Do you know for sure that it's corrupted, or do you say that because it won't play?
If it's truly corrupted, you probably won't be able to recover the whole thing, and you might not be able to recover anything. Corruption is the digital equivalent to dynamite.
Now, if it just won't play, you might be able to recover all the data, or most of it.
Do you get any messages when you try to open the file?