[theora-dev] A/V sync in Theora

Ralph Giles giles at xiph.org
Thu Jun 12 11:48:23 PDT 2003

On Thursday, June 12, 2003, at 07:16 pm, David Kuehling wrote:

> Forget my previous mail, it just starts getting somewhat clearer.  But 
> I
> think, that at least mplayer employs some kind of A/V sync strategy for
> AVI which takes information about the interleaving of audio and video
> packets into account (according to tech/formats.txt).  I frequently use
> mencoder to record from my v4l tuner card to avi.  Sound comes from my
> soundcard and is thus guaranteed to not be accurately synced with 
> video.
> I never encountered A/V desyncs even for long recordings.

As I understand it, AVI is fixed framerate the way theora is. It's hard 
to tell without knowing what mencoder is actually doing in your case, 
but if it's generating proper sync on the encode side there's no reason 
to expect if can't do the same for theora.

I didn't understand what you were talking about in my previous mail 
either. :) Dan explained a bit about the expectations around this. But 
yes, there's no support for a separate timecode. Theora is fixed 
framerate, and it's the encoder's job to supply accurately synced data.

I'm surprised you describe this as a problem with DVD though. I didn't 
think players were smart enough to adjust playback to match an external 


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