[theora] How to merge and cut theora videos, and how to synchronize sound?
jason at bluehome.net
Wed Nov 3 09:57:01 PDT 2010
I encode alot of these types of files (my MPEG TS files come from digital
television recordings) and routinely run into A/V sync problems with ffmpeg2theora.
This is entirely speculation on my side, and I have no data to back it up, but I
wonder if my recordings contain errors due to interference during the broadcast
or something. The computer's tuner reports consistently 99% signal quality for
whatever that's worth. Whatever the cause ffmpeg2theora doesn't seem to handle
I reported it to the ffmpeg2theora developer many moons ago but nothing ever
seemed to happen.
Unable to find a fix on my own, I have since stopped using ffmpeg2theora and
switched to HandBrake  for encoding these files.
HandBrake doesn't support the Ogg container, which I prefer. I tried to use
ffmpeg to change containers but it gave me a cryptic message about timestamps
that I don't recall right now, and couldn't find a solution to online, so it
seems that I'm stuck with my Theora & Vorbis stuff inside a Matroska container.
HandBrake also lacks some other features that ffmpeg2theora has, but it has no
problems keeping the audio & video in perfect sync.
Some people have said it must be a bug in FFmpeg, then, but HandBrake also uses
FFmpeg and as I've said doesn't exhibit these problems.
I'm not sure what HandBrake does differently than ffmpeg2theora but, if it's
true that the MPEG TS files do contain errors, then HandBrake is more robust in
handling them and ffmpeg2theora would do well to adopt that, I think. Part of
the "be liberal in what you accept; be conservative in what you send" idea
because I would like to switch back to ffmpeg2theora some day.
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