Hopefully somebody that writes capture software can answer some of these questions. I would like to know how the audio and video is captured, and how the relationship between the two streams work. The normal mode for Vdub is that the audio is locked to the video stream, how? And if that was the case, how is it possible for audio to be out of sync with the video? As far as I can tell, when recording, if there are lost frames, the 44.1 Khz sample rate is changed to compensate for the slower video rate. When playing back the file, the video will be playing back a bit faster, while the audio is locked at 44.1 Khz, no matter what speed it was recorded at. If the recording of the two streams were not locked, then the video would finnish before the audio was done. However, when the streams are locked, and since the audio was sampled at a lower speed, it will also finish faster when played back at normal speed. However, I have seen the case when I have lost 90 frames (3 sec), and end up with the audio being 3 seconds behind the video. How is this possible if the streams were locked when recoring? I have seen this with Vdub when playing bad VHS tapes with drop-outs. vdub is detecting the drop-outs, but is not compensating correctly for it. Since the audio clock on most audio capture cards is quite accurate, the best way would be to have the two streams run independent, and then combine the two when playing back or encoding. Even if the two streams get a frame off, that is still good sync.
I would like somebody to shead some light on the capture and playback of audio/video streams.