Progressive Audio Sync Problem

[celestial]

I'm using an ATI TV Wonder 650 to capture home movies from VHS. It works fine for short clips, but over longer periods, the audio progressively becomes more out of sync with the video (the audio is ahead of the video by a second or more after forty-five minutes to an hour or so of video). I've tried a few times, and there are no dropped frames occurring (or not a significant amount - it varies from capture to capture, from zero to two or three over the course of more than an hour, so I don't think this is the cause).

The computer should be more than capable of processing the video - it's a Core 2 Quad Q9300 with 4GB of memory, and I'm capturing to a 750GB SATA hard drive. I'm using Huffyuv to compress the video, with uncompressed PCM audio.

I'm not very knowledgeable about analog or digital video - what could be causing this, and how can I fix it?

[juhok]

Propable cause is the (capture) video and audio clocks running at a different rate. This can often be fixed by using right software which is smart enough to detect and fix the lag (like VirtualDub). There's a lot of threads about this, use search.