quick question on sync in avi file

[Ogilvy]

Hi, is there any app I can use to accurately measure the sync delay between audio and video in an .avi file please?

[redwudz]

You can use a software player like MPC and adjust the delay by ear, then read off the delay in the program and adjust it by adding a offset in the audio file using that number. Of course that will only work with a offset sync error. For AVI type files, I use VirtualDub to add the delay, positive or negative.

If the video and audio are different lengths, then a program like MediaInfo should give you the lengths of the separate files. You would notice this type of sync error as changing while the video plays. In the first type of sync error, the error stays the same throughout the length of the file. You would need to adjust the length of the video or the audio. Usually it's easier to adjust the audio. I use Audacity to stretch or shrink the audio playback time.

A combination of these two errors can be really difficult to fix.

I don't know how any program would know that the sync was wrong, you have to use your ears for that.

[Chris K]

If you want to skip the procedure of demuxing audio, processing in VirtualDub/Audacity and muxing again, you can try the audio "shift" and "stretch" options in Avanti. These will do it on the fly when you re-encode the audio stream. Both options can be used simultaneously.

Should be also possible to re-encode audio and copy video stream in one go.