AVSERVER(1)AVSERVER(1)NAME
avserver - avserver video server
SYNOPSIS
avserver [options]
DESCRIPTION
WARNING: avserver is unmaintained, largely broken and in need of a
complete rewrite. It probably won't work for you. Use at your own risk.
avserver is a streaming server for both audio and video. It supports
several live feeds, streaming from files and time shifting on live
feeds (you can seek to positions in the past on each live feed,
provided you specify a big enough feed storage in avserver.conf).
avserver runs in daemon mode by default; that is, it puts itself in the
background and detaches from its TTY, unless it is launched in debug
mode or a NoDaemon option is specified in the configuration file.
This documentation covers only the streaming aspects of avserver /
avconv. All questions about parameters for avconv, codec questions,
etc. are not covered here. Read avconv.html for more information.
How does it work?
avserver receives prerecorded files or FFM streams from some avconv
instance as input, then streams them over RTP/RTSP/HTTP.
An avserver instance will listen on some port as specified in the
configuration file. You can launch one or more instances of avconv and
send one or more FFM streams to the port where avserver is expecting to
receive them. Alternately, you can make avserver launch such avconv
instances at startup.
Input streams are called feeds, and each one is specified by a <Feed>
section in the configuration file.
For each feed you can have different output streams in various formats,
each one specified by a <Stream> section in the configuration file.
Status stream
avserver supports an HTTP interface which exposes the current status of
the server.
Simply point your browser to the address of the special status stream
specified in the configuration file.
For example if you have:
<Stream status.html>
Format status
# Only allow local people to get the status
ACL allow localhost
ACL allow 192.168.0.0 192.168.255.255
</Stream>
then the server will post a page with the status information when the
special stream status.html is requested.
What can this do?
When properly configured and running, you can capture video and audio
in real time from a suitable capture card, and stream it out over the
Internet to either Windows Media Player or RealAudio player (with some
restrictions).
It can also stream from files, though that is currently broken. Very
often, a web server can be used to serve up the files just as well.
It can stream prerecorded video from .ffm files, though it is somewhat
tricky to make it work correctly.
What do I need?
I use Linux on a 900 MHz Duron with a cheapo Bt848 based TV capture
card. I'm using stock Linux 2.4.17 with the stock drivers. [Actually
that isn't true, I needed some special drivers for my motherboard-based
sound card.]
I understand that FreeBSD systems work just fine as well.
How do I make it work?
First, build the kit. It *really* helps to have installed LAME first.
Then when you run the avserver ./configure, make sure that you have the
"--enable-libmp3lame" flag turned on.
LAME is important as it allows for streaming audio to Windows Media
Player. Don't ask why the other audio types do not work.
As a simple test, just run the following two command lines where
INPUTFILE is some file which you can decode with avconv:
./avserver -f doc/avserver.conf &
./avconv -i INPUTFILE http://localhost:8090/feed1.ffm
At this point you should be able to go to your Windows machine and fire
up Windows Media Player (WMP). Go to Open URL and enter
http://<linuxbox>:8090/test.asf
You should (after a short delay) see video and hear audio.
WARNING: trying to stream test1.mpg doesn't work with WMP as it tries
to transfer the entire file before starting to play. The same is true
of AVI files.
What happens next?
You should edit the avserver.conf file to suit your needs (in terms of
frame rates etc). Then install avserver and avconv, write a script to
start them up, and off you go.
Troubleshooting
I don't hear any audio, but video is fine.
Maybe you didn't install LAME, or got your ./configure statement wrong.
Check the avconv output to see if a line referring to MP3 is present.
If not, then your configuration was incorrect. If it is, then maybe
your wiring is not set up correctly. Maybe the sound card is not
getting data from the right input source. Maybe you have a really awful
audio interface (like I do) that only captures in stereo and also
requires that one channel be flipped. If you are one of these people,
then export 'AUDIO_FLIP_LEFT=1' before starting avconv.
The audio and video lose sync after a while.
Yes, they do.
After a long while, the video update rate goes way down in WMP.
Yes, it does. Who knows why?
WMP 6.4 behaves differently to WMP 7.
Yes, it does. Any thoughts on this would be gratefully received. These
differences extend to embedding WMP into a web page. [There are two
object IDs that you can use: The old one, which does not play well, and
the new one, which does (both tested on the same system). However, I
suspect that the new one is not available unless you have installed WMP
7].
What else can it do?
You can replay video from .ffm files that was recorded earlier.
However, there are a number of caveats, including the fact that the
avserver parameters must match the original parameters used to record
the file. If they do not, then avserver deletes the file before
recording into it. (Now that I write this, it seems broken).
You can fiddle with many of the codec choices and encoding parameters,
and there are a bunch more parameters that you cannot control. Post a
message to the mailing list if there are some 'must have' parameters.
Look in avserver.conf for a list of the currently available controls.
It will automatically generate the ASX or RAM files that are often used
in browsers. These files are actually redirections to the underlying
ASF or RM file. The reason for this is that the browser often fetches
the entire file before starting up the external viewer. The redirection
files are very small and can be transferred quickly. [The stream itself
is often 'infinite' and thus the browser tries to download it and never
finishes.]
Tips
* When you connect to a live stream, most players (WMP, RA, etc) want
to buffer a certain number of seconds of material so that they can
display the signal continuously. However, avserver (by default) starts
sending data in realtime. This means that there is a pause of a few
seconds while the buffering is being done by the player. The good news
is that this can be cured by adding a '?buffer=5' to the end of the
URL. This means that the stream should start 5 seconds in the past --
and so the first 5 seconds of the stream are sent as fast as the
network will allow. It will then slow down to real time. This
noticeably improves the startup experience.
You can also add a 'Preroll 15' statement into the avserver.conf that
will add the 15 second prebuffering on all requests that do not
otherwise specify a time. In addition, avserver will skip frames until
a key_frame is found. This further reduces the startup delay by not
transferring data that will be discarded.
* You may want to adjust the MaxBandwidth in the avserver.conf to limit
the amount of bandwidth consumed by live streams.
Why does the ?buffer / Preroll stop working after a time?
It turns out that (on my machine at least) the number of frames
successfully grabbed is marginally less than the number that ought to
be grabbed. This means that the timestamp in the encoded data stream
gets behind realtime. This means that if you say 'Preroll 10', then
when the stream gets 10 or more seconds behind, there is no Preroll
left.
Fixing this requires a change in the internals of how timestamps are
handled.
Does the "?date=" stuff work.
Yes (subject to the limitation outlined above). Also note that whenever
you start avserver, it deletes the ffm file (if any parameters have
changed), thus wiping out what you had recorded before.
The format of the "?date=xxxxxx" is fairly flexible. You should use one
of the following formats (the 'T' is literal):
* YYYY-MM-DDTHH:MM:SS (localtime)
* YYYY-MM-DDTHH:MM:SSZ (UTC)
You can omit the YYYY-MM-DD, and then it refers to the current day.
However note that ?date=16:00:00 refers to 16:00 on the current day --
this may be in the future and so is unlikely to be useful.
You use this by adding the ?date= to the end of the URL for the stream.
For example: http://localhost:8080/test.asf?date=2002-07-26T23:05:00.
OPTIONS
All the numerical options, if not specified otherwise, accept in input
a string representing a number, which may contain one of the
International System number postfixes, for example 'K', 'M', 'G'. If
'i' is appended after the postfix, powers of 2 are used instead of
powers of 10. The 'B' postfix multiplies the value for 8, and can be
appended after another postfix or used alone. This allows using for
example 'KB', 'MiB', 'G' and 'B' as postfix.
Options which do not take arguments are boolean options, and set the
corresponding value to true. They can be set to false by prefixing with
"no" the option name, for example using "-nofoo" in the command line
will set to false the boolean option with name "foo".
Stream specifiers
Some options are applied per-stream, e.g. bitrate or codec. Stream
specifiers are used to precisely specify which stream(s) does a given
option belong to.
A stream specifier is a string generally appended to the option name
and separated from it by a colon. E.g. "-codec:a:1 ac3" option contains
"a:1" stream specifer, which matches the second audio stream. Therefore
it would select the ac3 codec for the second audio stream.
A stream specifier can match several stream, the option is then applied
to all of them. E.g. the stream specifier in "-b:a 128k" matches all
audio streams.
An empty stream specifier matches all streams, for example "-codec
copy" or "-codec: copy" would copy all the streams without reencoding.
Possible forms of stream specifiers are:
stream_index
Matches the stream with this index. E.g. "-threads:1 4" would set
the thread count for the second stream to 4.
stream_type[:stream_index]
stream_type is one of: 'v' for video, 'a' for audio, 's' for
subtitle, 'd' for data and 't' for attachments. If stream_index is
given, then matches stream number stream_index of this type.
Otherwise matches all streams of this type.
p:program_id[:stream_index]
If stream_index is given, then matches stream number stream_index
in program with id program_id. Otherwise matches all streams in
this program.
Generic options
These options are shared amongst the av* tools.
-L Show license.
-h, -?, -help, --help
Show help.
-version
Show version.
-formats
Show available formats.
The fields preceding the format names have the following meanings:
D Decoding available
E Encoding available
-codecs
Show available codecs.
The fields preceding the codec names have the following meanings:
D Decoding available
E Encoding available
V/A/S
Video/audio/subtitle codec
S Codec supports slices
D Codec supports direct rendering
T Codec can handle input truncated at random locations instead of
only at frame boundaries
-bsfs
Show available bitstream filters.
-protocols
Show available protocols.
-filters
Show available libavfilter filters.
-pix_fmts
Show available pixel formats.
-sample_fmts
Show available sample formats.
-loglevel loglevel | -v loglevel
Set the logging level used by the library. loglevel is a number or
a string containing one of the following values:
quiet
panic
fatal
error
warning
info
verbose
debug
By default the program logs to stderr, if coloring is supported by
the terminal, colors are used to mark errors and warnings. Log
coloring can be disabled setting the environment variable
AV_LOG_FORCE_NOCOLOR or NO_COLOR, or can be forced setting the
environment variable AV_LOG_FORCE_COLOR. The use of the
environment variable NO_COLOR is deprecated and will be dropped in
a following Libav version.
AVOptions
These options are provided directly by the libavformat, libavdevice and
libavcodec libraries. To see the list of available AVOptions, use the
-help option. They are separated into two categories:
generic
These options can be set for any container, codec or device.
Generic options are listed under AVFormatContext options for
containers/devices and under AVCodecContext options for codecs.
private
These options are specific to the given container, device or codec.
Private options are listed under their corresponding
containers/devices/codecs.
For example to write an ID3v2.3 header instead of a default ID3v2.4 to
an MP3 file, use the id3v2_version private option of the MP3 muxer:
avconv -i input.flac -id3v2_version 3 out.mp3
All codec AVOptions are obviously per-stream, so the chapter on stream
specifiers applies to them
Note -nooption syntax cannot be used for boolean AVOptions, use -option
0/-option 1.
Note2 old undocumented way of specifying per-stream AVOptions by
prepending v/a/s to the options name is now obsolete and will be
removed soon.
Main options
-f configfile
Use configfile instead of /etc/avserver.conf.
-n Enable no-launch mode. This option disables all the Launch
directives within the various <Stream> sections. Since avserver
will not launch any avconv instances, you will have to launch them
manually.
-d Enable debug mode. This option increases log verbosity, directs log
messages to stdout and causes avserver to run in the foreground
rather than as a daemon.
SEE ALSOavconv(1), avplay(1), avprobe(1), the avserver.conf example and the
Libav HTML documentation
AUTHORS
The Libav developers
2013-05-20 AVSERVER(1)
