y4mtoppm(1)

💫 y4mtoppm — the MJPEG tools manual, but make it cute 💫

okay bestie, sit down, hydrate, because we're about to talk about y4mtoppm — a lil tool from the MJPEG tools family that takes your YUV4MPEG2 stream and turns it into a whole parade of raw PPM images. yes. it's giving "glow up, but for pixels." ✨

🌸 NAME 🌸

y4mtoppm — convert a YUV4MPEG2 stream into PPM images. that's it. that's the girl. 💅

🎀 SYNOPSIS 🎀

y4mtoppm [options]

🦋 DESCRIPTION 🦋

so here's the vibe: y4mtoppm takes a YUV4MPEG2 stream and converts it into a sequence of raw PPM images. one stream in, a whole little line-up of images out. iconic behavior fr fr.

Output goes to stdout — but bestie, feel free to have the shell redirect that into a file. that's literally what shells are for. 🫶

Input is read from stdin, just like every other YUV4MPEG2 filter and tool out there. consistency?? we love her. YUV4MPEG2 streams contain frames using the Y'CbCr colorspace (ITU-R BT.601), and y4mtoppm will convert each pixel to the usual R'G'B' colorspace that computer graphics peeps use. glow-up complete. 💖

now, the tea ☕: YUV4MPEG2 streams may (and honestly, often do!) have subsampled chroma planes. y4mtoppm can upsample "4:2:0 JPEG" streams using a simple, lousy algorithm — and when I say lousy, I mean lousy, no cap. 😭 Better results will be obtained using filters such as y4mscaler(1) which are capable of general-purpose subsampling operations. and if your stream has chroma subsampling modes other than 4:4:4 or 4:2:0-JPEG? y4mtoppm will simply fail. not a vibe check she passes, sorry. 💀

For interlaced streams, these operations are performed on each field individually. Fields can be output as separate PPM images in time-order (that's the default, bestie), or interleaved into full-frame images — that's what the -L flag is for, more on her below. 👑

If multiple PPM images are generated, they're just output one after another. simple. stacked. no separator drama. If you want to turn such a "multi-image" PPM stream/file into individual files, use pnmsplit. and a lil heads up: some PNM filters can process multi-image files/streams, but many written before June 2000 will only process the first image. ancient behavior, we don't claim her. 🙈

oh and — y4mtoppm and ppmtoy4m are inverses of each other 🎉 you can pipe the output of one into the other, and vice-versa. BUT. and this is a big but: 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 — though it can be reconstructed by supplying command-line arguments to ppmtoy4m. so like, keep receipts. 🧾

✨ 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.) main character move honestly. 👑
• -v [0,1,2] — Set the verbosity level, bestie. pick your energy:
  • 0 = warnings and errors only. silent-ish queen.
  • 1 = add informative messages, too.
  • 2 = add chatty debugging messages, too. she will NOT stop talking. 💬

🌈 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"

look at that pipeline. three tools, one dream. ✨

💜 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)

okay that's the whole page, bestie — every flag, every warning, every little caveat, all accounted for. periodt. 💅✨

this lil masterpiece was brought to you by the MJPEG Tools Team, dated 28 April 2004 — and yes, she's still serving. 🎀🦋💖