I work with ffmpeg a lot. I recommend that you don't try to build the rpms which are constantly out of date. ffmpeg is a moving target so I recommend compiling it from git. It's relatively easy and you can find most of the dependencies in either epel or rpmforge (lame, xvid, faac etc...). There are a few dependencies that you need to also compile yourself but only if you think you need those features (amr encoding, x264 etc..) x264 is also notoriously out of date in any repo. You'll want to compile that yourself as well.

Brandon