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y4mtoppm(1)		      MJPEG tools manual		   y4mtoppm(1)

NAME
       y4mtoppm - Convert YUV4MPEG2 stream to PPM images

SYNOPSIS
       y4mtoppm [options]

DESCRIPTION
       y4mtoppm converts a YUV4MPEG2 stream into a sequence of raw PPM images.

       Output  is  to  stdout  (but  feel free to have the shell redirect to a
       file).

       Input is read from stdin, like all other YUV4MPEG2 filters  and	tools.
       YUV4MPEG2  streams  contain  frames  using the Y'CbCr colorspace (ITU-R
       BT.601).	 y4mtoppm will convert each pixel to  the  usual  R'G'B'  col‐
       orspace used for computer graphics.

       YUV4MPEG2 streams may (often!) have subsampled chroma planes.  y4mtoppm
       can upsample "4:2:0 JPEG" streams  using	 a  simple,  lousy  algorithm.
       Better  results	will  be obtained using a filters such as y4mscaler(1)
       which are capable of general-purpose subsampling operations.   y4mtoppm
       will  fail  on  streams	which have chroma subsampling modes other than
       4:4:4 or 4:2:0-JPEG.

       For interlaced streams, these operations are performed  on  each	 field
       individually.   Fields  can  be	output as separate PPM images in time-
       order (default), or interleaved into full-frame images.

       If multiple PPM images are generated, they are simply output one	 after
       another.	 If you want to turn such a "multi-image" PPM stream/file into
       individual files, use pnmsplit.	(Some PNM filters can  process	multi-
       image  files/streams;  however, many written before June 2000 will only
       process the first image.)

       y4mtoppm and ppmtoy4m are inverses of each other; you can pipe the out‐
       put  of	one  into the other, and vice-versa.  Note that the colorspace
       (and subsampling) operations are lossy in both directions.   And,  when
       converting  to  PPM, information on interlacing and sample aspect ratio
       is lost (but can be reconstructed by supplying  command-line  arguments
       to ppmtoy4m).

OPTIONS
       y4mtoppm accepts the following options:

       -L   For	 interlaced streams, output a single PPM image for each frame,
	    containing two interleaved fields.	 (Otherwise,  two  PPM	images
	    will be generated for each frame; one per field.)

       -v [0,1,2]
	    Set verbosity level.
	     0 = warnings and errors only.
	     1 = add informative messages, too.
	     2 = add chatty debugging message, too.

EXAMPLES
       To  turn the first 15 frames of an (MJPEG or DV) AVI file into individ‐
       ual PPM files:

	    lav2yuv -f 15  your-video.avi  |  y4mtoppm	|  pnmsplit  -	"your-
	    video-%d.ppm"

AUTHOR
       This man page was written by Matt Marjanovic.
       If  you	have  questions, remarks, problems or you just want to contact
       the developers, the main mailing list for the MJPEG-tools is:
	 mjpeg-users@lists.sourceforge.net

       For more info, see our website at
	      http://mjpeg.sourceforge.net/

SEE ALSO
       ppm(5), pnm(5), ppmtoy4m(1),  mjpegtools(1),  mpeg2enc(1),  lav2yuv(1),
       pnmsplit(1), y4mscaler(1)

MJPEG Linux Square		 28 April 2004			   y4mtoppm(1)
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