Comment 11 for bug 412647

I just want to confirm that the frame dimensions may change during Ogg stream playback. Ogg allows concatenation of Ogg streams, meaning that "cat stream1.ogg stream2.ogg > stream.ogg" will produce a new, valid Ogg stream. This was mostly motivated to allow easy playlist streaming for e.g. web radio (read the data off disk, just push it out into the world).

So the frame dimensions can change, the framerate, the audio channel number, the audio sample rate...

Even codecs may change... if you concatenate an Ogg Vorbis (general purpose audio codec) file with an Ogg Speex (speech codec) file the resulting stream would still be valid Ogg - but I've yet to encounter a playback application that properly handles this. If you only support Ogg Theora + Vorbis (which would by far be the most common and useful combination) that's theoretical speaking anyway ;-)