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Framerate Cap, g/sync and brightness flickering (Odyssey G7)

Posted: 23 Apr 2021, 10:25
by PedroPortnoy
Hello, everyone!

First of all I'd like to thank all the members of this forum for all the tips I'v been able to take advantage of in the past.

I've recently purchased a Samsung Odyssey G7 27'' monitor and have been playing mostly Assassin's Creed Unity whithout noticing any of the famous brightness flickering associated with this monitor. I recently started playing another game (AC Chronicles: China) and started noting some severe flickering in the intro animations, and very faint flickering during gameplay.

After that I went back to AC Unity to search for it and actually noticed a tiny bit of flickering in some situations, but very hard to tell.

I've been playing AC Unity with NCP framerate cap set to 65 FPS (because some cosmetic physics are tied to Framerate in this game, like other AC games) with g-sync on and v-sync off, with no tearing and smooth gameplay, despite the eventual flickering.

I understand Brighness Flickering while using g-sync is due to monitors beiing brighter at higher refresh rates and that's why this monitor flickers a lot when the Framerate fluctuates around the lower limit of VRR range. Thanks to the information section on the OSD, i was able to confirm that the LFC was kicking in at anything lower than 90 FPS using nVidia Pendulum Demo and that, in fact, when going over and below that would cause visible flickering. Checking refresh rate during AC Unity gameplay confirmed it was around 130 Hz (2*65), but fluctuating from around 100 to 160 and it wouldńt go out of LFC.

I was able to change the VRR range to 50-240 (instead of 90-240) using CRU and tested it on Pendulum and it worked perfectly with no flickering. I even tried setting the pendulum interval to 65-65 to see if there was any fluctuation on the refresh rate, but it was a rock solid 64-65 Hz, no flickering whatsoever. I then tried AC Unity and still noticed the same faint flickering in some situations; when checking the OSD on the monitor, it woud go pretty fast from around 50 to 80 Hz, whick I suppose is the reason why there is flickering.

The next step was installing RTSS and checking if frametimes were unstable due to the Framerate cap: they were not. They were unbelievably stable actually, both in the AC games and in Pendulum and using either NCP framerate cap or RTSS framerate cap.

What I was able to notice is that the refresh rate on the OSD of my G7 would fluctuate a lot less in heavy scenes (like open space with a lot of NPC's, where it would stay within 62-68) compared to indoor scenes (50-80). It seems the lower the GPU load, the more instable the refresh rate of the monitor and the more flickering is noticeble.

So, after all that, I have some questions:

1- Why does the Refresh Rate of the monitor fluctuates in games with framerate cap but not in the pendulum demo locked to 65?

2- Is this due to Fullscreen Optimizations? (I disabled it but I'm not sure it actually makes the game run in Exclusive Fullscreen)

3- What can I do to be able to use framerate cap wthout flickering?

Important: if I run games uncapped, there is no refresh rate fluctuation or flickering at all, it just happens when capping framerates.

My specs:

CPU: i7 8700K @ 5.0 Ghz

Thank you in advance