yes just what MObermeier said.
You need to hook up the parking brake wire either to the parking brake switch or to a ground.
If you hook it up to the parking brake, the only way you can watch videos is if the parking brake is on. If you hook it up to a ground then you can watch videos all the time, but it is a danger then to others and yourself since you can watch videos while you drive. I also believe it is illegal to have a video playing in the drivers view in most states.