Table of Contents

Encoding Ogg Theora Video from Almost Anything

Encoding Ogg Theora videos using free software tools might not be obvious, since MEncoder has no Theora encoding support whatsoever and FFmpeg wants to use its own Theora encoder and Ogg multiplexer, which are broken and/or worse than libtheora. This means you have to rely on Theora-specific tools like the libtheora example encoder or FFmpeg2theora, which, unfortunately, don't support as many input formats.

If you have something that can be read by FFmpeg2theora, try using that, as that's probably the easiest way and it's available in Debian.

If you can't get your data into FFmpeg2theora directly, you can convert it to YUV4MPEG format using MPlayer or FFmpeg, and then pipe it.

From MPlayer

For anything that MPlayer can read, the command line to pipe to theora_encoder_example/ffmpeg2theora is: 

mplayer -really-quiet -nosound -vo yuv4mpeg:file=/dev/stdout inputfile \
| theora_encoder_example -v 7 -o out.ogv -

You can also substitute ffmpeg2theora for theora_encoder_example, since it supports the same options. The libtheora example encoder can be found in the Debian package libtheora-bin. The -v options sets the video quality.

From FFmpeg

You can do basically the same using FFmpeg instead of MPlayer. 

ffmpeg -an -i inputfile -f yuv4mpegpipe - \
| theora_encoder_example -v 7 -o out.ogv -

From your program

The basic approach of spawning subprocesses and pipes is IMHO easier if you want to encode output from your software into Theora than using GStreamer or libtheora directly

However, reading raw pixel data using MPlayer or FFmpeg is a bit tricky, so I'll show what I did to read 32 bit RGB data. The input is one second of 100×100 black pixels from /dev/zero: 

dd if=/dev/zero bs=40000 count=25 \
| mplayer -really-quiet -nosound -demuxer rawvideo -rawvideo w=100:h=100:fps=25:format=bgra -vo yuv4mpeg:file=/dev/stdout - \
| theora_encoder_example -v 7 -o out.ogv -

The same can be done using FFmpeg, however, ffmpeg cannot directly convert raw RGB to YUV4MPEG, so you need to spawn two FFmpeg processes for that. 

dd if=/dev/zero bs=40000 count=25 \
| ffmpeg -an -f rawvideo -pix_fmt rgb32 -s 100x100 -i - -f rawvideo -pix_fmt yuv420p - \
| ffmpeg -an -f rawvideo -pix_fmt yuv420p -s 100x100 -i - -f yuv4mpegpipe - \
| theora_encoder_example -v 7 -o out.ogv -