In fact it depends very much on the distro as it determines the applications you have available without having to hunt them down on the net and installing them yourself.
I just recently stumbled over http://www.dynebolic.org/
and it sounds exactly like what you are looking for. It is like KNOPPIX but spezialized towards video editing, supposedly even has some clustering stuff (mosix) built in.
I do not know if it is trustworthy, as it looks a lot like a hacker community thing, but I have not found any warnings yet (via google) and they are listed on freshmeat.net.
Good luck - I downloaded it and will try it later.