I have a project that uses a lot of flv files (not my choice, this is what I'm given). Premiere Pro doesn't recognise this CODEC but After Effects does! In fact, if I create an After Effects wrapper of this media (i.e., an After Effects project that simply has a composition congaing the media in its raw form), Premiere Pro then happily renders the content via After Effects. But I shouldn't have to do this. If After Effects supports a format, so should Premiere Pro and vice versa.