The syntax for FFMPEG video cropping is like:
ffmpeg -i input.avi -vf crop=439:455:73:15 -vcodec mjpeg -qscale 2 output.avi
The assumptions made above were that you wanted your output video to be:
with Motion JPEG output
-qscale 1 makes low compression (best possible MJPEG quality).
qscale can go from 1 to 31.
Obviously, change these pixel parameters to suit your particular video.