If you are using a Comcast cable box, you cannot use the DVD player unless you hook it up to your cable box so it plays on the "line input" channel of your television set. Instead of disconnecting and reconnecting the composite cables each time you watch a DVD, you can spend a few minutes hooking up the DVD player to your Comcast cable box.
Power off your DVD player and disconnect it from your television set. Keep the cables connected to your DVD player, as you will need them to hook up the DVD player to your Comcast cable box. You should have a yellow video cable and audio cables that are color-coded in red and white.
Power off your Comcast cable box and locate the "Video IN" and "Audio IN" connection ports on the back of the cable box.
Plug the yellow video cable from your DVD player in to the "Video IN" port on the back of your cable box. Connect the white audio cable to the left "Audio IN" port. Plug the red audio cable in to the right "Audio IN" port.