Why does A/V sometimes go out of sync?

[takearushfan]

Hi,
I was dealing with a DVD I was ripping and it occurred to me that there's a question I don't know the answer to:
Why does a rip's audio/video sometimes go out of sync? What exactly causes this?
I remember ripping The Day After and it was (literally) the only DVD that ever went out of sync. Someone told me to use FixVTS and that resolved the issue. However I'm still wondering what causes sync issues. Does it have something to do with the encoding process? What is it that's happening when a rip's A/V is out of sync?
Thanks,
Justin

[greyfalcon]

I'm anything but any expect on this stuff but the problem more than likely is during the stage of decryption, a lot of DVDs have unreferenced cells (from the copy protection) which can cause the audio to get out of sync when your converting it to the .avi

I rarely rip dvds anymore but I used to use a tool called RipIt4Me which you may find interesting already uses FixVTS as part of its normal routine. So the solution would lie with what your using to 'rip' the dvd, some people run Slysoft's AnyDVD in the background, though I don't know if it now has something to deal with this issue on its own or not, it didn't when I used it last. Whatever tool you use needs to be able to detect the unreferenced cells and remove them or when the rip to avi happens you have extra frames, which makes longer video and out of sync audio.

[takearushfan]

Hm. Well I use AutoGK but I've taken to the habit of running FixVTS manually before ripping a DVD. I also make sure to remove any encryption and protection. I just wondered how all my DVDs managed to convert fine, except for that one.

[jman98]

This is very rare and I cannot explain why it happened, but I have once or twice done a DVD rip of TV shows and had them go out of sync. The reason was that the audio started with the beginning of the episode but the video started with the production company logo as a short intro. Using a video editor was able to fix it. But I still have no idea why this happened. The DVD where I remember it happening for sure was season 1 of the NBC show The Office and that is one of the worst authored DVDs I've ever seen. All kinds of crazy stuff on that one. I had to listen the ripped audio by itself and watch the video separately to figure out what was going on in this case. So check to see if something like that happened on your rip.