So you're sure the youtube server converts the file to .flv itself; without spoiling or degrading the movie?
The quality will stay the same if it's a good quality .avi file. I'm not sure about the .flv. I know youtube converts the files though because you rip them from youtube they are always .flv
Yep that's why I want to find a converter to .flv, to prevent quality-loss.
But now I made a mp4-file, shrinked to 25 MB,
and check if it works.