Intel NUC8i7BEH - missing 4K refresh rates above 30 Hz

In an attempt to get TrueHD working in passthrough I decided to update both BIOS and HDMI firmware on my NUC.

So now I actually got TrueHD passthrough, yay!

But instead I am now missing refresh rates above 30 Hz for 4K resolution 3840x2160, which I am pretty sure was working before the upgrade.

I found this thread from Thomas_AR discussing HDMI firmware on the NUC8 too but they were not mentioning refresh rates I think: Intel NUC 8i5BEH - HDMI Sound problem

Current setup

LibreELEC-Generic.x86_64-9.95.4

Intel NUC8i7BEH -> Marantz SR8015 -> Sony XF90

BIOS: BECFL357.86A.0088.2021.0330.1431

HDMI firmware: 1.78.4.0.4 (MCDP2800_C21_C22_V1.78.4.0.4_LSPCON_MP_FHC_SIGNED_CMDB_BE_210309)

I have tried adding custom 50 Hz and 60 Hz refresh rates with xrandr but none of them were accepted by the system. It just reverted back to 30 Hz.

I have also tried creating kodi.conf with different parameters e.g.:

MESA_LOADER_DRIVER_OVERRIDE=i965
LIBVA_DRIVER_NAME=i965

But I didn't notice any difference at all.

Alright I think I have solved the issue now.

I just spent a few hours where I tried nearly all combinations of HDMI cables, HDMI inputs on the reciever, HDMI inputs on the TV, running HDMI through the reciever, and directly from NUC to TV.

I know that not all HDMI cables are equally good. But the cables I have been using recently until I upgraded the NUC, had worked just fine. But apparently they are no longer good enough for the NUC. They were even bought specifically on the 4K/8K specs!

But I am now back to my old Supra HF100 HDMI cables bought in 2018.

As if that wasn't enough, not all the HDMI ports on my TV are allowing the NUC to set >30 Hz refresh rates. Sigh..

And by the way I also still have TrueHD in passthrough.

I got a new NUC, NUC11TNBi7. It's running LE 10. Also got new Supra HD5 HDMI cables. Otherwise same setup.

Yesterday I wanted to watch some TrueHD stuff but as soon as the video started the audio just stopped, the audio output signal "froze"and nothing I did would change it except a reboot.

Eventually I switched the HDMI cable to the second port on the NUC. And now everything just works! The two HDMI ports on the NUC are 100% identical according to the specs as I read it.

Is this some mechanical issue with HDMI hardware? That it is just not robust enough in some way.

Or is it Intel HDMI hardware specifically which is poor quality?

I am just mystified by this behavior.

Edit:

It's getting pretty annoying...

HDMI port 1: Only 50, 59.94 and 60 Hz refresh rates work at 3840x2160, but TrueHD works fine.

HDMI port 2: All refresh rates at 3840x2160 works, but TrueHD does NOT work.

Edit 2:

Ok this is perhaps slightly embarrasing, apart from the fact I am debating myself here.

In my ignorance I had set the video signal format on the Marantz reciever to "Enhanced". I had also tried the "8K enhanced" which didn't make any difference by the way.

Only now I get the idea to set it to "Standard", and voilà all the refresh rates at 3840x2160 works and TrueHD also works.

So yeah I guess I didn't know what I was doing without realising it.