capturing using different compters for A/V = mux drift/sync issues

[drstrust]

I record audio and video on two different computers at the same time (since I have no mic jack on my camcorder, and I've never found a program that lets me record from a computer mic and a videocam at the same time) - then, when I try to add the WAV sound file to the video, it all starts off well, but then the audio starts to go out of sync/drifts within a few minutes. This happens with WMV, AVI and DIVX files as well.
I capture the video in a stream through FireWire directly from the camcorder into the computer
I'm using Nero 7.
I capture the audio with Audacity.
I've tried converting the WAV file to an AVI standard - the audio settings (freq) already in the AVI file - but no luck.
Windows Movie maker has the same problem with WMV files
I've tried the DIVX encoder and Windows Media Player, but no luck...
I've checked audio freq for match


Does anyone know to fix this?

OS: Windows Vista


Thanx------------

[redwudz]

My first guess is the the audio and video are of different lengths. That is one cause of sync drift. Another could be the DV transfer program dropping frames. Have you checked the running time of the video and compared it to the audio?

Audacity can be used to adjust the playing time of the audio file, though you may have to correct the pitch also if you make major changes.

If it's just a difference in file length, not too hard to fix. But if it's caused by dropped frames, the sync error may vary during the recording and that's not easy to fix.

And welcome to our forums.

[drstrust]

Have you checked the running time of the video and compared it to the audio?

Thank you, redwudz.

If I might clarify this a tad. With the files opened in a respective player/editor, if the numerical time displayed [ie 00:00:00] of the video file matches that of the audio file, then the file lengths are correct and should be in sync, right?

[redwudz]

Most of the time, if the audio and video are the same length, you are OK. But that may not account for missing frames or other problems. Audio offsets can also complicate things.

On the other hand, if the video and audio lengths are different, that may be the main problem.

[Nelson37]

When you capture with Firewire, the audio should come with the video. Have you investigated why this does not seem to be happening?