[noggin]

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?  

The bit-depth setting is reset to 8 bits when you reboot - it only lasts for the active session.  If you are rebooting as soon as you select 10 or 12 bit you are resetting it back to 8 bits.

You need to reboot or power on, issue the command BEFORE you play any media - and then play media.  Then you should get 10 or 12 bit output (depending on refresh rate)

The AMLogic devices seem to replay 10 bit Rec 2020 HDR10 content and in 8 bit mode will output it in 8 bit with an HDR EOTF flagged - so the material plays back in HDR but with only 8 bit depth you will get banding where you wouldn't with 10 bit content output at 10 bit or padded to 12 bit with 00s in the LSBs.