second input).

       On the other hand, if both input are in stereo, the output channels
       will be in the default order: a1, a2, b1, b2, and the channel layout
       will be arbitrarily set to 4.0, which may or may not be the expected
       value.

       All inputs must have the same sample rate, and format.

       If inputs do not have the same duration, the output will stop with the
       shortest.

       Examples

       ·   Merge two mono files into a stereo stream:

		   amovie=left.wav [l] ; amovie=right.mp3 [r] ; [l] [r] amerge

       ·   Multiple merges assuming 1 video stream and 6 audio streams in
	   input.mkv:

		   ffmpeg -i input.mkv -filter_complex "[0:1][0:2][0:3][0:4][0:5][0:6] amerge=inputs=6" -c:a pcm_s16le output.mkv

   amix
       Mixes multiple audio inputs into a single output.

       For example

	       ffmpeg -i INPUT1 -i INPUT2 -i INPUT3 -filter_complex amix=inputs=3:duration=first:dropout_transition=3 OUTPUT

       will mix 3 input audio streams to a single output with the same
       duration as the first input and a dropout transition time of 3 seconds.

       The filter accepts the following named parameters:

       inputs
	   Number of inputs. If unspecified, it defaults to 2.

       duration
	   How to determine the end-of-stream.

	   longest
	       Duration of longest input. (default)

	   shortest
	       Duration of shortest input.

	   first
	       Duration of first input.

       dropout_transition
	   Transition time, in seconds, for volume renormalization when an
	   input stream ends. The default value is 2 seconds.

   anull
       Pass the audio source unchanged to the output.

   apad
       Pad the end of a audio stream with silence, this can be used together
       with -shortest to extend audio streams to the same length as the video
       stream.

   aphaser
       Add a phasing effect to the input audio.

       A phaser filter creates series of peaks and troughs in the frequency
       spectrum.  The position of the peaks and troughs are modulated so that
       they vary over time, creating a sweeping effect.

       A description of the accepted parameters follows.

       in_gain
	   Set input gain. Default is 0.4.

       out_gain
	   Set output gain. Default is 0.74

       delay
	   Set delay in milliseconds. Default is 3.0.

       decay
	   Set decay. Default is 0.4.

       speed
	   Set modulation speed in Hz. Default is 0.5.

       type
	   Set modulation type. Default is triangular.

	   It accepts the following values:

	   triangular, t
	   sinusoidal, s

   aresample
       Resample the input audio to the specified parameters, using the
       libswresample library. If none are specified then the filter will
       automatically convert between its input and output.

       This filter is also able to stretch/squeeze the audio data to make it
       match the timestamps or to inject silence / cut out audio to make it
       match the timestamps, do a combination of both or do neither.

       The filter accepts the syntax [sample_rate:]resampler_options, where
       sample_rate expresses a sample rate and resampler_options is a list of
       key=value pairs, separated by ":". See the ffmpeg-resampler manual for
       the complete list of supported options.

       Examples

       ·   Resample the input audio to 44100Hz:

		   aresample=44100

       ·   Stretch/squeeze samples to the given timestamps, with a maximum of
	   1000 samples per second compensation:

		   aresample=async=1000

   asetnsamples
       Set the number of samples per each output audio frame.

       The last output packet may contain a different number of samples, as
       the filter will flush all the remaining samples when the input audio
       signal its end.

       The filter accepts the following options:

       nb_out_samples, n
	   Set the number of frames per each output audio frame. The number is
	   intended as the number of samples per each channel.	Default value
	   is 1024.

       pad, p
	   If set to 1, the filter will pad the last audio frame with zeroes,
	   so that the last frame will contain the same number of samples as
	   the previous ones. Default value is 1.

       For example, to set the number of per-frame samples to 1234 and disable
       padding for the last frame, use:

	       asetnsamples=n=1234:p=0

   asetrate
       Set the sample rate without altering the PCM data.  This will result in
       a change of speed and pitch.

       The filter accepts the following options:

       sample_rate, r
	   Set the output sample rate. Default is 44100 Hz.

   ashowinfo
       Show a line containing various information for each input audio frame.
       The input audio is not modified.

       The shown line contains a sequence of key/value pairs of the form
       key:value.

       A description of each shown parameter follows:

       n   sequential number of the input frame, starting from 0

       pts Presentation timestamp of the input frame, in time base units; the
	   time base depends on the filter input pad, and is usually
	   1/sample_rate.

       pts_time
	   presentation timestamp of the input frame in seconds

       pos position of the frame in the input stream, -1 if this information
	   in unavailable and/or meaningless (for example in case of synthetic
	   audio)

       fmt sample format

       chlayout
	   channel layout

       rate
	   sample rate for the audio frame

       nb_samples
	   number of samples (per channel) in the frame

       checksum
	   Adler-32 checksum (printed in hexadecimal) of the audio data. For
	   planar audio the data is treated as if all the planes were
	   concatenated.

       plane_checksums
	   A list of Adler-32 checksums for each data plane.

   astats
       Display time domain statistical information about the audio channels.
       Statistics are calculated and displayed for each audio channel and,
       where applicable, an overall figure is also given.

       The filter accepts the following option:

       length
	   Short window length in seconds, used for peak and trough RMS
	   measurement.	 Default is 0.05 (50 miliseconds). Allowed range is
	   "[0.1 - 10]".

       A description of each shown parameter follows:

       DC offset
	   Mean amplitude displacement from zero.

       Min level
	   Minimal sample level.

       Max level
	   Maximal sample level.

       Peak level dB
       RMS level dB
	   Standard peak and RMS level measured in dBFS.

       RMS peak dB
       RMS trough dB
	   Peak and trough values for RMS level measured over a short window.

       Crest factor
	   Standard ratio of peak to RMS level (note: not in dB).

       Flat factor
	   Flatness (i.e. consecutive samples with the same value) of the
	   signal at its peak levels (i.e. either Min level or Max level).

       Peak count
	   Number of occasions (not the number of samples) that the signal
	   attained either Min level or Max level.

   astreamsync
       Forward two audio streams and control the order the buffers are
       forwarded.

       The filter accepts the following options:

       expr, e
	   Set the expression deciding which stream should be forwarded next:
	   if the result is negative, the first stream is forwarded; if the
	   result is positive or zero, the second stream is forwarded. It can
	   use the following variables:

	   b1 b2
	       number of buffers forwarded so far on each stream

	   s1 s2
	       number of samples forwarded so far on each stream

	   t1 t2
	       current timestamp of each stream

	   The default value is "t1-t2", which means to always forward the
	   stream that has a smaller timestamp.

       Examples

       Stress-test "amerge" by randomly sending buffers on the wrong input,
       while avoiding too much of a desynchronization:

	       amovie=file.ogg [a] ; amovie=file.mp3 [b] ;
	       [a] [b] astreamsync=(2*random(1))-1+tanh(5*(t1-t2)) [a2] [b2] ;
	       [a2] [b2] amerge

   asyncts
       Synchronize audio data with timestamps by squeezing/stretching it
       and/or dropping samples/adding silence when needed.

       This filter is not built by default, please use aresample to do
       squeezing/stretching.

       The filter accepts the following named parameters:

       compensate
	   Enable stretching/squeezing the data to make it match the
	   timestamps. Disabled by default. When disabled, time gaps are
	   covered with silence.

       min_delta
	   Minimum difference between timestamps and audio data (in seconds)
	   to trigger adding/dropping samples. Default value is 0.1. If you
	   get non-perfect sync with this filter, try setting this parameter
	   to 0.

       max_comp
	   Maximum compensation in samples per second. Relevant only with
	   compensate=1.  Default value 500.

       first_pts
	   Assume the first pts should be this value. The time base is 1 /
	   sample rate.	 This allows for padding/trimming at the start of
	   stream. By default, no assumption is made about the first frame's
	   expected pts, so no padding or trimming is done. For example, this
	   could be set to 0 to pad the beginning with silence if an audio
	   stream starts after the video stream or to trim any samples with a
	   negative pts due to encoder delay.

   atempo
       Adjust audio tempo.

       The filter accepts exactly one parameter, the audio tempo. If not
       specified then the filter will assume nominal 1.0 tempo. Tempo must be
       in the [0.5, 2.0] range.

       Examples

       ·   Slow down audio to 80% tempo:

		   atempo=0.8

       ·   To speed up audio to 125% tempo:

		   atempo=1.25

   atrim
       Trim the input so that the output contains one continuous subpart of
       the input.

       This filter accepts the following options:

       start
	   Specify time of the start of the kept section, i.e. the audio
	   sample with the timestamp start will be the first sample in the
	   output.

       end Specify time of the first audio sample that will be dropped, i.e.
	   the audio sample immediately preceding the one with the timestamp
	   end will be the last sample in the output.

       start_pts
	   Same as start, except this option sets the start timestamp in
	   samples instead of seconds.

       end_pts
	   Same as end, except this option sets the end timestamp in samples
	   instead of seconds.

       duration
	   Specify maximum duration of the output.

       start_sample
	   Number of the first sample that should be passed to output.

       end_sample
	   Number of the first sample that should be dropped.

       start, end, duration are expressed as time duration specifications,
       check the "Time duration" section in the ffmpeg-utils manual.

       Note that the first two sets of the start/end options and the duration
       option look at the frame timestamp, while the _sample options simply
       count the samples that pass through the filter. So start/end_pts and
       start/end_sample will give different results when the timestamps are
       wrong, inexact or do not start at zero. Also note that this filter does
       not modify the timestamps. If you wish that the output timestamps start
       at zero, insert the asetpts filter after the atrim filter.

       If multiple start or end options are set, this filter tries to be
       greedy and keep all samples that match at least one of the specified
       constraints. To keep only the part that matches all the constraints at
       once, chain multiple atrim filters.

       The defaults are such that all the input is kept. So it is possible to
       set e.g.	 just the end values to keep everything before the specified
       time.

       Examples:

       ·   drop everything except the second minute of input

		   ffmpeg -i INPUT -af atrim=60:120

       ·   keep only the first 1000 samples

		   ffmpeg -i INPUT -af atrim=end_sample=1000

   bandpass
       Apply a two-pole Butterworth band-pass filter with central frequency
       frequency, and (3dB-point) band-width width.  The csg option selects a
       constant skirt gain (peak gain = Q) instead of the default: constant
       0dB peak gain.  The filter roll off at 6dB per octave (20dB per
       decade).

       The filter accepts the following options:

       frequency, f
	   Set the filter's central frequency. Default is 3000.

       csg Constant skirt gain if set to 1. Defaults to 0.

       width_type
	   Set method to specify band-width of filter.

	   h   Hz

	   q   Q-Factor

	   o   octave

	   s   slope

       width, w
	   Specify the band-width of a filter in width_type units.

   bandreject
       Apply a two-pole Butterworth band-reject filter with central frequency
       frequency, and (3dB-point) band-width width.  The filter roll off at
       6dB per octave (20dB per decade).

       The filter accepts the following options:

       frequency, f
	   Set the filter's central frequency. Default is 3000.

       width_type
	   Set method to specify band-width of filter.

	   h   Hz

	   q   Q-Factor

	   o   octave

	   s   slope

       width, w
	   Specify the band-width of a filter in width_type units.

   bass
       Boost or cut the bass (lower) frequencies of the audio using a two-pole
       shelving filter with a response similar to that of a standard hi-fi's
       tone-controls. This is also known as shelving equalisation (EQ).

       The filter accepts the following options:

       gain, g
	   Give the gain at 0 Hz. Its useful range is about -20 (for a large
	   cut) to +20 (for a large boost).  Beware of clipping when using a
	   positive gain.

       frequency, f
	   Set the filter's central frequency and so can be used to extend or
	   reduce the frequency range to be boosted or cut.  The default value
	   is 100 Hz.

       width_type
	   Set method to specify band-width of filter.

	   h   Hz

	   q   Q-Factor

	   o   octave

	   s   slope

       width, w
	   Determine how steep is the filter's shelf transition.

   biquad
       Apply a biquad IIR filter with the given coefficients.  Where b0, b1,
       b2 and a0, a1, a2 are the numerator and denominator coefficients
       respectively.

   channelmap
       Remap input channels to new locations.

       This filter accepts the following named parameters:

       channel_layout
	   Channel layout of the output stream.

       map Map channels from input to output. The argument is a '|'-separated
	   list of mappings, each in the "in_channel-out_channel" or
	   in_channel form. in_channel can be either the name of the input
	   channel (e.g. FL for front left) or its index in the input channel
	   layout.  out_channel is the name of the output channel or its index
	   in the output channel layout. If out_channel is not given then it
	   is implicitly an index, starting with zero and increasing by one
	   for each mapping.

       If no mapping is present, the filter will implicitly map input channels
       to output channels preserving index.

       For example, assuming a 5.1+downmix input MOV file

	       ffmpeg -i in.mov -filter 'channelmap=map=DL-FL|DR-FR' out.wav

       will create an output WAV file tagged as stereo from the downmix
       channels of the input.

       To fix a 5.1 WAV improperly encoded in AAC's native channel order

	       ffmpeg -i in.wav -filter 'channelmap=1|2|0|5|3|4:channel_layout=5.1' out.wav

   channelsplit
       Split each channel in input audio stream into a separate output stream.

       This filter accepts the following named parameters:

       channel_layout
	   Channel layout of the input stream. Default is "stereo".

       For example, assuming a stereo input MP3 file

	       ffmpeg -i in.mp3 -filter_complex channelsplit out.mkv

       will create an output Matroska file with two audio streams, one
       containing only the left channel and the other the right channel.

       To split a 5.1 WAV file into per-channel files

	       ffmpeg -i in.wav -filter_complex
	       'channelsplit=channel_layout=5.1[FL][FR][FC][LFE][SL][SR]'
	       -map '[FL]' front_left.wav -map '[FR]' front_right.wav -map '[FC]'
	       front_center.wav -map '[LFE]' lfe.wav -map '[SL]' side_left.wav -map '[SR]'
	       side_right.wav

   compand
       Compress or expand audio dynamic range.

       A description of the accepted options follows.

       attacks
       decays
	   Set list of times in seconds for each channel over which the
	   instantaneous level of the input signal is averaged to determine
	   its volume.	attacks refers to increase of volume and decays refers
	   to decrease of volume.  For most situations, the attack time
	   (response to the audio getting louder) should be shorter than the
	   decay time because the human ear is more sensitive to sudden loud
	   audio than sudden soft audio.  Typical value for attack is 0.3
	   seconds and for decay 0.8 seconds.

       points
	   Set list of points for transfer function, specified in dB relative
	   to maximum possible signal amplitude.  Each key points list need to
	   be defined using the following syntax: "x0/y0 x1/y1 x2/y2 ...".

	   The input values must be in strictly increasing order but the
	   transfer function does not have to be monotonically rising.	The
	   point "0/0" is assumed but may be overridden (by "0/out-dBn").
	   Typical values for the transfer function are "-70/-70 -60/-20".

       soft-knee
	   Set amount for which the points at where adjacent line segments on
	   the transfer function meet will be rounded. Defaults is 0.01.

       gain
	   Set additional gain in dB to be applied at all points on the
	   transfer function and allows easy adjustment of the overall gain.
	   Default is 0.

       volume
	   Set initial volume in dB to be assumed for each channel when
	   filtering starts.  This permits the user to supply a nominal level
	   initially, so that, for example, a very large gain is not applied
	   to initial signal levels before the companding has begun to
	   operate. A typical value for audio which is initially quiet is -90
	   dB. Default is 0.

       delay
	   Set delay in seconds. Default is 0. The input audio is analysed
	   immediately, but audio is delayed before being fed to the volume
	   adjuster. Specifying a delay approximately equal to the
	   attack/decay times allows the filter to effectively operate in
	   predictive rather than reactive mode.

       Examples

       ·   Make music with both quiet and loud passages suitable for listening
	   in a noisy environment:

		   compand=.3 .3:1 1:-90/-60 -60/-40 -40/-30 -20/-20:6:0:-90:0.2

       ·   Noise-gate for when the noise is at a lower level than the signal:

		   compand=.1 .1:.2 .2:-900/-900 -50.1/-900 -50/-50:.01:0:-90:.1

       ·   Here is another noise-gate, this time for when the noise is at a
	   higher level than the signal (making it, in some ways, similar to
	   squelch):

		   compand=.1 .1:.1 .1:-45.1/-45.1 -45/-900 0/-900:.01:45:-90:.1

   earwax
       Make audio easier to listen to on headphones.

       This filter adds `cues' to 44.1kHz stereo (i.e. audio CD format) audio
       so that when listened to on headphones the stereo image is moved from
       inside your head (standard for headphones) to outside and in front of
       the listener (standard for speakers).

       Ported from SoX.

   equalizer
       Apply a two-pole peaking equalisation (EQ) filter. With this filter,
       the signal-level at and around a selected frequency can be increased or
       decreased, whilst (unlike bandpass and bandreject filters) that at all
       other frequencies is unchanged.

       In order to produce complex equalisation curves, this filter can be
       given several times, each with a different central frequency.

       The filter accepts the following options:

       frequency, f
	   Set the filter's central frequency in Hz.

       width_type
	   Set method to specify band-width of filter.

	   h   Hz

	   q   Q-Factor

	   o   octave

	   s   slope

       width, w
	   Specify the band-width of a filter in width_type units.

       gain, g
	   Set the required gain or attenuation in dB.	Beware of clipping
	   when using a positive gain.

   highpass
       Apply a high-pass filter with 3dB point frequency.  The filter can be
       either single-pole, or double-pole (the default).  The filter roll off
       at 6dB per pole per octave (20dB per pole per decade).

       The filter accepts the following options:

       frequency, f
	   Set frequency in Hz. Default is 3000.

       poles, p
	   Set number of poles. Default is 2.

       width_type
	   Set method to specify band-width of filter.

	   h   Hz

	   q   Q-Factor

	   o   octave

	   s   slope

       width, w
	   Specify the band-width of a filter in width_type units.  Applies
	   only to double-pole filter.	The default is 0.707q and gives a
	   Butterworth response.

   join
       Join multiple input streams into one multi-channel stream.

       The filter accepts the following named parameters:

       inputs
	   Number of input streams. Defaults to 2.

       channel_layout
	   Desired output channel layout. Defaults to stereo.

       map Map channels from inputs to output. The argument is a '|'-separated
	   list of mappings, each in the "input_idx.in_channel-out_channel"
	   form. input_idx is the 0-based index of the input stream.
	   in_channel can be either the name of the input channel (e.g. FL for
	   front left) or its index in the specified input stream. out_channel
	   is the name of the output channel.

       The filter will attempt to guess the mappings when those are not
       specified explicitly. It does so by first trying to find an unused
       matching input channel and if that fails it picks the first unused
       input channel.

       E.g. to join 3 inputs (with properly set channel layouts)

	       ffmpeg -i INPUT1 -i INPUT2 -i INPUT3 -filter_complex join=inputs=3 OUTPUT

       To build a 5.1 output from 6 single-channel streams:

	       ffmpeg -i fl -i fr -i fc -i sl -i sr -i lfe -filter_complex
	       'join=inputs=6:channel_layout=5.1:map=0.0-FL|1.0-FR|2.0-FC|3.0-SL|4.0-SR|5.0-LFE'
	       out

   ladspa
       Load a LADSPA (Linux Audio Developer's Simple Plugin API) plugin.

       To enable compilation of this filter you need to configure FFmpeg with
       "--enable-ladspa".

       file, f
	   Specifies the name of LADSPA plugin library to load. If the
	   environment variable LADSPA_PATH is defined, the LADSPA plugin is
	   searched in each one of the directories specified by the colon
	   separated list in LADSPA_PATH, otherwise in the standard LADSPA
	   paths, which are in this order: HOME/.ladspa/lib/,
	   /usr/local/lib/ladspa/, /usr/lib/ladspa/.

       plugin, p
	   Specifies the plugin within the library. Some libraries contain
	   only one plugin, but others contain many of them. If this is not
	   set filter will list all available plugins within the specified
	   library.

       controls, c
	   Set the '|' separated list of controls which are zero or more
	   floating point values that determine the behavior of the loaded
	   plugin (for example delay, threshold or gain).  Controls need to be
	   defined using the following syntax:
	   c0=value0|c1=value1|c2=value2|..., where valuei is the value set on
	   the i-th control.  If controls is set to "help", all available
	   controls and their valid ranges are printed.

       sample_rate, s
	   Specify the sample rate, default to 44100. Only used if plugin have
	   zero inputs.

       nb_samples, n
	   Set the number of samples per channel per each output frame,
	   default is 1024. Only used if plugin have zero inputs.

       duration, d
	   Set the minimum duration of the sourced audio. See the function
	   "av_parse_time()" for the accepted format, also check the "Time
	   duration" section in the ffmpeg-utils manual.  Note that the
	   resulting duration may be greater than the specified duration, as
	   the generated audio is always cut at the end of a complete frame.
	   If not specified, or the expressed duration is negative, the audio
	   is supposed to be generated forever.	 Only used if plugin have zero
	   inputs.

       Examples

       ·   List all available plugins within amp (LADSPA example plugin)
	   library:

		   ladspa=file=amp

       ·   List all available controls and their valid ranges for "vcf_notch"
	   plugin from "VCF" library:

		   ladspa=f=vcf:p=vcf_notch:c=help

       ·   Simulate low quality audio equipment using "Computer Music Toolkit"
	   (CMT) plugin library:

		   ladspa=file=cmt:plugin=lofi:controls=c0=22|c1=12|c2=12

       ·   Add reverberation to the audio using TAP-plugins (Tom's Audio
	   Processing plugins):

		   ladspa=file=tap_reverb:tap_reverb

       ·   Generate white noise, with 0.2 amplitude:

		   ladspa=file=cmt:noise_source_white:c=c0=.2

       ·   Generate 20 bpm clicks using plugin "C* Click - Metronome" from the
	   "C* Audio Plugin Suite" (CAPS) library:

		   ladspa=file=caps:Click:c=c1=20'

       ·   Apply "C* Eq10X2 - Stereo 10-band equaliser" effect:

		   ladspa=caps:Eq10X2:c=c0=-48|c9=-24|c3=12|c4=2

       Commands

       This filter supports the following commands:

       cN  Modify the N-th control value.

	   If the specified value is not valid, it is ignored and prior one is
	   kept.

   lowpass
       Apply a low-pass filter with 3dB point frequency.  The filter can be
       either single-pole or double-pole (the default).	 The filter roll off
       at 6dB per pole per octave (20dB per pole per decade).

       The filter accepts the following options:

       frequency, f
	   Set frequency in Hz. Default is 500.

       poles, p
	   Set number of poles. Default is 2.

       width_type
	   Set method to specify band-width of filter.

	   h   Hz

	   q   Q-Factor

	   o   octave

	   s   slope

       width, w
	   Specify the band-width of a filter in width_type units.  Applies
	   only to double-pole filter.	The default is 0.707q and gives a
	   Butterworth response.

   pan
       Mix channels with specific gain levels. The filter accepts the output
       channel layout followed by a set of channels definitions.

       This filter is also designed to remap efficiently the channels of an
       audio stream.

       The filter accepts parameters of the form: "l:outdef:outdef:..."

       l   output channel layout or number of channels

       outdef
	   output channel specification, of the form:
	   "out_name=[gain*]in_name[+[gain*]in_name...]"

       out_name
	   output channel to define, either a channel name (FL, FR, etc.) or a
	   channel number (c0, c1, etc.)

       gain
	   multiplicative coefficient for the channel, 1 leaving the volume
	   unchanged

       in_name
	   input channel to use, see out_name for details; it is not possible
	   to mix named and numbered input channels

       If the `=' in a channel specification is replaced by `<', then the
       gains for that specification will be renormalized so that the total is
       1, thus avoiding clipping noise.

       Mixing examples

       For example, if you want to down-mix from stereo to mono, but with a
       bigger factor for the left channel:

	       pan=1:c0=0.9*c0+0.1*c1

       A customized down-mix to stereo that works automatically for 3-, 4-, 5-
       and 7-channels surround:

	       pan=stereo: FL < FL + 0.5*FC + 0.6*BL + 0.6*SL : FR < FR + 0.5*FC + 0.6*BR + 0.6*SR

       Note that ffmpeg integrates a default down-mix (and up-mix) system that
       should be preferred (see "-ac" option) unless you have very specific
       needs.

       Remapping examples

       The channel remapping will be effective if, and only if:

       *<gain coefficients are zeroes or ones,>
       *<only one input per channel output,>

       If all these conditions are satisfied, the filter will notify the user
       ("Pure channel mapping detected"), and use an optimized and lossless
       method to do the remapping.

       For example, if you have a 5.1 source and want a stereo audio stream by
       dropping the extra channels:

	       pan="stereo: c0=FL : c1=FR"

       Given the same source, you can also switch front left and front right
       channels and keep the input channel layout:

	       pan="5.1: c0=c1 : c1=c0 : c2=c2 : c3=c3 : c4=c4 : c5=c5"

       If the input is a stereo audio stream, you can mute the front left
       channel (and still keep the stereo channel layout) with:

	       pan="stereo:c1=c1"

       Still with a stereo audio stream input, you can copy the right channel
       in both front left and right:

	       pan="stereo: c0=FR : c1=FR"

   replaygain
       ReplayGain scanner filter. This filter takes an audio stream as an
       input and outputs it unchanged.	At end of filtering it displays
       "track_gain" and "track_peak".

   resample
       Convert the audio sample format, sample rate and channel layout. This
       filter is not meant to be used directly.

   silencedetect
       Detect silence in an audio stream.

       This filter logs a message when it detects that the input audio volume
       is less or equal to a noise tolerance value for a duration greater or
       equal to the minimum detected noise duration.

       The printed times and duration are expressed in seconds.

       The filter accepts the following options:

       duration, d
	   Set silence duration until notification (default is 2 seconds).

       noise, n
	   Set noise tolerance. Can be specified in dB (in case "dB" is
	   appended to the specified value) or amplitude ratio. Default is
	   -60dB, or 0.001.

       Examples

       ·   Detect 5 seconds of silence with -50dB noise tolerance:

		   silencedetect=n=-50dB:d=5

       ·   Complete example with ffmpeg to detect silence with 0.0001 noise
	   tolerance in silence.mp3:

		   ffmpeg -i silence.mp3 -af silencedetect=noise=0.0001 -f null -

   treble
       Boost or cut treble (upper) frequencies of the audio using a two-pole
       shelving filter with a response similar to that of a standard hi-fi's
       tone-controls. This is also known as shelving equalisation (EQ).

       The filter accepts the following options:

       gain, g
	   Give the gain at whichever is the lower of ~22 kHz and the Nyquist
	   frequency. Its useful range is about -20 (for a large cut) to +20
	   (for a large boost). Beware of clipping when using a positive gain.

       frequency, f
	   Set the filter's central frequency and so can be used to extend or
	   reduce the frequency range to be boosted or cut.  The default value
	   is 3000 Hz.

       width_type
	   Set method to specify band-width of filter.

	   h   Hz

	   q   Q-Factor

	   o   octave

	   s   slope

       width, w
	   Determine how steep is the filter's shelf transition.

   volume
       Adjust the input audio volume.

       The filter accepts the following options:

       volume
	   Expresses how the audio volume will be increased or decreased.

	   Output values are clipped to the maximum value.

	   The output audio volume is given by the relation:

		   <output_volume> = <volume> * <input_volume>

	   Default value for volume is 1.0.

       precision
	   Set the mathematical precision.

	   This determines which input sample formats will be allowed, which
	   affects the precision of the volume scaling.

	   fixed
	       8-bit fixed-point; limits input sample format to U8, S16, and
	       S32.

	   float
	       32-bit floating-point; limits input sample format to FLT.
	       (default)

	   double
	       64-bit floating-point; limits input sample format to DBL.

       Examples

       ·   Halve the input audio volume:

		   volume=volume=0.5
		   volume=volume=1/2
		   volume=volume=-6.0206dB

	   In all the above example the named key for volume can be omitted,
	   for example like in:

		   volume=0.5

       ·   Increase input audio power by 6 decibels using fixed-point
	   precision:

		   volume=volume=6dB:precision=fixed

   volumedetect
       Detect the volume of the input video.

       The filter has no parameters. The input is not modified. Statistics
       about the volume will be printed in the log when the input stream end
       is reached.

       In particular it will show the mean volume (root mean square), maximum
       volume (on a per-sample basis), and the beginning of a histogram of the
       registered volume values (from the maximum value to a cumulated 1/1000
       of the samples).

       All volumes are in decibels relative to the maximum PCM value.

       Examples

       Here is an excerpt of the output:

	       [Parsed_volumedetect_0  0xa23120] mean_volume: -27 dB
	       [Parsed_volumedetect_0  0xa23120] max_volume: -4 dB
	       [Parsed_volumedetect_0  0xa23120] histogram_4db: 6
	       [Parsed_volumedetect_0  0xa23120] histogram_5db: 62
	       [Parsed_volumedetect_0  0xa23120] histogram_6db: 286
	       [Parsed_volumedetect_0  0xa23120] histogram_7db: 1042
	       [Parsed_volumedetect_0  0xa23120] histogram_8db: 2551
	       [Parsed_volumedetect_0  0xa23120] histogram_9db: 4609
	       [Parsed_volumedetect_0  0xa23120] histogram_10db: 8409

       It means that:

       ·   The mean square energy is approximately -27 dB, or 10^-2.7.

       ·   The largest sample is at -4 dB, or more precisely between -4 dB and
	   -5 dB.

       ·   There are 6 samples at -4 dB, 62 at -5 dB, 286 at -6 dB, etc.

       In other words, raising the volume by +4 dB does not cause any
       clipping, raising it by +5 dB causes clipping for 6 samples, etc.

AUDIO SOURCES
       Below is a description of the currently available audio sources.

   abuffer
       Buffer audio frames, and make them available to the filter chain.

       This source is mainly intended for a programmatic use, in particular
       through the interface defined in libavfilter/asrc_abuffer.h.

       It accepts the following named parameters:

       time_base
	   Timebase which will be used for timestamps of submitted frames. It
	   must be either a floating-point number or in numerator/denominator
	   form.

       sample_rate
	   The sample rate of the incoming audio buffers.

       sample_fmt
	   The sample format of the incoming audio buffers.  Either a sample
	   format name or its corresponging integer representation from the
	   enum AVSampleFormat in libavutil/samplefmt.h

       channel_layout
	   The channel layout of the incoming audio buffers.  Either a channel
	   layout name from channel_layout_map in libavutil/channel_layout.c
	   or its corresponding integer representation from the AV_CH_LAYOUT_*
	   macros in libavutil/channel_layout.h

       channels
	   The number of channels of the incoming audio buffers.  If both
	   channels and channel_layout are specified, then they must be
	   consistent.

       Examples

	       abuffer=sample_rate=44100:sample_fmt=s16p:channel_layout=stereo

       will instruct the source to accept planar 16bit signed stereo at
       44100Hz.	 Since the sample format with name "s16p" corresponds to the
       number 6 and the "stereo" channel layout corresponds to the value 0x3,
       this is equivalent to:

	       abuffer=sample_rate=44100:sample_fmt=6:channel_layout=0x3

   aevalsrc
       Generate an audio signal specified by an expression.

       This source accepts in input one or more expressions (one for each
       channel), which are evaluated and used to generate a corresponding
       audio signal.

       This source accepts the following options:

       exprs
	   Set the '|'-separated expressions list for each separate channel.
	   In case the channel_layout option is not specified, the selected
	   channel layout depends on the number of provided expressions.

       channel_layout, c
	   Set the channel layout. The number of channels in the specified
	   layout must be equal to the number of specified expressions.

       duration, d
	   Set the minimum duration of the sourced audio. See the function
	   "av_parse_time()" for the accepted format.  Note that the resulting
	   duration may be greater than the specified duration, as the
	   generated audio is always cut at the end of a complete frame.

	   If not specified, or the expressed duration is negative, the audio
	   is supposed to be generated forever.

       nb_samples, n
	   Set the number of samples per channel per each output frame,
	   default to 1024.

       sample_rate, s
	   Specify the sample rate, default to 44100.

       Each expression in exprs can contain the following constants:

       n   number of the evaluated sample, starting from 0

       t   time of the evaluated sample expressed in seconds, starting from 0

       s   sample rate

       Examples

       ·   Generate silence:

		   aevalsrc=0

       ·   Generate a sin signal with frequency of 440 Hz, set sample rate to
	   8000 Hz:

		   aevalsrc="sin(440*2*PI*t):s=8000"

       ·   Generate a two channels signal, specify the channel layout (Front
	   Center + Back Center) explicitly:

		   aevalsrc="sin(420*2*PI*t)|cos(430*2*PI*t):c=FC|BC"

       ·   Generate white noise:

		   aevalsrc="-2+random(0)"

       ·   Generate an amplitude modulated signal:

		   aevalsrc="sin(10*2*PI*t)*sin(880*2*PI*t)"

       ·   Generate 2.5 Hz binaural beats on a 360 Hz carrier:

		   aevalsrc="0.1*sin(2*PI*(360-2.5/2)*t) | 0.1*sin(2*PI*(360+2.5/2)*t)"

   anullsrc
       Null audio source, return unprocessed audio frames. It is mainly useful
       as a template and to be employed in analysis / debugging tools, or as
       the source for filters which ignore the input data (for example the sox
       synth filter).

       This source accepts the following options:

       channel_layout, cl
	   Specify the channel layout, and can be either an integer or a
	   string representing a channel layout. The default value of
	   channel_layout is "stereo".

	   Check the channel_layout_map definition in
	   libavutil/channel_layout.c for the mapping between strings and
	   channel layout values.

       sample_rate, r
	   Specify the sample rate, and defaults to 44100.

       nb_samples, n
	   Set the number of samples per requested frames.

       Examples

       ·   Set the sample rate to 48000 Hz and the channel layout to
	   AV_CH_LAYOUT_MONO.

		   anullsrc=r=48000:cl=4

       ·   Do the same operation with a more obvious syntax:

		   anullsrc=r=48000:cl=mono

       All the parameters need to be explicitly defined.

   flite
       Synthesize a voice utterance using the libflite library.

       To enable compilation of this filter you need to configure FFmpeg with
       "--enable-libflite".

       Note that the flite library is not thread-safe.

       The filter accepts the following options:

       list_voices
	   If set to 1, list the names of the available voices and exit
	   immediately. Default value is 0.

       nb_samples, n
	   Set the maximum number of samples per frame. Default value is 512.

       textfile
	   Set the filename containing the text to speak.

       text
	   Set the text to speak.

       voice, v
	   Set the voice to use for the speech synthesis. Default value is
	   "kal". See also the list_voices option.

       Examples

       ·   Read from file speech.txt, and synthetize the text using the
	   standard flite voice:

		   flite=textfile=speech.txt

       ·   Read the specified text selecting the "slt" voice:

		   flite=text='So fare thee well, poor devil of a Sub-Sub, whose commentator I am':voice=slt

       ·   Input text to ffmpeg:

		   ffmpeg -f lavfi -i flite=text='So fare thee well, poor devil of a Sub-Sub, whose commentator I am':voice=slt

       ·   Make ffplay speak the specified text, using "flite" and the "lavfi"
	   device:

		   ffplay -f lavfi flite=text='No more be grieved for which that thou hast done.'

       For more information about libflite, check:
       <http://www.speech.cs.cmu.edu/flite/>

   sine
       Generate an audio signal made of a sine wave with amplitude 1/8.

       The audio signal is bit-exact.

       The filter accepts the following options:

       frequency, f
	   Set the carrier frequency. Default is 440 Hz.

       beep_factor, b
	   Enable a periodic beep every second with frequency beep_factor
	   times the carrier frequency. Default is 0, meaning the beep is
	   disabled.

       sample_rate, r
	   Specify the sample rate, default is 44100.

       duration, d
	   Specify the duration of the generated audio stream.

       samples_per_frame
	   Set the number of samples per output frame, default is 1024.

       Examples

       ·   Generate a simple 440 Hz sine wave:

		   sine

       ·   Generate a 220 Hz sine wave with a 880 Hz beep each second, for 5
	   seconds:

		   sine=220:4:d=5
		   sine=f=220:b=4:d=5
		   sine=frequency=220:beep_factor=4:duration=5

AUDIO SINKS
       Below is a description of the currently available audio sinks.

   abuffersink
       Buffer audio frames, and make them available to the end of filter
       chain.

       This sink is mainly intended for programmatic use, in particular
       through the interface defined in libavfilter/buffersink.h or the
       options system.

       It accepts a pointer to an AVABufferSinkContext structure, which
       defines the incoming buffers' formats, to be passed as the opaque
       parameter to "avfilter_init_filter" for initialization.

   anullsink
       Null audio sink, do absolutely nothing with the input audio. It is
       mainly useful as a template and to be employed in analysis / debugging
       tools.

VIDEO FILTERS
       When you configure your FFmpeg build, you can disable any of the
       existing filters using "--disable-filters".  The configure output will
       show the video filters included in your build.

       Below is a description of the currently available video filters.

   alphaextract
       Extract the alpha component from the input as a grayscale video. This
       is especially useful with the alphamerge filter.

   alphamerge
       Add or replace the alpha component of the primary input with the
       grayscale value of a second input. This is intended for use with
       alphaextract to allow the transmission or storage of frame sequences
       that have alpha in a format that doesn't support an alpha channel.

       For example, to reconstruct full frames from a normal YUV-encoded video
       and a separate video created with alphaextract, you might use:

	       movie=in_alpha.mkv [alpha]; [in][alpha] alphamerge [out]

       Since this filter is designed for reconstruction, it operates on frame
       sequences without considering timestamps, and terminates when either
       input reaches end of stream. This will cause problems if your encoding
       pipeline drops frames. If you're trying to apply an image as an overlay
       to a video stream, consider the overlay filter instead.

   ass
       Same as the subtitles filter, except that it doesn't require libavcodec
       and libavformat to work. On the other hand, it is limited to ASS
       (Advanced Substation Alpha) subtitles files.

   bbox
       Compute the bounding box for the non-black pixels in the input frame
       luminance plane.

       This filter computes the bounding box containing all the pixels with a
       luminance value greater than the minimum allowed value.	The parameters
       describing the bounding box are printed on the filter log.

       The filter accepts the following option:

       min_val
	   Set the minimal luminance value. Default is 16.

   blackdetect
       Detect video intervals that are (almost) completely black. Can be
       useful to detect chapter transitions, commercials, or invalid
       recordings. Output lines contains the time for the start, end and
       duration of the detected black interval expressed in seconds.

       In order to display the output lines, you need to set the loglevel at
       least to the AV_LOG_INFO value.

       The filter accepts the following options:

       black_min_duration, d
	   Set the minimum detected black duration expressed in seconds. It
	   must be a non-negative floating point number.

	   Default value is 2.0.

       picture_black_ratio_th, pic_th
	   Set the threshold for considering a picture "black".	 Express the
	   minimum value for the ratio:

		   <nb_black_pixels> / <nb_pixels>

	   for which a picture is considered black.  Default value is 0.98.

       pixel_black_th, pix_th
	   Set the threshold for considering a pixel "black".

	   The threshold expresses the maximum pixel luminance value for which
	   a pixel is considered "black". The provided value is scaled
	   according to the following equation:

		   <absolute_threshold> = <luminance_minimum_value> + <pixel_black_th> * <luminance_range_size>

	   luminance_range_size and luminance_minimum_value depend on the
	   input video format, the range is [0-255] for YUV full-range formats
	   and [16-235] for YUV non full-range formats.

	   Default value is 0.10.

       The following example sets the maximum pixel threshold to the minimum
       value, and detects only black intervals of 2 or more seconds:

	       blackdetect=d=2:pix_th=0.00

   blackframe
       Detect frames that are (almost) completely black. Can be useful to
       detect chapter transitions or commercials. Output lines consist of the
       frame number of the detected frame, the percentage of blackness, the
       position in the file if known or -1 and the timestamp in seconds.

       In order to display the output lines, you need to set the loglevel at
       least to the AV_LOG_INFO value.

       The filter accepts the following options:

       amount
	   Set the percentage of the pixels that have to be below the
	   threshold, defaults to 98.

       threshold, thresh
	   Set the threshold below which a pixel value is considered black,
	   defaults to 32.

   blend
       Blend two video frames into each other.

       It takes two input streams and outputs one stream, the first input is
       the "top" layer and second input is "bottom" layer.  Output terminates
       when shortest input terminates.

       A description of the accepted options follows.

       c0_mode
       c1_mode
       c2_mode
       c3_mode
       all_mode
	   Set blend mode for specific pixel component or all pixel components
	   in case of all_mode. Default value is "normal".

	   Available values for component modes are:

	   addition
	   and
	   average
	   burn
	   darken
	   difference
	   divide
	   dodge
	   exclusion
	   hardlight
	   lighten
	   multiply
	   negation
	   normal
	   or
	   overlay
	   phoenix
	   pinlight
	   reflect
	   screen
	   softlight
	   subtract
	   vividlight
	   xor
       c0_opacity
       c1_opacity
       c2_opacity
       c3_opacity
       all_opacity
	   Set blend opacity for specific pixel component or all pixel
	   components in case of all_opacity. Only used in combination with
	   pixel component blend modes.

       c0_expr
       c1_expr
       c2_expr
       c3_expr
       all_expr
	   Set blend expression for specific pixel component or all pixel
	   components in case of all_expr. Note that related mode options will
	   be ignored if those are set.

	   The expressions can use the following variables:

	   N   The sequential number of the filtered frame, starting from 0.

	   X
	   Y   the coordinates of the current sample

	   W
	   H   the width and height of currently filtered plane

	   SW
	   SH  Width and height scale depending on the currently filtered
	       plane. It is the ratio between the corresponding luma plane
	       number of pixels and the current plane ones. E.g. for YUV4:2:0
	       the values are "1,1" for the luma plane, and "0.5,0.5" for
	       chroma planes.

	   T   Time of the current frame, expressed in seconds.

	   TOP, A
	       Value of pixel component at current location for first video
	       frame (top layer).

	   BOTTOM, B
	       Value of pixel component at current location for second video
	       frame (bottom layer).

       shortest
	   Force termination when the shortest input terminates. Default is 0.

       repeatlast
	   Continue applying the last bottom frame after the end of the
	   stream. A value of 0 disable the filter after the last frame of the
	   bottom layer is reached.  Default is 1.

       Examples

       ·   Apply transition from bottom layer to top layer in first 10
	   seconds:

		   blend=all_expr='A*(if(gte(T,10),1,T/10))+B*(1-(if(gte(T,10),1,T/10)))'

       ·   Apply 1x1 checkerboard effect:

		   blend=all_expr='if(eq(mod(X,2),mod(Y,2)),A,B)'

   boxblur
       Apply boxblur algorithm to the input video.

       The filter accepts the following options:

       luma_radius, lr
       luma_power, lp
       chroma_radius, cr
       chroma_power, cp
       alpha_radius, ar
       alpha_power, ap

       A description of the accepted options follows.

       luma_radius, lr
       chroma_radius, cr
       alpha_radius, ar
	   Set an expression for the box radius in pixels used for blurring
	   the corresponding input plane.

	   The radius value must be a non-negative number, and must not be
	   greater than the value of the expression "min(w,h)/2" for the luma
	   and alpha planes, and of "min(cw,ch)/2" for the chroma planes.

	   Default value for luma_radius is "2". If not specified,
	   chroma_radius and alpha_radius default to the corresponding value
	   set for luma_radius.

	   The expressions can contain the following constants:

	   w
	   h   the input width and height in pixels

	   cw
	   ch  the input chroma image width and height in pixels

	   hsub
	   vsub
	       horizontal and vertical chroma subsample values. For example
	       for the pixel format "yuv422p" hsub is 2 and vsub is 1.

       luma_power, lp
       chroma_power, cp
       alpha_power, ap
	   Specify how many times the boxblur filter is applied to the
	   corresponding plane.

	   Default value for luma_power is 2. If not specified, chroma_power
	   and alpha_power default to the corresponding value set for
	   luma_power.

	   A value of 0 will disable the effect.

       Examples

       ·   Apply a boxblur filter with luma, chroma, and alpha radius set to
	   2:

		   boxblur=luma_radius=2:luma_power=1
		   boxblur=2:1

       ·   Set luma radius to 2, alpha and chroma radius to 0:

		   boxblur=2:1:cr=0:ar=0

       ·   Set luma and chroma radius to a fraction of the video dimension:

		   boxblur=luma_radius=min(h\,w)/10:luma_power=1:chroma_radius=min(cw\,ch)/10:chroma_power=1

   colorbalance
       Modify intensity of primary colors (red, green and blue) of input
       frames.

       The filter allows an input frame to be adjusted in the shadows,
       midtones or highlights regions for the red-cyan, green-magenta or blue-
       yellow balance.

       A positive adjustment value shifts the balance towards the primary
       color, a negative value towards the complementary color.

       The filter accepts the following options:

       rs
       gs
       bs  Adjust red, green and blue shadows (darkest pixels).

       rm
       gm
       bm  Adjust red, green and blue midtones (medium pixels).

       rh
       gh
       bh  Adjust red, green and blue highlights (brightest pixels).

	   Allowed ranges for options are "[-1.0, 1.0]". Defaults are 0.

       Examples

       ·   Add red color cast to shadows:

		   colorbalance=rs=.3

   colorchannelmixer
       Adjust video input frames by re-mixing color channels.

       This filter modifies a color channel by adding the values associated to
       the other channels of the same pixels. For example if the value to
       modify is red, the output value will be:

	       <red>=<red>*<rr> + <blue>*<rb> + <green>*<rg> + <alpha>*<ra>

       The filter accepts the following options:

       rr
       rg
       rb
       ra  Adjust contribution of input red, green, blue and alpha channels
	   for output red channel.  Default is 1 for rr, and 0 for rg, rb and
	   ra.

       gr
       gg
       gb
       ga  Adjust contribution of input red, green, blue and alpha channels
	   for output green channel.  Default is 1 for gg, and 0 for gr, gb
	   and ga.

       br
       bg
       bb
       ba  Adjust contribution of input red, green, blue and alpha channels
	   for output blue channel.  Default is 1 for bb, and 0 for br, bg and
	   ba.

       ar
       ag
       ab
       aa  Adjust contribution of input red, green, blue and alpha channels
	   for output alpha channel.  Default is 1 for aa, and 0 for ar, ag
	   and ab.

	   Allowed ranges for options are "[-2.0, 2.0]".

       Examples

       ·   Convert source to grayscale:

		   colorchannelmixer=.3:.4:.3:0:.3:.4:.3:0:.3:.4:.3

       ·   Simulate sepia tones:

		   colorchannelmixer=.393:.769:.189:0:.349:.686:.168:0:.272:.534:.131

   colormatrix
       Convert color matrix.

       The filter accepts the following options:

       src
       dst Specify the source and destination color matrix. Both values must
	   be specified.

	   The accepted values are:

	   bt709
	       BT.709

	   bt601
	       BT.601

	   smpte240m
	       SMPTE-240M

	   fcc FCC

       For example to convert from BT.601 to SMPTE-240M, use the command:

	       colormatrix=bt601:smpte240m

   copy
       Copy the input source unchanged to the output. Mainly useful for
       testing purposes.

   crop
       Crop the input video to given dimensions.

       The filter accepts the following options:

       w, out_w
	   Width of the output video. It defaults to "iw".  This expression is
	   evaluated only once during the filter configuration.

       h, out_h
	   Height of the output video. It defaults to "ih".  This expression
	   is evaluated only once during the filter configuration.

       x   Horizontal position, in the input video, of the left edge of the
	   output video.  It defaults to "(in_w-out_w)/2".  This expression is
	   evaluated per-frame.

       y   Vertical position, in the input video, of the top edge of the
	   output video.  It defaults to "(in_h-out_h)/2".  This expression is
	   evaluated per-frame.

       keep_aspect
	   If set to 1 will force the output display aspect ratio to be the
	   same of the input, by changing the output sample aspect ratio. It
	   defaults to 0.

       The out_w, out_h, x, y parameters are expressions containing the
       following constants:

       x
       y   the computed values for x and y. They are evaluated for each new
	   frame.

       in_w
       in_h
	   the input width and height

       iw
       ih  same as in_w and in_h

       out_w
       out_h
	   the output (cropped) width and height

       ow
       oh  same as out_w and out_h

       a   same as iw / ih

       sar input sample aspect ratio

       dar input display aspect ratio, it is the same as (iw / ih) * sar

       hsub
       vsub
	   horizontal and vertical chroma subsample values. For example for
	   the pixel format "yuv422p" hsub is 2 and vsub is 1.

       n   the number of input frame, starting from 0

       pos the position in the file of the input frame, NAN if unknown

       t   timestamp expressed in seconds, NAN if the input timestamp is
	   unknown

       The expression for out_w may depend on the value of out_h, and the
       expression for out_h may depend on out_w, but they cannot depend on x
       and y, as x and y are evaluated after out_w and out_h.

       The x and y parameters specify the expressions for the position of the
       top-left corner of the output (non-cropped) area. They are evaluated
       for each frame. If the evaluated value is not valid, it is approximated
       to the nearest valid value.

       The expression for x may depend on y, and the expression for y may
       depend on x.

       Examples

       ·   Crop area with size 100x100 at position (12,34).

		   crop=100:100:12:34

	   Using named options, the example above becomes:

		   crop=w=100:h=100:x=12:y=34

       ·   Crop the central input area with size 100x100:

		   crop=100:100

       ·   Crop the central input area with size 2/3 of the input video:

		   crop=2/3*in_w:2/3*in_h

       ·   Crop the input video central square:

		   crop=out_w=in_h
		   crop=in_h

       ·   Delimit the rectangle with the top-left corner placed at position
	   100:100 and the right-bottom corner corresponding to the right-
	   bottom corner of the input image:

		   crop=in_w-100:in_h-100:100:100

       ·   Crop 10 pixels from the left and right borders, and 20 pixels from
	   the top and bottom borders

		   crop=in_w-2*10:in_h-2*20

       ·   Keep only the bottom right quarter of the input image:

		   crop=in_w/2:in_h/2:in_w/2:in_h/2

       ·   Crop height for getting Greek harmony:

		   crop=in_w:1/PHI*in_w

       ·   Appply trembling effect:

		   crop=in_w/2:in_h/2:(in_w-out_w)/2+((in_w-out_w)/2)*sin(n/10):(in_h-out_h)/2 +((in_h-out_h)/2)*sin(n/7)

       ·   Apply erratic camera effect depending on timestamp:

		   crop=in_w/2:in_h/2:(in_w-out_w)/2+((in_w-out_w)/2)*sin(t*10):(in_h-out_h)/2 +((in_h-out_h)/2)*sin(t*13)"

       ·   Set x depending on the value of y:

		   crop=in_w/2:in_h/2:y:10+10*sin(n/10)

   cropdetect
       Auto-detect crop size.

       Calculate necessary cropping parameters and prints the recommended
       parameters through the logging system. The detected dimensions
       correspond to the non-black area of the input video.

       The filter accepts the following options:

       limit
	   Set higher black value threshold, which can be optionally specified
	   from nothing (0) to everything (255). An intensity value greater to
	   the set value is considered non-black. Default value is 24.

       round
	   Set the value for which the width/height should be divisible by.
	   The offset is automatically adjusted to center the video. Use 2 to
	   get only even dimensions (needed for 4:2:2 video). 16 is best when
	   encoding to most video codecs. Default value is 16.

       reset_count, reset
	   Set the counter that determines after how many frames cropdetect
	   will reset the previously detected largest video area and start
	   over to detect the current optimal crop area. Default value is 0.

	   This can be useful when channel logos distort the video area. 0
	   indicates never reset and return the largest area encountered
	   during playback.

   curves
       Apply color adjustments using curves.

       This filter is similar to the Adobe Photoshop and GIMP curves tools.
       Each component (red, green and blue) has its values defined by N key
       points tied from each other using a smooth curve. The x-axis represents
       the pixel values from the input frame, and the y-axis the new pixel
       values to be set for the output frame.

       By default, a component curve is defined by the two points (0;0) and
       (1;1). This creates a straight line where each original pixel value is
       "adjusted" to its own value, which means no change to the image.

       The filter allows you to redefine these two points and add some more. A
       new curve (using a natural cubic spline interpolation) will be define
       to pass smoothly through all these new coordinates. The new defined
       points needs to be strictly increasing over the x-axis, and their x and
       y values must be in the [0;1] interval.	If the computed curves
       happened to go outside the vector spaces, the values will be clipped
       accordingly.

       If there is no key point defined in "x=0", the filter will
       automatically insert a (0;0) point. In the same way, if there is no key
       point defined in "x=1", the filter will automatically insert a (1;1)
       point.

       The filter accepts the following options:

       preset
	   Select one of the available color presets. This option can be used
	   in addition to the r, g, b parameters; in this case, the later
	   options takes priority on the preset values.	 Available presets
	   are:

	   none
	   color_negative
	   cross_process
	   darker
	   increase_contrast
	   lighter
	   linear_contrast
	   medium_contrast
	   negative
	   strong_contrast
	   vintage

	   Default is "none".

       master, m
	   Set the master key points. These points will define a second pass
	   mapping. It is sometimes called a "luminance" or "value" mapping.
	   It can be used with r, g, b or all since it acts like a post-
	   processing LUT.

       red, r
	   Set the key points for the red component.

       green, g
	   Set the key points for the green component.

       blue, b
	   Set the key points for the blue component.

       all Set the key points for all components (not including master).  Can
	   be used in addition to the other key points component options. In
	   this case, the unset component(s) will fallback on this all
	   setting.

       psfile
	   Specify a Photoshop curves file (".asv") to import the settings
	   from.

       To avoid some filtergraph syntax conflicts, each key points list need
       to be defined using the following syntax: "x0/y0 x1/y1 x2/y2 ...".

       Examples

       ·   Increase slightly the middle level of blue:

		   curves=blue='0.5/0.58'

       ·   Vintage effect:

		   curves=r='0/0.11 .42/.51 1/0.95':g='0.50/0.48':b='0/0.22 .49/.44 1/0.8'

	   Here we obtain the following coordinates for each components:

	   red "(0;0.11) (0.42;0.51) (1;0.95)"

	   green
	       "(0;0) (0.50;0.48) (1;1)"

	   blue
	       "(0;0.22) (0.49;0.44) (1;0.80)"

       ·   The previous example can also be achieved with the associated
	   built-in preset:

		   curves=preset=vintage

       ·   Or simply:

		   curves=vintage

       ·   Use a Photoshop preset and redefine the points of the green
	   component:

		   curves=psfile='MyCurvesPresets/purple.asv':green='0.45/0.53'

   dctdnoiz
       Denoise frames using 2D DCT (frequency domain filtering).

       This filter is not designed for real time and can be extremely slow.

       The filter accepts the following options:

       sigma, s
	   Set the noise sigma constant.

	   This sigma defines a hard threshold of "3 * sigma"; every DCT
	   coefficient (absolute value) below this threshold with be dropped.

	   If you need a more advanced filtering, see expr.

	   Default is 0.

       overlap
	   Set number overlapping pixels for each block. Each block is of size
	   "16x16". Since the filter can be slow, you may want to reduce this
	   value, at the cost of a less effective filter and the risk of
	   various artefacts.

	   If the overlapping value doesn't allow to process the whole input
	   width or height, a warning will be displayed and according borders
	   won't be denoised.

	   Default value is 15.

       expr, e
	   Set the coefficient factor expression.

	   For each coefficient of a DCT block, this expression will be
	   evaluated as a multiplier value for the coefficient.

	   If this is option is set, the sigma option will be ignored.

	   The absolute value of the coefficient can be accessed through the c
	   variable.

       Examples

       Apply a denoise with a sigma of 4.5:

	       dctdnoiz=4.5

       The same operation can be achieved using the expression system:

	       dctdnoiz=e='gte(c, 4.5*3)'

   decimate
       Drop duplicated frames at regular intervals.

       The filter accepts the following options:

       cycle
	   Set the number of frames from which one will be dropped. Setting
	   this to N means one frame in every batch of N frames will be
	   dropped.  Default is 5.

       dupthresh
	   Set the threshold for duplicate detection. If the difference metric
	   for a frame is less than or equal to this value, then it is
	   declared as duplicate. Default is 1.1

       scthresh
	   Set scene change threshold. Default is 15.

       blockx
       blocky
	   Set the size of the x and y-axis blocks used during metric
	   calculations.  Larger blocks give better noise suppression, but
	   also give worse detection of small movements. Must be a power of
	   two. Default is 32.

       ppsrc
	   Mark main input as a pre-processed input and activate clean source
	   input stream. This allows the input to be pre-processed with
	   various filters to help the metrics calculation while keeping the
	   frame selection lossless. When set to 1, the first stream is for
	   the pre-processed input, and the second stream is the clean source
	   from where the kept frames are chosen. Default is 0.

       chroma
	   Set whether or not chroma is considered in the metric calculations.
	   Default is 1.

   delogo
       Suppress a TV station logo by a simple interpolation of the surrounding
       pixels. Just set a rectangle covering the logo and watch it disappear
       (and sometimes something even uglier appear - your mileage may vary).

       This filter accepts the following options:

       x
       y   Specify the top left corner coordinates of the logo. They must be
	   specified.

       w
       h   Specify the width and height of the logo to clear. They must be
	   specified.

       band, t
	   Specify the thickness of the fuzzy edge of the rectangle (added to
	   w and h). The default value is 4.

       show
	   When set to 1, a green rectangle is drawn on the screen to simplify
	   finding the right x, y, w, and h parameters.	 The default value is
	   0.

	   The rectangle is drawn on the outermost pixels which will be
	   (partly) replaced with interpolated values. The values of the next
	   pixels immediately outside this rectangle in each direction will be
	   used to compute the interpolated pixel values inside the rectangle.

       Examples

       ·   Set a rectangle covering the area with top left corner coordinates
	   0,0 and size 100x77, setting a band of size 10:

		   delogo=x=0:y=0:w=100:h=77:band=10

   deshake
       Attempt to fix small changes in horizontal and/or vertical shift. This
       filter helps remove camera shake from hand-holding a camera, bumping a
       tripod, moving on a vehicle, etc.

       The filter accepts the following options:

       x
       y
       w
       h   Specify a rectangular area where to limit the search for motion
	   vectors.  If desired the search for motion vectors can be limited
	   to a rectangular area of the frame defined by its top left corner,
	   width and height. These parameters have the same meaning as the
	   drawbox filter which can be used to visualise the position of the
	   bounding box.

	   This is useful when simultaneous movement of subjects within the
	   frame might be confused for camera motion by the motion vector
	   search.

	   If any or all of x, y, w and h are set to -1 then the full frame is
	   used. This allows later options to be set without specifying the
	   bounding box for the motion vector search.

	   Default - search the whole frame.

       rx
       ry  Specify the maximum extent of movement in x and y directions in the
	   range 0-64 pixels. Default 16.

       edge
	   Specify how to generate pixels to fill blanks at the edge of the
	   frame. Available values are:

	   blank, 0
	       Fill zeroes at blank locations

	   original, 1
	       Original image at blank locations

	   clamp, 2
	       Extruded edge value at blank locations

	   mirror, 3
	       Mirrored edge at blank locations

	   Default value is mirror.

       blocksize
	   Specify the blocksize to use for motion search. Range 4-128 pixels,
	   default 8.

       contrast
	   Specify the contrast threshold for blocks. Only blocks with more
	   than the specified contrast (difference between darkest and
	   lightest pixels) will be considered. Range 1-255, default 125.

       search
	   Specify the search strategy. Available values are:

	   exhaustive, 0
	       Set exhaustive search

	   less, 1
	       Set less exhaustive search.

	   Default value is exhaustive.

       filename
	   If set then a detailed log of the motion search is written to the
	   specified file.

       opencl
	   If set to 1, specify using OpenCL capabilities, only available if
	   FFmpeg was configured with "--enable-opencl". Default value is 0.

   drawbox
       Draw a colored box on the input image.

       This filter accepts the following options:

       x
       y   The expressions which specify the top left corner coordinates of
	   the box. Default to 0.

       width, w
       height, h
	   The expressions which specify the width and height of the box, if 0
	   they are interpreted as the input width and height. Default to 0.

       color, c
	   Specify the color of the box to write. For the general syntax of
	   this option, check the "Color" section in the ffmpeg-utils manual.
	   If the special value "invert" is used, the box edge color is the
	   same as the video with inverted luma.

       thickness, t
	   The expression which sets the thickness of the box edge. Default
	   value is 3.

	   See below for the list of accepted constants.

       The parameters for x, y, w and h and t are expressions containing the
       following constants:

       dar The input display aspect ratio, it is the same as (w / h) * sar.

       hsub
       vsub
	   horizontal and vertical chroma subsample values. For example for
	   the pixel format "yuv422p" hsub is 2 and vsub is 1.

       in_h, ih
       in_w, iw
	   The input width and height.

       sar The input sample aspect ratio.

       x
       y   The x and y offset coordinates where the box is drawn.

       w
       h   The width and height of the drawn box.

       t   The thickness of the drawn box.

	   These constants allow the x, y, w, h and t expressions to refer to
	   each other, so you may for example specify "y=x/dar" or "h=w/dar".

       Examples

       ·   Draw a black box around the edge of the input image:

		   drawbox

       ·   Draw a box with color red and an opacity of 50%:

		   drawbox=10:20:200:60:red@0.5

	   The previous example can be specified as:

		   drawbox=x=10:y=20:w=200:h=60:color=red@0.5

       ·   Fill the box with pink color:

		   drawbox=x=10:y=10:w=100:h=100:color=pink@0.5:t=max

       ·   Draw a 2-pixel red 2.40:1 mask:

		   drawbox=x=-t:y=0.5*(ih-iw/2.4)-t:w=iw+t*2:h=iw/2.4+t*2:t=2:c=red

   drawgrid
       Draw a grid on the input image.

       This filter accepts the following options:

       x
       y   The expressions which specify the coordinates of some point of grid
	   intersection (meant to configure offset). Both default to 0.

       width, w
       height, h
	   The expressions which specify the width and height of the grid
	   cell, if 0 they are interpreted as the input width and height,
	   respectively, minus "thickness", so image gets framed. Default to
	   0.

       color, c
	   Specify the color of the grid. For the general syntax of this
	   option, check the "Color" section in the ffmpeg-utils manual. If
	   the special value "invert" is used, the grid color is the same as
	   the video with inverted luma.

       thickness, t
	   The expression which sets the thickness of the grid line. Default
	   value is 1.

	   See below for the list of accepted constants.

       The parameters for x, y, w and h and t are expressions containing the
       following constants:

       dar The input display aspect ratio, it is the same as (w / h) * sar.

       hsub
       vsub
	   horizontal and vertical chroma subsample values. For example for
	   the pixel format "yuv422p" hsub is 2 and vsub is 1.

       in_h, ih
       in_w, iw
	   The input grid cell width and height.

       sar The input sample aspect ratio.

       x
       y   The x and y coordinates of some point of grid intersection (meant
	   to configure offset).

       w
       h   The width and height of the drawn cell.

       t   The thickness of the drawn cell.

	   These constants allow the x, y, w, h and t expressions to refer to
	   each other, so you may for example specify "y=x/dar" or "h=w/dar".

       Examples

       ·   Draw a grid with cell 100x100 pixels, thickness 2 pixels, with
	   color red and an opacity of 50%:

		   drawgrid=width=100:height=100:thickness=2:color=red@0.5

       ·   Draw a white 3x3 grid with an opacity of 50%:

		   drawgrid=w=iw/3:h=ih/3:t=2:c=white@0.5

   drawtext
       Draw text string or text from specified file on top of video using the
       libfreetype library.

       To enable compilation of this filter you need to configure FFmpeg with
       "--enable-libfreetype".

       Syntax

       The description of the accepted parameters follows.

       box Used to draw a box around text using background color.  Value
	   should be either 1 (enable) or 0 (disable).	The default value of
	   box is 0.

       boxcolor
	   The color to be used for drawing box around text. For the syntax of
	   this option, check the "Color" section in the ffmpeg-utils manual.

	   The default value of boxcolor is "white".

       expansion
	   Select how the text is expanded. Can be either "none", "strftime"
	   (deprecated) or "normal" (default). See the drawtext_expansion,
	   Text expansion section below for details.

       fix_bounds
	   If true, check and fix text coords to avoid clipping.

       fontcolor
	   The color to be used for drawing fonts. For the syntax of this
	   option, check the "Color" section in the ffmpeg-utils manual.

	   The default value of fontcolor is "black".

       fontfile
	   The font file to be used for drawing text. Path must be included.
	   This parameter is mandatory.

       fontsize
	   The font size to be used for drawing text.  The default value of
	   fontsize is 16.

       ft_load_flags
	   Flags to be used for loading the fonts.

	   The flags map the corresponding flags supported by libfreetype, and
	   are a combination of the following values:

	   default
	   no_scale
	   no_hinting
	   render
	   no_bitmap
	   vertical_layout
	   force_autohint
	   crop_bitmap
	   pedantic
	   ignore_global_advance_width
	   no_recurse
	   ignore_transform
	   monochrome
	   linear_design
	   no_autohint

	   Default value is "render".

	   For more information consult the documentation for the FT_LOAD_*
	   libfreetype flags.

       shadowcolor
	   The color to be used for drawing a shadow behind the drawn text.
	   For the syntax of this option, check the "Color" section in the
	   ffmpeg-utils manual.

	   The default value of shadowcolor is "black".

       shadowx
       shadowy
	   The x and y offsets for the text shadow position with respect to
	   the position of the text. They can be either positive or negative
	   values. Default value for both is "0".

       start_number
	   The starting frame number for the n/frame_num variable. The default
	   value is "0".

       tabsize
	   The size in number of spaces to use for rendering the tab.  Default
	   value is 4.

       timecode
	   Set the initial timecode representation in "hh:mm:ss[:;.]ff"
	   format. It can be used with or without text parameter.
	   timecode_rate option must be specified.

       timecode_rate, rate, r
	   Set the timecode frame rate (timecode only).

       text
	   The text string to be drawn. The text must be a sequence of UTF-8
	   encoded characters.	This parameter is mandatory if no file is
	   specified with the parameter textfile.

       textfile
	   A text file containing text to be drawn. The text must be a
	   sequence of UTF-8 encoded characters.

	   This parameter is mandatory if no text string is specified with the
	   parameter text.

	   If both text and textfile are specified, an error is thrown.

       reload
	   If set to 1, the textfile will be reloaded before each frame.  Be
	   sure to update it atomically, or it may be read partially, or even
	   fail.

       x
       y   The expressions which specify the offsets where text will be drawn
	   within the video frame. They are relative to the top/left border of
	   the output image.

	   The default value of x and y is "0".

	   See below for the list of accepted constants and functions.

       The parameters for x and y are expressions containing the following
       constants and functions:

       dar input display aspect ratio, it is the same as (w / h) * sar

       hsub
       vsub
	   horizontal and vertical chroma subsample values. For example for
	   the pixel format "yuv422p" hsub is 2 and vsub is 1.

       line_h, lh
	   the height of each text line

       main_h, h, H
	   the input height

       main_w, w, W
	   the input width

       max_glyph_a, ascent
	   the maximum distance from the baseline to the highest/upper grid
	   coordinate used to place a glyph outline point, for all the
	   rendered glyphs.  It is a positive value, due to the grid's
	   orientation with the Y axis upwards.

       max_glyph_d, descent
	   the maximum distance from the baseline to the lowest grid
	   coordinate used to place a glyph outline point, for all the
	   rendered glyphs.  This is a negative value, due to the grid's
	   orientation, with the Y axis upwards.

       max_glyph_h
	   maximum glyph height, that is the maximum height for all the glyphs
	   contained in the rendered text, it is equivalent to ascent -
	   descent.

       max_glyph_w
	   maximum glyph width, that is the maximum width for all the glyphs
	   contained in the rendered text

       n   the number of input frame, starting from 0

       rand(min, max)
	   return a random number included between min and max

       sar input sample aspect ratio

       t   timestamp expressed in seconds, NAN if the input timestamp is
	   unknown

       text_h, th
	   the height of the rendered text

       text_w, tw
	   the width of the rendered text

       x
       y   the x and y offset coordinates where the text is drawn.

	   These parameters allow the x and y expressions to refer each other,
	   so you can for example specify "y=x/dar".

       If libavfilter was built with "--enable-fontconfig", then fontfile can
       be a fontconfig pattern or omitted.

       Text expansion

       If expansion is set to "strftime", the filter recognizes strftime()
       sequences in the provided text and expands them accordingly. Check the
       documentation of strftime(). This feature is deprecated.

       If expansion is set to "none", the text is printed verbatim.

       If expansion is set to "normal" (which is the default), the following
       expansion mechanism is used.

       The backslash character '\', followed by any character, always expands
       to the second character.

       Sequence of the form "%{...}" are expanded. The text between the braces
       is a function name, possibly followed by arguments separated by ':'.
       If the arguments contain special characters or delimiters (':' or '}'),
       they should be escaped.

       Note that they probably must also be escaped as the value for the text
       option in the filter argument string and as the filter argument in the
       filtergraph description, and possibly also for the shell, that makes up
       to four levels of escaping; using a text file avoids these problems.

       The following functions are available:

       expr, e
	   The expression evaluation result.

	   It must take one argument specifying the expression to be
	   evaluated, which accepts the same constants and functions as the x
	   and y values. Note that not all constants should be used, for
	   example the text size is not known when evaluating the expression,
	   so the constants text_w and text_h will have an undefined value.

       gmtime
	   The time at which the filter is running, expressed in UTC.  It can
	   accept an argument: a strftime() format string.

       localtime
	   The time at which the filter is running, expressed in the local
	   time zone.  It can accept an argument: a strftime() format string.

       metadata
	   Frame metadata. It must take one argument specifying metadata key.

       n, frame_num
	   The frame number, starting from 0.

       pict_type
	   A 1 character description of the current picture type.

       pts The timestamp of the current frame, in seconds, with microsecond
	   accuracy.

       Examples

       ·   Draw "Test Text" with font FreeSerif, using the default values for
	   the optional parameters.

		   drawtext="fontfile=/usr/share/fonts/truetype/freefont/FreeSerif.ttf: text='Test Text'"

       ·   Draw 'Test Text' with font FreeSerif of size 24 at position x=100
	   and y=50 (counting from the top-left corner of the screen), text is
	   yellow with a red box around it. Both the text and the box have an
	   opacity of 20%.

		   drawtext="fontfile=/usr/share/fonts/truetype/freefont/FreeSerif.ttf: text='Test Text':\
			     x=100: y=50: fontsize=24: fontcolor=yellow@0.2: box=1: boxcolor=red@0.2"

	   Note that the double quotes are not necessary if spaces are not
	   used within the parameter list.

       ·   Show the text at the center of the video frame:

		   drawtext="fontsize=30:fontfile=FreeSerif.ttf:text='hello world':x=(w-text_w)/2:y=(h-text_h-line_h)/2"

       ·   Show a text line sliding from right to left in the last row of the
	   video frame. The file LONG_LINE is assumed to contain a single line
	   with no newlines.

		   drawtext="fontsize=15:fontfile=FreeSerif.ttf:text=LONG_LINE:y=h-line_h:x=-50*t"

       ·   Show the content of file CREDITS off the bottom of the frame and
	   scroll up.

		   drawtext="fontsize=20:fontfile=FreeSerif.ttf:textfile=CREDITS:y=h-20*t"

       ·   Draw a single green letter "g", at the center of the input video.
	   The glyph baseline is placed at half screen height.

		   drawtext="fontsize=60:fontfile=FreeSerif.ttf:fontcolor=green:text=g:x=(w-max_glyph_w)/2:y=h/2-ascent"

       ·   Show text for 1 second every 3 seconds:

		   drawtext="fontfile=FreeSerif.ttf:fontcolor=white:x=100:y=x/dar:enable=lt(mod(t\,3)\,1):text='blink'"

       ·   Use fontconfig to set the font. Note that the colons need to be
	   escaped.

		   drawtext='fontfile=Linux Libertine O-40\:style=Semibold:text=FFmpeg'

       ·   Print the date of a real-time encoding (see strftime(3)):

		   drawtext='fontfile=FreeSans.ttf:text=%{localtime:%a %b %d %Y}'

       For more information about libfreetype, check:
       <http://www.freetype.org/>.

       For more information about fontconfig, check:
       <http://freedesktop.org/software/fontconfig/fontconfig-user.html>.

   edgedetect
       Detect and draw edges. The filter uses the Canny Edge Detection
       algorithm.

       The filter accepts the following options:

       low
       high
	   Set low and high threshold values used by the Canny thresholding
	   algorithm.

	   The high threshold selects the "strong" edge pixels, which are then
	   connected through 8-connectivity with the "weak" edge pixels
	   selected by the low threshold.

	   low and high threshold values must be choosen in the range [0,1],
	   and low should be lesser or equal to high.

	   Default value for low is "20/255", and default value for high is
	   "50/255".

       Example:

	       edgedetect=low=0.1:high=0.4

   extractplanes
       Extract color channel components from input video stream into separate
       grayscale video streams.

       The filter accepts the following option:

       planes
	   Set plane(s) to extract.

	   Available values for planes are:

	   y
	   u
	   v
	   a
	   r
	   g
	   b

	   Choosing planes not available in the input will result in an error.
	   That means you cannot select "r", "g", "b" planes with "y", "u",
	   "v" planes at same time.

       Examples

       ·   Extract luma, u and v color channel component from input video
	   frame into 3 grayscale outputs:

		   ffmpeg -i video.avi -filter_complex 'extractplanes=y+u+v[y][u][v]' -map '[y]' y.avi -map '[u]' u.avi -map '[v]' v.avi

   fade
       Apply fade-in/out effect to input video.

       This filter accepts the following options:

       type, t
	   The effect type -- can be either "in" for fade-in, or "out" for a
	   fade-out effect.  Default is "in".

       start_frame, s
	   Specify the number of the start frame for starting to apply the
	   fade effect. Default is 0.

       nb_frames, n
	   The number of frames for which the fade effect has to last. At the
	   end of the fade-in effect the output video will have the same
	   intensity as the input video, at the end of the fade-out transition
	   the output video will be completely black.  Default is 25.

       alpha
	   If set to 1, fade only alpha channel, if one exists on the input.
	   Default value is 0.

       start_time, st
	   Specify the timestamp (in seconds) of the frame to start to apply
	   the fade effect. If both start_frame and start_time are specified,
	   the fade will start at whichever comes last.	 Default is 0.

       duration, d
	   The number of seconds for which the fade effect has to last. At the
	   end of the fade-in effect the output video will have the same
	   intensity as the input video, at the end of the fade-out transition
	   the output video will be completely black.  If both duration and
	   nb_frames are specified, duration is used. Default is 0.

       Examples

       ·   Fade in first 30 frames of video:

		   fade=in:0:30

	   The command above is equivalent to:

		   fade=t=in:s=0:n=30

       ·   Fade out last 45 frames of a 200-frame video:

		   fade=out:155:45
		   fade=type=out:start_frame=155:nb_frames=45

       ·   Fade in first 25 frames and fade out last 25 frames of a 1000-frame
	   video:

		   fade=in:0:25, fade=out:975:25

       ·   Make first 5 frames black, then fade in from frame 5-24:

		   fade=in:5:20

       ·   Fade in alpha over first 25 frames of video:

		   fade=in:0:25:alpha=1

       ·   Make first 5.5 seconds black, then fade in for 0.5 seconds:

		   fade=t=in:st=5.5:d=0.5

   field
       Extract a single field from an interlaced image using stride arithmetic
       to avoid wasting CPU time. The output frames are marked as non-
       interlaced.

       The filter accepts the following options:

       type
	   Specify whether to extract the top (if the value is 0 or "top") or
	   the bottom field (if the value is 1 or "bottom").

   fieldmatch
       Field matching filter for inverse telecine. It is meant to reconstruct
       the progressive frames from a telecined stream. The filter does not
       drop duplicated frames, so to achieve a complete inverse telecine
       "fieldmatch" needs to be followed by a decimation filter such as
       decimate in the filtergraph.

       The separation of the field matching and the decimation is notably
       motivated by the possibility of inserting a de-interlacing filter
       fallback between the two.  If the source has mixed telecined and real
       interlaced content, "fieldmatch" will not be able to match fields for
       the interlaced parts.  But these remaining combed frames will be marked
       as interlaced, and thus can be de-interlaced by a later filter such as
       yadif before decimation.

       In addition to the various configuration options, "fieldmatch" can take
       an optional second stream, activated through the ppsrc option. If
       enabled, the frames reconstruction will be based on the fields and
       frames from this second stream. This allows the first input to be pre-
       processed in order to help the various algorithms of the filter, while
       keeping the output lossless (assuming the fields are matched properly).
       Typically, a field-aware denoiser, or brightness/contrast adjustments
       can help.

       Note that this filter uses the same algorithms as TIVTC/TFM (AviSynth
       project) and VIVTC/VFM (VapourSynth project). The later is a light
       clone of TFM from which "fieldmatch" is based on. While the semantic
       and usage are very close, some behaviour and options names can differ.

       The filter accepts the following options:

       order
	   Specify the assumed field order of the input stream. Available
	   values are:

	   auto
	       Auto detect parity (use FFmpeg's internal parity value).

	   bff Assume bottom field first.

	   tff Assume top field first.

	   Note that it is sometimes recommended not to trust the parity
	   announced by the stream.

	   Default value is auto.

       mode
	   Set the matching mode or strategy to use. pc mode is the safest in
	   the sense that it won't risk creating jerkiness due to duplicate
	   frames when possible, but if there are bad edits or blended fields
	   it will end up outputting combed frames when a good match might
	   actually exist. On the other hand, pcn_ub mode is the most risky in
	   terms of creating jerkiness, but will almost always find a good
	   frame if there is one. The other values are all somewhere in
	   between pc and pcn_ub in terms of risking jerkiness and creating
	   duplicate frames versus finding good matches in sections with bad
	   edits, orphaned fields, blended fields, etc.

	   More details about p/c/n/u/b are available in p/c/n/u/b meaning
	   section.

	   Available values are:

	   pc  2-way matching (p/c)

	   pc_n
	       2-way matching, and trying 3rd match if still combed (p/c + n)

	   pc_u
	       2-way matching, and trying 3rd match (same order) if still
	       combed (p/c + u)

	   pc_n_ub
	       2-way matching, trying 3rd match if still combed, and trying
	       4th/5th matches if still combed (p/c + n + u/b)

	   pcn 3-way matching (p/c/n)

	   pcn_ub
	       3-way matching, and trying 4th/5th matches if all 3 of the
	       original matches are detected as combed (p/c/n + u/b)

	   The parenthesis at the end indicate the matches that would be used
	   for that mode assuming order=tff (and field on auto or top).

	   In terms of speed pc mode is by far the fastest and pcn_ub is the
	   slowest.

	   Default value is pc_n.

       ppsrc
	   Mark the main input stream as a pre-processed input, and enable the
	   secondary input stream as the clean source to pick the fields from.
	   See the filter introduction for more details. It is similar to the
	   clip2 feature from VFM/TFM.

	   Default value is 0 (disabled).

       field
	   Set the field to match from. It is recommended to set this to the
	   same value as order unless you experience matching failures with
	   that setting. In certain circumstances changing the field that is
	   used to match from can have a large impact on matching performance.
	   Available values are:

	   auto
	       Automatic (same value as order).

	   bottom
	       Match from the bottom field.

	   top Match from the top field.

	   Default value is auto.

       mchroma
	   Set whether or not chroma is included during the match comparisons.
	   In most cases it is recommended to leave this enabled. You should
	   set this to 0 only if your clip has bad chroma problems such as
	   heavy rainbowing or other artifacts. Setting this to 0 could also
	   be used to speed things up at the cost of some accuracy.

	   Default value is 1.

       y0
       y1  These define an exclusion band which excludes the lines between y0
	   and y1 from being included in the field matching decision. An
	   exclusion band can be used to ignore subtitles, a logo, or other
	   things that may interfere with the matching. y0 sets the starting
	   scan line and y1 sets the ending line; all lines in between y0 and
	   y1 (including y0 and y1) will be ignored. Setting y0 and y1 to the
	   same value will disable the feature.	 y0 and y1 defaults to 0.

       scthresh
	   Set the scene change detection threshold as a percentage of maximum
	   change on the luma plane. Good values are in the "[8.0, 14.0]"
	   range. Scene change detection is only relevant in case
	   combmatch=sc.  The range for scthresh is "[0.0, 100.0]".

	   Default value is 12.0.

       combmatch
	   When combatch is not none, "fieldmatch" will take into account the
	   combed scores of matches when deciding what match to use as the
	   final match. Available values are:

	   none
	       No final matching based on combed scores.

	   sc  Combed scores are only used when a scene change is detected.

	   full
	       Use combed scores all the time.

	   Default is sc.

       combdbg
	   Force "fieldmatch" to calculate the combed metrics for certain
	   matches and print them. This setting is known as micout in TFM/VFM
	   vocabulary.	Available values are:

	   none
	       No forced calculation.

	   pcn Force p/c/n calculations.

	   pcnub
	       Force p/c/n/u/b calculations.

	   Default value is none.

       cthresh
	   This is the area combing threshold used for combed frame detection.
	   This essentially controls how "strong" or "visible" combing must be
	   to be detected.  Larger values mean combing must be more visible
	   and smaller values mean combing can be less visible or strong and
	   still be detected. Valid settings are from "-1" (every pixel will
	   be detected as combed) to 255 (no pixel will be detected as
	   combed). This is basically a pixel difference value. A good range
	   is "[8, 12]".

	   Default value is 9.

       chroma
	   Sets whether or not chroma is considered in the combed frame
	   decision.  Only disable this if your source has chroma problems
	   (rainbowing, etc.) that are causing problems for the combed frame
	   detection with chroma enabled. Actually, using chroma=0 is usually
	   more reliable, except for the case where there is chroma only
	   combing in the source.

	   Default value is 0.

       blockx
       blocky
	   Respectively set the x-axis and y-axis size of the window used
	   during combed frame detection. This has to do with the size of the
	   area in which combpel pixels are required to be detected as combed
	   for a frame to be declared combed. See the combpel parameter
	   description for more info.  Possible values are any number that is
	   a power of 2 starting at 4 and going up to 512.

	   Default value is 16.

       combpel
	   The number of combed pixels inside any of the blocky by blockx size
	   blocks on the frame for the frame to be detected as combed. While
	   cthresh controls how "visible" the combing must be, this setting
	   controls "how much" combing there must be in any localized area (a
	   window defined by the blockx and blocky settings) on the frame.
	   Minimum value is 0 and maximum is "blocky x blockx" (at which point
	   no frames will ever be detected as combed). This setting is known
	   as MI in TFM/VFM vocabulary.

	   Default value is 80.

       p/c/n/u/b meaning

       p/c/n

       We assume the following telecined stream:

	       Top fields:     1 2 2 3 4
	       Bottom fields:  1 2 3 4 4

       The numbers correspond to the progressive frame the fields relate to.
       Here, the first two frames are progressive, the 3rd and 4th are combed,
       and so on.

       When "fieldmatch" is configured to run a matching from bottom
       (field=bottom) this is how this input stream get transformed:

	       Input stream:
			       T     1 2 2 3 4
			       B     1 2 3 4 4	 <-- matching reference

	       Matches:		     c c n n c

	       Output stream:
			       T     1 2 3 4 4
			       B     1 2 3 4 4

       As a result of the field matching, we can see that some frames get
       duplicated.  To perform a complete inverse telecine, you need to rely
       on a decimation filter after this operation. See for instance the
       decimate filter.

       The same operation now matching from top fields (field=top) looks like
       this:

	       Input stream:
			       T     1 2 2 3 4	 <-- matching reference
			       B     1 2 3 4 4

	       Matches:		     c c p p c

	       Output stream:
			       T     1 2 2 3 4
			       B     1 2 2 3 4

       In these examples, we can see what p, c and n mean; basically, they
       refer to the frame and field of the opposite parity:

       *<p matches the field of the opposite parity in the previous frame>
       *<c matches the field of the opposite parity in the current frame>
       *<n matches the field of the opposite parity in the next frame>

       u/b

       The u and b matching are a bit special in the sense that they match
       from the opposite parity flag. In the following examples, we assume
       that we are currently matching the 2nd frame (Top:2, bottom:2).
       According to the match, a 'x' is placed above and below each matched
       fields.

       With bottom matching (field=bottom):

	       Match:		c	  p	      n		 b	    u

				x	x		x	 x	    x
		 Top	      1 2 2	1 2 2	    1 2 2      1 2 2	  1 2 2
		 Bottom	      1 2 3	1 2 3	    1 2 3      1 2 3	  1 2 3
				x	  x	      x	       x	      x

	       Output frames:
				2	   1	      2		 2	    2
				2	   2	      2		 1	    3

       With top matching (field=top):

	       Match:		c	  p	      n		 b	    u

				x	  x	      x	       x	      x
		 Top	      1 2 2	1 2 2	    1 2 2      1 2 2	  1 2 2
		 Bottom	      1 2 3	1 2 3	    1 2 3      1 2 3	  1 2 3
				x	x		x	 x	    x

	       Output frames:
				2	   2	      2		 1	    2
				2	   1	      3		 2	    2

       Examples

       Simple IVTC of a top field first telecined stream:

	       fieldmatch=order=tff:combmatch=none, decimate

       Advanced IVTC, with fallback on yadif for still combed frames:

	       fieldmatch=order=tff:combmatch=full, yadif=deint=interlaced, decimate

   fieldorder
       Transform the field order of the input video.

       This filter accepts the following options:

       order
	   Output field order. Valid values are tff for top field first or bff
	   for bottom field first.

       Default value is tff.

       Transformation is achieved by shifting the picture content up or down
       by one line, and filling the remaining line with appropriate picture
       content.	 This method is consistent with most broadcast field order
       converters.

       If the input video is not flagged as being interlaced, or it is already
       flagged as being of the required output field order then this filter
       does not alter the incoming video.

       This filter is very useful when converting to or from PAL DV material,
       which is bottom field first.

       For example:

	       ffmpeg -i in.vob -vf "fieldorder=bff" out.dv

   fifo
       Buffer input images and send them when they are requested.

       This filter is mainly useful when auto-inserted by the libavfilter
       framework.

       The filter does not take parameters.

   format
       Convert the input video to one of the specified pixel formats.
       Libavfilter will try to pick one that is supported for the input to the
       next filter.

       This filter accepts the following parameters:

       pix_fmts
	   A '|'-separated list of pixel format names, for example
	   "pix_fmts=yuv420p|monow|rgb24".

       Examples

       ·   Convert the input video to the format yuv420p

		   format=pix_fmts=yuv420p

	   Convert the input video to any of the formats in the list

		   format=pix_fmts=yuv420p|yuv444p|yuv410p

   fps
       Convert the video to specified constant frame rate by duplicating or
       dropping frames as necessary.

       This filter accepts the following named parameters:

       fps Desired output frame rate. The default is 25.

       round
	   Rounding method.

	   Possible values are:

	   zero
	       zero round towards 0

	   inf round away from 0

	   down
	       round towards -infinity

	   up  round towards +infinity

	   near
	       round to nearest

	   The default is "near".

       start_time
	   Assume the first PTS should be the given value, in seconds. This
	   allows for padding/trimming at the start of stream. By default, no
	   assumption is made about the first frame's expected PTS, so no
	   padding or trimming is done.	 For example, this could be set to 0
	   to pad the beginning with duplicates of the first frame if a video
	   stream starts after the audio stream or to trim any frames with a
	   negative PTS.

       Alternatively, the options can be specified as a flat string:
       fps[:round].

       See also the setpts filter.

       Examples

       ·   A typical usage in order to set the fps to 25:

		   fps=fps=25

       ·   Sets the fps to 24, using abbreviation and rounding method to round
	   to nearest:

		   fps=fps=film:round=near

   framestep
       Select one frame every N-th frame.

       This filter accepts the following option:

       step
	   Select frame after every "step" frames.  Allowed values are
	   positive integers higher than 0. Default value is 1.

   frei0r
       Apply a frei0r effect to the input video.

       To enable compilation of this filter you need to install the frei0r
       header and configure FFmpeg with "--enable-frei0r".

       This filter accepts the following options:

       filter_name
	   The name to the frei0r effect to load. If the environment variable
	   FREI0R_PATH is defined, the frei0r effect is searched in each one
	   of the directories specified by the colon separated list in
	   FREIOR_PATH, otherwise in the standard frei0r paths, which are in
	   this order: HOME/.frei0r-1/lib/, /usr/local/lib/frei0r-1/,
	   /usr/lib/frei0r-1/.

       filter_params
	   A '|'-separated list of parameters to pass to the frei0r effect.

       A frei0r effect parameter can be a boolean (whose values are specified
       with "y" and "n"), a double, a color (specified by the syntax R/G/B,
       (R, G, and B being float numbers from 0.0 to 1.0) or by a color
       description specified in the "Color" section in the ffmpeg-utils
       manual), a position (specified by the syntax X/Y, X and Y being float
       numbers) and a string.

       The number and kind of parameters depend on the loaded effect. If an
       effect parameter is not specified the default value is set.

       Examples

       ·   Apply the distort0r effect, set the first two double parameters:

		   frei0r=filter_name=distort0r:filter_params=0.5|0.01

       ·   Apply the colordistance effect, take a color as first parameter:

		   frei0r=colordistance:0.2/0.3/0.4
		   frei0r=colordistance:violet
		   frei0r=colordistance:0x112233

       ·   Apply the perspective effect, specify the top left and top right
	   image positions:

		   frei0r=perspective:0.2/0.2|0.8/0.2

       For more information see: <http://frei0r.dyne.org>

   geq
       The filter accepts the following options:

       lum_expr, lum
	   Set the luminance expression.

       cb_expr, cb
	   Set the chrominance blue expression.

       cr_expr, cr
	   Set the chrominance red expression.

       alpha_expr, a
	   Set the alpha expression.

       red_expr, r
	   Set the red expression.

       green_expr, g
	   Set the green expression.

       blue_expr, b
	   Set the blue expression.

       The colorspace is selected according to the specified options. If one
       of the lum_expr, cb_expr, or cr_expr options is specified, the filter
       will automatically select a YCbCr colorspace. If one of the red_expr,
       green_expr, or blue_expr options is specified, it will select an RGB
       colorspace.

       If one of the chrominance expression is not defined, it falls back on
       the other one. If no alpha expression is specified it will evaluate to
       opaque value.  If none of chrominance expressions are specified, they
       will evaluate to the luminance expression.

       The expressions can use the following variables and functions:

       N   The sequential number of the filtered frame, starting from 0.

       X
       Y   The coordinates of the current sample.

       W
       H   The width and height of the image.

       SW
       SH  Width and height scale depending on the currently filtered plane.
	   It is the ratio between the corresponding luma plane number of
	   pixels and the current plane ones. E.g. for YUV4:2:0 the values are
	   "1,1" for the luma plane, and "0.5,0.5" for chroma planes.

       T   Time of the current frame, expressed in seconds.

       p(x, y)
	   Return the value of the pixel at location (x,y) of the current
	   plane.

       lum(x, y)
	   Return the value of the pixel at location (x,y) of the luminance
	   plane.

       cb(x, y)
	   Return the value of the pixel at location (x,y) of the blue-
	   difference chroma plane. Return 0 if there is no such plane.

       cr(x, y)
	   Return the value of the pixel at location (x,y) of the red-
	   difference chroma plane. Return 0 if there is no such plane.

       r(x, y)
       g(x, y)
       b(x, y)
	   Return the value of the pixel at location (x,y) of the
	   red/green/blue component. Return 0 if there is no such component.

       alpha(x, y)
	   Return the value of the pixel at location (x,y) of the alpha plane.
	   Return 0 if there is no such plane.

       For functions, if x and y are outside the area, the value will be
       automatically clipped to the closer edge.

       Examples

       ·   Flip the image horizontally:

		   geq=p(W-X\,Y)

       ·   Generate a bidimensional sine wave, with angle "PI/3" and a
	   wavelength of 100 pixels:

		   geq=128 + 100*sin(2*(PI/100)*(cos(PI/3)*(X-50*T) + sin(PI/3)*Y)):128:128

       ·   Generate a fancy enigmatic moving light:

		   nullsrc=s=256x256,geq=random(1)/hypot(X-cos(N*0.07)*W/2-W/2\,Y-sin(N*0.09)*H/2-H/2)^2*1000000*sin(N*0.02):128:128

       ·   Generate a quick emboss effect:

		   format=gray,geq=lum_expr='(p(X,Y)+(256-p(X-4,Y-4)))/2'

       ·   Modify RGB components depending on pixel position:

		   geq=r='X/W*r(X,Y)':g='(1-X/W)*g(X,Y)':b='(H-Y)/H*b(X,Y)'

   gradfun
       Fix the banding artifacts that are sometimes introduced into nearly
       flat regions by truncation to 8bit color depth.	Interpolate the
       gradients that should go where the bands are, and dither them.

       This filter is designed for playback only.  Do not use it prior to
       lossy compression, because compression tends to lose the dither and
       bring back the bands.

       This filter accepts the following options:

       strength
	   The maximum amount by which the filter will change any one pixel.
	   Also the threshold for detecting nearly flat regions. Acceptable
	   values range from .51 to 64, default value is 1.2, out-of-range
	   values will be clipped to the valid range.

       radius
	   The neighborhood to fit the gradient to. A larger radius makes for
	   smoother gradients, but also prevents the filter from modifying the
	   pixels near detailed regions. Acceptable values are 8-32, default
	   value is 16, out-of-range values will be clipped to the valid
	   range.

       Alternatively, the options can be specified as a flat string:
       strength[:radius]

       Examples

       ·   Apply the filter with a 3.5 strength and radius of 8:

		   gradfun=3.5:8

       ·   Specify radius, omitting the strength (which will fall-back to the
	   default value):

		   gradfun=radius=8

   haldclut
       Apply a Hald CLUT to a video stream.

       First input is the video stream to process, and second one is the Hald
       CLUT.  The Hald CLUT input can be a simple picture or a complete video
       stream.

       The filter accepts the following options:

       shortest
	   Force termination when the shortest input terminates. Default is 0.

       repeatlast
	   Continue applying the last CLUT after the end of the stream. A
	   value of 0 disable the filter after the last frame of the CLUT is
	   reached.  Default is 1.

       "haldclut" also has the same interpolation options as lut3d (both
       filters share the same internals).

       More information about the Hald CLUT can be found on Eskil Steenberg's
       website (Hald CLUT author) at
       <http://www.quelsolaar.com/technology/clut.html>.

       Workflow examples

       Hald CLUT video stream

       Generate an identity Hald CLUT stream altered with various effects:

	       ffmpeg -f lavfi -i haldclutsrc=8 -vf "hue=H=2*PI*t:s=sin(2*PI*t)+1, curves=cross_process" -t 10 -c:v ffv1 clut.nut

       Note: make sure you use a lossless codec.

       Then use it with "haldclut" to apply it on some random stream:

	       ffmpeg -f lavfi -i mandelbrot -i clut.nut -filter_complex '[0][1] haldclut' -t 20 mandelclut.mkv

       The Hald CLUT will be applied to the 10 first seconds (duration of
       clut.nut), then the latest picture of that CLUT stream will be applied
       to the remaining frames of the "mandelbrot" stream.

       Hald CLUT with preview

       A Hald CLUT is supposed to be a squared image of "Level*Level*Level" by
       "Level*Level*Level" pixels. For a given Hald CLUT, FFmpeg will select
       the biggest possible square starting at the top left of the picture.
       The remaining padding pixels (bottom or right) will be ignored. This
       area can be used to add a preview of the Hald CLUT.

       Typically, the following generated Hald CLUT will be supported by the
       "haldclut" filter:

	       ffmpeg -f lavfi -i haldclutsrc=8 -vf "
		  pad=iw+320 [padded_clut];
		  smptebars=s=320x256, split [a][b];
		  [padded_clut][a] overlay=W-320:h, curves=color_negative [main];
		  [main][b] overlay=W-320" -frames:v 1 clut.png

       It contains the original and a preview of the effect of the CLUT: SMPTE
       color bars are displayed on the right-top, and below the same color
       bars processed by the color changes.

       Then, the effect of this Hald CLUT can be visualized with:

	       ffplay input.mkv -vf "movie=clut.png, [in] haldclut"

   hflip
       Flip the input video horizontally.

       For example to horizontally flip the input video with ffmpeg:

	       ffmpeg -i in.avi -vf "hflip" out.avi

   histeq
       This filter applies a global color histogram equalization on a per-
       frame basis.

       It can be used to correct video that has a compressed range of pixel
       intensities.  The filter redistributes the pixel intensities to
       equalize their distribution across the intensity range. It may be
       viewed as an "automatically adjusting contrast filter". This filter is
       useful only for correcting degraded or poorly captured source video.

       The filter accepts the following options:

       strength
	   Determine the amount of equalization to be applied.	As the
	   strength is reduced, the distribution of pixel intensities more-
	   and-more approaches that of the input frame. The value must be a
	   float number in the range [0,1] and defaults to 0.200.

       intensity
	   Set the maximum intensity that can generated and scale the output
	   values appropriately.  The strength should be set as desired and
	   then the intensity can be limited if needed to avoid washing-out.
	   The value must be a float number in the range [0,1] and defaults to
	   0.210.

       antibanding
	   Set the antibanding level. If enabled the filter will randomly vary
	   the luminance of output pixels by a small amount to avoid banding
	   of the histogram. Possible values are "none", "weak" or "strong".
	   It defaults to "none".

   histogram
       Compute and draw a color distribution histogram for the input video.

       The computed histogram is a representation of distribution of color
       components in an image.

       The filter accepts the following options:

       mode
	   Set histogram mode.

	   It accepts the following values:

	   levels
	       standard histogram that display color components distribution
	       in an image.  Displays color graph for each color component.
	       Shows distribution of the Y, U, V, A or R, G, B components,
	       depending on input format, in current frame. Bellow each graph
	       is color component scale meter.

	   color
	       chroma values in vectorscope, if brighter more such chroma
	       values are distributed in an image.  Displays chroma values
	       (U/V color placement) in two dimensional graph (which is called
	       a vectorscope). It can be used to read of the hue and
	       saturation of the current frame. At a same time it is a
	       histogram.  The whiter a pixel in the vectorscope, the more
	       pixels of the input frame correspond to that pixel (that is the
	       more pixels have this chroma value).  The V component is
	       displayed on the horizontal (X) axis, with the leftmost side
	       being V = 0 and the rightmost side being V = 255.  The U
	       component is displayed on the vertical (Y) axis, with the top
	       representing U = 0 and the bottom representing U = 255.

	       The position of a white pixel in the graph corresponds to the
	       chroma value of a pixel of the input clip. So the graph can be
	       used to read of the hue (color flavor) and the saturation (the
	       dominance of the hue in the color).  As the hue of a color
	       changes, it moves around the square. At the center of the
	       square, the saturation is zero, which means that the
	       corresponding pixel has no color. If you increase the amount of
	       a specific color, while leaving the other colors unchanged, the
	       saturation increases, and you move towards the edge of the
	       square.

	   color2
	       chroma values in vectorscope, similar as "color" but actual
	       chroma values are displayed.

	   waveform
	       per row/column color component graph. In row mode graph in the
	       left side represents color component value 0 and right side
	       represents value = 255. In column mode top side represents
	       color component value = 0 and bottom side represents value =
	       255.

	   Default value is "levels".

       level_height
	   Set height of level in "levels". Default value is 200.  Allowed
	   range is [50, 2048].

       scale_height
	   Set height of color scale in "levels". Default value is 12.
	   Allowed range is [0, 40].

       step
	   Set step for "waveform" mode. Smaller values are useful to find out
	   how much of same luminance values across input rows/columns are
	   distributed.	 Default value is 10. Allowed range is [1, 255].

       waveform_mode
	   Set mode for "waveform". Can be either "row", or "column".  Default
	   is "row".

       waveform_mirror
	   Set mirroring mode for "waveform". 0 means unmirrored, 1 means
	   mirrored. In mirrored mode, higher values will be represented on
	   the left side for "row" mode and at the top for "column" mode.
	   Default is 0 (unmirrored).

       display_mode
	   Set display mode for "waveform" and "levels".  It accepts the
	   following values:

	   parade
	       Display separate graph for the color components side by side in
	       "row" waveform mode or one below other in "column" waveform
	       mode for "waveform" histogram mode. For "levels" histogram mode
	       per color component graphs are placed one bellow other.

	       This display mode in "waveform" histogram mode makes it easy to
	       spot color casts in the highlights and shadows of an image, by
	       comparing the contours of the top and the bottom of each
	       waveform.  Since whites, grays, and blacks are characterized by
	       exactly equal amounts of red, green, and blue, neutral areas of
	       the picture should display three waveforms of roughly equal
	       width/height.  If not, the correction is easy to make by making
	       adjustments to level the three waveforms.

	   overlay
	       Presents information that's identical to that in the "parade",
	       except that the graphs representing color components are
	       superimposed directly over one another.

	       This display mode in "waveform" histogram mode can make it
	       easier to spot the relative differences or similarities in
	       overlapping areas of the color components that are supposed to
	       be identical, such as neutral whites, grays, or blacks.

	   Default is "parade".

       levels_mode
	   Set mode for "levels". Can be either "linear", or "logarithmic".
	   Default is "linear".

       Examples

       ·   Calculate and draw histogram:

		   ffplay -i input -vf histogram

   hqdn3d
       High precision/quality 3d denoise filter. This filter aims to reduce
       image noise producing smooth images and making still images really
       still. It should enhance compressibility.

       It accepts the following optional parameters:

       luma_spatial
	   a non-negative float number which specifies spatial luma strength,
	   defaults to 4.0

       chroma_spatial
	   a non-negative float number which specifies spatial chroma
	   strength, defaults to 3.0*luma_spatial/4.0

       luma_tmp
	   a float number which specifies luma temporal strength, defaults to
	   6.0*luma_spatial/4.0

       chroma_tmp
	   a float number which specifies chroma temporal strength, defaults
	   to luma_tmp*chroma_spatial/luma_spatial

   hue
       Modify the hue and/or the saturation of the input.

       This filter accepts the following options:

       h   Specify the hue angle as a number of degrees. It accepts an
	   expression, and defaults to "0".

       s   Specify the saturation in the [-10,10] range. It accepts an
	   expression and defaults to "1".

       H   Specify the hue angle as a number of radians. It accepts an
	   expression, and defaults to "0".

       b   Specify the brightness in the [-10,10] range. It accepts an
	   expression and defaults to "0".

       h and H are mutually exclusive, and can't be specified at the same
       time.

       The b, h, H and s option values are expressions containing the
       following constants:

       n   frame count of the input frame starting from 0

       pts presentation timestamp of the input frame expressed in time base
	   units

       r   frame rate of the input video, NAN if the input frame rate is
	   unknown

       t   timestamp expressed in seconds, NAN if the input timestamp is
	   unknown

       tb  time base of the input video

       Examples

       ·   Set the hue to 90 degrees and the saturation to 1.0:

		   hue=h=90:s=1

       ·   Same command but expressing the hue in radians:

		   hue=H=PI/2:s=1

       ·   Rotate hue and make the saturation swing between 0 and 2 over a
	   period of 1 second:

		   hue="H=2*PI*t: s=sin(2*PI*t)+1"

       ·   Apply a 3 seconds saturation fade-in effect starting at 0:

		   hue="s=min(t/3\,1)"

	   The general fade-in expression can be written as:

		   hue="s=min(0\, max((t-START)/DURATION\, 1))"

       ·   Apply a 3 seconds saturation fade-out effect starting at 5 seconds:

		   hue="s=max(0\, min(1\, (8-t)/3))"

	   The general fade-out expression can be written as:

		   hue="s=max(0\, min(1\, (START+DURATION-t)/DURATION))"

       Commands

       This filter supports the following commands:

       b
       s
       h
       H   Modify the hue and/or the saturation and/or brightness of the input
	   video.  The command accepts the same syntax of the corresponding
	   option.

	   If the specified expression is not valid, it is kept at its current
	   value.

   idet
       Detect video interlacing type.

       This filter tries to detect if the input is interlaced or progressive,
       top or bottom field first.

       The filter accepts the following options:

       intl_thres
	   Set interlacing threshold.

       prog_thres
	   Set progressive threshold.

   il
       Deinterleave or interleave fields.

       This filter allows to process interlaced images fields without
       deinterlacing them. Deinterleaving splits the input frame into 2 fields
       (so called half pictures). Odd lines are moved to the top half of the
       output image, even lines to the bottom half.  You can process (filter)
       them independently and then re-interleave them.

       The filter accepts the following options:

       luma_mode, l
       chroma_mode, c
       alpha_mode, a
	   Available values for luma_mode, chroma_mode and alpha_mode are:

	   none
	       Do nothing.

	   deinterleave, d
	       Deinterleave fields, placing one above the other.

	   interleave, i
	       Interleave fields. Reverse the effect of deinterleaving.

	   Default value is "none".

       luma_swap, ls
       chroma_swap, cs
       alpha_swap, as
	   Swap luma/chroma/alpha fields. Exchange even & odd lines. Default
	   value is 0.

   interlace
       Simple interlacing filter from progressive contents. This interleaves
       upper (or lower) lines from odd frames with lower (or upper) lines from
       even frames, halving the frame rate and preserving image height.

		  Original	  Original	       New Frame
		  Frame 'j'	 Frame 'j+1'		 (tff)
		 ==========	 ===========	   ==================
		   Line 0  -------------------->    Frame 'j' Line 0
		   Line 1	   Line 1  ---->   Frame 'j+1' Line 1
		   Line 2 --------------------->    Frame 'j' Line 2
		   Line 3	   Line 3  ---->   Frame 'j+1' Line 3
		    ...		    ...			  ...
	       New Frame + 1 will be generated by Frame 'j+2' and Frame 'j+3' and so on

       It accepts the following optional parameters:

       scan
	   determines whether the interlaced frame is taken from the even (tff
	   - default) or odd (bff) lines of the progressive frame.

       lowpass
	   Enable (default) or disable the vertical lowpass filter to avoid
	   twitter interlacing and reduce moire patterns.

   kerndeint
       Deinterlace input video by applying Donald Graft's adaptive kernel
       deinterling. Work on interlaced parts of a video to produce progressive
       frames.

       The description of the accepted parameters follows.

       thresh
	   Set the threshold which affects the filter's tolerance when
	   determining if a pixel line must be processed. It must be an
	   integer in the range [0,255] and defaults to 10. A value of 0 will
	   result in applying the process on every pixels.

       map Paint pixels exceeding the threshold value to white if set to 1.
	   Default is 0.

       order
	   Set the fields order. Swap fields if set to 1, leave fields alone
	   if 0. Default is 0.

       sharp
	   Enable additional sharpening if set to 1. Default is 0.

       twoway
	   Enable twoway sharpening if set to 1. Default is 0.

       Examples

       ·   Apply default values:

		   kerndeint=thresh=10:map=0:order=0:sharp=0:twoway=0

       ·   Enable additional sharpening:

		   kerndeint=sharp=1

       ·   Paint processed pixels in white:

		   kerndeint=map=1

   lut3d
       Apply a 3D LUT to an input video.

       The filter accepts the following options:

       file
	   Set the 3D LUT file name.

	   Currently supported formats:

	   3dl AfterEffects

	   cube
	       Iridas

	   dat DaVinci

	   m3d Pandora

       interp
	   Select interpolation mode.

	   Available values are:

	   nearest
	       Use values from the nearest defined point.

	   trilinear
	       Interpolate values using the 8 points defining a cube.

	   tetrahedral
	       Interpolate values using a tetrahedron.

   lut, lutrgb, lutyuv
       Compute a look-up table for binding each pixel component input value to
       an output value, and apply it to input video.

       lutyuv applies a lookup table to a YUV input video, lutrgb to an RGB
       input video.

       These filters accept the following options:

       c0  set first pixel component expression

       c1  set second pixel component expression

       c2  set third pixel component expression

       c3  set fourth pixel component expression, corresponds to the alpha
	   component

       r   set red component expression

       g   set green component expression

       b   set blue component expression

       a   alpha component expression

       y   set Y/luminance component expression

       u   set U/Cb component expression

       v   set V/Cr component expression

       Each of them specifies the expression to use for computing the lookup
       table for the corresponding pixel component values.

       The exact component associated to each of the c* options depends on the
       format in input.

       The lut filter requires either YUV or RGB pixel formats in input,
       lutrgb requires RGB pixel formats in input, and lutyuv requires YUV.

       The expressions can contain the following constants and functions:

       w
       h   the input width and height

       val input value for the pixel component

       clipval
	   the input value clipped in the minval-maxval range

       maxval
	   maximum value for the pixel component

       minval
	   minimum value for the pixel component

       negval
	   the negated value for the pixel component value clipped in the
	   minval-maxval range , it corresponds to the expression
	   "maxval-clipval+minval"

       clip(val)
	   the computed value in val clipped in the minval-maxval range

       gammaval(gamma)
	   the computed gamma correction value of the pixel component value
	   clipped in the minval-maxval range, corresponds to the expression
	   "pow((clipval-minval)/(maxval-minval)\,gamma)*(maxval-minval)+minval"

       All expressions default to "val".

       Examples

       ·   Negate input video:

		   lutrgb="r=maxval+minval-val:g=maxval+minval-val:b=maxval+minval-val"
		   lutyuv="y=maxval+minval-val:u=maxval+minval-val:v=maxval+minval-val"

	   The above is the same as:

		   lutrgb="r=negval:g=negval:b=negval"
		   lutyuv="y=negval:u=negval:v=negval"

       ·   Negate luminance:

		   lutyuv=y=negval

       ·   Remove chroma components, turns the video into a graytone image:

		   lutyuv="u=128:v=128"

       ·   Apply a luma burning effect:

		   lutyuv="y=2*val"

       ·   Remove green and blue components:

		   lutrgb="g=0:b=0"

       ·   Set a constant alpha channel value on input:

		   format=rgba,lutrgb=a="maxval-minval/2"

       ·   Correct luminance gamma by a 0.5 factor:

		   lutyuv=y=gammaval(0.5)

       ·   Discard least significant bits of luma:

		   lutyuv=y='bitand(val, 128+64+32)'

   mergeplanes
       Merge color channel components from several video streams.

       The filter accepts up to 4 input streams, and merge selected input
       planes to the output video.

       This filter accepts the following options:

       mapping
	   Set input to output plane mapping. Default is 0.

	   The mappings is specified as a bitmap. It should be specified as a
	   hexadecimal number in the form 0xAa[Bb[Cc[Dd]]]. 'Aa' describes the
	   mapping for the first plane of the output stream. 'A' sets the
	   number of the input stream to use (from 0 to 3), and 'a' the plane
	   number of the corresponding input to use (from 0 to 3). The rest of
	   the mappings is similar, 'Bb' describes the mapping for the output
	   stream second plane, 'Cc' describes the mapping for the output
	   stream third plane and 'Dd' describes the mapping for the output
	   stream fourth plane.

       format
	   Set output pixel format. Default is "yuva444p".

       Examples

       ·   Merge three gray video streams of same width and height into single
	   video stream:

		   [a0][a1][a2]mergeplanes=0x001020:yuv444p

       ·   Merge 1st yuv444p stream and 2nd gray video stream into yuva444p
	   video stream:

		   [a0][a1]mergeplanes=0x00010210:yuva444p

       ·   Swap Y and A plane in yuva444p stream:

		   format=yuva444p,mergeplanes=0x03010200:yuva444p

       ·   Swap U and V plane in yuv420p stream:

		   format=yuv420p,mergeplanes=0x000201:yuv420p

       ·   Cast a rgb24 clip to yuv444p:

		   format=rgb24,mergeplanes=0x000102:yuv444p

   mcdeint
       Apply motion-compensation deinterlacing.

       It needs one field per frame as input and must thus be used together
       with yadif=1/3 or equivalent.

       This filter accepts the following options:

       mode
	   Set the deinterlacing mode.

	   It accepts one of the following values:

	   fast
	   medium
	   slow
	       use iterative motion estimation

	   extra_slow
	       like slow, but use multiple reference frames.

	   Default value is fast.

       parity
	   Set the picture field parity assumed for the input video. It must
	   be one of the following values:

	   0, tff
	       assume top field first

	   1, bff
	       assume bottom field first

	   Default value is bff.

       qp  Set per-block quantization parameter (QP) used by the internal
	   encoder.

	   Higher values should result in a smoother motion vector field but
	   less optimal individual vectors. Default value is 1.

   mp
       Apply an MPlayer filter to the input video.

       This filter provides a wrapper around some of the filters of
       MPlayer/MEncoder.

       This wrapper is considered experimental. Some of the wrapped filters
       may not work properly and we may drop support for them, as they will be
       implemented natively into FFmpeg. Thus you should avoid depending on
       them when writing portable scripts.

       The filter accepts the parameters: filter_name[:=]filter_params

       filter_name is the name of a supported MPlayer filter, filter_params is
       a string containing the parameters accepted by the named filter.

       The list of the currently supported filters follows:

       eq2
       eq
       fspp
       ilpack
       pp7
       softpulldown
       uspp

       The parameter syntax and behavior for the listed filters are the same
       of the corresponding MPlayer filters. For detailed instructions check
       the "VIDEO FILTERS" section in the MPlayer manual.

       Examples

       ·   Adjust gamma, brightness, contrast:

		   mp=eq2=1.0:2:0.5

       See also mplayer(1), <http://www.mplayerhq.hu/>.

   mpdecimate
       Drop frames that do not differ greatly from the previous frame in order
       to reduce frame rate.

       The main use of this filter is for very-low-bitrate encoding (e.g.
       streaming over dialup modem), but it could in theory be used for fixing
       movies that were inverse-telecined incorrectly.

       A description of the accepted options follows.

       max Set the maximum number of consecutive frames which can be dropped
	   (if positive), or the minimum interval between dropped frames (if
	   negative). If the value is 0, the frame is dropped unregarding the
	   number of previous sequentially dropped frames.

	   Default value is 0.

       hi
       lo
       frac
	   Set the dropping threshold values.

	   Values for hi and lo are for 8x8 pixel blocks and represent actual
	   pixel value differences, so a threshold of 64 corresponds to 1 unit
	   of difference for each pixel, or the same spread out differently
	   over the block.

	   A frame is a candidate for dropping if no 8x8 blocks differ by more
	   than a threshold of hi, and if no more than frac blocks (1 meaning
	   the whole image) differ by more than a threshold of lo.

	   Default value for hi is 64*12, default value for lo is 64*5, and
	   default value for frac is 0.33.

   negate
       Negate input video.

       This filter accepts an integer in input, if non-zero it negates the
       alpha component (if available). The default value in input is 0.

   noformat
       Force libavfilter not to use any of the specified pixel formats for the
       input to the next filter.

       This filter accepts the following parameters:

       pix_fmts
	   A '|'-separated list of pixel format names, for example
	   "pix_fmts=yuv420p|monow|rgb24".

       Examples

       ·   Force libavfilter to use a format different from yuv420p for the
	   input to the vflip filter:

		   noformat=pix_fmts=yuv420p,vflip

       ·   Convert the input video to any of the formats not contained in the
	   list:

		   noformat=yuv420p|yuv444p|yuv410p

   noise
       Add noise on video input frame.

       The filter accepts the following options:

       all_seed
       c0_seed
       c1_seed
       c2_seed
       c3_seed
	   Set noise seed for specific pixel component or all pixel components
	   in case of all_seed. Default value is 123457.

       all_strength, alls
       c0_strength, c0s
       c1_strength, c1s
       c2_strength, c2s
       c3_strength, c3s
	   Set noise strength for specific pixel component or all pixel
	   components in case all_strength. Default value is 0. Allowed range
	   is [0, 100].

       all_flags, allf
       c0_flags, c0f
       c1_flags, c1f
       c2_flags, c2f
       c3_flags, c3f
	   Set pixel component flags or set flags for all components if
	   all_flags.  Available values for component flags are:

	   a   averaged temporal noise (smoother)

	   p   mix random noise with a (semi)regular pattern

	   t   temporal noise (noise pattern changes between frames)

	   u   uniform noise (gaussian otherwise)

       Examples

       Add temporal and uniform noise to input video:

	       noise=alls=20:allf=t+u

   null
       Pass the video source unchanged to the output.

   ocv
       Apply video transform using libopencv.

       To enable this filter install libopencv library and headers and
       configure FFmpeg with "--enable-libopencv".

       This filter accepts the following parameters:

       filter_name
	   The name of the libopencv filter to apply.

       filter_params
	   The parameters to pass to the libopencv filter. If not specified
	   the default values are assumed.

       Refer to the official libopencv documentation for more precise
       information:
       <http://opencv.willowgarage.com/documentation/c/image_filtering.html>

       Follows the list of supported libopencv filters.

       dilate

       Dilate an image by using a specific structuring element.	 This filter
       corresponds to the libopencv function "cvDilate".

       It accepts the parameters: struct_el|nb_iterations.

       struct_el represents a structuring element, and has the syntax:
       colsxrows+anchor_xxanchor_y/shape

       cols and rows represent the number of columns and rows of the
       structuring element, anchor_x and anchor_y the anchor point, and shape
       the shape for the structuring element, and can be one of the values
       "rect", "cross", "ellipse", "custom".

       If the value for shape is "custom", it must be followed by a string of
       the form "=filename". The file with name filename is assumed to
       represent a binary image, with each printable character corresponding
       to a bright pixel. When a custom shape is used, cols and rows are
       ignored, the number or columns and rows of the read file are assumed
       instead.

       The default value for struct_el is "3x3+0x0/rect".

       nb_iterations specifies the number of times the transform is applied to
       the image, and defaults to 1.

       Follow some example:

	       # use the default values
	       ocv=dilate

	       # dilate using a structuring element with a 5x5 cross, iterate two times
	       ocv=filter_name=dilate:filter_params=5x5+2x2/cross|2

	       # read the shape from the file diamond.shape, iterate two times
	       # the file diamond.shape may contain a pattern of characters like this:
	       #   *
	       #  ***
	       # *****
	       #  ***
	       #   *
	       # the specified cols and rows are ignored (but not the anchor point coordinates)
	       ocv=dilate:0x0+2x2/custom=diamond.shape|2

       erode

       Erode an image by using a specific structuring element.	This filter
       corresponds to the libopencv function "cvErode".

       The filter accepts the parameters: struct_el:nb_iterations, with the
       same syntax and semantics as the dilate filter.

       smooth

       Smooth the input video.

       The filter takes the following parameters:
       type|param1|param2|param3|param4.

       type is the type of smooth filter to apply, and can be one of the
       following values: "blur", "blur_no_scale", "median", "gaussian",
       "bilateral". The default value is "gaussian".

       param1, param2, param3, and param4 are parameters whose meanings depend
       on smooth type. param1 and param2 accept integer positive values or 0,
       param3 and param4 accept float values.

       The default value for param1 is 3, the default value for the other
       parameters is 0.

       These parameters correspond to the parameters assigned to the libopencv
       function "cvSmooth".

   overlay
       Overlay one video on top of another.

       It takes two inputs and one output, the first input is the "main" video
       on which the second input is overlayed.

       This filter accepts the following parameters:

       A description of the accepted options follows.

       x
       y   Set the expression for the x and y coordinates of the overlayed
	   video on the main video. Default value is "0" for both expressions.
	   In case the expression is invalid, it is set to a huge value
	   (meaning that the overlay will not be displayed within the output
	   visible area).

       eval
	   Set when the expressions for x, and y are evaluated.

	   It accepts the following values:

	   init
	       only evaluate expressions once during the filter initialization
	       or when a command is processed

	   frame
	       evaluate expressions for each incoming frame

	   Default value is frame.

       shortest
	   If set to 1, force the output to terminate when the shortest input
	   terminates. Default value is 0.

       format
	   Set the format for the output video.

	   It accepts the following values:

	   yuv420
	       force YUV420 output

	   yuv444
	       force YUV444 output

	   rgb force RGB output

	   Default value is yuv420.

       rgb (deprecated)
	   If set to 1, force the filter to accept inputs in the RGB color
	   space. Default value is 0. This option is deprecated, use format
	   instead.

       repeatlast
	   If set to 1, force the filter to draw the last overlay frame over
	   the main input until the end of the stream. A value of 0 disables
	   this behavior. Default value is 1.

       The x, and y expressions can contain the following parameters.

       main_w, W
       main_h, H
	   main input width and height

       overlay_w, w
       overlay_h, h
	   overlay input width and height

       x
       y   the computed values for x and y. They are evaluated for each new
	   frame.

       hsub
       vsub
	   horizontal and vertical chroma subsample values of the output
	   format. For example for the pixel format "yuv422p" hsub is 2 and
	   vsub is 1.

       n   the number of input frame, starting from 0

       pos the position in the file of the input frame, NAN if unknown

       t   timestamp expressed in seconds, NAN if the input timestamp is
	   unknown

       Note that the n, pos, t variables are available only when evaluation is
       done per frame, and will evaluate to NAN when eval is set to init.

       Be aware that frames are taken from each input video in timestamp
       order, hence, if their initial timestamps differ, it is a good idea to
       pass the two inputs through a setpts=PTS-STARTPTS filter to have them
       begin in the same zero timestamp, as it does the example for the movie
       filter.

       You can chain together more overlays but you should test the efficiency
       of such approach.

       Commands

       This filter supports the following commands:

       x
       y   Modify the x and y of the overlay input.  The command accepts the
	   same syntax of the corresponding option.

	   If the specified expression is not valid, it is kept at its current
	   value.

       Examples

       ·   Draw the overlay at 10 pixels from the bottom right corner of the
	   main video:

		   overlay=main_w-overlay_w-10:main_h-overlay_h-10

	   Using named options the example above becomes:

		   overlay=x=main_w-overlay_w-10:y=main_h-overlay_h-10

       ·   Insert a transparent PNG logo in the bottom left corner of the
	   input, using the ffmpeg tool with the "-filter_complex" option:

		   ffmpeg -i input -i logo -filter_complex 'overlay=10:main_h-overlay_h-10' output

       ·   Insert 2 different transparent PNG logos (second logo on bottom
	   right corner) using the ffmpeg tool:

		   ffmpeg -i input -i logo1 -i logo2 -filter_complex 'overlay=x=10:y=H-h-10,overlay=x=W-w-10:y=H-h-10' output

       ·   Add a transparent color layer on top of the main video, "WxH" must
	   specify the size of the main input to the overlay filter:

		   color=color=red@.3:size=WxH [over]; [in][over] overlay [out]

       ·   Play an original video and a filtered version (here with the
	   deshake filter) side by side using the ffplay tool:

		   ffplay input.avi -vf 'split[a][b]; [a]pad=iw*2:ih[src]; [b]deshake[filt]; [src][filt]overlay=w'

	   The above command is the same as:

		   ffplay input.avi -vf 'split[b], pad=iw*2[src], [b]deshake, [src]overlay=w'

       ·   Make a sliding overlay appearing from the left to the right top
	   part of the screen starting since time 2:

		   overlay=x='if(gte(t,2), -w+(t-2)*20, NAN)':y=0

       ·   Compose output by putting two input videos side to side:

		   ffmpeg -i left.avi -i right.avi -filter_complex "
		   nullsrc=size=200x100 [background];
		   [0:v] setpts=PTS-STARTPTS, scale=100x100 [left];
		   [1:v] setpts=PTS-STARTPTS, scale=100x100 [right];
		   [background][left]	    overlay=shortest=1	     [background+left];
		   [background+left][right] overlay=shortest=1:x=100 [left+right]
		   "

       ·   Chain several overlays in cascade:

		   nullsrc=s=200x200 [bg];
		   testsrc=s=100x100, split=4 [in0][in1][in2][in3];
		   [in0] lutrgb=r=0, [bg]   overlay=0:0	    [mid0];
		   [in1] lutrgb=g=0, [mid0] overlay=100:0   [mid1];
		   [in2] lutrgb=b=0, [mid1] overlay=0:100   [mid2];
		   [in3] null,	     [mid2] overlay=100:100 [out0]

   owdenoise
       Apply Overcomplete Wavelet denoiser.

       The filter accepts the following options:

       depth
	   Set depth.

	   Larger depth values will denoise lower frequency components more,
	   but slow down filtering.

	   Must be an int in the range 8-16, default is 8.

       luma_strength, ls
	   Set luma strength.

	   Must be a double value in the range 0-1000, default is 1.0.

       chroma_strength, cs
	   Set chroma strength.

	   Must be a double value in the range 0-1000, default is 1.0.

   pad
       Add paddings to the input image, and place the original input at the
       given coordinates x, y.

       This filter accepts the following parameters:

       width, w
       height, h
	   Specify an expression for the size of the output image with the
	   paddings added. If the value for width or height is 0, the
	   corresponding input size is used for the output.

	   The width expression can reference the value set by the height
	   expression, and vice versa.

	   The default value of width and height is 0.

       x
       y   Specify an expression for the offsets where to place the input
	   image in the padded area with respect to the top/left border of the
	   output image.

	   The x expression can reference the value set by the y expression,
	   and vice versa.

	   The default value of x and y is 0.

       color
	   Specify the color of the padded area. For the syntax of this
	   option, check the "Color" section in the ffmpeg-utils manual.

	   The default value of color is "black".

       The value for the width, height, x, and y options are expressions
       containing the following constants:

       in_w
       in_h
	   the input video width and height

       iw
       ih  same as in_w and in_h

       out_w
       out_h
	   the output width and height, that is the size of the padded area as
	   specified by the width and height expressions

       ow
       oh  same as out_w and out_h

       x
       y   x and y offsets as specified by the x and y expressions, or NAN if
	   not yet specified

       a   same as iw / ih

       sar input sample aspect ratio

       dar input display aspect ratio, it is the same as (iw / ih) * sar

       hsub
       vsub
	   horizontal and vertical chroma subsample values. For example for
	   the pixel format "yuv422p" hsub is 2 and vsub is 1.

       Examples

       ·   Add paddings with color "violet" to the input video. Output video
	   size is 640x480, the top-left corner of the input video is placed
	   at column 0, row 40:

		   pad=640:480:0:40:violet

	   The example above is equivalent to the following command:

		   pad=width=640:height=480:x=0:y=40:color=violet

       ·   Pad the input to get an output with dimensions increased by 3/2,
	   and put the input video at the center of the padded area:

		   pad="3/2*iw:3/2*ih:(ow-iw)/2:(oh-ih)/2"

       ·   Pad the input to get a squared output with size equal to the
	   maximum value between the input width and height, and put the input
	   video at the center of the padded area:

		   pad="max(iw\,ih):ow:(ow-iw)/2:(oh-ih)/2"

       ·   Pad the input to get a final w/h ratio of 16:9:

		   pad="ih*16/9:ih:(ow-iw)/2:(oh-ih)/2"

       ·   In case of anamorphic video, in order to set the output display
	   aspect correctly, it is necessary to use sar in the expression,
	   according to the relation:

		   (ih * X / ih) * sar = output_dar
		   X = output_dar / sar

	   Thus the previous example needs to be modified to:

		   pad="ih*16/9/sar:ih:(ow-iw)/2:(oh-ih)/2"

       ·   Double output size and put the input video in the bottom-right
	   corner of the output padded area:

		   pad="2*iw:2*ih:ow-iw:oh-ih"

   perspective
       Correct perspective of video not recorded perpendicular to the screen.

       A description of the accepted parameters follows.

       x0
       y0
       x1
       y1
       x2
       y2
       x3
       y3  Set coordinates expression for top left, top right, bottom left and
	   bottom right corners.  Default values are "0:0:W:0:0:H:W:H" with
	   which perspective will remain unchanged.

	   The expressions can use the following variables:

	   W
	   H   the width and height of video frame.

       interpolation
	   Set interpolation for perspective correction.

	   It accepts the following values:

	   linear
	   cubic

	   Default value is linear.

   phase
       Delay interlaced video by one field time so that the field order
       changes.

       The intended use is to fix PAL movies that have been captured with the
       opposite field order to the film-to-video transfer.

       A description of the accepted parameters follows.

       mode
	   Set phase mode.

	   It accepts the following values:

	   t   Capture field order top-first, transfer bottom-first.  Filter
	       will delay the bottom field.

	   b   Capture field order bottom-first, transfer top-first.  Filter
	       will delay the top field.

	   p   Capture and transfer with the same field order. This mode only
	       exists for the documentation of the other options to refer to,
	       but if you actually select it, the filter will faithfully do
	       nothing.

	   a   Capture field order determined automatically by field flags,
	       transfer opposite.  Filter selects among t and b modes on a
	       frame by frame basis using field flags. If no field information
	       is available, then this works just like u.

	   u   Capture unknown or varying, transfer opposite.  Filter selects
	       among t and b on a frame by frame basis by analyzing the images
	       and selecting the alternative that produces best match between
	       the fields.

	   T   Capture top-first, transfer unknown or varying.	Filter selects
	       among t and p using image analysis.

	   B   Capture bottom-first, transfer unknown or varying.  Filter
	       selects among b and p using image analysis.

	   A   Capture determined by field flags, transfer unknown or varying.
	       Filter selects among t, b and p using field flags and image
	       analysis. If no field information is available, then this works
	       just like U. This is the default mode.

	   U   Both capture and transfer unknown or varying.  Filter selects
	       among t, b and p using image analysis only.

   pixdesctest
       Pixel format descriptor test filter, mainly useful for internal
       testing. The output video should be equal to the input video.

       For example:

	       format=monow, pixdesctest

       can be used to test the monowhite pixel format descriptor definition.

   pp
       Enable the specified chain of postprocessing subfilters using
       libpostproc. This library should be automatically selected with a GPL
       build ("--enable-gpl").	Subfilters must be separated by '/' and can be
       disabled by prepending a '-'.  Each subfilter and some options have a
       short and a long name that can be used interchangeably, i.e. dr/dering
       are the same.

       The filters accept the following options:

       subfilters
	   Set postprocessing subfilters string.

       All subfilters share common options to determine their scope:

       a/autoq
	   Honor the quality commands for this subfilter.

       c/chrom
	   Do chrominance filtering, too (default).

       y/nochrom
	   Do luminance filtering only (no chrominance).

       n/noluma
	   Do chrominance filtering only (no luminance).

       These options can be appended after the subfilter name, separated by a
       '|'.

       Available subfilters are:

       hb/hdeblock[|difference[|flatness]]
	   Horizontal deblocking filter

	   difference
	       Difference factor where higher values mean more deblocking
	       (default: 32).

	   flatness
	       Flatness threshold where lower values mean more deblocking
	       (default: 39).

       vb/vdeblock[|difference[|flatness]]
	   Vertical deblocking filter

	   difference
	       Difference factor where higher values mean more deblocking
	       (default: 32).

	   flatness
	       Flatness threshold where lower values mean more deblocking
	       (default: 39).

       ha/hadeblock[|difference[|flatness]]
	   Accurate horizontal deblocking filter

	   difference
	       Difference factor where higher values mean more deblocking
	       (default: 32).

	   flatness
	       Flatness threshold where lower values mean more deblocking
	       (default: 39).

       va/vadeblock[|difference[|flatness]]
	   Accurate vertical deblocking filter

	   difference
	       Difference factor where higher values mean more deblocking
	       (default: 32).

	   flatness
	       Flatness threshold where lower values mean more deblocking
	       (default: 39).

       The horizontal and vertical deblocking filters share the difference and
       flatness values so you cannot set different horizontal and vertical
       thresholds.

       h1/x1hdeblock
	   Experimental horizontal deblocking filter

       v1/x1vdeblock
	   Experimental vertical deblocking filter

       dr/dering
	   Deringing filter

       tn/tmpnoise[|threshold1[|threshold2[|threshold3]]], temporal noise
       reducer
	   threshold1
	       larger -> stronger filtering

	   threshold2
	       larger -> stronger filtering

	   threshold3
	       larger -> stronger filtering

       al/autolevels[:f/fullyrange], automatic brightness / contrast
       correction
	   f/fullyrange
	       Stretch luminance to "0-255".

       lb/linblenddeint
	   Linear blend deinterlacing filter that deinterlaces the given block
	   by filtering all lines with a "(1 2 1)" filter.

       li/linipoldeint
	   Linear interpolating deinterlacing filter that deinterlaces the
	   given block by linearly interpolating every second line.

       ci/cubicipoldeint
	   Cubic interpolating deinterlacing filter deinterlaces the given
	   block by cubically interpolating every second line.

       md/mediandeint
	   Median deinterlacing filter that deinterlaces the given block by
	   applying a median filter to every second line.

       fd/ffmpegdeint
	   FFmpeg deinterlacing filter that deinterlaces the given block by
	   filtering every second line with a "(-1 4 2 4 -1)" filter.

       l5/lowpass5
	   Vertically applied FIR lowpass deinterlacing filter that
	   deinterlaces the given block by filtering all lines with a "(-1 2 6
	   2 -1)" filter.

       fq/forceQuant[|quantizer]
	   Overrides the quantizer table from the input with the constant
	   quantizer you specify.

	   quantizer
	       Quantizer to use

       de/default
	   Default pp filter combination ("hb|a,vb|a,dr|a")

       fa/fast
	   Fast pp filter combination ("h1|a,v1|a,dr|a")

       ac  High quality pp filter combination ("ha|a|128|7,va|a,dr|a")

       Examples

       ·   Apply horizontal and vertical deblocking, deringing and automatic
	   brightness/contrast:

		   pp=hb/vb/dr/al

       ·   Apply default filters without brightness/contrast correction:

		   pp=de/-al

       ·   Apply default filters and temporal denoiser:

		   pp=default/tmpnoise|1|2|3

       ·   Apply deblocking on luminance only, and switch vertical deblocking
	   on or off automatically depending on available CPU time:

		   pp=hb|y/vb|a

   psnr
       Obtain the average, maximum and minimum PSNR (Peak Signal to Noise
       Ratio) between two input videos.

       This filter takes in input two input videos, the first input is
       considered the "main" source and is passed unchanged to the output. The
       second input is used as a "reference" video for computing the PSNR.

       Both video inputs must have the same resolution and pixel format for
       this filter to work correctly. Also it assumes that both inputs have
       the same number of frames, which are compared one by one.

       The obtained average PSNR is printed through the logging system.

       The filter stores the accumulated MSE (mean squared error) of each
       frame, and at the end of the processing it is averaged across all
       frames equally, and the following formula is applied to obtain the
       PSNR:

	       PSNR = 10*log10(MAX^2/MSE)

       Where MAX is the average of the maximum values of each component of the
       image.

       The description of the accepted parameters follows.

       stats_file, f
	   If specified the filter will use the named file to save the PSNR of
	   each individual frame.

       The file printed if stats_file is selected, contains a sequence of
       key/value pairs of the form key:value for each compared couple of
       frames.

       A description of each shown parameter follows:

       n   sequential number of the input frame, starting from 1

       mse_avg
	   Mean Square Error pixel-by-pixel average difference of the compared
	   frames, averaged over all the image components.

       mse_y, mse_u, mse_v, mse_r, mse_g, mse_g, mse_a
	   Mean Square Error pixel-by-pixel average difference of the compared
	   frames for the component specified by the suffix.

       psnr_y, psnr_u, psnr_v, psnr_r, psnr_g, psnr_b, psnr_a
	   Peak Signal to Noise ratio of the compared frames for the component
	   specified by the suffix.

       For example:

	       movie=ref_movie.mpg, setpts=PTS-STARTPTS [main];
	       [main][ref] psnr="stats_file=stats.log" [out]

       On this example the input file being processed is compared with the
       reference file ref_movie.mpg. The PSNR of each individual frame is
       stored in stats.log.

   pullup
       Pulldown reversal (inverse telecine) filter, capable of handling mixed
       hard-telecine, 24000/1001 fps progressive, and 30000/1001 fps
       progressive content.

       The pullup filter is designed to take advantage of future context in
       making its decisions. This filter is stateless in the sense that it
       does not lock onto a pattern to follow, but it instead looks forward to
       the following fields in order to identify matches and rebuild
       progressive frames.

       To produce content with an even framerate, insert the fps filter after
       pullup, use "fps=24000/1001" if the input frame rate is 29.97fps,
       "fps=24" for 30fps and the (rare) telecined 25fps input.

       The filter accepts the following options:

       jl
       jr
       jt
       jb  These options set the amount of "junk" to ignore at the left,
	   right, top, and bottom of the image, respectively. Left and right
	   are in units of 8 pixels, while top and bottom are in units of 2
	   lines.  The default is 8 pixels on each side.

       sb  Set the strict breaks. Setting this option to 1 will reduce the
	   chances of filter generating an occasional mismatched frame, but it
	   may also cause an excessive number of frames to be dropped during
	   high motion sequences.  Conversely, setting it to -1 will make
	   filter match fields more easily.  This may help processing of video
	   where there is slight blurring between the fields, but may also
	   cause there to be interlaced frames in the output.  Default value
	   is 0.

       mp  Set the metric plane to use. It accepts the following values:

	   l   Use luma plane.

	   u   Use chroma blue plane.

	   v   Use chroma red plane.

	   This option may be set to use chroma plane instead of the default
	   luma plane for doing filter's computations. This may improve
	   accuracy on very clean source material, but more likely will
	   decrease accuracy, especially if there is chroma noise (rainbow
	   effect) or any grayscale video.  The main purpose of setting mp to
	   a chroma plane is to reduce CPU load and make pullup usable in
	   realtime on slow machines.

       For best results (without duplicated frames in the output file) it is
       necessary to change the output frame rate. For example, to inverse
       telecine NTSC input:

	       ffmpeg -i input -vf pullup -r 24000/1001 ...

   removelogo
       Suppress a TV station logo, using an image file to determine which
       pixels comprise the logo. It works by filling in the pixels that
       comprise the logo with neighboring pixels.

       The filter accepts the following options:

       filename, f
	   Set the filter bitmap file, which can be any image format supported
	   by libavformat. The width and height of the image file must match
	   those of the video stream being processed.

       Pixels in the provided bitmap image with a value of zero are not
       considered part of the logo, non-zero pixels are considered part of the
       logo. If you use white (255) for the logo and black (0) for the rest,
       you will be safe. For making the filter bitmap, it is recommended to
       take a screen capture of a black frame with the logo visible, and then
       using a threshold filter followed by the erode filter once or twice.

       If needed, little splotches can be fixed manually. Remember that if
       logo pixels are not covered, the filter quality will be much reduced.
       Marking too many pixels as part of the logo does not hurt as much, but
       it will increase the amount of blurring needed to cover over the image
       and will destroy more information than necessary, and extra pixels will
       slow things down on a large logo.

   rotate
       Rotate video by an arbitrary angle expressed in radians.

       The filter accepts the following options:

       A description of the optional parameters follows.

       angle, a
	   Set an expression for the angle by which to rotate the input video
	   clockwise, expressed as a number of radians. A negative value will
	   result in a counter-clockwise rotation. By default it is set to
	   "0".

	   This expression is evaluated for each frame.

       out_w, ow
	   Set the output width expression, default value is "iw".  This
	   expression is evaluated just once during configuration.

       out_h, oh
	   Set the output height expression, default value is "ih".  This
	   expression is evaluated just once during configuration.

       bilinear
	   Enable bilinear interpolation if set to 1, a value of 0 disables
	   it. Default value is 1.

       fillcolor, c
	   Set the color used to fill the output area not covered by the
	   rotated image. For the generalsyntax of this option, check the
	   "Color" section in the ffmpeg-utils manual. If the special value
	   "none" is selected then no background is printed (useful for
	   example if the background is never shown).

	   Default value is "black".

       The expressions for the angle and the output size can contain the
       following constants and functions:

       n   sequential number of the input frame, starting from 0. It is always
	   NAN before the first frame is filtered.

       t   time in seconds of the input frame, it is set to 0 when the filter
	   is configured. It is always NAN before the first frame is filtered.

       hsub
       vsub
	   horizontal and vertical chroma subsample values. For example for
	   the pixel format "yuv422p" hsub is 2 and vsub is 1.

       in_w, iw
       in_h, ih
	   the input video width and heigth

       out_w, ow
       out_h, oh
	   the output width and heigth, that is the size of the padded area as
	   specified by the width and height expressions

       rotw(a)
       roth(a)
	   the minimal width/height required for completely containing the
	   input video rotated by a radians.

	   These are only available when computing the out_w and out_h
	   expressions.

       Examples

       ·   Rotate the input by PI/6 radians clockwise:

		   rotate=PI/6

       ·   Rotate the input by PI/6 radians counter-clockwise:

		   rotate=-PI/6

       ·   Apply a constant rotation with period T, starting from an angle of
	   PI/3:

		   rotate=PI/3+2*PI*t/T

       ·   Make the input video rotation oscillating with a period of T
	   seconds and an amplitude of A radians:

		   rotate=A*sin(2*PI/T*t)

       ·   Rotate the video, output size is choosen so that the whole rotating
	   input video is always completely contained in the output:

		   rotate='2*PI*t:ow=hypot(iw,ih):oh=ow'

       ·   Rotate the video, reduce the output size so that no background is
	   ever shown:

		   rotate=2*PI*t:ow='min(iw,ih)/sqrt(2)':oh=ow:c=none

       Commands

       The filter supports the following commands:

       a, angle
	   Set the angle expression.  The command accepts the same syntax of
	   the corresponding option.

	   If the specified expression is not valid, it is kept at its current
	   value.

   sab
       Apply Shape Adaptive Blur.

       The filter accepts the following options:

       luma_radius, lr
	   Set luma blur filter strength, must be a value in range 0.1-4.0,
	   default value is 1.0. A greater value will result in a more blurred
	   image, and in slower processing.

       luma_pre_filter_radius, lpfr
	   Set luma pre-filter radius, must be a value in the 0.1-2.0 range,
	   default value is 1.0.

       luma_strength, ls
	   Set luma maximum difference between pixels to still be considered,
	   must be a value in the 0.1-100.0 range, default value is 1.0.

       chroma_radius, cr
	   Set chroma blur filter strength, must be a value in range 0.1-4.0.
	   A greater value will result in a more blurred image, and in slower
	   processing.

       chroma_pre_filter_radius, cpfr
	   Set chroma pre-filter radius, must be a value in the 0.1-2.0 range.

       chroma_strength, cs
	   Set chroma maximum difference between pixels to still be
	   considered, must be a value in the 0.1-100.0 range.

       Each chroma option value, if not explicitly specified, is set to the
       corresponding luma option value.

   scale
       Scale (resize) the input video, using the libswscale library.

       The scale filter forces the output display aspect ratio to be the same
       of the input, by changing the output sample aspect ratio.

       If the input image format is different from the format requested by the
       next filter, the scale filter will convert the input to the requested
       format.

       Options

       The filter accepts the following options, or any of the options
       supported by the libswscale scaler.

       See the ffmpeg-scaler manual for the complete list of scaler options.

       width, w
       height, h
	   Set the output video dimension expression. Default value is the
	   input dimension.

	   If the value is 0, the input width is used for the output.

	   If one of the values is -1, the scale filter will use a value that
	   maintains the aspect ratio of the input image, calculated from the
	   other specified dimension. If both of them are -1, the input size
	   is used

	   See below for the list of accepted constants for use in the
	   dimension expression.

       interl
	   Set the interlacing mode. It accepts the following values:

	   1   Force interlaced aware scaling.

	   0   Do not apply interlaced scaling.

	   -1  Select interlaced aware scaling depending on whether the source
	       frames are flagged as interlaced or not.

	   Default value is 0.

       flags
	   Set libswscale scaling flags. See the ffmpeg-scaler manual for the
	   complete list of values. If not explictly specified the filter
	   applies the default flags.

       size, s
	   Set the video size. For the syntax of this option, check the "Video
	   size" section in the ffmpeg-utils manual.

       in_color_matrix
       out_color_matrix
	   Set in/output YCbCr color space type.

	   This allows the autodetected value to be overridden as well as
	   allows forcing a specific value used for the output and encoder.

	   If not specified, the color space type depends on the pixel format.

	   Possible values:

	   auto
	       Choose automatically.

	   bt709
	       Format conforming to International Telecommunication Union
	       (ITU) Recommendation BT.709.

	   fcc Set color space conforming to the United States Federal
	       Communications Commission (FCC) Code of Federal Regulations
	       (CFR) Title 47 (2003) 73.682 (a).

	   bt601
	       Set color space conforming to:

	       ·   ITU Radiocommunication Sector (ITU-R) Recommendation BT.601

	       ·   ITU-R Rec. BT.470-6 (1998) Systems B, B1, and G

	       ·   Society of Motion Picture and Television Engineers (SMPTE)
		   ST 170:2004

	   smpte240m
	       Set color space conforming to SMPTE ST 240:1999.

       in_range
       out_range
	   Set in/output YCbCr sample range.

	   This allows the autodetected value to be overridden as well as
	   allows forcing a specific value used for the output and encoder. If
	   not specified, the range depends on the pixel format. Possible
	   values:

	   auto
	       Choose automatically.

	   jpeg/full/pc
	       Set full range (0-255 in case of 8-bit luma).

	   mpeg/tv
	       Set "MPEG" range (16-235 in case of 8-bit luma).

       force_original_aspect_ratio
	   Enable decreasing or increasing output video width or height if
	   necessary to keep the original aspect ratio. Possible values:

	   disable
	       Scale the video as specified and disable this feature.

	   decrease
	       The output video dimensions will automatically be decreased if
	       needed.

	   increase
	       The output video dimensions will automatically be increased if
	       needed.

	   One useful instance of this option is that when you know a specific
	   device's maximum allowed resolution, you can use this to limit the
	   output video to that, while retaining the aspect ratio. For
	   example, device A allows 1280x720 playback, and your video is
	   1920x800. Using this option (set it to decrease) and specifying
	   1280x720 to the command line makes the output 1280x533.

	   Please note that this is a different thing than specifying -1 for w
	   or h, you still need to specify the output resolution for this
	   option to work.

       The values of the w and h options are expressions containing the
       following constants:

       in_w
       in_h
	   the input width and height

       iw
       ih  same as in_w and in_h

       out_w
       out_h
	   the output (scaled) width and height

       ow
       oh  same as out_w and out_h

       a   same as iw / ih

       sar input sample aspect ratio

       dar input display aspect ratio. Calculated from "(iw / ih) * sar".

       hsub
       vsub
	   horizontal and vertical chroma subsample values. For example for
	   the pixel format "yuv422p" hsub is 2 and vsub is 1.

       Examples

       ·   Scale the input video to a size of 200x100:

		   scale=w=200:h=100

	   This is equivalent to:

		   scale=200:100

	   or:

		   scale=200x100

       ·   Specify a size abbreviation for the output size:

		   scale=qcif

	   which can also be written as:

		   scale=size=qcif

       ·   Scale the input to 2x:

		   scale=w=2*iw:h=2*ih

       ·   The above is the same as:

		   scale=2*in_w:2*in_h

       ·   Scale the input to 2x with forced interlaced scaling:

		   scale=2*iw:2*ih:interl=1

       ·   Scale the input to half size:

		   scale=w=iw/2:h=ih/2

       ·   Increase the width, and set the height to the same size:

		   scale=3/2*iw:ow

       ·   Seek for Greek harmony:

		   scale=iw:1/PHI*iw
		   scale=ih*PHI:ih

       ·   Increase the height, and set the width to 3/2 of the height:

		   scale=w=3/2*oh:h=3/5*ih

       ·   Increase the size, but make the size a multiple of the chroma
	   subsample values:

		   scale="trunc(3/2*iw/hsub)*hsub:trunc(3/2*ih/vsub)*vsub"

       ·   Increase the width to a maximum of 500 pixels, keep the same input
	   aspect ratio:

		   scale=w='min(500\, iw*3/2):h=-1'

   separatefields
       The "separatefields" takes a frame-based video input and splits each
       frame into its components fields, producing a new half height clip with
       twice the frame rate and twice the frame count.

       This filter use field-dominance information in frame to decide which of
       each pair of fields to place first in the output.  If it gets it wrong
       use setfield filter before "separatefields" filter.

   setdar, setsar
       The "setdar" filter sets the Display Aspect Ratio for the filter output
       video.

       This is done by changing the specified Sample (aka Pixel) Aspect Ratio,
       according to the following equation:

	       <DAR> = <HORIZONTAL_RESOLUTION> / <VERTICAL_RESOLUTION> * <SAR>

       Keep in mind that the "setdar" filter does not modify the pixel
       dimensions of the video frame. Also the display aspect ratio set by
       this filter may be changed by later filters in the filterchain, e.g. in
       case of scaling or if another "setdar" or a "setsar" filter is applied.

       The "setsar" filter sets the Sample (aka Pixel) Aspect Ratio for the
       filter output video.

       Note that as a consequence of the application of this filter, the
       output display aspect ratio will change according to the equation
       above.

       Keep in mind that the sample aspect ratio set by the "setsar" filter
       may be changed by later filters in the filterchain, e.g. if another
       "setsar" or a "setdar" filter is applied.

       The filters accept the following options:

       r, ratio, dar ("setdar" only), sar ("setsar" only)
	   Set the aspect ratio used by the filter.

	   The parameter can be a floating point number string, an expression,
	   or a string of the form num:den, where num and den are the
	   numerator and denominator of the aspect ratio. If the parameter is
	   not specified, it is assumed the value "0".	In case the form
	   "num:den" is used, the ":" character should be escaped.

       max Set the maximum integer value to use for expressing numerator and
	   denominator when reducing the expressed aspect ratio to a rational.
	   Default value is 100.

       Examples

       ·   To change the display aspect ratio to 16:9, specify one of the
	   following:

		   setdar=dar=1.77777
		   setdar=dar=16/9
		   setdar=dar=1.77777

       ·   To change the sample aspect ratio to 10:11, specify:

		   setsar=sar=10/11

       ·   To set a display aspect ratio of 16:9, and specify a maximum
	   integer value of 1000 in the aspect ratio reduction, use the
	   command:

		   setdar=ratio=16/9:max=1000

   setfield
       Force field for the output video frame.

       The "setfield" filter marks the interlace type field for the output
       frames. It does not change the input frame, but only sets the
       corresponding property, which affects how the frame is treated by
       following filters (e.g. "fieldorder" or "yadif").

       The filter accepts the following options:

       mode
	   Available values are:

	   auto
	       Keep the same field property.

	   bff Mark the frame as bottom-field-first.

	   tff Mark the frame as top-field-first.

	   prog
	       Mark the frame as progressive.

   showinfo
       Show a line containing various information for each input video frame.
       The input video is not modified.

       The shown line contains a sequence of key/value pairs of the form
       key:value.

       A description of each shown parameter follows:

       n   sequential number of the input frame, starting from 0

       pts Presentation TimeStamp of the input frame, expressed as a number of
	   time base units. The time base unit depends on the filter input
	   pad.

       pts_time
	   Presentation TimeStamp of the input frame, expressed as a number of
	   seconds

       pos position of the frame in the input stream, -1 if this information
	   in unavailable and/or meaningless (for example in case of synthetic
	   video)

       fmt pixel format name

       sar sample aspect ratio of the input frame, expressed in the form
	   num/den

       s   size of the input frame. For the syntax of this option, check the
	   "Video size" section in the ffmpeg-utils manual.

       i   interlaced mode ("P" for "progressive", "T" for top field first,
	   "B" for bottom field first)

       iskey
	   1 if the frame is a key frame, 0 otherwise

       type
	   picture type of the input frame ("I" for an I-frame, "P" for a
	   P-frame, "B" for a B-frame, "?" for unknown type).  Check also the
	   documentation of the "AVPictureType" enum and of the
	   "av_get_picture_type_char" function defined in libavutil/avutil.h.

       checksum
	   Adler-32 checksum (printed in hexadecimal) of all the planes of the
	   input frame

       plane_checksum
	   Adler-32 checksum (printed in hexadecimal) of each plane of the
	   input frame, expressed in the form "[c0 c1 c2 c3]"

   smartblur
       Blur the input video without impacting the outlines.

       The filter accepts the following options:

       luma_radius, lr
	   Set the luma radius. The option value must be a float number in the
	   range [0.1,5.0] that specifies the variance of the gaussian filter
	   used to blur the image (slower if larger). Default value is 1.0.

       luma_strength, ls
	   Set the luma strength. The option value must be a float number in
	   the range [-1.0,1.0] that configures the blurring. A value included
	   in [0.0,1.0] will blur the image whereas a value included in
	   [-1.0,0.0] will sharpen the image. Default value is 1.0.

       luma_threshold, lt
	   Set the luma threshold used as a coefficient to determine whether a
	   pixel should be blurred or not. The option value must be an integer
	   in the range [-30,30]. A value of 0 will filter all the image, a
	   value included in [0,30] will filter flat areas and a value
	   included in [-30,0] will filter edges. Default value is 0.

       chroma_radius, cr
	   Set the chroma radius. The option value must be a float number in
	   the range [0.1,5.0] that specifies the variance of the gaussian
	   filter used to blur the image (slower if larger). Default value is
	   1.0.

       chroma_strength, cs
	   Set the chroma strength. The option value must be a float number in
	   the range [-1.0,1.0] that configures the blurring. A value included
	   in [0.0,1.0] will blur the image whereas a value included in
	   [-1.0,0.0] will sharpen the image. Default value is 1.0.

       chroma_threshold, ct
	   Set the chroma threshold used as a coefficient to determine whether
	   a pixel should be blurred or not. The option value must be an
	   integer in the range [-30,30]. A value of 0 will filter all the
	   image, a value included in [0,30] will filter flat areas and a
	   value included in [-30,0] will filter edges. Default value is 0.

       If a chroma option is not explicitly set, the corresponding luma value
       is set.

   stereo3d
       Convert between different stereoscopic image formats.

       The filters accept the following options:

       in  Set stereoscopic image format of input.

	   Available values for input image formats are:

	   sbsl
	       side by side parallel (left eye left, right eye right)

	   sbsr
	       side by side crosseye (right eye left, left eye right)

	   sbs2l
	       side by side parallel with half width resolution (left eye
	       left, right eye right)

	   sbs2r
	       side by side crosseye with half width resolution (right eye
	       left, left eye right)

	   abl above-below (left eye above, right eye below)

	   abr above-below (right eye above, left eye below)

	   ab2l
	       above-below with half height resolution (left eye above, right
	       eye below)

	   ab2r
	       above-below with half height resolution (right eye above, left
	       eye below)

	   al  alternating frames (left eye first, right eye second)

	   ar  alternating frames (right eye first, left eye second)

	       Default value is sbsl.

       out Set stereoscopic image format of output.

	   Available values for output image formats are all the input formats
	   as well as:

	   arbg
	       anaglyph red/blue gray (red filter on left eye, blue filter on
	       right eye)

	   argg
	       anaglyph red/green gray (red filter on left eye, green filter
	       on right eye)

	   arcg
	       anaglyph red/cyan gray (red filter on left eye, cyan filter on
	       right eye)

	   arch
	       anaglyph red/cyan half colored (red filter on left eye, cyan
	       filter on right eye)

	   arcc
	       anaglyph red/cyan color (red filter on left eye, cyan filter on
	       right eye)

	   arcd
	       anaglyph red/cyan color optimized with the least squares
	       projection of dubois (red filter on left eye, cyan filter on
	       right eye)

	   agmg
	       anaglyph green/magenta gray (green filter on left eye, magenta
	       filter on right eye)

	   agmh
	       anaglyph green/magenta half colored (green filter on left eye,
	       magenta filter on right eye)

	   agmc
	       anaglyph green/magenta colored (green filter on left eye,
	       magenta filter on right eye)

	   agmd
	       anaglyph green/magenta color optimized with the least squares
	       projection of dubois (green filter on left eye, magenta filter
	       on right eye)

	   aybg
	       anaglyph yellow/blue gray (yellow filter on left eye, blue
	       filter on right eye)

	   aybh
	       anaglyph yellow/blue half colored (yellow filter on left eye,
	       blue filter on right eye)

	   aybc
	       anaglyph yellow/blue colored (yellow filter on left eye, blue
	       filter on right eye)

	   aybd
	       anaglyph yellow/blue color optimized with the least squares
	       projection of dubois (yellow filter on left eye, blue filter on
	       right eye)

	   irl interleaved rows (left eye has top row, right eye starts on
	       next row)

	   irr interleaved rows (right eye has top row, left eye starts on
	       next row)

	   ml  mono output (left eye only)

	   mr  mono output (right eye only)

	   Default value is arcd.

       Examples

       ·   Convert input video from side by side parallel to anaglyph
	   yellow/blue dubois:

		   stereo3d=sbsl:aybd

       ·   Convert input video from above bellow (left eye above, right eye
	   below) to side by side crosseye.

		   stereo3d=abl:sbsr

   spp
       Apply a simple postprocessing filter that compresses and decompresses
       the image at several (or - in the case of quality level 6 - all) shifts
       and average the results.

       The filter accepts the following options:

       quality
	   Set quality. This option defines the number of levels for
	   averaging. It accepts an integer in the range 0-6. If set to 0, the
	   filter will have no effect. A value of 6 means the higher quality.
	   For each increment of that value the speed drops by a factor of
	   approximately 2.  Default value is 3.

       qp  Force a constant quantization parameter. If not set, the filter
	   will use the QP from the video stream (if available).

       mode
	   Set thresholding mode. Available modes are:

	   hard
	       Set hard thresholding (default).

	   soft
	       Set soft thresholding (better de-ringing effect, but likely
	       blurrier).

       use_bframe_qp
	   Enable the use of the QP from the B-Frames if set to 1. Using this
	   option may cause flicker since the B-Frames have often larger QP.
	   Default is 0 (not enabled).

   subtitles
       Draw subtitles on top of input video using the libass library.

       To enable compilation of this filter you need to configure FFmpeg with
       "--enable-libass". This filter also requires a build with libavcodec
       and libavformat to convert the passed subtitles file to ASS (Advanced
       Substation Alpha) subtitles format.

       The filter accepts the following options:

       filename, f
	   Set the filename of the subtitle file to read. It must be
	   specified.

       original_size
	   Specify the size of the original video, the video for which the ASS
	   file was composed. For the syntax of this option, check the "Video
	   size" section in the ffmpeg-utils manual. Due to a misdesign in ASS
	   aspect ratio arithmetic, this is necessary to correctly scale the
	   fonts if the aspect ratio has been changed.

       charenc
	   Set subtitles input character encoding. "subtitles" filter only.
	   Only useful if not UTF-8.

       If the first key is not specified, it is assumed that the first value
       specifies the filename.

       For example, to render the file sub.srt on top of the input video, use
       the command:

	       subtitles=sub.srt

       which is equivalent to:

	       subtitles=filename=sub.srt

   super2xsai
       Scale the input by 2x and smooth using the Super2xSaI (Scale and
       Interpolate) pixel art scaling algorithm.

       Useful for enlarging pixel art images without reducing sharpness.

   swapuv
       Swap U & V plane.

   telecine
       Apply telecine process to the video.

       This filter accepts the following options:

       first_field
	   top, t
	       top field first

	   bottom, b
	       bottom field first The default value is "top".

       pattern
	   A string of numbers representing the pulldown pattern you wish to
	   apply.  The default value is 23.

	       Some typical patterns:

	       NTSC output (30i):
	       27.5p: 32222
	       24p: 23 (classic)
	       24p: 2332 (preferred)
	       20p: 33
	       18p: 334
	       16p: 3444

	       PAL output (25i):
	       27.5p: 12222
	       24p: 222222222223 ("Euro pulldown")
	       16.67p: 33
	       16p: 33333334

   thumbnail
       Select the most representative frame in a given sequence of consecutive
       frames.

       The filter accepts the following options:

       n   Set the frames batch size to analyze; in a set of n frames, the
	   filter will pick one of them, and then handle the next batch of n
	   frames until the end. Default is 100.

       Since the filter keeps track of the whole frames sequence, a bigger n
       value will result in a higher memory usage, so a high value is not
       recommended.

       Examples

       ·   Extract one picture each 50 frames:

		   thumbnail=50

       ·   Complete example of a thumbnail creation with ffmpeg:

		   ffmpeg -i in.avi -vf thumbnail,scale=300:200 -frames:v 1 out.png

   tile
       Tile several successive frames together.

       The filter accepts the following options:

       layout
	   Set the grid size (i.e. the number of lines and columns). For the
	   syntax of this option, check the "Video size" section in the
	   ffmpeg-utils manual.

       nb_frames
	   Set the maximum number of frames to render in the given area. It
	   must be less than or equal to wxh. The default value is 0, meaning
	   all the area will be used.

       margin
	   Set the outer border margin in pixels.

       padding
	   Set the inner border thickness (i.e. the number of pixels between
	   frames). For more advanced padding options (such as having
	   different values for the edges), refer to the pad video filter.

       color
	   Specify the color of the unused areaFor the syntax of this option,
	   check the "Color" section in the ffmpeg-utils manual. The default
	   value of color is "black".

       Examples

       ·   Produce 8x8 PNG tiles of all keyframes (-skip_frame nokey) in a
	   movie:

		   ffmpeg -skip_frame nokey -i file.avi -vf 'scale=128:72,tile=8x8' -an -vsync 0 keyframes%03d.png

	   The -vsync 0 is necessary to prevent ffmpeg from duplicating each
	   output frame to accomodate the originally detected frame rate.

       ·   Display 5 pictures in an area of "3x2" frames, with 7 pixels
	   between them, and 2 pixels of initial margin, using mixed flat and
	   named options:

		   tile=3x2:nb_frames=5:padding=7:margin=2

   tinterlace
       Perform various types of temporal field interlacing.

       Frames are counted starting from 1, so the first input frame is
       considered odd.

       The filter accepts the following options:

       mode
	   Specify the mode of the interlacing. This option can also be
	   specified as a value alone. See below for a list of values for this
	   option.

	   Available values are:

	   merge, 0
	       Move odd frames into the upper field, even into the lower
	       field, generating a double height frame at half frame rate.

	   drop_odd, 1
	       Only output even frames, odd frames are dropped, generating a
	       frame with unchanged height at half frame rate.

	   drop_even, 2
	       Only output odd frames, even frames are dropped, generating a
	       frame with unchanged height at half frame rate.

	   pad, 3
	       Expand each frame to full height, but pad alternate lines with
	       black, generating a frame with double height at the same input
	       frame rate.

	   interleave_top, 4
	       Interleave the upper field from odd frames with the lower field
	       from even frames, generating a frame with unchanged height at
	       half frame rate.

	   interleave_bottom, 5
	       Interleave the lower field from odd frames with the upper field
	       from even frames, generating a frame with unchanged height at
	       half frame rate.

	   interlacex2, 6
	       Double frame rate with unchanged height. Frames are inserted
	       each containing the second temporal field from the previous
	       input frame and the first temporal field from the next input
	       frame. This mode relies on the top_field_first flag. Useful for
	       interlaced video displays with no field synchronisation.

	   Numeric values are deprecated but are accepted for backward
	   compatibility reasons.

	   Default mode is "merge".

       flags
	   Specify flags influencing the filter process.

	   Available value for flags is:

	   low_pass_filter, vlfp
	       Enable vertical low-pass filtering in the filter.  Vertical
	       low-pass filtering is required when creating an interlaced
	       destination from a progressive source which contains high-
	       frequency vertical detail. Filtering will reduce interlace
	       'twitter' and Moire patterning.

	       Vertical low-pass filtering can only be enabled for mode
	       interleave_top and interleave_bottom.

   transpose
       Transpose rows with columns in the input video and optionally flip it.

       This filter accepts the following options:

       dir Specify the transposition direction.

	   Can assume the following values:

	   0, 4, cclock_flip
	       Rotate by 90 degrees counterclockwise and vertically flip
	       (default), that is:

		       L.R     L.l
		       . . ->  . .
		       l.r     R.r

	   1, 5, clock
	       Rotate by 90 degrees clockwise, that is:

		       L.R     l.L
		       . . ->  . .
		       l.r     r.R

	   2, 6, cclock
	       Rotate by 90 degrees counterclockwise, that is:

		       L.R     R.r
		       . . ->  . .
		       l.r     L.l

	   3, 7, clock_flip
	       Rotate by 90 degrees clockwise and vertically flip, that is:

		       L.R     r.R
		       . . ->  . .
		       l.r     l.L

	   For values between 4-7, the transposition is only done if the input
	   video geometry is portrait and not landscape. These values are
	   deprecated, the "passthrough" option should be used instead.

	   Numerical values are deprecated, and should be dropped in favor of
	   symbolic constants.

       passthrough
	   Do not apply the transposition if the input geometry matches the
	   one specified by the specified value. It accepts the following
	   values:

	   none
	       Always apply transposition.

	   portrait
	       Preserve portrait geometry (when height >= width).

	   landscape
	       Preserve landscape geometry (when width >= height).

	   Default value is "none".

       For example to rotate by 90 degrees clockwise and preserve portrait
       layout:

	       transpose=dir=1:passthrough=portrait

       The command above can also be specified as:

	       transpose=1:portrait

   trim
       Trim the input so that the output contains one continuous subpart of
       the input.

       This filter accepts the following options:

       start
	   Specify time of the start of the kept section, i.e. the frame with
	   the timestamp start will be the first frame in the output.

       end Specify time of the first frame that will be dropped, i.e. the
	   frame immediately preceding the one with the timestamp end will be
	   the last frame in the output.

       start_pts
	   Same as start, except this option sets the start timestamp in
	   timebase units instead of seconds.

       end_pts
	   Same as end, except this option sets the end timestamp in timebase
	   units instead of seconds.

       duration
	   Specify maximum duration of the output.

       start_frame
	   Number of the first frame that should be passed to output.

       end_frame
	   Number of the first frame that should be dropped.

       start, end, duration are expressed as time duration specifications,
       check the "Time duration" section in the ffmpeg-utils manual.

       Note that the first two sets of the start/end options and the duration
       option look at the frame timestamp, while the _frame variants simply
       count the frames that pass through the filter. Also note that this
       filter does not modify the timestamps. If you wish that the output
       timestamps start at zero, insert a setpts filter after the trim filter.

       If multiple start or end options are set, this filter tries to be
       greedy and keep all the frames that match at least one of the specified
       constraints. To keep only the part that matches all the constraints at
       once, chain multiple trim filters.

       The defaults are such that all the input is kept. So it is possible to
       set e.g.	 just the end values to keep everything before the specified
       time.

       Examples:

       ·   drop everything except the second minute of input

		   ffmpeg -i INPUT -vf trim=60:120

       ·   keep only the first second

		   ffmpeg -i INPUT -vf trim=duration=1

   unsharp
       Sharpen or blur the input video.

       It accepts the following parameters:

       luma_msize_x, lx
	   Set the luma matrix horizontal size. It must be an odd integer
	   between 3 and 63, default value is 5.

       luma_msize_y, ly
	   Set the luma matrix vertical size. It must be an odd integer
	   between 3 and 63, default value is 5.

       luma_amount, la
	   Set the luma effect strength. It can be a float number, reasonable
	   values lay between -1.5 and 1.5.

	   Negative values will blur the input video, while positive values
	   will sharpen it, a value of zero will disable the effect.

	   Default value is 1.0.

       chroma_msize_x, cx
	   Set the chroma matrix horizontal size. It must be an odd integer
	   between 3 and 63, default value is 5.

       chroma_msize_y, cy
	   Set the chroma matrix vertical size. It must be an odd integer
	   between 3 and 63, default value is 5.

       chroma_amount, ca
	   Set the chroma effect strength. It can be a float number,
	   reasonable values lay between -1.5 and 1.5.

	   Negative values will blur the input video, while positive values
	   will sharpen it, a value of zero will disable the effect.

	   Default value is 0.0.

       opencl
	   If set to 1, specify using OpenCL capabilities, only available if
	   FFmpeg was configured with "--enable-opencl". Default value is 0.

       All parameters are optional and default to the equivalent of the string
       '5:5:1.0:5:5:0.0'.

       Examples

       ·   Apply strong luma sharpen effect:

		   unsharp=luma_msize_x=7:luma_msize_y=7:luma_amount=2.5

       ·   Apply strong blur of both luma and chroma parameters:

		   unsharp=7:7:-2:7:7:-2

   vidstabdetect
       Analyze video stabilization/deshaking. Perform pass 1 of 2, see
       vidstabtransform for pass 2.

       This filter generates a file with relative translation and rotation
       transform information about subsequent frames, which is then used by
       the vidstabtransform filter.

       To enable compilation of this filter you need to configure FFmpeg with
       "--enable-libvidstab".

       This filter accepts the following options:

       result
	   Set the path to the file used to write the transforms information.
	   Default value is transforms.trf.

       shakiness
	   Set how shaky the video is and how quick the camera is. It accepts
	   an integer in the range 1-10, a value of 1 means little shakiness,
	   a value of 10 means strong shakiness. Default value is 5.

       accuracy
	   Set the accuracy of the detection process. It must be a value in
	   the range 1-15. A value of 1 means low accuracy, a value of 15
	   means high accuracy. Default value is 9.

       stepsize
	   Set stepsize of the search process. The region around minimum is
	   scanned with 1 pixel resolution. Default value is 6.

       mincontrast
	   Set minimum contrast. Below this value a local measurement field is
	   discarded. Must be a floating point value in the range 0-1. Default
	   value is 0.3.

       tripod
	   Set reference frame number for tripod mode.

	   If enabled, the motion of the frames is compared to a reference
	   frame in the filtered stream, identified by the specified number.
	   The idea is to compensate all movements in a more-or-less static
	   scene and keep the camera view absolutely still.

	   If set to 0, it is disabled. The frames are counted starting from
	   1.

       show
	   Show fields and transforms in the resulting frames. It accepts an
	   integer in the range 0-2. Default value is 0, which disables any
	   visualization.

       Examples

       ·   Use default values:

		   vidstabdetect

       ·   Analyze strongly shaky movie and put the results in file
	   mytransforms.trf:

		   vidstabdetect=shakiness=10:accuracy=15:result="mytransforms.trf"

       ·   Visualize the result of internal transformations in the resulting
	   video:

		   vidstabdetect=show=1

       ·   Analyze a video with medium shakiness using ffmpeg:

		   ffmpeg -i input -vf vidstabdetect=shakiness=5:show=1 dummy.avi

   vidstabtransform
       Video stabilization/deshaking: pass 2 of 2, see vidstabdetect for pass
       1.

       Read a file with transform information for each frame and
       apply/compensate them. Together with the vidstabdetect filter this can
       be used to deshake videos. See also
       <http://public.hronopik.de/vid.stab>. It is important to also use the
       unsharp filter, see below.

       To enable compilation of this filter you need to configure FFmpeg with
       "--enable-libvidstab".

       This filter accepts the following options:

       input
	   path to the file used to read the transforms (default:
	   transforms.trf)

       smoothing
	   number of frames (value*2 + 1) used for lowpass filtering the
	   camera movements (default: 10). For example a number of 10 means
	   that 21 frames are used (10 in the past and 10 in the future) to
	   smoothen the motion in the video. A larger values leads to a
	   smoother video, but limits the acceleration of the camera (pan/tilt
	   movements).

       maxshift
	   maximal number of pixels to translate frames (default: -1 no limit)

       maxangle
	   maximal angle in radians (degree*PI/180) to rotate frames (default:
	   -1 no limit)

       crop
	   How to deal with borders that may be visible due to movement
	   compensation. Available values are:

	   keep
	       keep image information from previous frame (default)

	   black
	       fill the border black

       invert
	   0   keep transforms normal (default)

	   1   invert transforms

       relative
	   consider transforms as

	   0   absolute

	   1   relative to previous frame (default)

       zoom
	   percentage to zoom (default: 0)

	   >0  zoom in

	   <0  zoom out

       optzoom
	   set optimal zooming to avoid borders

	   0   disabled

	   1   optimal static zoom value is determined (only very strong
	       movements will lead to visible borders) (default)

	   2   optimal adaptive zoom value is determined (no borders will be
	       visible)

	   Note that the value given at zoom is added to the one calculated
	   here.

       interpol
	   type of interpolation

	   Available values are:

	   no  no interpolation

	   linear
	       linear only horizontal

	   bilinear
	       linear in both directions (default)

	   bicubic
	       cubic in both directions (slow)

       tripod
	   virtual tripod mode means that the video is stabilized such that
	   the camera stays stationary. Use also "tripod" option of
	   vidstabdetect.

	   0   off (default)

	   1   virtual tripod mode: equivalent to "relative=0:smoothing=0"

       Examples

       ·   typical call with default default values:
	    (note the unsharp filter which is always recommended)

		   ffmpeg -i inp.mpeg -vf vidstabtransform,unsharp=5:5:0.8:3:3:0.4 inp_stabilized.mpeg

       ·   zoom in a bit more and load transform data from a given file

		   vidstabtransform=zoom=5:input="mytransforms.trf"

       ·   smoothen the video even more

		   vidstabtransform=smoothing=30

   vflip
       Flip the input video vertically.

       For example, to vertically flip a video with ffmpeg:

	       ffmpeg -i in.avi -vf "vflip" out.avi

   vignette
       Make or reverse a natural vignetting effect.

       The filter accepts the following options:

       angle, a
	   Set lens angle expression as a number of radians.

	   The value is clipped in the "[0,PI/2]" range.

	   Default value: "PI/5"

       x0
       y0  Set center coordinates expressions. Respectively "w/2" and "h/2" by
	   default.

       mode
	   Set forward/backward mode.

	   Available modes are:

	   forward
	       The larger the distance from the central point, the darker the
	       image becomes.

	   backward
	       The larger the distance from the central point, the brighter
	       the image becomes.  This can be used to reverse a vignette
	       effect, though there is no automatic detection to extract the
	       lens angle and other settings (yet). It can also be used to
	       create a burning effect.

	   Default value is forward.

       eval
	   Set evaluation mode for the expressions (angle, x0, y0).

	   It accepts the following values:

	   init
	       Evaluate expressions only once during the filter
	       initialization.

	   frame
	       Evaluate expressions for each incoming frame. This is way
	       slower than the init mode since it requires all the scalers to
	       be re-computed, but it allows advanced dynamic expressions.

	   Default value is init.

       dither
	   Set dithering to reduce the circular banding effects. Default is 1
	   (enabled).

       aspect
	   Set vignette aspect. This setting allows to adjust the shape of the
	   vignette.  Setting this value to the SAR of the input will make a
	   rectangular vignetting following the dimensions of the video.

	   Default is "1/1".

       Expressions

       The alpha, x0 and y0 expressions can contain the following parameters.

       w
       h   input width and height

       n   the number of input frame, starting from 0

       pts the PTS (Presentation TimeStamp) time of the filtered video frame,
	   expressed in TB units, NAN if undefined

       r   frame rate of the input video, NAN if the input frame rate is
	   unknown

       t   the PTS (Presentation TimeStamp) of the filtered video frame,
	   expressed in seconds, NAN if undefined

       tb  time base of the input video

       Examples

       ·   Apply simple strong vignetting effect:

		   vignette=PI/4

       ·   Make a flickering vignetting:

		   vignette='PI/4+random(1)*PI/50':eval=frame

   w3fdif
       Deinterlace the input video ("w3fdif" stands for "Weston 3 Field
       Deinterlacing Filter").

       Based on the process described by Martin Weston for BBC R&D, and
       implemented based on the de-interlace algorithm written by Jim
       Easterbrook for BBC R&D, the Weston 3 field deinterlacing filter uses
       filter coefficients calculated by BBC R&D.

       There are two sets of filter coefficients, so called "simple": and
       "complex". Which set of filter coefficients is used can be set by
       passing an optional parameter:

       filter
	   Set the interlacing filter coefficients. Accepts one of the
	   following values:

	   simple
	       Simple filter coefficient set.

	   complex
	       More-complex filter coefficient set.

	   Default value is complex.

       deint
	   Specify which frames to deinterlace. Accept one of the following
	   values:

	   all Deinterlace all frames,

	   interlaced
	       Only deinterlace frames marked as interlaced.

	   Default value is all.

   yadif
       Deinterlace the input video ("yadif" means "yet another deinterlacing
       filter").

       This filter accepts the following options:

       mode
	   The interlacing mode to adopt, accepts one of the following values:

	   0, send_frame
	       output 1 frame for each frame

	   1, send_field
	       output 1 frame for each field

	   2, send_frame_nospatial
	       like "send_frame" but skip spatial interlacing check

	   3, send_field_nospatial
	       like "send_field" but skip spatial interlacing check

	   Default value is "send_frame".

       parity
	   The picture field parity assumed for the input interlaced video,
	   accepts one of the following values:

	   0, tff
	       assume top field first

	   1, bff
	       assume bottom field first

	   -1, auto
	       enable automatic detection

	   Default value is "auto".  If interlacing is unknown or decoder does
	   not export this information, top field first will be assumed.

       deint
	   Specify which frames to deinterlace. Accept one of the following
	   values:

	   0, all
	       deinterlace all frames

	   1, interlaced
	       only deinterlace frames marked as interlaced

	   Default value is "all".

VIDEO SOURCES
       Below is a description of the currently available video sources.

   buffer
       Buffer video frames, and make them available to the filter chain.

       This source is mainly intended for a programmatic use, in particular
       through the interface defined in libavfilter/vsrc_buffer.h.

       This source accepts the following options:

       video_size
	   Specify the size (width and height) of the buffered video frames.
	   For the syntax of this option, check the "Video size" section in
	   the ffmpeg-utils manual.

       width
	   Input video width.

       height
	   Input video height.

       pix_fmt
	   A string representing the pixel format of the buffered video
	   frames.  It may be a number corresponding to a pixel format, or a
	   pixel format name.

       time_base
	   Specify the timebase assumed by the timestamps of the buffered
	   frames.

       frame_rate
	   Specify the frame rate expected for the video stream.

       pixel_aspect, sar
	   Specify the sample aspect ratio assumed by the video frames.

       sws_param
	   Specify the optional parameters to be used for the scale filter
	   which is automatically inserted when an input change is detected in
	   the input size or format.

       For example:

	       buffer=width=320:height=240:pix_fmt=yuv410p:time_base=1/24:sar=1

       will instruct the source to accept video frames with size 320x240 and
       with format "yuv410p", assuming 1/24 as the timestamps timebase and
       square pixels (1:1 sample aspect ratio).	 Since the pixel format with
       name "yuv410p" corresponds to the number 6 (check the enum
       AVPixelFormat definition in libavutil/pixfmt.h), this example
       corresponds to:

	       buffer=size=320x240:pixfmt=6:time_base=1/24:pixel_aspect=1/1

       Alternatively, the options can be specified as a flat string, but this
       syntax is deprecated:

       width:height:pix_fmt:time_base.num:time_base.den:pixel_aspect.num:pixel_aspect.den[:sws_param]

   cellauto
       Create a pattern generated by an elementary cellular automaton.

       The initial state of the cellular automaton can be defined through the
       filename, and pattern options. If such options are not specified an
       initial state is created randomly.

       At each new frame a new row in the video is filled with the result of
       the cellular automaton next generation. The behavior when the whole
       frame is filled is defined by the scroll option.

       This source accepts the following options:

       filename, f
	   Read the initial cellular automaton state, i.e. the starting row,
	   from the specified file.  In the file, each non-whitespace
	   character is considered an alive cell, a newline will terminate the
	   row, and further characters in the file will be ignored.

       pattern, p
	   Read the initial cellular automaton state, i.e. the starting row,
	   from the specified string.

	   Each non-whitespace character in the string is considered an alive
	   cell, a newline will terminate the row, and further characters in
	   the string will be ignored.

       rate, r
	   Set the video rate, that is the number of frames generated per
	   second.  Default is 25.

       random_fill_ratio, ratio
	   Set the random fill ratio for the initial cellular automaton row.
	   It is a floating point number value ranging from 0 to 1, defaults
	   to 1/PHI.

	   This option is ignored when a file or a pattern is specified.

       random_seed, seed
	   Set the seed for filling randomly the initial row, must be an
	   integer included between 0 and UINT32_MAX. If not specified, or if
	   explicitly set to -1, the filter will try to use a good random seed
	   on a best effort basis.

       rule
	   Set the cellular automaton rule, it is a number ranging from 0 to
	   255.	 Default value is 110.

       size, s
	   Set the size of the output video. For the syntax of this option,
	   check the "Video size" section in the ffmpeg-utils manual.

	   If filename or pattern is specified, the size is set by default to
	   the width of the specified initial state row, and the height is set
	   to width * PHI.

	   If size is set, it must contain the width of the specified pattern
	   string, and the specified pattern will be centered in the larger
	   row.

	   If a filename or a pattern string is not specified, the size value
	   defaults to "320x518" (used for a randomly generated initial
	   state).

       scroll
	   If set to 1, scroll the output upward when all the rows in the
	   output have been already filled. If set to 0, the new generated row
	   will be written over the top row just after the bottom row is
	   filled.  Defaults to 1.

       start_full, full
	   If set to 1, completely fill the output with generated rows before
	   outputting the first frame.	This is the default behavior, for
	   disabling set the value to 0.

       stitch
	   If set to 1, stitch the left and right row edges together.  This is
	   the default behavior, for disabling set the value to 0.

       Examples

       ·   Read the initial state from pattern, and specify an output of size
	   200x400.

		   cellauto=f=pattern:s=200x400

       ·   Generate a random initial row with a width of 200 cells, with a
	   fill ratio of 2/3:

		   cellauto=ratio=2/3:s=200x200

       ·   Create a pattern generated by rule 18 starting by a single alive
	   cell centered on an initial row with width 100:

		   cellauto=p=@s=100x400:full=0:rule=18

       ·   Specify a more elaborated initial pattern:

		   cellauto=p='@@ @ @@':s=100x400:full=0:rule=18

   mandelbrot
       Generate a Mandelbrot set fractal, and progressively zoom towards the
       point specified with start_x and start_y.

       This source accepts the following options:

       end_pts
	   Set the terminal pts value. Default value is 400.

       end_scale
	   Set the terminal scale value.  Must be a floating point value.
	   Default value is 0.3.

       inner
	   Set the inner coloring mode, that is the algorithm used to draw the
	   Mandelbrot fractal internal region.

	   It shall assume one of the following values:

	   black
	       Set black mode.

	   convergence
	       Show time until convergence.

	   mincol
	       Set color based on point closest to the origin of the
	       iterations.

	   period
	       Set period mode.

	   Default value is mincol.

       bailout
	   Set the bailout value. Default value is 10.0.

       maxiter
	   Set the maximum of iterations performed by the rendering algorithm.
	   Default value is 7189.

       outer
	   Set outer coloring mode.  It shall assume one of following values:

	   iteration_count
	       Set iteration cound mode.

	   normalized_iteration_count
	       set normalized iteration count mode.

	   Default value is normalized_iteration_count.

       rate, r
	   Set frame rate, expressed as number of frames per second. Default
	   value is "25".

       size, s
	   Set frame size. For the syntax of this option, check the "Video
	   size" section in the ffmpeg-utils manual. Default value is
	   "640x480".

       start_scale
	   Set the initial scale value. Default value is 3.0.

       start_x
	   Set the initial x position. Must be a floating point value between
	   -100 and 100. Default value is
	   -0.743643887037158704752191506114774.

       start_y
	   Set the initial y position. Must be a floating point value between
	   -100 and 100. Default value is
	   -0.131825904205311970493132056385139.

   mptestsrc
       Generate various test patterns, as generated by the MPlayer test
       filter.

       The size of the generated video is fixed, and is 256x256.  This source
       is useful in particular for testing encoding features.

       This source accepts the following options:

       rate, r
	   Specify the frame rate of the sourced video, as the number of
	   frames generated per second. It has to be a string in the format
	   frame_rate_num/frame_rate_den, an integer number, a float number or
	   a valid video frame rate abbreviation. The default value is "25".

       duration, d
	   Set the video duration of the sourced video. The accepted syntax
	   is:

		   [-]HH:MM:SS[.m...]
		   [-]S+[.m...]

	   See also the function "av_parse_time()".

	   If not specified, or the expressed duration is negative, the video
	   is supposed to be generated forever.

       test, t
	   Set the number or the name of the test to perform. Supported tests
	   are:

	   dc_luma
	   dc_chroma
	   freq_luma
	   freq_chroma
	   amp_luma
	   amp_chroma
	   cbp
	   mv
	   ring1
	   ring2
	   all

	   Default value is "all", which will cycle through the list of all
	   tests.

       For example the following:

	       testsrc=t=dc_luma

       will generate a "dc_luma" test pattern.

   frei0r_src
       Provide a frei0r source.

       To enable compilation of this filter you need to install the frei0r
       header and configure FFmpeg with "--enable-frei0r".

       This source accepts the following options:

       size
	   The size of the video to generate. For the syntax of this option,
	   check the "Video size" section in the ffmpeg-utils manual.

       framerate
	   Framerate of the generated video, may be a string of the form
	   num/den or a frame rate abbreviation.

       filter_name
	   The name to the frei0r source to load. For more information
	   regarding frei0r and how to set the parameters read the section
	   frei0r in the description of the video filters.

       filter_params
	   A '|'-separated list of parameters to pass to the frei0r source.

       For example, to generate a frei0r partik0l source with size 200x200 and
       frame rate 10 which is overlayed on the overlay filter main input:

	       frei0r_src=size=200x200:framerate=10:filter_name=partik0l:filter_params=1234 [overlay]; [in][overlay] overlay

   life
       Generate a life pattern.

       This source is based on a generalization of John Conway's life game.

       The sourced input represents a life grid, each pixel represents a cell
       which can be in one of two possible states, alive or dead. Every cell
       interacts with its eight neighbours, which are the cells that are
       horizontally, vertically, or diagonally adjacent.

       At each interaction the grid evolves according to the adopted rule,
       which specifies the number of neighbor alive cells which will make a
       cell stay alive or born. The rule option allows to specify the rule to
       adopt.

       This source accepts the following options:

       filename, f
	   Set the file from which to read the initial grid state. In the
	   file, each non-whitespace character is considered an alive cell,
	   and newline is used to delimit the end of each row.

	   If this option is not specified, the initial grid is generated
	   randomly.

       rate, r
	   Set the video rate, that is the number of frames generated per
	   second.  Default is 25.

       random_fill_ratio, ratio
	   Set the random fill ratio for the initial random grid. It is a
	   floating point number value ranging from 0 to 1, defaults to 1/PHI.
	   It is ignored when a file is specified.

       random_seed, seed
	   Set the seed for filling the initial random grid, must be an
	   integer included between 0 and UINT32_MAX. If not specified, or if
	   explicitly set to -1, the filter will try to use a good random seed
	   on a best effort basis.

       rule
	   Set the life rule.

	   A rule can be specified with a code of the kind "SNS/BNB", where NS
	   and NB are sequences of numbers in the range 0-8, NS specifies the
	   number of alive neighbor cells which make a live cell stay alive,
	   and NB the number of alive neighbor cells which make a dead cell to
	   become alive (i.e. to "born").  "s" and "b" can be used in place of
	   "S" and "B", respectively.

	   Alternatively a rule can be specified by an 18-bits integer. The 9
	   high order bits are used to encode the next cell state if it is
	   alive for each number of neighbor alive cells, the low order bits
	   specify the rule for "borning" new cells. Higher order bits encode
	   for an higher number of neighbor cells.  For example the number
	   6153 = "(12<<9)+9" specifies a stay alive rule of 12 and a born
	   rule of 9, which corresponds to "S23/B03".

	   Default value is "S23/B3", which is the original Conway's game of
	   life rule, and will keep a cell alive if it has 2 or 3 neighbor
	   alive cells, and will born a new cell if there are three alive
	   cells around a dead cell.

       size, s
	   Set the size of the output video. For the syntax of this option,
	   check the "Video size" section in the ffmpeg-utils manual.

	   If filename is specified, the size is set by default to the same
	   size of the input file. If size is set, it must contain the size
	   specified in the input file, and the initial grid defined in that
	   file is centered in the larger resulting area.

	   If a filename is not specified, the size value defaults to
	   "320x240" (used for a randomly generated initial grid).

       stitch
	   If set to 1, stitch the left and right grid edges together, and the
	   top and bottom edges also. Defaults to 1.

       mold
	   Set cell mold speed. If set, a dead cell will go from death_color
	   to mold_color with a step of mold. mold can have a value from 0 to
	   255.

       life_color
	   Set the color of living (or new born) cells.

       death_color
	   Set the color of dead cells. If mold is set, this is the first
	   color used to represent a dead cell.

       mold_color
	   Set mold color, for definitely dead and moldy cells.

	   For the syntax of these 3 color options, check the "Color" section
	   in the ffmpeg-utils manual.

       Examples

       ·   Read a grid from pattern, and center it on a grid of size 300x300
	   pixels:

		   life=f=pattern:s=300x300

       ·   Generate a random grid of size 200x200, with a fill ratio of 2/3:

		   life=ratio=2/3:s=200x200

       ·   Specify a custom rule for evolving a randomly generated grid:

		   life=rule=S14/B34

       ·   Full example with slow death effect (mold) using ffplay:

		   ffplay -f lavfi life=s=300x200:mold=10:r=60:ratio=0.1:death_color=#C83232:life_color=#00ff00,scale=1200:800:flags=16

   color, haldclutsrc, nullsrc, rgbtestsrc, smptebars, smptehdbars, testsrc
       The "color" source provides an uniformly colored input.

       The "haldclutsrc" source provides an identity Hald CLUT. See also
       haldclut filter.

       The "nullsrc" source returns unprocessed video frames. It is mainly
       useful to be employed in analysis / debugging tools, or as the source
       for filters which ignore the input data.

       The "rgbtestsrc" source generates an RGB test pattern useful for
       detecting RGB vs BGR issues. You should see a red, green and blue
       stripe from top to bottom.

       The "smptebars" source generates a color bars pattern, based on the
       SMPTE Engineering Guideline EG 1-1990.

       The "smptehdbars" source generates a color bars pattern, based on the
       SMPTE RP 219-2002.

       The "testsrc" source generates a test video pattern, showing a color
       pattern, a scrolling gradient and a timestamp. This is mainly intended
       for testing purposes.

       The sources accept the following options:

       color, c
	   Specify the color of the source, only available in the "color"
	   source. For the syntax of this option, check the "Color" section in
	   the ffmpeg-utils manual.

       level
	   Specify the level of the Hald CLUT, only available in the
	   "haldclutsrc" source. A level of "N" generates a picture of "N*N*N"
	   by "N*N*N" pixels to be used as identity matrix for 3D lookup
	   tables. Each component is coded on a "1/(N*N)" scale.

       size, s
	   Specify the size of the sourced video. For the syntax of this
	   option, check the "Video size" section in the ffmpeg-utils manual.
	   The default value is "320x240".

	   This option is not available with the "haldclutsrc" filter.

       rate, r
	   Specify the frame rate of the sourced video, as the number of
	   frames generated per second. It has to be a string in the format
	   frame_rate_num/frame_rate_den, an integer number, a float number or
	   a valid video frame rate abbreviation. The default value is "25".

       sar Set the sample aspect ratio of the sourced video.

       duration, d
	   Set the video duration of the sourced video. The accepted syntax
	   is:

		   [-]HH[:MM[:SS[.m...]]]
		   [-]S+[.m...]

	   See also the function "av_parse_time()".

	   If not specified, or the expressed duration is negative, the video
	   is supposed to be generated forever.

       decimals, n
	   Set the number of decimals to show in the timestamp, only available
	   in the "testsrc" source.

	   The displayed timestamp value will correspond to the original
	   timestamp value multiplied by the power of 10 of the specified
	   value. Default value is 0.

       For example the following:

	       testsrc=duration=5.3:size=qcif:rate=10

       will generate a video with a duration of 5.3 seconds, with size 176x144
       and a frame rate of 10 frames per second.

       The following graph description will generate a red source with an
       opacity of 0.2, with size "qcif" and a frame rate of 10 frames per
       second.

	       color=c=red@0.2:s=qcif:r=10

       If the input content is to be ignored, "nullsrc" can be used. The
       following command generates noise in the luminance plane by employing
       the "geq" filter:

	       nullsrc=s=256x256, geq=random(1)*255:128:128

       Commands

       The "color" source supports the following commands:

       c, color
	   Set the color of the created image. Accepts the same syntax of the
	   corresponding color option.

VIDEO SINKS
       Below is a description of the currently available video sinks.

   buffersink
       Buffer video frames, and make them available to the end of the filter
       graph.

       This sink is mainly intended for a programmatic use, in particular
       through the interface defined in libavfilter/buffersink.h or the
       options system.

       It accepts a pointer to an AVBufferSinkContext structure, which defines
       the incoming buffers' formats, to be passed as the opaque parameter to
       "avfilter_init_filter" for initialization.

   nullsink
       Null video sink, do absolutely nothing with the input video. It is
       mainly useful as a template and to be employed in analysis / debugging
       tools.

MULTIMEDIA FILTERS
       Below is a description of the currently available multimedia filters.

   avectorscope
       Convert input audio to a video output, representing the audio vector
       scope.

       The filter is used to measure the difference between channels of stereo
       audio stream. A monoaural signal, consisting of identical left and
       right signal, results in straight vertical line. Any stereo separation
       is visible as a deviation from this line, creating a Lissajous figure.
       If the straight (or deviation from it) but horizontal line appears this
       indicates that the left and right channels are out of phase.

       The filter accepts the following options:

       mode, m
	   Set the vectorscope mode.

	   Available values are:

	   lissajous
	       Lissajous rotated by 45 degrees.

	   lissajous_xy
	       Same as above but not rotated.

	   Default value is lissajous.

       size, s
	   Set the video size for the output. For the syntax of this option,
	   check the "Video size" section in the ffmpeg-utils manual. Default
	   value is "400x400".

       rate, r
	   Set the output frame rate. Default value is 25.

       rc
       gc
       bc  Specify the red, green and blue contrast. Default values are 40,
	   160 and 80.	Allowed range is "[0, 255]".

       rf
       gf
       bf  Specify the red, green and blue fade. Default values are 15, 10 and
	   5.  Allowed range is "[0, 255]".

       zoom
	   Set the zoom factor. Default value is 1. Allowed range is "[1,
	   10]".

       Examples

       ·   Complete example using ffplay:

		   ffplay -f lavfi 'amovie=input.mp3, asplit [a][out1];
				[a] avectorscope=zoom=1.3:rc=2:gc=200:bc=10:rf=1:gf=8:bf=7 [out0]'

   concat
       Concatenate audio and video streams, joining them together one after
       the other.

       The filter works on segments of synchronized video and audio streams.
       All segments must have the same number of streams of each type, and
       that will also be the number of streams at output.

       The filter accepts the following options:

       n   Set the number of segments. Default is 2.

       v   Set the number of output video streams, that is also the number of
	   video streams in each segment. Default is 1.

       a   Set the number of output audio streams, that is also the number of
	   video streams in each segment. Default is 0.

       unsafe
	   Activate unsafe mode: do not fail if segments have a different
	   format.

       The filter has v+a outputs: first v video outputs, then a audio
       outputs.

       There are nx(v+a) inputs: first the inputs for the first segment, in
       the same order as the outputs, then the inputs for the second segment,
       etc.

       Related streams do not always have exactly the same duration, for
       various reasons including codec frame size or sloppy authoring. For
       that reason, related synchronized streams (e.g. a video and its audio
       track) should be concatenated at once. The concat filter will use the
       duration of the longest stream in each segment (except the last one),
       and if necessary pad shorter audio streams with silence.

       For this filter to work correctly, all segments must start at timestamp
       0.

       All corresponding streams must have the same parameters in all
       segments; the filtering system will automatically select a common pixel
       format for video streams, and a common sample format, sample rate and
       channel layout for audio streams, but other settings, such as
       resolution, must be converted explicitly by the user.

       Different frame rates are acceptable but will result in variable frame
       rate at output; be sure to configure the output file to handle it.

       Examples

       ·   Concatenate an opening, an episode and an ending, all in bilingual
	   version (video in stream 0, audio in streams 1 and 2):

		   ffmpeg -i opening.mkv -i episode.mkv -i ending.mkv -filter_complex \
		     '[0:0] [0:1] [0:2] [1:0] [1:1] [1:2] [2:0] [2:1] [2:2]
		      concat=n=3:v=1:a=2 [v] [a1] [a2]' \
		     -map '[v]' -map '[a1]' -map '[a2]' output.mkv

       ·   Concatenate two parts, handling audio and video separately, using
	   the (a)movie sources, and adjusting the resolution:

		   movie=part1.mp4, scale=512:288 [v1] ; amovie=part1.mp4 [a1] ;
		   movie=part2.mp4, scale=512:288 [v2] ; amovie=part2.mp4 [a2] ;
		   [v1] [v2] concat [outv] ; [a1] [a2] concat=v=0:a=1 [outa]

	   Note that a desync will happen at the stitch if the audio and video
	   streams do not have exactly the same duration in the first file.

   ebur128
       EBU R128 scanner filter. This filter takes an audio stream as input and
       outputs it unchanged. By default, it logs a message at a frequency of
       10Hz with the Momentary loudness (identified by "M"), Short-term
       loudness ("S"), Integrated loudness ("I") and Loudness Range ("LRA").

       The filter also has a video output (see the video option) with a real
       time graph to observe the loudness evolution. The graphic contains the
       logged message mentioned above, so it is not printed anymore when this
       option is set, unless the verbose logging is set. The main graphing
       area contains the short-term loudness (3 seconds of analysis), and the
       gauge on the right is for the momentary loudness (400 milliseconds).

       More information about the Loudness Recommendation EBU R128 on
       <http://tech.ebu.ch/loudness>.

       The filter accepts the following options:

       video
	   Activate the video output. The audio stream is passed unchanged
	   whether this option is set or no. The video stream will be the
	   first output stream if activated. Default is 0.

       size
	   Set the video size. This option is for video only. For the syntax
	   of this option, check the "Video size" section in the ffmpeg-utils
	   manual. Default and minimum resolution is "640x480".

       meter
	   Set the EBU scale meter. Default is 9. Common values are 9 and 18,
	   respectively for EBU scale meter +9 and EBU scale meter +18. Any
	   other integer value between this range is allowed.

       metadata
	   Set metadata injection. If set to 1, the audio input will be
	   segmented into 100ms output frames, each of them containing various
	   loudness information in metadata.  All the metadata keys are
	   prefixed with "lavfi.r128.".

	   Default is 0.

       framelog
	   Force the frame logging level.

	   Available values are:

	   info
	       information logging level

	   verbose
	       verbose logging level

	   By default, the logging level is set to info. If the video or the
	   metadata options are set, it switches to verbose.

       Examples

       ·   Real-time graph using ffplay, with a EBU scale meter +18:

		   ffplay -f lavfi -i "amovie=input.mp3,ebur128=video=1:meter=18 [out0][out1]"

       ·   Run an analysis with ffmpeg:

		   ffmpeg -nostats -i input.mp3 -filter_complex ebur128 -f null -

   interleave, ainterleave
       Temporally interleave frames from several inputs.

       "interleave" works with video inputs, "ainterleave" with audio.

       These filters read frames from several inputs and send the oldest
       queued frame to the output.

       Input streams must have a well defined, monotonically increasing frame
       timestamp values.

       In order to submit one frame to output, these filters need to enqueue
       at least one frame for each input, so they cannot work in case one
       input is not yet terminated and will not receive incoming frames.

       For example consider the case when one input is a "select" filter which
       always drop input frames. The "interleave" filter will keep reading
       from that input, but it will never be able to send new frames to output
       until the input will send an end-of-stream signal.

       Also, depending on inputs synchronization, the filters will drop frames
       in case one input receives more frames than the other ones, and the
       queue is already filled.

       These filters accept the following options:

       nb_inputs, n
	   Set the number of different inputs, it is 2 by default.

       Examples

       ·   Interleave frames belonging to different streams using ffmpeg:

		   ffmpeg -i bambi.avi -i pr0n.mkv -filter_complex "[0:v][1:v] interleave" out.avi

       ·   Add flickering blur effect:

		   select='if(gt(random(0), 0.2), 1, 2)':n=2 [tmp], boxblur=2:2, [tmp] interleave

   perms, aperms
       Set read/write permissions for the output frames.

       These filters are mainly aimed at developers to test direct path in the
       following filter in the filtergraph.

       The filters accept the following options:

       mode
	   Select the permissions mode.

	   It accepts the following values:

	   none
	       Do nothing. This is the default.

	   ro  Set all the output frames read-only.

	   rw  Set all the output frames directly writable.

	   toggle
	       Make the frame read-only if writable, and writable if read-
	       only.

	   random
	       Set each output frame read-only or writable randomly.

       seed
	   Set the seed for the random mode, must be an integer included
	   between 0 and "UINT32_MAX". If not specified, or if explicitly set
	   to "-1", the filter will try to use a good random seed on a best
	   effort basis.

       Note: in case of auto-inserted filter between the permission filter and
       the following one, the permission might not be received as expected in
       that following filter. Inserting a format or aformat filter before the
       perms/aperms filter can avoid this problem.

   select, aselect
       Select frames to pass in output.

       This filter accepts the following options:

       expr, e
	   Set expression, which is evaluated for each input frame.

	   If the expression is evaluated to zero, the frame is discarded.

	   If the evaluation result is negative or NaN, the frame is sent to
	   the first output; otherwise it is sent to the output with index
	   "ceil(val)-1", assuming that the input index starts from 0.

	   For example a value of 1.2 corresponds to the output with index
	   "ceil(1.2)-1 = 2-1 = 1", that is the second output.

       outputs, n
	   Set the number of outputs. The output to which to send the selected
	   frame is based on the result of the evaluation. Default value is 1.

       The expression can contain the following constants:

       n   the sequential number of the filtered frame, starting from 0

       selected_n
	   the sequential number of the selected frame, starting from 0

       prev_selected_n
	   the sequential number of the last selected frame, NAN if undefined

       TB  timebase of the input timestamps

       pts the PTS (Presentation TimeStamp) of the filtered video frame,
	   expressed in TB units, NAN if undefined

       t   the PTS (Presentation TimeStamp) of the filtered video frame,
	   expressed in seconds, NAN if undefined

       prev_pts
	   the PTS of the previously filtered video frame, NAN if undefined

       prev_selected_pts
	   the PTS of the last previously filtered video frame, NAN if
	   undefined

       prev_selected_t
	   the PTS of the last previously selected video frame, NAN if
	   undefined

       start_pts
	   the PTS of the first video frame in the video, NAN if undefined

       start_t
	   the time of the first video frame in the video, NAN if undefined

       pict_type (video only)
	   the type of the filtered frame, can assume one of the following
	   values:

	   I
	   P
	   B
	   S
	   SI
	   SP
	   BI
       interlace_type (video only)
	   the frame interlace type, can assume one of the following values:

	   PROGRESSIVE
	       the frame is progressive (not interlaced)

	   TOPFIRST
	       the frame is top-field-first

	   BOTTOMFIRST
	       the frame is bottom-field-first

       consumed_sample_n (audio only)
	   the number of selected samples before the current frame

       samples_n (audio only)
	   the number of samples in the current frame

       sample_rate (audio only)
	   the input sample rate

       key 1 if the filtered frame is a key-frame, 0 otherwise

       pos the position in the file of the filtered frame, -1 if the
	   information is not available (e.g. for synthetic video)

       scene (video only)
	   value between 0 and 1 to indicate a new scene; a low value reflects
	   a low probability for the current frame to introduce a new scene,
	   while a higher value means the current frame is more likely to be
	   one (see the example below)

       The default value of the select expression is "1".

       Examples

       ·   Select all frames in input:

		   select

	   The example above is the same as:

		   select=1

       ·   Skip all frames:

		   select=0

       ·   Select only I-frames:

		   select='eq(pict_type\,I)'

       ·   Select one frame every 100:

		   select='not(mod(n\,100))'

       ·   Select only frames contained in the 10-20 time interval:

		   select=between(t\,10\,20)

       ·   Select only I frames contained in the 10-20 time interval:

		   select=between(t\,10\,20)*eq(pict_type\,I)

       ·   Select frames with a minimum distance of 10 seconds:

		   select='isnan(prev_selected_t)+gte(t-prev_selected_t\,10)'

       ·   Use aselect to select only audio frames with samples number > 100:

		   aselect='gt(samples_n\,100)'

       ·   Create a mosaic of the first scenes:

		   ffmpeg -i video.avi -vf select='gt(scene\,0.4)',scale=160:120,tile -frames:v 1 preview.png

	   Comparing scene against a value between 0.3 and 0.5 is generally a
	   sane choice.

       ·   Send even and odd frames to separate outputs, and compose them:

		   select=n=2:e='mod(n, 2)+1' [odd][even]; [odd] pad=h=2*ih [tmp]; [tmp][even] overlay=y=h

   sendcmd, asendcmd
       Send commands to filters in the filtergraph.

       These filters read commands to be sent to other filters in the
       filtergraph.

       "sendcmd" must be inserted between two video filters, "asendcmd" must
       be inserted between two audio filters, but apart from that they act the
       same way.

       The specification of commands can be provided in the filter arguments
       with the commands option, or in a file specified by the filename
       option.

       These filters accept the following options:

       commands, c
	   Set the commands to be read and sent to the other filters.

       filename, f
	   Set the filename of the commands to be read and sent to the other
	   filters.

       Commands syntax

       A commands description consists of a sequence of interval
       specifications, comprising a list of commands to be executed when a
       particular event related to that interval occurs. The occurring event
       is typically the current frame time entering or leaving a given time
       interval.

       An interval is specified by the following syntax:

	       <START>[-<END>] <COMMANDS>;

       The time interval is specified by the START and END times.  END is
       optional and defaults to the maximum time.

       The current frame time is considered within the specified interval if
       it is included in the interval [START, END), that is when the time is
       greater or equal to START and is lesser than END.

       COMMANDS consists of a sequence of one or more command specifications,
       separated by ",", relating to that interval.  The syntax of a command
       specification is given by:

	       [<FLAGS>] <TARGET> <COMMAND> <ARG>

       FLAGS is optional and specifies the type of events relating to the time
       interval which enable sending the specified command, and must be a non-
       null sequence of identifier flags separated by "+" or "|" and enclosed
       between "[" and "]".

       The following flags are recognized:

       enter
	   The command is sent when the current frame timestamp enters the
	   specified interval. In other words, the command is sent when the
	   previous frame timestamp was not in the given interval, and the
	   current is.

       leave
	   The command is sent when the current frame timestamp leaves the
	   specified interval. In other words, the command is sent when the
	   previous frame timestamp was in the given interval, and the current
	   is not.

       If FLAGS is not specified, a default value of "[enter]" is assumed.

       TARGET specifies the target of the command, usually the name of the
       filter class or a specific filter instance name.

       COMMAND specifies the name of the command for the target filter.

       ARG is optional and specifies the optional list of argument for the
       given COMMAND.

       Between one interval specification and another, whitespaces, or
       sequences of characters starting with "#" until the end of line, are
       ignored and can be used to annotate comments.

       A simplified BNF description of the commands specification syntax
       follows:

	       <COMMAND_FLAG>  ::= "enter" | "leave"
	       <COMMAND_FLAGS> ::= <COMMAND_FLAG> [(+|"|")<COMMAND_FLAG>]
	       <COMMAND>       ::= ["[" <COMMAND_FLAGS> "]"] <TARGET> <COMMAND> [<ARG>]
	       <COMMANDS>      ::= <COMMAND> [,<COMMANDS>]
	       <INTERVAL>      ::= <START>[-<END>] <COMMANDS>
	       <INTERVALS>     ::= <INTERVAL>[;<INTERVALS>]

       Examples

       ·   Specify audio tempo change at second 4:

		   asendcmd=c='4.0 atempo tempo 1.5',atempo

       ·   Specify a list of drawtext and hue commands in a file.

		   # show text in the interval 5-10
		   5.0-10.0 [enter] drawtext reinit 'fontfile=FreeSerif.ttf:text=hello world',
			    [leave] drawtext reinit 'fontfile=FreeSerif.ttf:text=';

		   # desaturate the image in the interval 15-20
		   15.0-20.0 [enter] hue s 0,
			     [enter] drawtext reinit 'fontfile=FreeSerif.ttf:text=nocolor',
			     [leave] hue s 1,
			     [leave] drawtext reinit 'fontfile=FreeSerif.ttf:text=color';

		   # apply an exponential saturation fade-out effect, starting from time 25
		   25 [enter] hue s exp(25-t)

	   A filtergraph allowing to read and process the above command list
	   stored in a file test.cmd, can be specified with:

		   sendcmd=f=test.cmd,drawtext=fontfile=FreeSerif.ttf:text='',hue

   setpts, asetpts
       Change the PTS (presentation timestamp) of the input frames.

       "setpts" works on video frames, "asetpts" on audio frames.

       This filter accepts the following options:

       expr
	   The expression which is evaluated for each frame to construct its
	   timestamp.

       The expression is evaluated through the eval API and can contain the
       following constants:

       FRAME_RATE
	   frame rate, only defined for constant frame-rate video

       PTS the presentation timestamp in input

       N   the count of the input frame for video or the number of consumed
	   samples, not including the current frame for audio, starting from
	   0.

       NB_CONSUMED_SAMPLES
	   the number of consumed samples, not including the current frame
	   (only audio)

       NB_SAMPLES, S
	   the number of samples in the current frame (only audio)

       SAMPLE_RATE, SR
	   audio sample rate

       STARTPTS
	   the PTS of the first frame

       STARTT
	   the time in seconds of the first frame

       INTERLACED
	   tell if the current frame is interlaced

       T   the time in seconds of the current frame

       POS original position in the file of the frame, or undefined if
	   undefined for the current frame

       PREV_INPTS
	   previous input PTS

       PREV_INT
	   previous input time in seconds

       PREV_OUTPTS
	   previous output PTS

       PREV_OUTT
	   previous output time in seconds

       RTCTIME
	   wallclock (RTC) time in microseconds. This is deprecated, use
	   time(0) instead.

       RTCSTART
	   wallclock (RTC) time at the start of the movie in microseconds

       TB  timebase of the input timestamps

       Examples

       ·   Start counting PTS from zero

		   setpts=PTS-STARTPTS

       ·   Apply fast motion effect:

		   setpts=0.5*PTS

       ·   Apply slow motion effect:

		   setpts=2.0*PTS

       ·   Set fixed rate of 25 frames per second:

		   setpts=N/(25*TB)

       ·   Set fixed rate 25 fps with some jitter:

		   setpts='1/(25*TB) * (N + 0.05 * sin(N*2*PI/25))'

       ·   Apply an offset of 10 seconds to the input PTS:

		   setpts=PTS+10/TB

       ·   Generate timestamps from a "live source" and rebase onto the
	   current timebase:

		   setpts='(RTCTIME - RTCSTART) / (TB * 1000000)'

       ·   Generate timestamps by counting samples:

		   asetpts=N/SR/TB

   settb, asettb
       Set the timebase to use for the output frames timestamps.  It is mainly
       useful for testing timebase configuration.

       This filter accepts the following options:

       expr, tb
	   The expression which is evaluated into the output timebase.

       The value for tb is an arithmetic expression representing a rational.
       The expression can contain the constants "AVTB" (the default timebase),
       "intb" (the input timebase) and "sr" (the sample rate, audio only).
       Default value is "intb".

       Examples

       ·   Set the timebase to 1/25:

		   settb=expr=1/25

       ·   Set the timebase to 1/10:

		   settb=expr=0.1

       ·   Set the timebase to 1001/1000:

		   settb=1+0.001

       ·   Set the timebase to 2*intb:

		   settb=2*intb

       ·   Set the default timebase value:

		   settb=AVTB

   showspectrum
       Convert input audio to a video output, representing the audio frequency
       spectrum.

       The filter accepts the following options:

       size, s
	   Specify the video size for the output. For the syntax of this
	   option, check the "Video size" section in the ffmpeg-utils manual.
	   Default value is "640x512".

       slide
	   Specify if the spectrum should slide along the window. Default
	   value is 0.

       mode
	   Specify display mode.

	   It accepts the following values:

	   combined
	       all channels are displayed in the same row

	   separate
	       all channels are displayed in separate rows

	   Default value is combined.

       color
	   Specify display color mode.

	   It accepts the following values:

	   channel
	       each channel is displayed in a separate color

	   intensity
	       each channel is is displayed using the same color scheme

	   Default value is channel.

       scale
	   Specify scale used for calculating intensity color values.

	   It accepts the following values:

	   lin linear

	   sqrt
	       square root, default

	   cbrt
	       cubic root

	   log logarithmic

	   Default value is sqrt.

       saturation
	   Set saturation modifier for displayed colors. Negative values
	   provide alternative color scheme. 0 is no saturation at all.
	   Saturation must be in [-10.0, 10.0] range.  Default value is 1.

       The usage is very similar to the showwaves filter; see the examples in
       that section.

       Examples

       ·   Large window with logarithmic color scaling:

		   showspectrum=s=1280x480:scale=log

       ·   Complete example for a colored and sliding spectrum per channel
	   using ffplay:

		   ffplay -f lavfi 'amovie=input.mp3, asplit [a][out1];
				[a] showspectrum=mode=separate:color=intensity:slide=1:scale=cbrt [out0]'

   showwaves
       Convert input audio to a video output, representing the samples waves.

       The filter accepts the following options:

       size, s
	   Specify the video size for the output. For the syntax of this
	   option, check the "Video size" section in the ffmpeg-utils manual.
	   Default value is "600x240".

       mode
	   Set display mode.

	   Available values are:

	   point
	       Draw a point for each sample.

	   line
	       Draw a vertical line for each sample.

	   Default value is "point".

       n   Set the number of samples which are printed on the same column. A
	   larger value will decrease the frame rate. Must be a positive
	   integer. This option can be set only if the value for rate is not
	   explicitly specified.

       rate, r
	   Set the (approximate) output frame rate. This is done by setting
	   the option n. Default value is "25".

       Examples

       ·   Output the input file audio and the corresponding video
	   representation at the same time:

		   amovie=a.mp3,asplit[out0],showwaves[out1]

       ·   Create a synthetic signal and show it with showwaves, forcing a
	   frame rate of 30 frames per second:

		   aevalsrc=sin(1*2*PI*t)*sin(880*2*PI*t):cos(2*PI*200*t),asplit[out0],showwaves=r=30[out1]

   split, asplit
       Split input into several identical outputs.

       "asplit" works with audio input, "split" with video.

       The filter accepts a single parameter which specifies the number of
       outputs. If unspecified, it defaults to 2.

       Examples

       ·   Create two separate outputs from the same input:

		   [in] split [out0][out1]

       ·   To create 3 or more outputs, you need to specify the number of
	   outputs, like in:

		   [in] asplit=3 [out0][out1][out2]

       ·   Create two separate outputs from the same input, one cropped and
	   one padded:

		   [in] split [splitout1][splitout2];
		   [splitout1] crop=100:100:0:0	   [cropout];
		   [splitout2] pad=200:200:100:100 [padout];

       ·   Create 5 copies of the input audio with ffmpeg:

		   ffmpeg -i INPUT -filter_complex asplit=5 OUTPUT

   zmq, azmq
       Receive commands sent through a libzmq client, and forward them to
       filters in the filtergraph.

       "zmq" and "azmq" work as a pass-through filters. "zmq" must be inserted
       between two video filters, "azmq" between two audio filters.

       To enable these filters you need to install the libzmq library and
       headers and configure FFmpeg with "--enable-libzmq".

       For more information about libzmq see: <http://www.zeromq.org/>

       The "zmq" and "azmq" filters work as a libzmq server, which receives
       messages sent through a network interface defined by the bind_address
       option.

       The received message must be in the form:

	       <TARGET> <COMMAND> [<ARG>]

       TARGET specifies the target of the command, usually the name of the
       filter class or a specific filter instance name.

       COMMAND specifies the name of the command for the target filter.

       ARG is optional and specifies the optional argument list for the given
       COMMAND.

       Upon reception, the message is processed and the corresponding command
       is injected into the filtergraph. Depending on the result, the filter
       will send a reply to the client, adopting the format:

	       <ERROR_CODE> <ERROR_REASON>
	       <MESSAGE>

       MESSAGE is optional.

       Examples

       Look at tools/zmqsend for an example of a zmq client which can be used
       to send commands processed by these filters.

       Consider the following filtergraph generated by ffplay

	       ffplay -dumpgraph 1 -f lavfi "
	       color=s=100x100:c=red  [l];
	       color=s=100x100:c=blue [r];
	       nullsrc=s=200x100, zmq [bg];
	       [bg][l]	 overlay      [bg+l];
	       [bg+l][r] overlay=x=100 "

       To change the color of the left side of the video, the following
       command can be used:

	       echo Parsed_color_0 c yellow | tools/zmqsend

       To change the right side:

	       echo Parsed_color_1 c pink | tools/zmqsend

MULTIMEDIA SOURCES
       Below is a description of the currently available multimedia sources.

   amovie
       This is the same as movie source, except it selects an audio stream by
       default.

   movie
       Read audio and/or video stream(s) from a movie container.

       This filter accepts the following options:

       filename
	   The name of the resource to read (not necessarily a file but also a
	   device or a stream accessed through some protocol).

       format_name, f
	   Specifies the format assumed for the movie to read, and can be
	   either the name of a container or an input device. If not specified
	   the format is guessed from movie_name or by probing.

       seek_point, sp
	   Specifies the seek point in seconds, the frames will be output
	   starting from this seek point, the parameter is evaluated with
	   "av_strtod" so the numerical value may be suffixed by an IS
	   postfix. Default value is "0".

       streams, s
	   Specifies the streams to read. Several streams can be specified,
	   separated by "+". The source will then have as many outputs, in the
	   same order. The syntax is explained in the ``Stream specifiers''
	   section in the ffmpeg manual. Two special names, "dv" and "da"
	   specify respectively the default (best suited) video and audio
	   stream. Default is "dv", or "da" if the filter is called as
	   "amovie".

       stream_index, si
	   Specifies the index of the video stream to read. If the value is
	   -1, the best suited video stream will be automatically selected.
	   Default value is "-1". Deprecated. If the filter is called
	   "amovie", it will select audio instead of video.

       loop
	   Specifies how many times to read the stream in sequence.  If the
	   value is less than 1, the stream will be read again and again.
	   Default value is "1".

	   Note that when the movie is looped the source timestamps are not
	   changed, so it will generate non monotonically increasing
	   timestamps.

       This filter allows to overlay a second video on top of main input of a
       filtergraph as shown in this graph:

	       input -----------> deltapts0 --> overlay --> output
						   ^
						   |
	       movie --> scale--> deltapts1 -------+

       Examples

       ·   Skip 3.2 seconds from the start of the avi file in.avi, and overlay
	   it on top of the input labelled as "in":

		   movie=in.avi:seek_point=3.2, scale=180:-1, setpts=PTS-STARTPTS [over];
		   [in] setpts=PTS-STARTPTS [main];
		   [main][over] overlay=16:16 [out]

       ·   Read from a video4linux2 device, and overlay it on top of the input
	   labelled as "in":

		   movie=/dev/video0:f=video4linux2, scale=180:-1, setpts=PTS-STARTPTS [over];
		   [in] setpts=PTS-STARTPTS [main];
		   [main][over] overlay=16:16 [out]

       ·   Read the first video stream and the audio stream with id 0x81 from
	   dvd.vob; the video is connected to the pad named "video" and the
	   audio is connected to the pad named "audio":

		   movie=dvd.vob:s=v:0+#0x81 [video] [audio]

SEE ALSO
       ffmpeg(1), ffplay(1), ffprobe(1), ffserver(1), libavfilter(3)

AUTHORS
       The FFmpeg developers.

       For details about the authorship, see the Git history of the project
       (git://source.ffmpeg.org/ffmpeg), e.g. by typing the command git log in
       the FFmpeg source directory, or browsing the online repository at
       <http://source.ffmpeg.org>.

       Maintainers for the specific components are listed in the file
       MAINTAINERS in the source code tree.

				  2014-02-24		     FFMPEG-FILTERS(1)
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