Is there any way to uncompress a DVD movie? I'd like to try to uncompress a movie to see if it improves the quality?
It is uncompressed to RGB during playback and you won't notice any difference actually creating an uncompressed file. You could try using ffdshow to post process. Doing a nice lanczos upsize, sharpening, etc. Maybe you can notice some difference then?
There's no way to get the original files back from a compressed copy because the compression is lossy (ie it throws out information) and there's no way for any program to know what data was in the original.