you CANT save replays! thats not how they work!
they arent video files, they are percentage files telling hte game what goes where and when.. thats why when you watch a replay you can hit square and have "dive mode" that goes along with the music... and well.. since you CAN do that, that means that it isnt a video!
..because you cant exactly go to the movie theater and scream at the video to see if it will change.. no! you cant! because its already happened; your just watching a REPLAY of what DID happen.. and it cant be edited from a standing point
the way replays work (in ALL games) is in percentages. it tells the system what (or who) is in the game, lists their names, and gives them all percentages of gas, brake, steering, and such.. therefore its not a video file.