Audio sync troubles when capturing

Hi. I am using Vdub 1.7.0 to capture from my bt878 capture card. I capture to Xvid at 320x240 with mp3 audio. I use Lame 3.98 ACM mp3 codec for capture. Now, the audio is getting out of sync throughout the captures. The audio does begin in sync at the beginning of the file, but as time goes on, the audio is delayed (must use negative delay values while watching in Media Player Classic to correct the delay.) I have tried switching to Lame 3.97 ACM, still problem persists. I tried changing the sample rate of the audio capture from 48khz to 44.1khz, didn't work. I tried changing the "timing settings" in Vdub capture to "sync video to audio" rather than "sync audio to video." After 10 minutes of video, the audio is delayed by about 200ms. What else can I try?

Is it a constantly increasing error? After 10 minutes it's x ms, after 20 minutes it's x*2? Then it's a video frame rate problem, it's either slightly too slow or slightly too fast. (This can happen if you're capturing at 30fps but use 29.97fps for the video, or vice versa.) Try 1.7.3, on the off chance it helps, too. Tons of 1.7.x bugs fixed.

Hey Foxy. Yes, the delay is constant and linear, so after 10 minutes: 200ms; 20 minutes: 400ms etc... I think you might be right about the framerate, and that is what I am trying right now. The capture framerate was 30fps, I set it to 29.97 now. We'll see if that works.

All right. I tried 29.97 and it didn't work. So now I am trying a different framerate. Selecting the frarmerate from the bottom of the Vdub interface, I chose "nearest ms" 29.41fps.

29.41fps didn't work either. I'm running out of things to try.

Hi! Load the file into VirtualDub and from the "Video" dropdown menu, select "Framerate" - and then select "Change so video and audio durations match"

Hey seta. I know that would correct the problem after the capture is complete. But I also know that it is an issue with the Lame ACM codec. If I capture to PCM, no problems. But that wastes alot of space.

Capturing audio as anything other than Uncompressed PCM (.WAV) format has always been problematic, regardless of .MP3 codec used. I'd suggest you capture with PCM and then convert to .MP3. It doesn't take all that much extra time and you'll be a happy camper ;>}

Okay, I think I may have found my problem here. Using PCM, I was still getting async audio. So it wasn't just Lame ACM tthat was giving me problems. So I tried changing my video codec to uncompressed, and it worked. So Xvid was the problem. The problem was using B-Frames in Xvid.