Log in

View Full Version : mpeg2 with AC3: audio out of sync


tedder
30th December 2007, 01:30
So I'm using fccHandler to open mpeg2 files. The audio is AC3- gspot says the specs are "0xbd[0x80]:48000Hz 448 kb/s tot , stereo (2/0)". It's CBR.

When I play it in Windows Media Player, it seems fine. When I load it in virtualdub and play, the audio is out of sync. In a 30 minute clip, it'll be out by about 500msec by the end, but much less at the beginning- so I can't simply skew it slightly and get it in sync.

Why is that? I've changed Framerate to "Adjust framerate so audio and video lengths match." The source rate adjustment says current=59.940, change..match=59.974.

Here's a test clip from near the end of the 30min file. I encoded it to xvid, but the problem is in VirtualDub, not the encoded file:
http://perljam.net/tmp/sync-test-1.avi

-ted

tedder
30th December 2007, 02:51
Here's the file info from Virtualdub.

Again, it syncs fine in Windows Media Player, but doesn't sync in VirtualDub preview or in the final file.
http://perljam.net/tmp/sync-file-info.gif
http://perljam.net/tmp/sync-file-info.gif

Obviously the skew given there isn't terribly helpful, since it gets worse as the show goes on.

superdragonpoop
22nd January 2008, 07:33
It's not just you :) I am having the same issue. I'm using auto gordian-knot to encode xvid-AC3. It's perfectly in sync in the beginning and gets progressively worse as the video progresses. After about 2.25 hrs it's about 3-4 seconds out of sync. I've encoded the same vid to xvid-mp3 and there is no sync problem. I haven't found any solution yet.

edit to state the obvious: AGK passes through virtualdub

superdragonpoop
22nd January 2008, 07:53
While this doesn't resolve the original issue of why it's going out of synch, there's a program that will allow you to fix the audio synch by specifying the offset at the beginning and the offset at the end of the file. It's called "AC3 Delay Corrector" you'll also have to find a copy of "Gfawin23.ocx" for the program to function.

setarip_old
22nd January 2008, 08:49
@tedder

Hi!

Do you have the same situation if you use VirtualDubMOD (alone) instead of VirtualDub (including the experimental MPEG2 plugin by "fccHandler")?