After downmix audio video sync problem

[adarkenigma]

i am attempting to re-compress old avi files which has high quality audio streams in order to save some space. most of the avi's have ac3 5.1 audio streams. after i down mix them and re-merge them to avi i get sync problem.

what i am doing is

1. loading avi in VirtualDubMod and saving audio stream in wav or demuxing ( i have tried both)

2. then disabling audio stream in VirtualDubMod and re-compressing avi with lower bitrate
( i am satisfied with re-compressed video stream)

3. downmixing 5.1 ac3 (or wav) to 2.0. i have tried couple of ways to do this
i tried Tranzcode_v0.40(beta), tried BeLight-0.22beta9 also AC3Machine.
( i wasnt sure if downmixing was the problem so i have tried output in wav, ac3 and mp3 formates .. but all with 2.0)

4. I merge avi with ac3(or wav) using VirtualDubMod

i have also tried to leave sample rate, bit rate and sample size intact in downmixed audio streams in order to narrow down the problem. but no success yet

so i was wondering what i am doing wrong here?

any help or point in right direction is appreciated.

thanks

[first]

download dgindex(http://neuron2.net/dgmpgdec/dgmpgdec.html) and open source in it and save after making ur audio setting.the audio file formed have the "delay(in ms)"in its name,use this in ur belight.
hope u get it fine