2013 Passat oem remote signal wire to reverse camera question?

[hardtland]

I have a 2013 Passat SEL Premium that had a digital OEM backup camera. Had to replace the head unit with aftermarket and tried a digital to analog converter for the oem camera and it didn’t work. Have 3 wires from the OEM camera. Solid power (red), reverse remote signal wire (blue) and ground (brown). The reverse signal wire throws voltage when put into reverse so I figured I could just use that wire. But it distorts the camera image. I’m not educated in how remote signal wires work but I’m trying to wire this dang camera without having to use a manual switch. Son keeps forgetting to turn it off (via manual switch) and it drains the battery if left on without driving for a couple days. Is there a switch out there that will open the circuit when the reverse single comes on? Or, is there another way to do it? Again if I wire directly to the red it is on all the time and works (or through a switch to turn it off and on), but not currently using the blue remote signal wire (live when placed into reverse, but doesn’t work as main power source to aftermarket backup camera. Any help is greatly appreciated.