audio synch

[omicron]

I have this file, that I know contains bad frames. I will want to add subtitles to this, so my objective is to keep as close as possible to the original file - I would rather mask the bad frames than cut them out, just so that I have an easier time keeping my subs in synch.



My plan is to save the sound track as an uncompressed wav file, then to add this as an additional available stream in VirtualDub Mod, disabling the original sound track. Then I plan on checking my video for bad frames, masking them, so as to save a "cleaned" file made up of my original video where bad frames are masked, coupled with the edited uncompressed sound track that would be in full synch with my video.

This file I would then use as source, add subtitles, and frame serve to TMPGEnc.

That's the plan, but somehow I cannot get to get an uncompressed wav file that would be of equal duration to the original soundtrack:

[/img]http://home.euphonynet.be/famille_minne_huybrecht/audio%20streams.jpg[/img]

As you can see, the original sound file is 1:39:52.86, whilst the uncompressed was is 1:38:31.92. Sure enough, this leads to serious synch issues.

I wonder what I am doing wrong, and how to go about this issue ?

Thanks.

[proxyx99]

I'd start with DivX fixer... You can stretch audio without pitch change later on in Vegas or restore sync in Womble MPEG Wizard...

[mats.hogberg]

I'd say - find a decent source. IMO, bad AVIs are 99 times out of 100 not worth the trouble dealing with.

/Mats

[omicron]

Thank you both for your comments.

I did pass the file through DivFix and this seems to make the problem bigger. DivFix identifies almost the same bad frames as Vdub (Mod or MP3freeze) identifies, but then not exactly. I let DivFix rebuild the index, but now Vdub can't decompress / save the wav part - in addition, the "DivFixed" avi is now 2minutes 25 secs shorter than the original, and I don't understand why.

After wasting so much time on this, I believe I am going to follow Mats' advice.

What bugs me most though, is not to understand what's happening. This bugs me more than the time I lost.

Cheers

[FulciLives]

You can try to load the original DivX AVI into GOLDWAVE and after it loads save the audio to a PCM WAV file.

That usually does the trick ... but ... I have never worked with DivX/XviD AVI files that have had bad frames ... so who knows?

It is worth trying though

- John "FulciLives" Coleman

[proxyx99]

My take, fix it with DivX fix and encode to MPEG. strip audio then and start working on sync (in smaller chunks (10-20 min).

[mats.hogberg]

DivFix and this seems to make the problem bigger.

This about sums my expriences with DivFix up too.

/Mats

[lacywest]

I'd start with DivX fixer... You can stretch audio without pitch change later on in Vegas or restore sync in Womble MPEG Wizard...

The file is a AVI file .... how would Womble MPEG Wizard ... do this ??

I have had the problem of AVI files losing sync with the audio !! ... many times. Especially AVI files using Variable audio streams ... I hate it when I have to deal with them ... I prefer audio streams with a constant bitrate.

[proxyx99]

You skipped the most important part in your quote "encode to MPEG". Good for Womble.