hi all, i don't know if it's an useful reply, but this is what i'm using to convent a dv - avi (720x480) to a beautiful, deinterlace, 640x480, mpeg with keyframe everyframe:
ffmpeg -i stop.avi -vcodec mpeg2video -cropleft 40 -cropright 40 -sameq -deinterlace -intra -g 1 -an stop_final.mpeg
pat