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.
Input is read from stdin, like all other YUV4MPEG2 filters
and tools.
Output is to stdout (but feel free to have the shell redi
rect to a file). YUV4MPEG2 streams contain 4:2:0 subsam
pled frames using the Y'CbCr colorspace (ITU-R BT.601).
y4mtoppm will upsample each frame (to 4:4:4) and convert
each pixel to the usual R'G'B' colorspace used for com
puter graphics.
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 out
put one after another. If you want to turn such a "multiimage" PPM stream/file into individual files, use pnm
split. (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 subsampling and colorspace 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 argu
ments to ppmtoy4m).
OPTIONS
y4mtoppm accepts the following options:
- -L For interlaced streams, output a single PPM image for
- each frame, containing two interleaved fields. (Oth
erwise, two PPM images will be generated for each
frame; one per field.) - -S mode
- Set chroma supersampling mode. (default: 420_jpeg)
420_jpeg - 4:2:0 JPEG/MPEG-1, interstitial cositing
- 420_mpeg2 - 4:2:0 MPEG-2, horizontal cositing [NOT
- YET IMPLEMENTED]
- Changing the supersampling mode from the default
won't necessarily make anything better. This option
is just for experimenting. - -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/