[mythtv-users] avidemux2 nuv->avi sync problems

Chris Petersen lists at forevermore.net
Wed Aug 18 17:11:03 EDT 2004


> On the other hand, if the audio glitch theory is correct, maybe the
> glitches occur regularly enough to achieve the same effect.

Beirdo could also be right in thinking that avidemux2 has problems if 
there is a missing/corrupt video frame somewhere.  Or audio.

>>I will resume begging for this to be added to mythtranscode
> So, how far away are we from that?  With software MPEG-4, if you
> transcode after editing the cutlist, it doesn't re-encode the video,
> it just makes the cuts.  If you run mythtranscode on an MPEG4 nuv,
> what comes out on the FIFOs?

the fifos contain unencoded/raw audio and video data.  Which means that 
doing anything with it will be reencoding, and thus losing quality from 
the original mpeg4 or rtjpeg.

> I guess my question is, is this a matter of gluing existing pieces
> together, or something more?

I haven't looked at the code (and probably wouldn't understand much of 
it if I did), but I'm assuming that since mythtranscode uses libavcodec, 
it could merely demultiplex the nuv file, and multiplex it into an avi 
container.  Heck, I'd even be happy with demultiplexed AV data without 
an avi container -- would probably make some other things like pure-mp3 
export a LOT easier to do.

The only issues to deal with would be sync-related if there are missing 
frames, etc.  I think if there have been commercials removed, the file 
might need to have its equivalent of GOP's renumbered or whatever it is 
that restores sync within the file itself (I really don't understand a 
lot of this stuff) -- maybe it already does this when cutting.

-Chris


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