pnmtoy4m - Convert PNM/PAM images to YUV4MPEG2 stream

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pnmtoy4m(1) MJPEG tools manual pnmtoy4m(1)

pnmtoy4m - Convert PNM/PAM images to YUV4MPEG2 stream

pnmtoy4m [options] [ filename ]

pnmtoy4m converts one or more raw PPM, PGM, PBM, or PAM images into a
YUV4MPEG2 stream ready for further processing by other video tools.
These three (or four) image formats are collectively referred to as
"PNM images".

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 PNM image, read from stdin or from the optional
filename. The input may contain multiple PNM images concatenated
together; pnmtoy4m will read and process them sequentially. All images
must have identical size and format. Input images can be interpreted
as whole progressive frames, pairs of interleaved fields, or as sequen‐
tial fields (read in pairs of images) to be output as either interlaced
or progressive frames. PPM and PGM images must have 8 bits per channel
(i.e. 'maxval' must be 255).

PPM input images should be in the usual R'G'B' colorspace. They are
converted to the Y'CbCr colorspace (ITU-R BT.601) before being output
to a "4:4:4" (non-subsampled) YUV4MPEG2 stream. If chroma subsampling
is required (e.g. to 4:2:0 for MPEG), the output should be further
piped through a program such as y4mscaler.

PGM images should be in the standard full-range ([0,255]) grayscale
colorspace. PGM and PBM images will be converted to BT.601 luma and
output as "MONO" (luma-only) YUV4MPEG2 streams.

The PAM format is a newer superset of the PNM formats; the precise con‐
tents of a PAM image is defined by the TUPLTYPE header tag. pnmtoy4m
handles TUPLTYPE "GRAYSCALE" as PGM, "RGB" as PPM, and "RGB_ALPHA" as
PPM with an 8-bit alpha channel. (The alpha channel is converted to
BT.601 luma as is appropriate for YUV4MPEG2 streams.)

pnmtoy4m and y4mtopnm are inverses of each other; you can pipe the out‐
put of one into the other, and vice-versa. Note that the colorspace
operations are lossy in both directions. And, when converting to PNM,
information on interlacing and sample aspect ratio is lost (but can be
reconstructed by supplying command-line arguments to pnmtoy4m).

pnmtoy4m accepts the following options:

-o num
Frame offset: skip output of the first 'num' frames. (default:

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

-B Interpret data as being BGR rather than RGB.

-r Repeat last input frame until output is complete. If '-n 0' is
also specified, last input frame will be repeated forever.

-D x Treat each PNM image as a single (de-interleaved) field instead of
a full frame. The argument specifies the interpretation:
t - the first image is a top-field
b - the first image is a bottom-field

With this option, two input images will be required per output
frame. Be careful: mismatched "-I" and "-D" options can invert
the temporal or spatial order of the fields (or both).

-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 inte‐
ger 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 the output interlacing mode, encoded in the output stream.
(Default is to match "-D" if given, or 'p' if not.)
p - progressive, non-interlaced
t - top/upper-field-first interlaced
b - bottom/lower-field-first interlaced

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

To convert a file containing a single PPM file into a stream of 15
(identical) frames:

pnmtoy4m -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 | pnmtoy4m | yuvplay

This manual 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:

For more info, see our website at

pam(5), pbm(5), pgm(5), pnm(5), ppm(5), y4mtopnm(1), mjpegtools(1),
mpeg2enc(1), y4mscaler(1), yuv2lav(1), yuvplay(1)

MJPEG Linux Square 28 April 2004 pnmtoy4m(1)