Reverse camera Not functioning with ignition on
 

I have bought CANLINE 7019 MULTIMEDIA GPS/ DVD/ player with reverse camera and have it installed in 2007 Automatic Passat from a workshop.
http://www.youtube.com/watch?v=rJQ3ou23lFQ
The problem is reverse camera only works when the ignition is off and displays No signal when turning on the Ignition.
Here is step by step information.

Insert the key in to power on.
Put the car in reverse gear.(R)
Output on the DVD display will change to back Camera and works OK.
Put the car back to Parking (P)
Turn on ignition.
Put the car to reverse gear.
Output of the DVD display switched to reverse camera but then display No signal

The workshop guys claimed that he has connected the wires correctly and the issue is related to a lock in the player that disable display of Video contents when the car is in driving mode.
This is absolutely ok when it comes to playing a DVD which only works when handbrake is on but for Camera there should be solution.
Wonder if anyone has gone through the same situation and have a solution ?

Thanks