Unreal Engine 4 games flicker with gsync in dark areas

[tygeezy]

I’ve noticed off behavior in unreal 4 based games. If I’m using gsync compatibility on my oled I get light pulsing or flickering in dark areas. My frametimes are stable, so I don’t believe it to be the frametime spikes that have been know to cause this behavior.

phpBB [video]

This isn’t my video, but it’s another user with the same display in an unreal 4 engine title.

phpBB [video]

Another user talks about flickering in blair witch which is again a UE4 title.

"Played Blair Witch the game today and finally gsync causes issue like I mentioned earlier. During night scenes in the game with the whole screen being almost dark grey, there’s intermittent flashing when the character walks around (which causes fps fluctuation and activates gsync)."

https://www.avsforum.com/forum/40-oled- ... st59292992

Disabling gsync removes the flicker. Another odd thing about unreal engine 4 games I’ve noticed is I can’t get them to tear. With gsync off and with vsync off, even at driver level I can’t induce frame tearing. I increased FPS cap over my refresh rate of 120 and it did indeed go above that framerate. So vsync isn’t on.

A user on unreal forums suggested that perhaps fast sync is baked into unreal engine 4 because they noticed the same issue.

“ The only reason for this I can figure out is that UE4 would somehow have hardcoded "FastSync" in, which basically drops frames that are not drawn in time for next screen update and prevents tearing that way, but even if I go to nVidia control panel to make sure even FastSync is off, I am still not getting any screen tearing.”

https://forums.unrealengine.com/develop ... l-engine-4

Whatever causes unreal engine 4 games not to tear even without vsync has me thinking it causes issues with gsync/vrr. I’d like to see what some of the experts around here think though.

[jorimt]

I’ve noticed off behavior in unreal 4 based games. If I’m using gsync compatibility on my oled I get light pulsing or flickering in dark areas. My frametimes are stable, so I don’t believe it to be the frametime spikes that have been know to cause this behavior.

Is this possibly related to gamma shift with Instant Game Response enabled on the C9 (near black-level flicker issues)?
https://www.avsforum.com/forum/40-oled- ... st59520454

Another odd thing about unreal engine 4 games I’ve noticed is I can’t get them to tear. With gsync off and with vsync off, even at driver level I can’t induce frame tearing. I increased FPS cap over my refresh rate of 120 and it did indeed go above that framerate. So vsync isn’t on.

A user on unreal forums suggested that perhaps fast sync is baked into unreal engine 4 because they noticed the same issue.

The framerate can go over the refresh rate and not induce tearing with V-SYNC off if the game is running in borderless windowed mode (DWM triple-buffer-style V-SYNC solution). I wonder if in certain configurations that's what you're seeing; UE4 forcing a form of borderless even with fullscreen enabled?

I’d like to see what some of the experts around here think though.

I did recently purchase a 48" CX, but ironically, I only have a 1080 Ti (no OLED VRR support), and I don't plan on upgrading until the 3000 series, which should (hopefully) release any time here.

Once I do, I'll be able to (unofficially) investigate these sort of issues myself, but even then, I don't know if the CX has the same problems as the previous model(s) in VRR mode.

[tygeezy]

I’ve noticed off behavior in unreal 4 based games. If I’m using gsync compatibility on my oled I get light pulsing or flickering in dark areas. My frametimes are stable, so I don’t believe it to be the frametime spikes that have been know to cause this behavior.

Is this possibly related to gamma shift with Instant Game Response enabled on the C9 (near black-level flicker issues)?
https://www.avsforum.com/forum/40-oled- ... st59520454

Another odd thing about unreal engine 4 games I’ve noticed is I can’t get them to tear. With gsync off and with vsync off, even at driver level I can’t induce frame tearing. I increased FPS cap over my refresh rate of 120 and it did indeed go above that framerate. So vsync isn’t on.

A user on unreal forums suggested that perhaps fast sync is baked into unreal engine 4 because they noticed the same issue.

The framerate can go over the refresh rate and not induce tearing with V-SYNC off if the game is running in borderless windowed mode (DWM triple-buffer-style V-SYNC solution). I wonder if in certain configurations that's what you're seeing; UE4 forcing a form of borderless even with fullscreen enabled?

I’d like to see what some of the experts around here think though.

I did recently purchase a 48" CX, but ironically, I only have a 1080 Ti (no OLED VRR support), and I don't plan on upgrading until the 3000 series, which should (hopefully) release any time here.

Once I do, I'll be able to (unofficially) investigate these sort of issues myself, but even then, I don't know if the CX has the same problems as the previous model(s) in VRR mode.

the issues exist with both borderless and full screen. I actually bought the steam version of sea of thieves to test out full screen exclusive and it still had the issue. Borderlands 3 has it for me and I use exclusive fullscreen. The only non unreal engine 4 game i've seen this same issue with is destiny 2.

https://www.youtube.com/watch?v=xc1wyyWlFXI

Also im aware of the near gamma shift fix not be activated in auto low latency mode. I however dont think this is the issue because it happens also in darker scenes, but not near black. Like that brown color of the boat it still flickers as long as the overall luminescence is low.

It doesn't happen in games like modern warfare, far cry 5, gunfire reborn, and i've been bale to make the scene dark without flickering. Also, whats up with no tearing with vsync not being on and not being in borderless? It's like that with all unreal 4 games ive tested.

[jorimt]

Also im aware of the near gamma shift fix not be activated in auto low latency mode. I however dont think this is the issue because it happens also in darker scenes, but not near black. Like that brown color of the boat it still flickers as long as the overall luminescence is low.

It doesn't happen in games like modern warfare, far cry 5, gunfire reborn, and i've been bale to make the scene dark without flickering.

Could still be enough within the near-black range of the TV to bounce between one gamma step and another with VRR, and the severity could vary depending on the out-of-box gamma calibration of the given unit. Really hard to say without hands on experience, so I can't speak much more on it until I have, and the CX may differ.

And while it is weird it doesn't occur in some games, and it does in others, there's too many unknown variables (out-of-box gamma calibration, TV settings, firmware, drivers, system settings, framerate at the time of flicker, etc) to narrow it down just from a handful of user reports and a couple of short video clips.

That, and VRR on an OLED (and software-level nonetheless) is bound to have differences from (module-based) LCD, which is the only personal experience I have.

Also, whats up with no tearing with vsync not being on and not being in borderless? It's like that with all unreal 4 games ive tested.

I have the Microsoft Store version of SoT. I loaded it up on my XB271HU (1440p IPS G-SYNC @165Hz), disabled G-SYNC, launched the game, made sure V-SYNC was disabled and it was set to fullscreen in-game, and, hovering in the 100-120 range, I was definitely getting tearing, though it was indeed more slight than in some other games at the same FPS.

I then launched it on my CX at 60Hz with the same settings, and hovering around 84 FPS, the tearing was obvious.

I didn't even have fullscreen optimizations disabled (if that indeed does anything for this game). Perhaps specific to your system? Have you tried at 60Hz? The tearing should be more apparent at that refresh rate.

[tygeezy]

Also im aware of the near gamma shift fix not be activated in auto low latency mode. I however dont think this is the issue because it happens also in darker scenes, but not near black. Like that brown color of the boat it still flickers as long as the overall luminescence is low.

It doesn't happen in games like modern warfare, far cry 5, gunfire reborn, and i've been bale to make the scene dark without flickering.

Could still be enough within the near-black range of the TV to bounce between one gamma step and another with VRR, and the severity could vary depending on the out-of-box gamma calibration of the given unit. Really hard to say without hands on experience, so I can't speak much more on it until I have, and the CX may differ.

And while it is weird it doesn't occur in some games, and it does in others, there's too many unknown variables (out-of-box gamma calibration, TV settings, firmware, drivers, system settings, framerate at the time of flicker, etc) to narrow it down just from a handful of user reports and a couple of short video clips.

That, and VRR on an OLED (and software-level nonetheless) is bound to have differences from (module-based) LCD, which is the only personal experience I have.

Also, whats up with no tearing with vsync not being on and not being in borderless? It's like that with all unreal 4 games ive tested.

I have the Microsoft Store version of SoT. I loaded it up on my XB271HU (1440p IPS G-SYNC @165Hz), disabled G-SYNC, launched the game, made sure V-SYNC was disabled and it was set to fullscreen in-game, and, hovering in the 100-120 range, I was definitely getting tearing, though it was indeed more slight than in some other games at the same FPS.

I then launched it on my CX at 60Hz with the same settings, and hovering around 84 FPS, the tearing was obvious.

I didn't even have fullscreen optimizations disabled (if that indeed does anything for this game). Perhaps specific to your system? Have you tried at 60Hz? The tearing should be more apparent at that refresh rate.

I don’t have sea of thieves installed anymore but I went ahead and loaded up borderlands 3. I set it to 60 hz and didn’t see any tearing.... Which is strange because it’s usually very noticeable at 60 hz. Frost byte engine games and the pendulum demo year horribly at 60 hz.

Also, still not convinced it’s the gamma shift. I had vsync on in control panel and cranked up framerate so it was locked at 120 hz and it stopped pulsing. This is with gsync on just hitting refresh ceiling.

If you look very closely at the frame time graph these pulses coincide with very tiny bumps in the line graph. Maybe it’s showing up with unreal engine 4 games because they are stutter prone? Even the smallest spike registering seems to produce it. Although the smaller the spike the less noticeable the pulsing is and it’s only detectable I’m very low luminance Scenes.

phpBB [video]

If you look ever so closely you can see little flickers and notice every so small frametime bumps. I tried lowering the FPS even into the 40’s and I still get these tiny spikes that cause this.

Edit: zoomed in here so you get a clear view of the frametime graph. These ever so slightly tiny bumps is enough to cause this.Im using nvidia framerate capper here. I had been using the in game capper and wanted to see if a more accurate capper would mitigate the problem. It seems to have helped a little bit, but it’s still there.

phpBB [video]

[jorimt]

I don’t have sea of thieves installed anymore but I went ahead and loaded up borderlands 3. I set it to 60 hz and didn’t see any tearing.... Which is strange because it’s usually very noticeable at 60 hz. Frost byte engine games and the pendulum demo year horribly at 60 hz.

I don't have BL3, so can't say. All I know is that I was able to trigger visible tearing in a UE4 game on two different displays at two different refresh rates.

Also, still not convinced it’s the gamma shift. I had vsync on in control panel and cranked up framerate so it was locked at 120 hz and it stopped pulsing. This is with gsync on just hitting refresh ceiling.

I didn't say it was gamma shift, I just said it was one of many possibilities. It could still be a contributing factor. If you say that it is only happening with G-SYNC, and only at lower framerates (?), or during frametime spikes (which are brief instances of very low framerate), then there is precedence to this, even with LCD G-SYNC.

Even hardware G-SYNC on an LCD monitor can flicker at very low framerates (such as loading screens). This is because, to control the refresh rate, G-SYNC pads out the VBLANK between frames, so at say, ~45Hz (discounting whatever LFC is being applied), there can be a longer than usual period of blankness between the previous and next frame.

Now, LCD has very slow pixel transitions (aka GtG) compared to OLED (which has an almost zero GtG equivalent), so add that with low refresh rates (which are framerates and visa versa) during G-SYNC operation, and then throw in the fact that OLED dithers at lower shades (a dither process that, in some cases, is being altered in game mode; e.g. absence of near-black chroma overshoot fix), and is being forced to physically refresh itself slower than usual in these instances, and you may easily get what you're seeing.

So, to sum up, from what you're saying, framerate/refresh rate may be the trigger with G-SYNC; lower = more possible flicker, higher = less possible flicker. If this is the case, I'm honestly not sure if there is a 100% viable fix, even on LG's side. It may be a physical limitation where OLED w/VRR is concerned.

Again though, just an educated guess. Without hands on experience, any further comments are going to be pure conjecture on my part.

[tygeezy]

I don’t have sea of thieves installed anymore but I went ahead and loaded up borderlands 3. I set it to 60 hz and didn’t see any tearing.... Which is strange because it’s usually very noticeable at 60 hz. Frost byte engine games and the pendulum demo year horribly at 60 hz.

I don't have BL3, so can't say. All I know is that I was able to trigger visible tearing in a UE4 game on two different displays at two different refresh rates.

Also, still not convinced it’s the gamma shift. I had vsync on in control panel and cranked up framerate so it was locked at 120 hz and it stopped pulsing. This is with gsync on just hitting refresh ceiling.

I didn't say it was gamma shift, I just said it was one of many possibilities. It could still be a contributing factor. If you say that it is only happening with G-SYNC, and only at lower framerates (?), or during frametime spikes (which are brief instances of very low framerate), then there is precedence to this, even with LCD G-SYNC.

Even hardware G-SYNC on an LCD monitor can flicker at very low framerates (such as loading screens). This is because, to control the refresh rate, G-SYNC pads out the VBLANK between frames, so at say, ~45Hz (discounting whatever LFC is being applied), there can be a longer than usual period of blankness between the previous and next frame.

Now, LCD has very slow pixel transitions (aka GtG) compared to OLED (which has an almost zero GtG equivalent), so add that with low refresh rates (which are framerates and visa versa) during G-SYNC operation, and then throw in the fact that OLED dithers at lower shades (a dither process that, in some cases, is being altered in game mode; e.g. absence of near-black chroma overshoot fix), and is being forced to physically refresh itself slower than usual in these instances, and you may easily get what you're seeing.

So, to sum up, from what you're saying, framerate/refresh rate may be the trigger with G-SYNC; lower = more possible flicker, higher = less possible flicker. If this is the case, I'm honestly not sure if there is a 100% viable fix, even on LG's side. It may be a physical limitation where OLED w/VRR is concerned.

Again though, just an educated guess. Without hands on experience, any further comments are going to be pure conjecture on my part.

It happens at high frame rates too. If you notice that second video it’s running at 116 FPS. I used Ukralne low latency mode so it was calling below the refresh rate. Each of those tiny little bumps coincided with a flicker. Using nvidia a capper made it less frequent than the in game capper, but it’s still noticeable and at all framerates.

I think unreal engine 4 games are very susceptible to this flicker because almost or the games on that engine seem to have lots of microstutter. Smoother running games with more gradual frametime variance doesn’t seem to have as much of an issue. For example I can’t reproduce on far cry 5 and I can only reproduce on modern warfare in the very dark menu. Even spots darker in game than day borderlands 3 doesn’t have detectable flicker. It’s very odd.

[jorimt]

It happens at high frame rates too. If you notice that second video it’s running at 116 FPS. I used Ukralne low latency mode so it was calling below the refresh rate. Each of those tiny little bumps coincided with a flicker. Using nvidia a capper made it less frequent than the in game capper, but it’s still noticeable and at all framerates.

I think unreal engine 4 games are very susceptible to this flicker because almost or the games on that engine seem to have lots of microstutter. Smoother running games with more gradual frametime variance doesn’t seem to have as much of an issue. For example I can’t reproduce on far cry 5 and I can only reproduce on modern warfare in the very dark menu. Even spots darker in game than day borderlands 3 doesn’t have detectable flicker. It’s very odd.

If the flicker is coinciding with each of those "bumps," those are frametime spikes (no matter how brief or subtle), and it means even if the framerate is otherwise very high, those instances are still causing it to become very low, then high again.

G-SYNC tends to have a slight "re-initialization" period when there is a sudden, abrupt transition from a very high framerate to a very low framerate (or visa-versa), which could be triggering this, or at least making it more noticeable on OLED tech.

Does this happen in the same instances with G-SYNC on + V-SYNC off?

[tygeezy]

It happens at high frame rates too. If you notice that second video it’s running at 116 FPS. I used Ukralne low latency mode so it was calling below the refresh rate. Each of those tiny little bumps coincided with a flicker. Using nvidia a capper made it less frequent than the in game capper, but it’s still noticeable and at all framerates.

I think unreal engine 4 games are very susceptible to this flicker because almost or the games on that engine seem to have lots of microstutter. Smoother running games with more gradual frametime variance doesn’t seem to have as much of an issue. For example I can’t reproduce on far cry 5 and I can only reproduce on modern warfare in the very dark menu. Even spots darker in game than day borderlands 3 doesn’t have detectable flicker. It’s very odd.

If the flicker is coinciding with each of those "bumps," those are frametime spikes (no matter how brief or subtle), and it means even if the framerate is otherwise very high, those instances are still causing it to become very low, then high again.

G-SYNC tends to have a slight "re-initialization" period when there is a sudden, abrupt transition from a very high framerate to a very low framerate (or visa-versa), which could be triggering this, or at least making it more noticeable on OLED tech.

Does this happen in the same instances with G-SYNC on + V-SYNC off?

Yes it coincides with the bumps and yes it happens with gsync on plus vsync off. These spikes I dont think are large enough to drop it below the vrr floor. Here is a video of using the in game capper which isnt as smooth as nvidias with larger spikes being recorded. These spikes you would think wouldnt be large enough to induce flicker, but they do on oled.

phpBB [video]

[jorimt]

These spikes I dont think are large enough to drop it below the vrr floor.

They don't have to drop it below the VRR floor to cause this.

For instance, even on a G-SYNC module, with G-SYNC on + V-SYNC off, a frametime spike can cause a tear within the G-SYNC range. It just needs to be an abrupt enough jump from a higher to lower framerate or visa-versa.

Once I have a VRR (OLED) capable card, it will be interesting to see if the CX has this same issue.