It's a known problem for *some* hardware-mpeg2-card captures. It doesn't happen all the time... quite infrequently with broadcast/cable sources, actually. It's caused by the card having a glitch in an A or V frame and then throwing it away. It just adjusts the timestampe to compensate. Particularly problematic captures are those from analog tape (VHS, 8mm, etc)... tape players typically put out pretty lousy signal quality. The quality isn't normally perceivable, but it could be missing some sync info, have the timing off a bit, etc... people don't mind, but capture cards have major issues with small timing glitches.Most likely due to changing A/V sync within the MPEG2 stream. It's a known problem without a known (bug-free) solution.
Cory,
Is this just a known issue for hardware-MPEG2-card recorded streams, or all MPEG2 streams in general? I regularly record DVB and PVR-350 streams here in the UK, demux them, edit them, and then burn to DVD with no issues at all (using Project X (Java) to demux and fix, Cuttermaran to edit [uses mplex], and then DVD Hive [uses dvdauthor, mplex, and mkisofs] to create ISO images). I sometimes also reencode edited MPEG2 streams that have been through the demux/remux process into XVID/DIV5 with no A/V sync problems.
Most linux-based tools use the same backend tools to do the processing. Basically, anything that relies on stripping A and V streams apart and then remuxing them will break. The PTS info is at the PS level... once it's been ripped into PES or ES, the sync info is gone. Digital broadcasts (like HD or DVB) will most likely be better mastered without the varying sync (although not necessarily).Does this problem affect all popular linux-based tools mentioned in this thread? I use the above tools on my Win2K box because they are all GUI-driven and, having not tried other tools and because they worked, have not looked at others. It'd sure be good to be able to do it all driven from a GUI on my myth box from the sofa!
Notable programs that definately *are* broken are any scripts that strip A/V and remux, or those that use avidemux. Avidemux cannot deal with varying sync.
-Cory
************************************************************************* * Cory Papenfuss * * Electrical Engineering candidate Ph.D. graduate student * * Virginia Polytechnic Institute and State University * *************************************************************************
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