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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'
   colorspace 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
   output 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
   individual 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)



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