ac3 Audio format

[atr232000]

Please
help i have a .avi file that the audio is a ac3 format the problem is the hole file is a massive 1.5 gig and i want to commpess it to a sweet 700 meg.
anyway i used vertual dub to save the audio as .wav then used azid to make the file stable but when i used TMPGEnc Plus to merge the original avi and the ripped .ac3 file to make a mpeg 2 file but the video and audio are not in sync.
how can i correct this
please help me

[setarip]

Under TMPGEnc's "Advanced" tab, put a check mark next to and click on "Source Range". When the adjustment window appears, you'll note an audio delay adjustment at the bottom. Enter the appropriate positive or negative number...

[atr232000]

ok well the audio start ok and in sync but as it goes though the film it getts a bigger delay
i did a audio gap correct of -1500 and i did a test and the first bit i got it in sync and it was great that was in the middle of the movie
then i did a clip from the start of the movie and its all out off sync again with all the same settings
i carnt get my head round this as the both audio file and video file play for 1 hour 55 min but the sync is good at the beginning but realy bad at the end