Audio out of synch and I'm buying a gun.

[Nutts]

Hi

I've used Blaze media pro to convert my avi's to mpg and never had a problem before. Now I've got an avi where the audio is out of synch with the video and I'm wondering if there is a program designed to help me get the audio in check.

I'm using DVD-Lab to author my movies and have demuxed it but the 'fix audio delay' feature confuses me since I have no idea how much of a delay I need to install without compiling it several times with different set values. Surely there's an easier way to get this done.

Thanks.

[setarip_old]

Now I've got an avi where the audio is out of synch with the videoLoad the file into VirtualDub, VirtualDubMod, or NanDub.
Set BOTH "Video"(VirtualDub, VirtualDubMod and NanDub) and "Audio"
(VirtualDub and NanDub - VirtualDubMOD>"Streams>"Stream list") to "Direct Stream Copy".

A) If the difference between audio and video is constant throughout the video:

From the "Audio" dropdown menu, select "Interleaving" (For VirtualDubMOD, rightclick on the listed audiostream and then select "Interleaving")

Under "Audio skew correction", set an appropriate number of
milliseconds (positive or negative) in the box labelled "Delay audio track by"

Save with a new filename


B) If the difference increases as the movie plays:

From under the "Video" dropdown menu, select "Framerate" - and select "Change so video and audio durations match"

Save with a new filename

Let us know of your success ;>}

[Nutts]

I downloaded Virtualdub. Loaded the file into it and got this message:

"AVI: Variable bitrate (VBR) audio detected. VBR audio in AVI is non-standard and you may encounter sync errors up to 22481ms when attempting to extract WAV files or processing the audio in Direct Stream Copy mode. Full Processing mode is recommended to decompress or recompress the audio. (bitrate: 131.7 ± 28.2 kbps)"

I have no idea what this is telling me to do.

The delay appears to be constant so I followed step 'A'. This is my question...is the program telling me that the audio is 22481ms out? I entered the figure, waited an hour and found a file that was 36GB and the audio was completely out to lunch. Popping in and out and way out of synch. So I tried a negitive interger and same problem.

The Mpg file I converted the avi to is out of synch worse. How can I determine extactly how many ms too input? And I take it that I can recompress the avi file with Virtualdub, correct?

[CWR03]

You obviously didn't save it in Direct Copy mode, and you should be using VirtualDubMod since your video contains VBR audio.

The delay is a matter of trial and error. 1000ms = 1 second. It makes no difference what the number says - just estimate the required parameter by how far off the audio is from the video, then save it and play the new file. If it's not right, adjust it, save it again, etc.

[Nutts]

Yes. Direct copy is a must. I didn't have a problem after using VirtualDub. And fast, too. VirtualDubMod gave me an output file that stalled in the player. Though I may have just had a bad install.

What is VBR audio exactly? How can I identify it? Does it cause problems? Are there alternatives or is it the best type of audio or do we even have choice?

Thanks guys.

[Carpo]

What is VBR audio exactly? How can I identify it? Does it cause problems? Are there alternatives or is it the best type of audio or do we even have choice?

VBR = Variable bitrate, audio encoded in this have different amount of bits assigned to where they are required, some areas may require more bits than others, you can see if you have vbr mp3s or most other audio by playing them in winamp and look at the bitrate box - it should change quite a lot, only real issues is the one you have found it can cause sync issues

best type, well that is subjective - what is best for one may not be best for another, and the question which is best is not really one you should ask here - its more a trial and error session with what you think best suits your needs and which you think sounds better

[setarip_old]

How can I identify it?When you originally created the .AVI, what audio format did you select?

[weaver4]

You obviously didn't save it in Direct Copy mode, and you should be using VirtualDubMod since your video contains VBR audio.

The delay is a matter of trial and error. 1000ms = 1 second. It makes no difference what the number says - just estimate the required parameter by how far off the audio is from the video, then save it and play the new file. If it's not right, adjust it, save it again, etc.

You can play it in media player classic and change the audio delay until you have it right and then use VDM to delay the audio the correct amount.

[CWR03]

What is VBR audio exactly? How can I identify it?
By opening the encoded file with GSpot or with VirtualDub(Mod) as you have done.
Does it cause problems?
Not if you select "No" when prompted to rewrite the header.
Are there alternatives or is it the best type of audio or do we even have choice?
The alternatives are to use the original AC3 audio (which takes more file size) or use CBR audio when encoding your .AVI in the first place. If you're not encoding them yourself, you should probably re-read the forum rules (http://forum.doom9.org/forum-rules.htm), particularly #6.