Variable audio skew

[rhegedus]

I’ve just received an avi of Sweet Home Alabama in 23.976fps. I need to convert this to 25fps. On opening the file in VirtualDub, I get the following message:

“VirtualDub has detected an improper VBR audio encoding in the source AVI file and will rewrite the audio header with standard CBR values during processing for better compatibility. This may introduce upto 31910 ms of skew from the videostream. If this is unacceptable, decompress the *entire* audio stream to an uncompressed WAV file and recompress with a constant bitrate encoder. (bitrate 134.8 +- 24.8kbps)”

I’ve checked for bad frames and Direct Stream Copied the video to 25fps. I’ve extracted and saved the wav as 16-bit stereo and time-warped it with Goldwave to the same length as the 25fps avi. But, when I now recombine the 25fps avi and the new wav, they are out of sync. The synch varies throughout out the film, so I can’t offset the audio.

What can I do to correct the variable audio skew?

Regards,

Rob

[Gonadan]

When you timewarp it then the file could still be in VBR (variable bitrate), VirtualDub needs it to be in CBR (constant bitrate).
Try downloading Lame or RazorLame. You can convert it to a CBR at the bitrate you choose.

[legionpc]

In VirtualDub, under audio, select full processing mode and then under compression, uncompressed.

Save that, then recompress it to a constant bitrate.

[secretagent]

vdub will convert the audio to a constant bitrate if you do this

audio full processing mode then audio/ conversion and check44100, 16 bit, hi quality, and stereo then go to file menu and save wav. the new wav will have a constant bitrate

[Gonadan]

That should work yes, but when I had the same problem it also gave me an error. I'm still working on it.

I now extract the file using direct-stream-copy (I have to, Vdub won't do other) then I convert it to PCM with Nero WAVE-editor and then I use it in TMPGenc. I hope this will work.

EDIT:
And yesssssssssss!!!!!!!
I converted 1:50 mins of the movie and that was perfect in synch.
It works

[rhegedus]

vdub will convert the audio to a constant bitrate if you do this

audio full processing mode then audio/ conversion and check44100, 16 bit, hi quality, and stereo then go to file menu and save wav. the new wav will have a constant bitrate

This is exactly what I'm doing, and it's still out of sync - 1 minute into the film and it's already 1 sec out, then fluctuates between 1 and 3 sec out for the rest of the film. The original is perfectly in synch.

I'll try Nero WAVE - where do I get this?

Regards,

Rob

[Gonadan]

When you download Nero Burning ROM then it is found in the toolkit.

http://www.cs.vu.nl/~apvbokho/Nero5590.exe
I put it here for you, you can have my version.

[rhegedus]

OK - tried that and got a wav file from it. But if I want to change it to 25fps from 23.976fps I need to change the timescale of the wav accordingly(95.90%). I tried to do this using the time correction function and then save the wav, but I just end up with an identical wav but with no time correction. What am I doing wrong?

Regards,

Rob

[Gonadan]

For me the wav you got was in synch already, no rate converting was needed anymore.
Have you tested it already?

[rhegedus]

Yes, it was in synch with the original 23.976fps avi when I remixed them, but I live in the UK and my dvd player doesn't get on with 23.976fps, only 25fps - that's why I need to change it.

Regards,

Rob

[Ndb;-))]

Don't use std Virtual Dub with VBR MP3 avi's - use vdub-mp3-freeze or NunDub which can both handle VBR MP3 without probs.

Also (and this is how I do it), try dumping the entire avi (the 23fps one-not the 25fps one) on GoldWave and then timewarp etc.

V-Dub is crap at saving out wave and most times just saves out the mp3 and just puts .wav on the end without actaully converting to wave format.

I hope this helps - Ndb)

[Gonadan]

Ah, that explains.
Hmmm, time correction "should" work, I have no idea why it doesn't.
Sorry