[hdmkv]

What would be interesting is if you connected that LE S912 box again to your Epson PJ and then SSH Logged in and issued a:

Code:

cat /sys/class/amhdmitx/amhdmitx0/disp_cap

You can then see exactly what HDMI EDID negotiated display and colorspace modes the S912 is reading from the Epson PJ.
These can then be tweaked and put in a disp_cap file in the .kodi/userdata folder when using LE.      

@wrxtasy, just tried what you had suggested several weeks ago. A different S912 box, a Tanix T92 2GB/16GB. Running LE off a mSD card. When I issue the command above, here's what I get...



Before I get back to LE, some background on my Epson 5040UB and what has worked and not worked, at least w/nVidia Shield TV & Zidoo X9S players. I know Epson 5040UB supports 4K "12-bit" up to 30Hz, and anything above in 8-bit only. I say "12-bit" instead of "10-bit" as that's what the PJ likes or maybe just sees. I never see it getting or showing 10-bit, always 8- or 12-bit only. With my nVidia Shield, I've forced the resolution to [email protected] (@23.976/24/30 also work) as it's the only way the Shield allows me to then pick 4:2:2 12-bit Rec2020 in the HDMI advanced menu...


Then, when I play a 4K HDR 23.976 movie, whether via Kodi, Amazon or Netflix, I get beautiful HDR. Here's a screenshot w/Kodi of 'Dunkirk' in HDR.

So, now back to the Tanix S912 box and LE. I set the Kodi UI to 4K@24 (also tried 23.976, 29.970 & 30), then ran variations of these, rebooting each time...
echo '444,10bit' > /sys/class/amhdmitx/amhdmitx0/attr
echo '444,12bit' > /sys/class/amhdmitx/amhdmitx0/attr
echo '422,10bit' > /sys/class/amhdmitx/amhdmitx0/attr
echo '422,12bit' > /sys/class/amhdmitx/amhdmitx0/attr
echo '420,10bit' > /sys/class/amhdmitx/amhdmitx0/attr
echo '420,12bit' > /sys/class/amhdmitx/amhdmitx0/attr

But, I still get 8-bit playback with any of the above, with HDR however. PQ looks almost identical to Shield's at 12-bit, but think Shield's might be better (or it's just placebo, w/me expecting it is as it's showing 12- vs. 8-bit). In any case, is there a way to force 12-bit in LE? The commands I entered didn't as the Kodi UI and video playback show 8-bit. Could be that because Epson 5040UB is limited to 10.2Gbps and can't do 10/12-bit above 30Hz, LE is limiting the box to 8-bit across the board, regardless of videos at less than 30Hz?