download the codecs package from mplayer website and
mkdir /usr/local/lib/codecs
tar xjvf essential~.bz2
cd essen~
mv * /usr/local/lib/codecs
cd
then unpack and compile mplayer
tar xjvf MPlayer~.bz2 or tar xzvf MPlayer~.tar.gz if in tar.gz format
cd MPlayer~
./configure --help
scroll thru the options and use what you want
I usually have xvid already installed, as well as lame, toolame, and any other special helper apps you might want
the configure script will usually find most of them on its own and list them at the end, if it doesnt, add it to the configure script like this:
./configure --enable-mp3lame -----that would add mp3lame to mplayer's capabilities
if it complains of not finding a library, you may have to point it to where it is with --include-lib=(directory) see ./configure help for options and syntax
mplayer/mencoder can do an awful lot of things, streaming video, re-encoding/decoding, tv tuner input, you name it mplayer probably can do it