[mythtv-users] Nonlinear MPEG2 editor that doesn't suck?

Cory Papenfuss papenfuss at juneau.me.vt.edu
Wed Dec 15 00:50:27 UTC 2004

> 	Has anyone found such a beast?  I've got an PVR-250 captured bunch of 
> old 8mm home video footage that I'm trying to put together into a DVD. I'm 
> trying to cut up a couple of 4GB 704x480 streams into a few dozen clips.  I'd 
> like to paste them together into a DVD with 1 chapter per clip.  Issues 
> include:
 	Pseudo-replying to myself.  I'm having some sync issues with some 
of these tape transfers and I've developed a theory.  Perhaps someone who 
is more familiar with the MPEG2 streaming can help.

 	I've been using avidemux in the past to recrunch pvr-250 recorded 
streams onto DVD.  Not too much difficulty, and it appears that I always 
get a 66ms difference between audio and video.  With this tape transfer, 
however, it appears that the A/V sync amount changes as the tape recording 
goes on.  Maybe because the pvr-250 had to do weird things because the VCR 
that was playing the recording did odd things at the cut?

 	Anyway, it appears that a signifcant cleanup can be done with the 
dvb-mplex and/or replex utility on the raw IVTV stream.  It generates a 
number of PTS-related errors such as:

video DTS inconsistent:  0:02:42.144  0:02:42.144  0:02:42.061  0:02:41.728 diff:  0:00:00.082
video PTS inconsistent:  0:02:42.178  0:02:42.178  0:02:42.095  0:02:41.761  diff:  0:00:00.083
video PTS inconsistent:  0:02:42.211  0:02:42.211  0:02:42.128  0:02:41.794  diff:  0:00:00.082
video PTS inconsistent:  0:02:42.345  0:02:42.345  0:02:42.262  0:02:41.928  diff:  0:00:00.082
video DTS inconsistent:  0:02:42.244  0:02:42.244  0:02:42.162  0:02:41.828 diff:  0:00:00.082

 	So the question is this:  Does the ivtv driver output clean MPEG2 
that's consistent from end to end, or does it have glitches in it?  It 
would appear to be the latter, and the PTS can change mid-stream and goof 
up post-processing.

 	Food for thought.


* Cory Papenfuss							*
* Electrical Engineering candidate Ph.D. graduate student               *
* Virginia Polytechnic Institute and State University 			*

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