Audio Sync Problems with MPEG2

greenspun.com : LUSENET : Video CD : One Thread

OK, the deal is that I want to do a Divx Rip of a MPEG2 VCD but the goddamn audio gets out of sync by about 4 seconds by the end of the file (there are 2 CD's.)

DVD2AVI seems to be the only thing to even have half a chance at opening and converting the files (I've tried everything else I could find out here.) Anyway, DVD2AVI does a fantastic job on the video (like it does always) but the mpeg audio stream gets exported to .mpa format and it's 4 seconds longer than it should be...stretched by fours seconds...ain't it a bitch.

I even tried Time Compressing the entire file (1 hours worth) in Wavelab to the specific size VirtualDub reported the movie length was, but it didn't quite come out right even though the specific lengths of the video and audio were precise in length down to a 1,000th of a second.

Does anyone know how to extract audio only from these new MPEG2 VCD's since TMPGEnc will not even open the file and neither will anything else for that matter but DVD2AVI. Very irritating. Am I missing something?

-- Jack (computerdoc@scene-1.com), January 05, 2002

Answers

It's kind of hard to help because what you're saying is not correct. There is no such thing as a MPEG-2 VCD. Are you talking about making SVCDs? These use MPEG-2 video. VCDs use MPEG-1 video. Sounds to me like you're doing something wrong in the encoding process. There are some very good guides to making DivX discs at www.doom9.net that might help you. A/v sync problems are quite common in DivX rips, unfortunately. One thing that has worked for me is to use VirtualDub to remux the audio and video and use an offset in the audio mux. Use a negative offset if the audio comes later than the mouth movement.I had a pretty stubborn a/v sync problem that I corrected with an offset of something like -100 (not sure of the exact units, but you can probably figure it out). There are guides to doing all kinds of nasty audio edits to fix this kind of problem, but usually a remux with the right offset is a lot quicker and will do just as good a job. If you want to extract files from the original VCD, I have read good things about VCDgear. A web search should locate it for you. It might even be at doom9 for all I know.

-- Jason (Jason.Shumate@equant.com), January 07, 2002.

Moderation questions? read the FAQ