Are you trying to play videos in landscape mode or portrait mode?
In portrait mode on a 5600 : -vop rotate=1,scale=236:-2,rotate=6 -geometry 87:2
-]taken from mplayer 1.2 shell source
The scale value 236 is number of pixels in the x axis, it will resize the y proportionately.
The geometry value is the location on the screen where you want it to appear ( upper left hand corner )
I am not sure how the rotate option works though.
In landscape mode : -fs