[theora] Indexing Ogg files for faster seeking

[Chris Pearce]

Just an update on my recent progress on Ogg indexing...

I've updated my indexer [ http://github.com/cpearce/OggIndex ] so that 
the master branch now injects keyframe indexes into a Skeleton 3.1 track 
(rather than an index track...). I've also added an index validator to 
that repository, so that anyone can verify that the presentation time 
reported by the keypoints in the indexes are actually correct. This 
means if anyone wants to write tools to mess with indexes, they can 
immediately know if the indexes being output are valid.

I've also had some patches committed to ffmpeg2theora svn, so that it 
now outputs valid indexes. Keypoints were previously incorrect in a few 
edge cases, and didn't take into account the preroll needed for vorbis.

We're planning on shipping support for keyframe index assisted seek in 
Firefox 3.7, which will ship sometime next year.


Chris P.