Just bought the new Apple TV 4K to add to my system. Here's what I've got:
Apple TV 4K
Sony 55" 4K HDR TV - XBR-55X850D
Sony Receiver - STR-DH550
Apple TV 4K is connected to my receiver via HDMI on the BD/DVD HDMI port using a brand new Belkin Ultra High Speed HDMI Cable that supports up to 4096x2160 resolution and bandwidth up to 48 Gbps. Receiver's HDMI out goes to my Sony TV. No issues there.
I want to be able to control the volume on my receiver with the Apple TV remote, but in the Settings menu on the Apple TV I'm only getting options for controlling the TV using IR (infrared) and the Receiver using IR.
I press HOME on the Receiver remote to go to Settings > HDMI Settings, and I have "Control for HDMI" set to "On". I've tried having "Pass Through" set to both "Auto" and "On" and no matter what I do to these settings I can't get the Apple TV 4K to let me control the receivers volume via HDMI.
Here's another fun wrinkle to throw in...
When I had my 4th Generation Apple TV (1080p), the receiver's settings menu (when accessed) would overlay on the Apple TV's image on the television. Since connecting my Apple TV 4K, when I press "Home" on the receiver remote, the entire screen is filled with the receiver's menu (after the screen blinks green for a second as if it's changing inputs), AND if I set the Apple TV 4K to "Receiver using IR" in the Remote settings, when I change the volume the entire screen goes black with the numerical volume graphic in the lower right of the screen. On my 4th Gen Apple TV it would just occupy a small square in the lower left and I could continue viewing my content without interruption.