@Paul,
a USB KVM would work if the consoles were all simple inputs. That's true for the Raspberry where the controller board emulates a usb key board ( buttons -> controller board -> usb -> raspberry).
Unfortunately modern consoles (like PS4) expect more than that. the "PS" button is needed evertyime you want to start a session and is complex to generate. This is very well done by some manufacturer who provide enhanced controller boards for this specific purpose. I am not planning to reinvent the wheel and just use what they have done.
regarding the HDMI control, I have an HDMI switch that I wil control with a raspberry / this is not only to switch the HDMI source but also to control the screen on/off to limit kids playtime. [If you are interested to know more, I have a coin acceptor that will connect to a raspberry which will set a timer based on the amount of coins/tokens that are inserted and then will power off the screen with CEC commands. I did not want to fiddle with sending IR to the TV or the HDMI Switch]. But as i said this part is sorted, it is just the players input routing that needs to be figured out.
@Dave,
I looked into the multiplexer and that looks very good. only downside is that I would need to have many of them. If I am not mistaken a 16 channel would catter for 2 inputs / 4 consoles (2 bits for console choice and the other 2 for the 2 controls).
Correct me if I am wrong:
I would then need 10 of those to achieve 20 inputs for one player. While doable, is there any other multiplexer you can think of that could do better? I looked online but anything with more that 16 channel is starting to get pricey. Also, with that mux I would limit myself to 4 consoles. I am pretty sure I will add one more one day... :-(. So to be safe, i would need 20 of those instead. (1 mux / button). The 16 outputs would be a bit wasted but give room up to 16 consoles. a bit overkill.
@ Dave again.
I did not get the "A/ B/ C/ D paralparallel port printer switches". how would you implement this, I am not familiar with it
thanks!