go to in expert mode and make a anaphornic video.
To read more on this opreation, go to the follow website : http://www.ffmpeg.org
Now to help you a little, i give a command line in example :
-s 640x272 -aspect 16:9 -croptop 58 -cropbottom 62
You can input this values in editing mode on the expert mode window.
Have a nice day.