Looking at most posts around here, AviSynth is the way to go.
The most definitive thread - butbthere are dozens more - is the Dark Jedi thread - all 132 pages of it.
There are now 3 versions of this and a Blu Ray version in progress. All using the 2006 GOUT as the source. The V3 is particularly good as the video is amazing and it contains all known audio versions including the restored Monomix for the first film as well as a recreated 5.1 mix by another OT.com member.
Following links from that thread will give you a real insight of what has been done so far.
Good luck.