What does an Annodex file contain?

Annodex is an Ogg file container with a Skeleton description track, a CMML annotation track, and audio-visual tracks of e.g. Vorbis, Theora, Speex. The audio-visual and annotation tracks are multiplexed (temporally interleaved).

Multiple annotation tracks (CMML) and multiple audio-visual tracks are also possible, though there have not been many experiments with such content yet.