audio not in sync after reencode regardless of program

[madymo3d]

I know this is an ongoing problem with many people. I have tried some solutions found in the forums within my ability to resolve it, but still have the problem.

I have a 2 hour TV cap in 3 files using Leadtek Winfast XP 2000 Deluxe in 640x480 MPEG2. I've edited out the commercials using Ulead Video Studio 7 and ended up with 2 files. The audio is in perfect sync in both files. Now when I try to author the 2 files, (one is 1 hour 20 min, the second only about 10 minutes), the resulting file audio is progressively out of sync during the 1 hour 20 min segment and becomes in sync when the 2nd segment starts. I've tried Ulead Movie Studio 2.5, Ulead Video Studio 7, Tmpgenc Plus, Pinnacle 8. All with the same result, whether I encode at 44kHz or 48kHz, at original resolution or @352x480. This leads me to believe that the source file has a problem and not the programs. But why would the source file, which has been reencoded once when I took out the commercials, be in sync become out of sync when I author it? Anyone got suggestions?

My system is Soyo KT600 Dragon Plus v.1 running AMD XP2000, WinME.

More fundamental question is, why is audio sync such a common problem? Seems to me (and I recognize my knowledge is only basic and overly simplistic) that once the video frame rate and audio sample rate are known, it shouldn't be hard to keep the 2 in sync. Is it rounding error?

[ZippyP.]

I suggest that you capture straight to a DVD compliant resolution and 48 KHz audio then cut out the commercials in the authoring step. No conversion necessary.

[bugster]

I have a 2 hour TV cap in 3 files using Leadtek Winfast XP 2000 Deluxe in 640x480 MPEG2.

I've edited out the commercials using Ulead Video Studio 7 and ended up with 2 files....

This leads me to believe that the source file has a problem and not the programs. But why would the source file, which has been reencoded once when I took out the commercials, be in sync become out of sync when I author it?

You captured and encoded directly to mpeg-2. In cases like this, the video and audio streams contain 'timestamps' or sync information that players use to keep them in sync, irrespective of missing frames.

When you edited, I would hazard a guess that the files were not re-encoded, just spliced, with headers corrected etc. So the timestamp or synchro info remains in tact.

When you author, the two streams are de-multiplexed, losing the synchro info. They are then re-multiplexed in VOB format ( a little different from mpeg). If there where any dropped video frames, the audio sync would be lost because of this. It only takes a few dropped frames for the loss of sync to be quite noticeable.

If my theory is correct, I am not sure if ZippyP's suggestion would work or not as its the de-multiplex/re-multiplex that causes the problem.

Fixing the loss of sync in this case is tricky as you will need to either remove bits of audio or ad duplicate frames to replace the lost ones. Not sure how you would do this.

Of course I could be completley wrong and there were no dropped frames when you performed your capture!

[madymo3d]

Oops, my apologies, I used the term "author" prematurely. The reencoded file is still MPEG2. I guess technically I'm joining the 2 segments, but making the resolution and audio DVD compliant. That's why I was thinking authoring.

[Forum Troll]

I had this same problem. VideoReDo fixed it. Get it. You'll thank me later.