Sorry to post in such an old thread, but I have a problem that sticks close to it.
Right at the moment i'm trying to convert the THX Wow trailer to PAL. The clip is telecined. Therefore I tried it with Avisynth using Decomb. The result was a absolutely smooth playing PAL clip which lastet 20 seconds shorter than the original NTSC clip.
After that I decoded the original 5.1 Dolby track to six wav files and changed the lenght to the lenght of the new PAL clip (which had the effect of a slight pitch change, but that didn't matter so far).
Now here's my problem: although the PAL video and the adjusted audio track do have exactly the same lenght, audio gets out of sync after about 30 seconds of playback. I really can't see where the problem is.
One thing to add: during the first 30 seconds the original clip had pure NTSC. After that the part which is mostly FILM begins.