So, my solution to this problem, automatic audio input switcher. Basically, the system will detect which audio input has a signal, and switch to it using a solid state MUX.
The project is in early state. Prototype circuit works on a breadbord. First test PCB done and sent to the factory.
Operations: Stereo input is muxed using 10k resistors and AC coupled into an amplifier. (100x) Then, the signal is compared to a reference voltage using a comparator which charges a CAP. A MCU will then poll the output of the comparator and trigger the MUX (ADG409) to switch on the output.