Yes but the non-420 modes are not coming through. Can you post cat /sys/class/amhdmitx/amhdmitx0/edid and cat /sys/class/amhdmitx/amhdmitx0/rawedid please @LubosD
In particular, Kodi’s handling of artwork (poster, fanart, thumbnail, etc.) is a real problem when setting the GUI to 4K.
When caching artwork, Kodi grabs whatever artwork source you have, then reduces the resolution to match the <imageres> and <fanartres> settings (default for OSMC a height of 540 pixels for posters, and 720 pixels for fanart) if necessary. Then, this reduced resolution image is then used whenever the GUI needs to display the image.
This means a poster that takes up 75% of the vertical space would be scaled up from 540 pixels to 810 on a 1080p GUI, which looks OK, but not great. On a 4K GUI, though, it will be 1620 pixels high, and that will look pretty bad, since the algorithm used is very basic. The <imagescalingalgorithm> setting is only used when creating the initial small image (downscaling), not when scaling up on the GUI. This is supposed to change with Leia, but I don’t know it if has. Even so, a 3x upscale is still a lot, even for lanczos or a bicubic spline.
A solution to this is to increase the <imageres> and <fanartres> settings, but making them large enough that a 4K GUI looks good will result in a massive cache database (about 1GB per 75 videos with a full set of images).
I’m looking into this, but do you realise you will never get 10 bits at 4k60Hz? You may well find sending 10-bit 4k60Hz video at 1080p60Hz gives you a better picture (less banding).
No, I had no idea. I don’t understand the full relationship between chroma subsampling and HDR. Does 4:2:0 preclude 10-bits or is it something else you see in the EDID?
HDR is always 10-bit (or more). But you can send only 8 of those 10 bits and no device in the HDMI chain will complain. You just get banding on HDR displays because HDR stretches the highlights in the picture.
Any bitdepth can be used with any chroma subsampling except 422 with 16 bits IIRC.
Your beamer can handle a TMDS clock rate of up to 300MHz on which you can send 4k60Hz at 4:2:0, 8-bit but 10-bit needs a clock-rate 25% higher.
Just for future reference: in order to get 600 MHz bandwidth witb Denon’s receivers, one has to go to Video settings and switch the 4K mode to “Enhanced”.
If this is not selected, the receiver will clamp to 300 MHz regardless of what the projector or the cabling can do.