After digging into Denon and Onkyo's manuals...
The ARC is not an independent input. It will "piggyback" on some other input, when enabled. With Denon it will always piggyback on TV input, so it has to be selected for ARC to work.
With Onkyo you can explicitly prioritize which of the possible sources (ARC, HDMI, optical/coax, analog) takes precedence if more than one if available for a given input. That's why they allow to still reassign HDMI when HDMI-CEC is enabled - but they suggest you don't do that (i.e., if you do it and don't understand what you're doing, it's your own problem).
In any case, you still need HDMI-CEC to tell AVR that it needs to start this piggybacking of ARC over some other input. Now it's clear why AVR has to switch to "TV input" when TV is tuned to the tuner - you need both - HDMI-CEC and AVR on the correct input, for the ARC to activate.
Samsung TVs can also activate ARC using Anynet+ menu (which is HDMI-CEC too).
Can some owner of Denon tell what OSD languages are available in the menu? I can't find that in the manual.
The ARC is not an independent input. It will "piggyback" on some other input, when enabled. With Denon it will always piggyback on TV input, so it has to be selected for ARC to work.
With Onkyo you can explicitly prioritize which of the possible sources (ARC, HDMI, optical/coax, analog) takes precedence if more than one if available for a given input. That's why they allow to still reassign HDMI when HDMI-CEC is enabled - but they suggest you don't do that (i.e., if you do it and don't understand what you're doing, it's your own problem).
In any case, you still need HDMI-CEC to tell AVR that it needs to start this piggybacking of ARC over some other input. Now it's clear why AVR has to switch to "TV input" when TV is tuned to the tuner - you need both - HDMI-CEC and AVR on the correct input, for the ARC to activate.
Samsung TVs can also activate ARC using Anynet+ menu (which is HDMI-CEC too).
Can some owner of Denon tell what OSD languages are available in the menu? I can't find that in the manual.
























what a poorly executed technology 
