Ogg demuxer seeks poorly for Theora

Seeking in theora files results in the playing garbage until the next keyframe. E.g. seek around in http://people.xiph.org/~greg/video/ytcompare/bbb_theora-ptalarbvorm_376kbit.ogv

Either it should snap the seek to keyframes or (better) it should seek to the desired frame, read the required keyframe number from the granpos, then silently decode forward to the requested frame.

The latter behaviour is what firefox does (for example), it's more user friendly for files with long keyframe intervals and it's compatible with rolling intra (http://myrandomnode.dyndns.org:8080/~gmaxwell/theora/rolling_iframe_2.ogv), files without distinct keyframes but which are still seekable, which isn't a standard behaviour but may become one in the future.