7900xtx: 12bpc @ 4k/120hz on LG C1 CRU Help Request - (solved)

[username00]

Earlier this year, I recall being able to use CRU to get full 12bpc at 120hz in 4K. Now, I just happened to notice that I can only enable 10bpc at 120hz and 12bpc at 60hz.

When new Adrenalin drivers were released, I always used DDU for a clean install - then ran CRU with that .bin file, restart64, rebooted, and 12bpc at 120hz was available as an option.

I've attached screenshots from CRU - showing the Detailed resolutions in the CTA-861 block, the CRU Main screen, and the red ink that appears when I try to add a custom detailed resolution in that main screen.

Am I missing something or can someone help? Thanks much!

System specs: MSI B650 Pro, 7700x, 7900xtx, 32GB RAM, Win 11 Pro, LG C1 48

           

[username00]

Got it working. The key is the HDMI 2.1 Support and the following changes from default:

both Maximum FRL rates to 48 Gbps (12 x 4 lanes)
Maximum slices: 4 slices up to 340 MHz ( 5kB max chunk)

Stream Compression: Enable all but the last two.

Source: Reddit OLED Gaming Settings

Figures 4 and 5

Note: I did change the second FRL max from 24 to 48.

Hope this helps someone else. Cheers.

       

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Now of course the question becomes - is there any harm to doing this? If the TV itself is a 10bit panel (40Gbps), but the card supports the full 48Gbps - does it really matter and are these gains imperceptible?

[ToastyX]

You should only need to set the FRL rate to 48 Gbps. You shouldn't need DSC for 3840x2160 @ 120 Hz at 12 bpc. Does the C1 even support DSC?

As for any harm, I don't think there would be, but there might be a reason why they limited it to 40 Gbps. Someone reported an increase in signal errors in the HDMI diagnostics screen at 48 Gbps, so maybe the C1 can't fully handle it, or maybe it was the cable.

Whether 12 bpc would have any benefit with a 10 bpc panel would depend on what processing the TV does and whether the output can be dithered to simulate 12 bpc. Even with true 12 bpc, whether the difference is perceptible would depend on what content you are looking at and whether the software supports greater than 8 bpc output.