Video integration on Lexus Nav. Screen

We do alot of aftermarket lexus work.  1 of our standard options is a reverse act. back-up cam displayed on the factory nav. screen.  My tech who knows how to do this just left to work elsewhere and my other tech. and myself don't know how he was doing this.. Can anyone help???

there are two wires to get the factory dvd player to play on the nav screen. my guess is that you should be able to get the the video input on that screen as well.   The wire that you need to get the video to turn on are the light green (that gets cut and grounded,its the parking brake wire) the other wire is the PURPLE / red( Ithink it was pin nine but check first , its the speed sense i have always put a awitch on this too keep the nav accurate) this was on a 04/ gx470

my guess is the colors will be the same you just need your viedo in wire that information i dont have yet. make sure you test all these wires first the colors might not be the same.