XviD to DivX (AVI/MP4) sound sync problems

[mkgordon]

I converted an Xvid .avi to DivX .avi last night.

I used the MPEG4 [.AVI] (ffmpeg) codec.

"This is the codec known as "libavcodec mpeg-4". Compatible with DivX 4 and DivX 5 players and introduced by the ffmpeg open-source project, it's an incredibly fast encoding engine, now Altivec optimized, and also one of the highest quality MPEG-4 codecs around, constantly improved. Use it when speed is your first choice." -ffmpegX web help.

I did this conversion because my DVD player was showing a very jerky, stop-motion-esque video when playing the XviD burned to DVD, despite being MP4 and DivX certified. I wondered if a true DivX would play better. Well, after the conversion, the DVD video certainly looked a lot better. But the sound went out of a sync during the recoding. The performers's mouths moved a fraction of a second before the sound, making it look like the sound was completely out of sync. Why would ffmpegX move the sound during this type of recode? Is there an setting I could use to avoid it?

Thanks,

Mike

[major]

The source may have a variable framerate at some point. Try the equivalent codec with mencoder instead of ffmpeg engine.

[jagabo]

Try simply remultiplexing the audio and video with VirtualDub.

File -> Open Video File
Video -> Direct Stream Copy
File -> Save as AVI

It will only take a few minutes and may fix the problem.

[mkgordon]

Major - thanks. Will try that. Is there any way to inspect a file for issues like that in advance of waiting for one codec to process the file, only to find a sync problem? Would I be better to use the mencoder codec all the time, despite the speed hit?

Jagabo - thanks, but isn't VirtualDub a PC app? I figured having posted in the ffmpegX forum, the fact that I use a Mac (iMac G5 2.0GHz) would have been implicit.

[jagabo]

isn't VirtualDub a PC app? I figured having posted in the ffmpegX forum, the fact that I use a Mac (iMac G5 2.0GHz) would have been implicit.

Sorry, I saw your first post from the front page and didn't notice which forum you posted in.

[major]

Almost all sync issues arise with NTSC/NTSC FILM framerates (PAL are only rarely affected) not properly encoded and/or with framerate changes and/or with misleading headers.