Why does the AV sync go bad when re-encoding MPEG2s???

[funkydude74]

Hi all. I'm trying to convert a 90 minute program that is roughly 5400MB big at 8000kbps down to about 4300MB at 6400kbps. I use Ulead Video Studio 7 and open the recorded program, do the cut trims to the start and end that I don't want, then re-encode it, but this results in the audio and video being out of sync. Actually it's a bit weird as in the first 10 minutes of the program the sync appears to be good but near the arse end the sync is shithouse . It's like the sync gradually goes out of phase further in the video I think.

Anyways just wondering WHY are these MPEG2 videos so fussy when re-encoding???

The only method I can think of is to separate the audio from the video and re-encode the video and joing the audio up with the re-encoded video.

If anyone can help me find an easy solution to this problem I'd most appreciate it.

Cheers
Troy

[SaSi]

By your description, it appears that you are encoding with the wrong frame rate. If the video is 25fps and you are encoding at 23.976 or the other way round, it will cause a gradual shift in sync. A 40 minute clip will end up with a 1.5 minute shift.

The other thing I've found is that some applications don't like VBR audio for input.

I use VirtualDUB Mod, open the MPEG file, trim it, re-encode it to DivX with a constant quality of 4 and highest performance setting then re-encode it to MPEG-2. Mainconcept, Tmpgenc or CCE Basic are good encoding choices.

[reboot]

Why re-ecnode to divx, then re-encode to mpeg?
Open the file in tmpgenc, re-encode the way you want it. Let tmpgenc do the audio at the same time as video. I've had a lot less headaches this way. If you demux first, and use separate apps to re-encode video/audio, then remux, something is definitely (usually) going to go out of whack). One step, instead of two.

[bugster]

I use VirtualDUB Mod, open the MPEG file, trim it, re-encode it to DivX with a constant quality of 4 and highest performance setting then re-encode it to MPEG-2. Mainconcept, Tmpgenc or CCE Basic are good encoding choices.

Don't re-encode to divx, waste of time, effort and disk space. Just frameserve from vdubmod to TmpGenc.