Audio/Video Sync

[Sebby]

Hi,

I'm having a bit of trouble converting a DivX MPEG-4 Low-Motion AVI with stereo Fraunhofer MP3 audio to VCD. I've converted loads of my DivXs to VCD and never had a problem before with audio/video sync.

I'm following this guide - http://www.vcdhelp.com/tmpgenc.htm - so I've ripped the sound to a wave file first using VirtualDub and then encoded the video and audio using TMPGEnc. I've definately got all the settings right, etc, so I can't think what it could be.

There is no problem in the original DivX with audio and video sync. Unfortunately, I can't play around with the "audio gap correct" in TMPGEnc as the gap is not the same throughout the encoded movie - it starts off in sync and then loses sync by about 2 seconds. So it looks like I'm going to have to get to the bottom of the cause!

If anyone could help, I'd be ever so grateful - thanks

[ZippyP.]

Never had a problem with A/V sync!? Lucky you! Sounds like there may be a glitch in the AVI file. Did you "scan video stream for errors" in Vdub then select "direct stream copy" in audio and video and then save the avi, if there was errors? It's important to do that before any conversions. I found Vdub doesn't catch all errors though, and have had to locate them manually by converting small clips until I found where the A/V went out of sync. Then I manually clipped that part out of the file. See the guides for repairing and/or cutting AVI's with Vdub. Good luck.

[p_l]

And if VDub gives you that message about VBR when you load your AVI, it may not work properly when you scan for bad frames. The VDUB MP3 method suggested in King John's Guide to Bad Frames V2 really fixed the problem for me.

Hope it helps you too.

[Sebby]

Thanks for your replies, everyone.

Naively, I didn't realise you could have bad frames in a DVD-rip. After scanning my AVI, I found about 800 bad frames, which I have now removed. This could have easily been the cause of the 2 second sync problem.

Why is it that bad frames do not affect the playback of the DivX where sync is concerned, but they do when you convert to VCD?

I will try encoding again and let you know the results.

Thanks again

[Sebby]

Thanks everyone - it worked. Seemed that bad frames was causing the audio and video sync to be lost.

So why is it that when you watch the DivX there are no sync problems, but once you convert to VCD, they appear?

Thanks again.

[p_l]

I couldn't tell you why, but it does happen on a fairly regular basis. That's why it's always a good idea to check for bad frames before converting. At least there's a way of fixing it if some are detected.