get mplayer, best video player there is PERIOD, for any system
google for it, install the codec package too
it will play ANYTHING, its also allows you to rip DVD's and change formats/scaling of movies as well as quite a few other tricks.Has onscreen keyboard shortcuts to change brightness/contrast/sound synch/color saturation/volume etc etc
Its also better if your going to do decoding/encoding to get ffmpeg,transcode,libdvdcss,libdvdread, and libjmpeg I think its called, then download mplayer source and compile it
If you want just the mplayer package ready to go, goto
http://www.linuxpackages.net