I can help in the sense that I can prevent you wasting any more time on this by advising you it doesn't work like that. If you notice when you play replays on your PS3, it loads the track up. That's because it's replaying game data thru the GT5 graphic engine, rather than simply playing back a video. Hence the PC can't make sense of this data.
If you want to create PC viewwable content, you'll have to play the clips back on your PS3 whilst videoing your tv.
Unless anyone knows different, that is...