[x86-64] GBM and RGB Colorspace on Intel Graphics

_saiko · May 30, 2025 at 9:55 PM

Hello,

So I was running an ancient LE8 (Kodi 17) installation on Intel NUC and was running in full/full/full (Kodi/gfx driver/TV) RGB color space - cristal black colors and never had an issue with color space there.
Btw the HW is a NUC7i5BNH with i5-7260U and Intel Graphics 640.

Fast forward today, finally decided to upgrade to LE12 and noticed that my blacks are washed out. Of course, I double-checked that Kodi and TV are still set to full (0-255).
Finally looked at the WM level (didn't try it with the kernel command) and noticed that the "Broadcast RGB" was set to automatic, and apparently the driver looks at HDMI info frames and decides it should use limited instead of full.
This I verified with the following

Code

# modetest -M i915 -c
(...)
        101 Broadcast RGB:
                flags: enum
                enums: Automatic=0 Full=1 Limited 16:235=2
                value: 0
(...)

After forcing the Full mode with kmstest -c DP-1 -P "Broadcast RGB=1" < /dev/null (and restarting Kodi) things are back on track.

I am now using a simple autostart.sh script

Code

# cat /storage/.config/autostart.sh

#!/bin/sh
# wait a moment for DRM to settle, then force Full RGB
sleep 2
kmstest -c DP-1 -P "Broadcast RGB=1" < /dev/null

This forces the colors pace to full on boot and I am happy.

My question is, can this be a feature request that this behavior can be setup through LE in the GUI as this is hardly intuitive for an average user?

**chewitt** · May 31, 2025 at 8:41 AM

In short, no, because it should be implemented in Kodi and not handled locally for LE. It's been half-investigated by Kwiboo in the past, see https://github.com/xbmc/xbmc/pull/14358, but that PR includes a pile of other things that were a little ahead of the kernel DRM framework maturing and it was closed.

If you want to make a feature request, it should be done in the Kodi forum as this would be a Kodi feature.

_saiko · May 31, 2025 at 11:50 AM

Hm, I see.

But from my limited understanding this is a setting that is beneath the application, it's something on the OS layer is it not?

How can it be a feature request for an application devs that aren't responsible for the OS where the app is running on? The LE is a pre-built distribution that includes the app, but the choice of the WM, distribution, kernel and all is up to the LE team, and I believe this setting could be handled on that level and could be possibly a simple knob in the LE installer or configurator.
At the very least, people could get some hints about this issue and how to solve it through a Wiki or in the installation guide.

Thanks though, i will try to submit the feature request at Kodi then.