the best configuration is this... for all kind of video...
root
leafpad /home/user/.mplayer/config
or
nano ~/.mplayer/config
and delete all and write in it

ao = pulse
aspect=16:10
screenw=848
screenh=480
subq=4:bframes=2:b_pyramid=normal:weight_b


thanks to the previous advice this is a successfull of mostly for all avi and kind of type of video.
(the most important line is the last one that's "subq=4:bframes=2:b_pyramid=normal:weight_b")

byez