I am currently writing a simple Theora video encoder, which uses libogg, libvorbis and libtheora. Currently, I can submit frames to the Theora encoder, and PCM samples to the Vorbis encoder, pass the resulting packets to Ogg streams (one for Theora and one for Vorbis) and get pages out.
When the program starts, it flushes the headers first from the Theora encoder, then from the Vorbis encoder to the output file (obviously, both streams have unique serial numbers). Then, I write interleaved pages to the file from both of the streams.
When writing just the video, or just the audio, I am able to play back the output in mplayer just fine, however when I attempt to write both, I get the following:
Ogg demuxer error : we met an unknown stream
I'm guessing I'm doing the multiplexing wrong. I have read through the documentation for multiplexing streams on Xiph.org, and I can't see where I differ. I cannot seem to find any example code for doing this, short of going through the source of an open-source encoder (which I'm having some trouble understanding). Would anyone be able to explain how to multiplex streams correctly using libogg? I'm trying to do this in C on Ubuntu 10.04, using the libraries from the Ubuntu repository.
Many thanks in advance!
Tom
Ok, for anyone who was reading this, I have to some extent solved it.
You should not flush all of the the header packets from each stream - just the first (setup) packet, which for Vorbis and Theora gets its own page by default. Put the other header packets into their respective streams, but do not flush until the setup pages from all streams have been written to the file.
Once you have done this, try to keep the streams as closely sync'd as possible (mplayer gave some errors for me when they got too far out). At 24fps video and 44.1 KHz audio, 1 frame should span 1837.5 audio samples (with PCM audio, this is 7,350 bytes).
If anyone else has any tips / info, it would be good to hear - I've never done anything with audio / video before!
Thanks! Tom