try this link and read the docs:

http://plugindoc.mozdev.org/linux.html

dhughes wrote:
> Hello,
> I've been trying to get mplayer working in mozilla in Linux. Real
> player would hang, so does mplayer. I installed version 9.0 with an rpm
> and copied it into my local user directory. Mozilla just hangs when I
> try to access any media on the web like real media or the Lord of the
> Rings quicktime link.
>
>
>
>