As I mentioned in my initial post on this issue, my AV source devices are: (1) Cox DVR; (2) AppleTV (V4 - latest), and (3) Sony Blu Ray player. I have the Blu Ray player configured to send bitstream (not PCM) to the receiver, and that is working so that the receiver does the decoding, which is what I want. There is nothing to change on the Cox DVR - it only outputs LPCM via HDMI. However, the AppleTV 4 does seem to have an option to switch audio between "Auto" and "Dolby Surround". The problem is (in typical Apple fashion) this option is not documented by Apple. In addition, I have found very large threads on the AppleTV support boards discussing what these options really do. In sum, no-one seems to know for sure what they do. As tvOS has been updated, the behavior has apparently changed - but again, no-one is sure. (And AppleTV 4 behaves differently than AppleTV3!) It seems as though "Auto" generates LPCM (encoded with the correct number of source tracks), but that the AVR doesn't always use the channels as intended. Selecting "Dolby Surround" seems to produce Dolby Surround - sometimes with 2 channels, sometimes with more. The other source of confusion here is that the AppleTV source material encoding also varies - iTunes Movies, Netflix videos, HBO, etc. all have different surround encoding - and in fact, items within Netflix vary too. It is really hard to figure out what is being delivered to the receiver. The front panel on the Sony STR-DN850 does provide some information about what is being sent to the receiver and that helps - but it scrolls off quickly. (And, some posters on the Apple Support Forum claim that their AVR doesn't report the correct surround/channel mode for these feeds.)
So, I have some additional questions:
(1) Other than the (scrolling) front panel display, is there any way to see, in detail, the signal being received by the AVR?
(2) Does anyone have experience with Netflix as a AV source? Are there AVR settings that are optimal for this source?
This is all so crazy - and the complexity is mind-numbing.