The Rockford Fosgate DSR1 Digital Signal Processor with iDataLink is an excellent solution on paper for integration of stock factory automotive stereos that retain stock operation. (Including factory head unit operation, and steering wheel controls.) The DSR1 allows per-channel levelling, time delay, and band, high, and low pass filtration. The DSP allows for 8 discreet channels out at line level, after the automotive CAMBUS data is decoded on the Rockford Fosgate side, and routed via cables and decoding by the iDataLink Maestro side of things.
In this particular implementation, I've found that the system works as described for Apple iPhone, but not for Android. (S22 Ultra, and S8.) When ...