[theora-dev] Theora packets with granulepos of -1

[ogg.k.ogg.k at googlemail.com]

> operation and if I read your method I see that I understand it right... but
> ok, I haven't verified the first frame if it's starting at 0 or 1, I thought
> this is specified exactly.

This is specified exactly, but there was a change some time ago, from
timing for start time to end time (to match Vorbis' behavior). You can
also have a starting offset.

> Recently I encoded another theora stream which has a length of about 4
> minutes. And here I don't get a keyframe every 64th frame even if I name it
> in the ffmpeg2theora command line parameters. The keyframe distance varies
> as the oggzdump output shows:

A keyframe will be forced after the max number of frames, but an
encoder is free to insert a keyframe at any time (eg, when the image
changes enough for a keyframe to be worth it in terms of size).
You could potentially have a stream with only keyframes I think.