Audio sync problems/xvid to m2v problems

[dr.gre]

Hey guys, i wasnt really sure where to post this but im having a problem with taking a downloaded avi (xvid) and converting/burning it to a dvd. Now i wasnt sure where to post this becuase i dont know if the problem is with the conversion or the audio. But heres whats wrong. Every time (and i mean everytime with any avi file) i try to convert an avi to an m2v and then burn the file to a dvd i get an audio out of sync problem. Heres exactly what i do.
1) I first use virtualdub mp3 freeze to make a direct stream copy of the movie without any audio.
2) I then take the new movie without any audio and convert it to an m2v using tmpgenc (direct show priority is already raised).
3) After its done encoding the video i take the original avi and extract ac3 audio from it using ffmpeg.
4) i then take the audio and the m2v and author them and burn the m with dvd-lab
After im done i play the dvd and the audio starts in sync but it slowly and gradually gets too slow for the video and the video gets ahead of the audio. I dont know how to fix this. Everytime i encode any movie i always get this problem. Also when i looked at the m2v video length it says its like 6 or 8 seconds shorter than it should be. for example, one avi was 1:40:57 but after i encoded it it was 1:40:51, thats a big differenc. but when i played the m2v it still played to 1:40:57 so whats up with that? And when i resample the audio so thats its 1:40:51 the audio becomes way too fast for the video. Its almost impossible for me to gwet the audio and the video in sync. I really want help because all of my friends are burning dvds just fine and im the only one with all the problems.

[teegee420]

In situations like this it's often worth your while just to buy the DVD. Fixing gradual loss of sync is a bitch to do and I normally just delete these kinds of files. If you are still willing to try you might find some useful info in this thread.