I have a video file, but I want the sound as an Mp3

[DMBFan23]

I have some videos of dave playing some stuff live, which I watch on my computer. but, I want to isolate the sound part of it and play that on my iPod.

is there a program out there that can do this electronically, like reverse engineer the file or something and isolate just the sound portion of it? I could always put a mic next to my speaker and record it that way, but the quality would be TERRIBLE.