Bug Report Lower part of picture gets blurry on high resolution

[W4RH4WK]

I am struggling with an issue where the lower part of the picture gets blurry upon using a high resolution.
See the provided screenshot and pay attention to the readability of the text at the bottom.
(I needed to crop the image so I could upload it here.)

My Base Resolution and Output Resolution are set to 3440x1440, the native resolution of my monitor.
I am recording at 100 FPS; however, altering this value does not affect the issue.
Rate Control is set to Lossless, Rescale Output is disabled.
The issue happens with both, CPU and GPU encoding.

I also tried using different video players (VLC, Windows Default); both show the exact same issue.

After some investigation it seems that this issue occurs as soon as the output resolution becomes greater than 2^22 pixel.
Altering Color Format did not affect the issue either, except for selecting RGB in which case the encoder was overloaded.

Edit: Link to the corresponding bug https://obsproject.com/mantis/view.php?id=624

 

[Suslik V]

I think this is decoding issue. Try player without deblocking filter.
What the sense to use NV12 together with lossless?

 

[W4RH4WK]

I think this is decoding issue. Try player without deblocking filter.
What the sense to use NV12 together with lossless?

By now, I tried VLC, WIndows Movies, and MPC.
If there is a way to enable / disable the deblocking filter in any of them, please point it out to me and I'll try.
Nevertheless, the issue is still visible when uploading the video to Youtube, which is my use-case.

NV12 was the default and I did not lookup the differences between the Color Formats.
I don't plan on using lossless; however, the issue is present in other modes too and I wanted to rule out the possibility of it being a compression artifact.

 

[W4RH4WK]

To rule out the possibility of this issue caused by the player I tried the following.

1. Set the Base Resolution and Output Resolution to 2560x1440 (which does not trigger the issue). Scaling the output to 3440x1440. Of course the picture is now stretched, but the fonts look fine otherwise.

2. Rescale the output to 2560x1080. Of course with this setting, the overall image is blurry, but you can still see that the picture is even more blurry at the bottom, compared to the top.

Therefore, after trying 4 different players and these two scenarios, I don't think it's a decoder issue.

 

[Suslik V]

OK I did some tests. Unfortunately, FFmpeg itself has no such issue. Issue is present if I444 selected as format in OBS too. More over, the artifacts cover whole canvas no matter where elements lies. Maybe bug somewhere in OBS. It needs more time to investigate.

 

[W4RH4WK]

I attached the link to the corresponding entry in the bug tracker. Let me know if there is anything I can help you with.