Problem with Sync' of Video & Audio after Demux & Mu

[VEBouto]

Hi,
I have made some music DVD's, using DVD Decrypter to De-mux the Video and Audio Tracks(directly from the DVD-rom). After converting any AC-3 files to Wave i then Edit (Increase or decrease the volume) in Sound Forge 7.0 and then save the new file as a Mpeg 1 Layer 2 (Main Concepts) Audio File.
The problem is that when i mux or re-attach the Video file back to the new Audio file using TMPG Enc Mpeg Tools....the finished video is sometimes out of sync'. I thought that sync' problems were only something you had when capturing from an external VCR or Video Camera and not from Demux and then Multiplexing.
I compared the length of the old wave file and the new Mpeg 1 file, but the length is the same, so where is the sync' problem coming from?
Any help would be greatly appreciated.
Thanks.

[dafreak]

are you doing anything to the video? such as converting framerates?

are you changing the sample rate of the audio? make sure your sample rate is at 48000 hz for dvd audio.

[VEBouto]

Hi, i am pretty sure the sample rate is 44,000 so maybe that is why its happening.
Thanks for the tip...i'll try converting to 48,000 tonight.