I’ve never seen “Birth of a Nation” — a fact I’m not too troubled by — but at the Idea Festival I did take in “Rebirth of a Nation.” It’s a fascinating remix by DJ Spooky, aka Paul Miller, that cuts up scenes in the film to great and thought-provoking effect. You can check out a clip on Spooky’s website, but it doesn’t quite compare to seeing the film with a live musical accompaniment at the very theater where it’s said that D. W. Griffith himself used to work. (I think, however, this may be a Louisville urban legend — looks like the theater didn’t open until 1925, by which time Griffith’s iconic racist film was already 10 years old.)