What's up, man? I'm glad to finally help you, because I think you helped me once. I believe you have to specify a video after aa:help. I tested it with mplayer -vo aa:help fn.wmv |less.
I'm not sure about building it into an mpeg. Sounds very possible, though. Probably something more complex than mplayer -v aa vid.avi >> vid.mpeg
Hope this helps,