I speculate that the audio signal at the Optical Audio Out of the 3rd generation Apple TV is always the same audio signal within the HDMI output.
I further speculate that that's the reason behind eliminating the Optical Audio Out connector in the 4th generation Apple TV.
Hence one does not need to worry about losing Optical-Out when replacing an ATV3 with an ATV4 provided that either:
- the TV has Audio Return Channel (ARC), which would take the audio signal from HDMI and pass it onto the receiver. (Here I'm thinking of a user who never uses the audio amplifier on the TV and who always switches the receiver on, even when watching TV.) ARC is important since you wouldn't want to keep the TV on during all the time you're just listening to music.
- the receiver has HDMI input (older receivers don't). If the receiver has HDMI input/output, then the ATV4's HDMI would connect to the receiver and from there to the TV. Hence, again, the TV can remain off while you're listening to music.
Is my understanding correct? Am I missing something?
Here is the setup I have in mind:
As you can see, there is no "return" involved here. So the feature that I'm looking for could more plausibly be called "audio pass-through". This audio pass-through works fine when a TV is on (by necessity!). The question then is what guarantees there are for it to continue working when a TV is off.