The idea was floated at Ani-nouto more than a year ago, but now I had an opportunity to try it out.
The DVD of DearS that I watched had a strange glitch: dd-ing the image gave an I/O error 770 KB in. The disc was badly scratched, so I buffed it (even bought a new kit). It looks much better now, but the error remained. But then, I noticed that libcss fails to crack a couple of keys... which may be relevant. The content is watcheable with mplayer.