u/NoxarCZ

Recently I've upgraded to a 4K monitor, which is nice, but also faced some UI scaling issues in older programs/games like Europa Universalis 4, where even the fonts are raster based.

In the attached picture you can see comparison between native 4K with in-game 1.5x UI scaling (blurry, distorted text and icons) vs. 1440p with 1.0x UI scaling, upscaled by Lossless Scaling to fullscreen, much better!

EDIT: the LS1 sharpening is set to "2", but even with sharpening turned off it looks better than the in-game scaling.

I was in a market for a 4K monitor, but didn't feel like dealing with OLED issues (VRR flicker, text fringing) nor did I want to spend that much money.

Based on reviews by KitGuru and others I landed on the AOC U27G4R - seemed to have good pixel response time, decent contrast (for an IPS panel) and overall great value.

I've ran into a major issue however:

• 160 Hz mode forces DSC (display stream compression) ON, despite me using an HDMI 2.1 cable which has enough bandwidth to not require it. This is most likely because the monitor also has DisplayPort 1.4 inputs, which lack the bandwidth. It seems AOC was too lazy to add one more button for toggling DSC on/off...
• Gsync doesn't work properly in all games with DSC ON - for example in Cyberpunk it was fine, but in Trackmania 2020 it would be permanently stuck in regular Vsync mode (falling back to 80 fps to prevent tearing, which caused stutter). This is evident in Windows advanced display settings too, see comparison
• The only way to make Gsync work consistently is to turn DSC OFF, but this limits you to 120 Hz
• I've tried the unofficial hack for bypassing DSC in regedit, but it didn't work and made my Nvidia driver crash - had to reset this setting via a different monitor
• For some godforsaken reason switching to the "UHD 120 Hz" mode shifts the gamma, making the colors look extremely washed out. It took me a while to figure out this setting was causing it, but essentially 2.4/2.6 gamma with DSC OFF is equivalent to 2.2 gamma with DSC ON (160 Hz mode)

Why is DSC a problem?

• Causes latency due to forcing composed flip and not allowing independent flip and MPO - see explanation
• Can cause long black screens when alt tabbing from fullscreen apps, especially on 4000 series Nvidia cards. This seems to be tied to an architectural issue - small display heads
• Disables integer scaling, DSR and DLDSR options in Nvidia app

If variable refresh rate (Gsync) is important to you and/or you want to run 160 Hz without DSC and it's issues, do not buy this monitor.
Personally I'm not sure yet if I'm going to return it. Perhaps if I find a similiar 4K panel at the same price point which can run without DSC, but this information is hard to come by, as most manufacturers and reviewers alike don't bother mentioning it.

If you have any monitor suggestions, I'd be glad to hear them :)