Audio Skew in VirtualDub

[analein]

HELP!

I have been using Virtualdub to edit AVI files. I am not doing anything fancy - I am simply cutting out pieces of the video and joining them back together. I am not re-encoding - it is just a direct stream copy of both video and audio.

Recently, when I open the source 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 up to 32546 ms of skew from the video stream. If this is unacceptable, decompress the *entire* audio stream to an uncompressed WAV file and recompress with a constant bitrate encoder. (bitrate: 111.1 +_ 13.9 kbps)"

The amount of skew and the suggested bitrate at the end of the message vary for each source file. Ignoring the message and going about my business predictably skews the audio in the final product.

How do I do what Virtualdub is suggesting? I am very new at this, and I have no idea how to decompress the entire audio stream to an uncompressed WAV file or how to recompress it with a constant bitrate encoder. In another post, somebody suggested using AVIMUXGUI in response to the same message, but I have no idea how to use that program either or what exactly it is for. Can somebody outline the steps for either fixing the skew problem mentioned in Virtualdub or for using AVIMUXGUI to cut out selected sections of an AVI file and put them together? Thanks!

ESL

[Laddydaddy]

For the audio choose "full processing mode" and for the video choose " direct stream copy". When you save your avi your new file will have an uncompressed wav file.

[junkmalle]

In VirtualDub or VirtualDubMPEG2 this usually works for me:

1) Audio -> Full Processing Mode (decompress audio)
2) File -> Save WAV (save as a WAV file)
3) Audio -> WAV Audio (use that WAV file as the source)
4) Audio -> Compression (select compression you want)

[ukb007]

Hi analein

Your .avi has a variable bit-rate audio, and this is unacceptable to VDub, which prefers to work with constant bit-rate audio. Since you are cutting pieces off from a single parent file and joining some of them together, you can and should ignore the VDub warning. VDub will open your video like a good boy and will not balk again for the same opened file.

If you do prefer CBR audio which has no merits over VBR audio, then you can use any good audio processing software (CoolEdit / GoldWave / SoundForge) and extract the audio as .wav, and then re-compress it with the same software back to cbr form. Letting VDub do it will induce skew, which will mess up things.

Thanks.

[Josef K]

One of the easiest ways to change audio to PCM (one click method) is to use Decompress.exe that comes with AVI2VCD

From the About box:

This program is an *.avi to uncompressed PCM audio *.avi converter. It accepts an input avi which has both audio and video, and if the audio is compressed, decompresses it to PCM. The video remains unchanged. Whatever format the video portion is in remains untouched. If the input avi audio is not compressed, the audio remains unchanged.