What program within Gordian Knot strips the audio and syncs it with the video.I am trying to strip the audio from an avi file, encode the video and rejoin it with TMPGenc DVD Author. I end up with a good looking DVD file but the sound is out of sync.
So you have an avi with AC3 audio and you want to demux it? I would suggest VirtualDubMod or AVIMuxGUI.
If the sound becomes out-of-sync, as I wrote in http://forums.afterdawn.com/thread_view.cfm/129217, you need to extract the sound in an uncompressed form, first (Stream__Stream List__Save WAV in VirtualDubMod (I don't think that 'demuxing' will solve the un-sync problem, since the stream remains compressed) or Audio__Full stream processing mode and Fiele__Save WAv in VirtualDub), and to use this uncompresses WAV with TMPGenc.