If you are running mplayer from xterm, make sure to provide it with '-quiet' (otherwise output to console eats too much of the resources) and '-benchmark' options. Also if you run it as root, it may have problems getting configuration options, so you may want to add '-framedrop', '-noslices' and maybe some other options. Make sure that mplayer is using 'omapfb' driver for video output and 'sdl' for audio (with libmad decoder). Thanks.

edit: Anyway, better try to play this video in the 'standard' mplayer GUI till it finishes itself. After the playback finishes (I hope it will not crash ), press 'Report' button to get the screen with statistics. The information about the number of dropped frames will be at the very bottom. The default configuration should be theoretically best tuned.