When using a 7.1 receiver & speaker setup over HDMI with Xbox One, set to the default of "7.1 Uncompressed" - Blu-ray movies, and games work just fine. Sound comes out of the expected channels, and all 7.1 channels work if the content supports it. That all works great and as expected, which is why I imagine more people aren't screaming about this.
However, when using apps, like Netflix, or Plex (or really anything else), everything goes wrong as follows:
If the source content is 5.1, then audio for the the surround channel (SL and SR - the speakers to your sides in a 7.1 setup) gets redirected for some reason, to the rear surround channel (SBL and SBR - the speakers behind you in 7.1). The main surround (side surround) speakers aren't used at all.
If the source content is 7.1, then the audio for both surround channels (side and rear, aka SL, SR, SBL, and SBR) - are also routed to the rear surround channel (SBL and SBR). The main surround (side surround) speakers again, aren't used at all.
This makes no sense, I have no idea why this is the case. It doesn't happen on PS4 - which also supports 7.1. It doesn't happen on Xbox 360 either, which only supported 5.1. It's unique to the One.
The only way to "fix" this that I've seen, is to go into Settings on the Xbox One, and change the Sound mode to Bitstream, and choose either DD or DTS. And yeah, that works - the surround (side surround, SL and SR) speakers get used properly then for these applications. But not only is this a pain (lots of clicks/steps just to get to that menu everytime), but it also prevents you from enjoying 7.1 content in 7.1 - because the rear surround channel info (SBL and SBR) then get routed to the side surround (SL and SR). And, every time you want to use a Blu-ray movie or Game, you have to go back into settings, and change it back to 7.1 Uncompressed again, to get true 7.1 from those sources. So it's not really a fix at all, it's a bandaid.
Look, I know this sounds like #fwp, but playing media thru Netflix, Plex, other media apps, and even the Xbox One's own HDMI In, was a major selling point for me and the primary reason I just picked one up. I don't play games as much as I used to (getting older, yada yada sigh), so this is a serious problem for me. I'm back to using my old, fullsize Xbox 360 to use Plex and Netflix, because it's easier than monkeying around with the settings in Xbox One to "fix" this temporarily, and now my Xbox One is hardly getting used.
Combined with the lack of an extension cable for the Kinect 2.0 sensor (I have a home theater that uses a Projector, so 9 feet is laughably short for me), I am seriously considering returning my Xbox One now, (I'm still in the return period).