Sounds as if you are interested in benchmarking, try the -benchmark option.

From the ubuntu man page

-benchmark

Prints some statistics on CPU usage and dropped frames at the
end of playback. Use in combination with -nosound and -vo null
for benchmarking only the video codec.
NOTE: With this option MPlayer will also ignore frame duration
when playing only video (you can think of that as infinite fps).

mplayer -benchmark -nosound -vo null your_file