First buffer from theoradec always has segment.start timestamp
Submitted by Jan Schmidt
I've encountered an error with splitmuxsrc and reverse playback. The first buffer from oggdemux for a file fragment always has timestamp NONE. Theoradec/ videodecoder guess a timestamp equal to segment->start which is normally OK, except here.
With splitmuxsrc, it each fragment is a separate ogg file, so there'll be a first buffer for each part with timestamp NONE.
TBH, I'm not sure how we should fix it. Either oggdemux needs to be able to work out the correct timestamp to put on the first theora packet in a stream, or theoradec needs to somehow work backward from the 2nd packet to calculate the timestamp for the first. videodecoder might be able to do the 2nd if it defers guessing a timestamp until it's pushing out the reverse buffers.