because of licensing, you need to compile it yourself and install the codecs from their website.
You can probably use the rpm-packages on their homepage, too.
->
http://www.mplayerhq.hu/design7/dload.html
Look for the "Binary codecs" there and install them to... dunno, read the README in the codec-tar.gz
I could post my compiled version of on my website so you can download it, but you won't have a GUI.
I could make a README file, so that most things should be easy...