Avic-d2 and itouch

You can't plays video through the DVD player in the car, You can add external DVD player and plug in video and left and right audio jacks on the back of the player.
Then you select Aux input from the source menu, Or as I do I load MP4 videos on the Iphone4 connect to the same jacks on the back,You will need a composite video and audio cable from I store $40.

You can play the video on your player, and see to it if there is an input jack at the back of your unit, such as rca jack,mini jack or special connector , and try to set the menu botton if there is an input selector.