ppmtoy4m(1)

NAME

ppmtoy4m - Convert PPM images to YUV4MPEG2 stream

SYNOPSIS

ppmtoy4m [options] [ filename ]

DESCRIPTION

ppmtoy4m converts one or more raw PPM images into a YUV4MPEG2 stream ready for further processing by the
mpeg2enc(1) MPEG encoder and image processing filters like yuvscaler(1).

Output is to stdout to facilitate piping to other MJPEG
tools. The size of the output frame(s) is determined from
the (first) input image.

Input is a 'raw' format PPM image, read from stdin or from
the optional filename. The input may contain multiple PPM
images concatenated together; ppmtoy4m will read and pro
cess them sequentially. All images must have identical
size and format. Input images can be interpreted as whole
progressive frames, interleaved fields, or (in pairs) as
sequential fields. The input images must have 8 bits per
channel (i.e. 'maxval' must be 255).

Input images should be in the usual R'G'B' colorspace.
They are converted to the Y'CbCr colorspace (ITU-R BT.601)
and chroma subsampled before output.

ppmtoy4m and y4mtoppm 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

ppmtoy4m accepts the following options:

-o num

Frame offset: skip output of the first 'num' frames.
(default: 0)

-n num

Output a total of 'num' output frames. Use '0' to
specify all frames. (default: 0)

-F n:d

Set framerate encoded in output stream, as an exact
integer ratio. (default: 30000:1001) Common rates
are:

24000:1001 - NTSC 3:2 pulldown converted film

24:1 - native film
25:1 - PAL/SECAM

30000:1001 - NTSC video

50:1 - PAL field rate

60000:1001 - NTSC field rate

-A n:d

Set pixel aspect ratio encoded in output stream, as
an exact integer ratio. (default: 1:1) Common
ratios are:

1:1 - square pixels (computer graphics)

10:11 - CCIR-601 NTSC
59:54 - CCIR-601 PAL

-I x Set interlacing mode, used to interpret the PPM

image(s), and also encoded in output stream.
(default: 'p')

p - progressive, non-interlaced
t - top/upper-field-first interlaced
b - bottom/lower-field-first interlaced

-L For interlaced streams, treat each PPM image as two

interleaved fields. (Otherwise, two PPM images will
be read for each frame; one per field.)

-r Repeat last input frame until output is complete. If

'-n 0' is also specified, last input frame will be
repeated forever.

-S mode

Set chroma subsampling mode. (default: 420_jpeg)

420_jpeg - 4:2:0 JPEG/MPEG-1, interstitial cositing

420_mpeg2 - 4:2:0 MPEG-2, horizontal cositing

Changing the subsampling 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 convert a file containing a single PPM file into a
stream of 15 (identical) frames:

ppmtoy4m -n 15 -r some-image.ppm

To convert a series of Targa format images (in the current
directory) to a YUV4MPEG2 stream displayed by yuvplay:

ls *.tga | xargs -n1 tgatoppm | ppmtoy4m | yuvplay

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), y4mtoppm(1), mjpegtools(1), mpeg2enc(1), yuvs caler(1), yuv2lav(1), yuvplay(1)

MJPEG Linux Square 28 October 2001 ppmtoy4m(1)