Nvidia 2080ti GFX output modifies pixels?

I am developing a display port capture device, I am trying to capture the display port output from the 2080TI GFX card.
I am using Ubuntu 18.04 with the 440 drivers. The resolution I am trying to capture is 3840x4320.
I have setup an 3840x4320 bitmap as the background for linux. On the secondary DP output, I have the resolution set to 3840x4320, so the background image is fullscreen. Now I capture this image, but the image is not identical to the bitmap I have set for the background. I have disabled the “dithering” and “antialiasing” options in the nvidia-settings application. The image looks visually identical to the bitmap used as the background, but if you compare pixel by pixel it is different. I do not think it is a signal integrity issue because the image I capture is always the same. Also the values of each individual pixel when they are different may differ by 1 or so. If it was a signal integrity issue, I would expect random bits to be different, or the CRC of the static image I capture would change.
Is is possible the 2080TIO GFX is doing some kind of “on-the-fly” processing and changing the pixel values slightly when displaying? How can I be sure the 2080TI outputs the exact pixels of the background bitmap unchanged?

Does anyone at Nvidia have any comment for me?
Thank you.

Did you ever figure out how to solve this? Nvidia cards from the RTX series are doing some type of hardware dithering that is not possible to disable at this moment it seems. On a 10bit monitor this effect is very obvious, if i plug in an older GPU like a Quadro K4200 or K600 and connect my monitor to those cards that image is no longer being “tempered” with.

Hi,
The project got canceled, so I can’t recall exactly what was done.
However, I think I upgraded the drivers and then used the “nvidia-settings” GUI application to disable the dithering (like I did in the original post). nvidia-settings GUI, GPU-0->DP-0->Controls, they need to set “Dithering” to “Disabled”.
I also made sure the nvidia card was sending a signal with a pixel frequency less than 1075MHz. You might have to make a custom resolution if you are close to that rate. Then I made sure I had short high quality DP cables.
And if I recall correctly, I think Linux might also doing some kind of modification of the pixels as well, but honestly I forget if that was an issue or not. Sorry for that.
After all these steps were done, I recall I could always capture the correct data.