support for 30-bit color on GeForce

The Windows driver 431.70 added support for 30-bit color on GeForce and TITAN GPUs.
https://www.nvidia.de/Download/driverResults.aspx/149151/de

Is 30 bit also available for Linux?

I am running 435.17-3 with a Gefore 1050Ti + HDMI + Eizo CS2730 but I still see banding with some test images. I have added 30 bit option to xorg.conf and xwininfo shows 30 bit:

xwininfo: Window id: 0x1ed (the root window) (has no name)

  Absolute upper-left X:  0
  Absolute upper-left Y:  0
  Relative upper-left X:  0
  Relative upper-left Y:  0
  Width: 2560
  Height: 1440
  Depth: 30
  Visual: 0x21
  Visual Class: TrueColor
  Border width: 0
  Class: InputOutput
  Colormap: 0x20 (installed)
  Bit Gravity State: ForgetGravity
  Window Gravity State: NorthWestGravity
  Backing Store State: NotUseful
  Save Under State: no
  Map State: IsViewable
  Override Redirect State: no
  Corners:  +0+0  -0+0  -0-0  +0-0
  -geometry 2560x1440+0+0

Do I miss anything?

nvidia-bug-report.log.gz (1.13 MB)

Please see this:
https://download.nvidia.com/XFree86/Linux-x86_64/384.98/README/depth30.html
HDMI: no dice, use DP.

ok. I did that. I had a DisplayPort cable flying around. But no difference. I see banding in the gryslae image.

So the quetsion remains open: Does the nvidia driver for Linux support 30 bit color depth?

In general it does support this. Sometimes this is a bit fiddly since for some reasons, it will use dithering. The main pitfall is that most DEs like Gnome/Mate don’t support this so you will get wrong colors and mouse clicks won’t have effect.
Please set

Option "ModeDebug" "true"

in the device section of your xorg.conf, then run nvidia-bug-report.sh as root and attach the resulting .gz file to your post. Hovering the mouse over an existing post of yours will reveal a paperclip icon.
https://devtalk.nvidia.com/default/topic/1043347/announcements/attaching-files-to-forum-topics-posts/

Here you go. debug output is attached.

You have two xorg configs:
/etc/X11/xorg.conf
/etc/X11/xorg.conf.d/my-xorg.conf
that’s not advisable, please remove one. Furthermore, you have ForceCompositionPipeline=On set, don’t know if that’s compatible with depth 30, please remove it.

I did what you suggested, but it does not make a difference. Please see the attached screenshot of gimp-2.99 with the a test PSD file I found on the internet (https://cdn.photographylife.com/wp-content/uploads/2014/07/10-Bit-Test-Ramp.zip)

https://www.dropbox.com/s/imye5az5zh06pcm/gimp-24bit-30bit.png?dl=0
This screenshot shows the 24 bit display on the left and the 30 bit display on the right. Same banding in both.

The screenshot is an 8bit png, so that doesn’t really help with seeing any difference.
According to the Xorg log, 30bit depth should be active, also no dithering is enabled. So it’s a bit odd. Maybe some problem with gimp, do these pictures help?
https://github.com/jursonovicst/gradient

The whole point of this screenshot was to show you that in reality the 30 bit image shows the exact same banding as the 24 bit image. The screenshot is just a visual evidence to underline my point.

This is the same. regardless if I do 24 bit or 30 bit I see the same banding.

I am really lost. The nvidia-settings app shows “Depth 30”. xwininfo shows “Depth 30”. The monitor is for sure capable of 30 bit. And the cable is DisplayPort provided by Eizo. I have a ticket pending with Gigabyte to see if the graphics card is limited (GIGABYTE GeForce GTX 1050 Ti OC 4G). I am running out of ideas what else to check.

Is anybody else here in the forum successfully running a GeForce GTX 1050 Ti with 30 bit?

One further reason comes to my mind, so far when inexplicable color problems and banding appeared the reason was a broken icc profile.
Looks like color profile handling was only added very recently to xfce:
https://simon.shimmerproject.org/2019/02/19/color-profile-support-for-xfce/

I have the EIZO color profiles activate which came with the monitor. One for 5000 K and one for 6500 K. Makes no difference. And the same is true with gnome by the way.

Have you verified you have no issues under Windows installed on the same PC?

No. I have no Windows available.

https://www.microsoft.com/en-us/evalcenter/evaluate-windows-10-enterprise

Thank you for that link. But besides of the availability of Windows installation files,
I do not have a partition where I can install it. I am afraid I can not test that.

Did you ever try a different driver, e.g. v390 to check if this is some driver regression?