I also have some major color banding issues with Denon AVR x1400H and the Xbox One X + LG OLED B6.
Xbox One X: all enabled in video settings to play HDR games, in this case The Witcher 3 with the new patch.
x1400H: 4k signal mode = enhanced for 10 bit hdr
LG B6: Deep Color enabled on the HDMI port
Basically, 8-bit 1080p/4K = no color banding at all (HDR and YCC 4:2:2 disabled).
HDR BT.2020 extreme color banding (Pixel depth never show in the AVR HDMI INFO screen when using HDR) (HDR and YCC 4:2:2 enabled)
Common factor as I have seen, is that when the AVR does not display the pixel depth, I will get strange colors or not the correct view on either HDR / SDR content.
So for now, I have to disable HDR on the Xbox due to the banding.
It also seems like the Xbox will never use 4:2:2, I only see 8/10bit and 4:2:0 with 1080P/4K via the AVR info.
Like others, I have color banding on the Insect demo with HDR enabled, none with HDR off.
I even entered HDMI Diagnostic and set "no limit" on the 4K signal on GAME HDMI Input on the AVR, seems like 4k Signal Enhanced is setting the limit to 4K30.
Pretty sure its a bug on MS side with the Xbox and how the YCC 4:2:2 behaves, as I've never seen it actually kick in. Also the Denon AVR struggles with banding somehow.
When I connect the Xbox directly to the TV, with HDR and YCC 4:2:2 enabled, it is NO banding either. But then I can't see pixel depth via the AVR.
Anyone have some briliant ideas on what I can test next?