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New Nvidia driver Gsync support - Gsync Ceilling problems

Talk about NVIDIA G-SYNC, a variable refresh rate (VRR) technology. G-SYNC eliminates stutters, tearing, and reduces input lag. List of G-SYNC Monitors.

New Nvidia driver Gsync support - Gsync Ceilling problems

Postby Notty_PT » 15 Jan 2019, 16:10

After testing the new Nvidia drivers on some monitors, I reach the conclusion that this "Gsync" driver enabled is very imprecise. Even when limiting framerate with RTSS or other precise methods 3 fps away from the refresh rate, it will still hit that refresh increasing input lag.

This was tested on both certified monitors and non certified monitors. So my advice is to cap framerate way lower, 10 fps at least. You can notice this easily if you enable and disable Gsync during your gameplay on your monitor. The input lag difference will be pretty easy to spot.
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Re: New Nvidia driver Gsync support - Gsync Ceilling problem

Postby Q83Ia7ta » 15 Jan 2019, 16:38

May be that's the nvidia plan how to discredit free-sync technology and it's monitors?
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Re: New Nvidia driver Gsync support - Gsync Ceilling problem

Postby jorimt » 15 Jan 2019, 16:42

Notty_PT wrote:After testing the new Nvidia drivers on some monitors, I reach the conclusion that this "Gsync" driver enabled is very imprecise. Even when limiting framerate with RTSS or other precise methods 3 fps away from the refresh rate, it will still hit that refresh increasing input lag.

This was tested on both certified monitors and non certified monitors. So my advice is to cap framerate way lower, 10 fps at least. You can notice this easily if you enable and disable Gsync during your gameplay on your monitor. The input lag difference will be pretty easy to spot.

Early days, lots of unknowns.

While it is very possible what you described is happening in the upper VRR range, it's also very possible that it can, at times, be the driver's software-only LFC working in a spotty manner, and bumping you in and out of the VRR range whenever there is even the slightest micro-frametime spike, creating a similar effect.

To rule that out, have you tried a 120 FPS cap at 144Hz with VRR + V-SYNC on or off? I find that such a cap can bring the VRR into a range that reduces the frametime variances enough that there is little to no tearing with G-SYNC + V-SYNC "Off" on a G-SYNC monitor, at least.

Also, who knows if the V-SYNC component (frametime compensation for 100% tearing prevention) is working with the Nvidia driver on FreeSync monitors at this point.

Q83Ia7ta wrote:May be that's the nvidia plan how to discredit free-sync technology and it's monitors?

If anything, it certainly could become an indirect upselling maneuver for users with Nvidia GPUs paired with supported FreeSync monitors, but I'd give it a few more driver releases first.
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Re: New Nvidia driver Gsync support - Gsync Ceilling problem

Postby Notty_PT » 15 Jan 2019, 16:47

jorimt wrote:
Notty_PT wrote:After testing the new Nvidia drivers on some monitors, I reach the conclusion that this "Gsync" driver enabled is very imprecise. Even when limiting framerate with RTSS or other precise methods 3 fps away from the refresh rate, it will still hit that refresh increasing input lag.

This was tested on both certified monitors and non certified monitors. So my advice is to cap framerate way lower, 10 fps at least. You can notice this easily if you enable and disable Gsync during your gameplay on your monitor. The input lag difference will be pretty easy to spot.

Early days, lots of unknowns.

While it is very possible what you described is happening in the upper VRR range, it's also very possible that it can, at times, be the driver's software-only LFC working in a spotty manner, and bumping you in and out of the VRR range whenever there is even the slightest micro-frametime spike, creating a similar effect.

To rule that out, have you tried a 120 FPS cap at 144Hz with VRR + V-SYNC on or off? I find that such a cap can bring the VRR into a range that reduces the frametime variances enough that there is little to no tearing with G-SYNC + V-SYNC "Off" on a G-SYNC monitor, at least.

Also, who knows if the V-SYNC component (frametime compensation for 100% tearing prevention) is working with the Nvidia driver on FreeSync monitors at this point.

Q83Ia7ta wrote:May be that's the nvidia plan how to discredit free-sync technology and it's monitors?

If anything, it certainly could become an indirect upselling maneuver, but I'd give it a few more driver releases first.


To be honest I didn´t try the 120fps cap, but I will try that next on the monitors I have here!

It is still happening at 134fps cap on a 144hz monitor. I think it is exactly what you described. It seems like it is bumping me in and out of the VRR range whenever there is even the slightest micro-frametime spike! Because I left the OSD on the screen and could see the refresh rate all over the place if I only cap at 141 or even 138, and reaching 144hz a lot of times.

Next I will try to cap 120 like you suggested and I will report back here.
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Re: New Nvidia driver Gsync support - Gsync Ceilling problem

Postby jorimt » 15 Jan 2019, 17:39

Notty_PT wrote:Because I left the OSD on the screen and could see the refresh rate all over the place if I only cap at 141 or even 138, and reaching 144hz a lot of times.

On a side note here, if you're talking about the monitor's built-in, real-time variable refresh rate meter, you can't go solely by that to determine if it is bouncing in and out of the VRR range; if it's fluctuating, VRR is working, simple as that.

I experienced the same issue (monitor's VRR meter jumping to 144 periodically, even with an appropriate FPS cap) on both my personal G-SYNC monitor, and the 240Hz monitor I used for the article a couple of years back. However, the high-speed camera tests showed that these fluctuations on the monitor's VRR meter (including when each spiked to 144/240 with a -2 FPS limit) did not affect input lag, and the monitor was well within the VRR range regardless.

In other words, those meter jumps to 144, even with an FPS cap, could be false positives, and can't necessarily be relied on.

What should be relied on instead is user feel, and more optimally, high-speed camera tests.

I'm not sure if you've ever owned a G-SYNC monitor, or if you've read my article in full, but this is what I suggest when testing G-SYNC functionality on a FreeSync monitor:

1. Use only an Nvidia approved FreeSync model (one with existing LFC support, optimally), to rule out any monitor-specific behavior.
2. Always ensure that the built-in VRR meter is fluctuating.
3. Try both G-SYNC + V-SYNC "On" (NVCP) and G-SYNC + V-SYNC "Off."

With G-SYNC + V-SYNC "Off" + a -3 FPS limit, it is normal to see partial tearing near the bottom of the screen in the upper FPS range, and to see full tearing in the lower range during a frametime spike. You will not experience a significant difference in input lag in this scenario if you're jumping in and out of the VRR range, even with an FPS limit in place, because G-SYNC will allow tearing inside it's own range, where necessary.

With G-SYNC + V-SYNC "On" + -3 FPS limit, it should never tear, but if it is jumping in and out of the VRR range in the upper FPS range, intermittent stutter could be evident as it does. This would mean with current driver implementation, a -3 FPS limit isn't sufficient, and since V-SYNC is on in this scenario, you may feel an increase in input lag when it exceeds the VRR range. However, intermittent stutter could also be caused by frametime spikes, which happens at the lower range with G-SYNC + V-SYNC "On". The stutter or input lag in these instances could also be exacerbated by lacking/insufficient LFC functionality at the driver level, which is hard enough to get right with an actual hardware module.
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Re: New Nvidia driver Gsync support - Gsync Ceilling problem

Postby Notty_PT » 15 Jan 2019, 21:51

So I tested it all. At 120fps cap I rarely hit the 144hz ceilling and the input lag is lower than at anything capped higher than 120. However for me to fully avoid hitting the ceilling, I had to cap to 114fps. From this point I never hit it again.

Regarding the OSD information I assure you that I´m hitting the Gsync ceilling! I feel it input lag wise and sometimes even a subtle tear line appears. Once I drop the framerate cap the input lag starts improving, even at lower framerates (as long as I don´t drop it to 100fps of course) and the tear line is completly gone. Even at 120fps, hitting the 144hz ceilling rarely, I can´t spot the tearline.

This was tested on a Nvidia certified monitor Asus XG248Q, and on ViewSonic XG2402 and Msi Optix MAG241C, both freesync monitors.

It is what it is, who knows if they will improve it on upcoming drivers, but for now, for people playing multiplayer competitive shooters I would either turn Gsync OFF or just cap framerate to 114fps/120fps.
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Re: New Nvidia driver Gsync support - Gsync Ceilling problem

Postby jorimt » 15 Jan 2019, 23:45

Notty_PT wrote:Regarding the OSD information I assure you that I´m hitting the Gsync ceilling! I feel it input lag wise and sometimes even a subtle tear line appears. Once I drop the framerate cap the input lag starts improving, even at lower framerates (as long as I don´t drop it to 100fps of course) and the tear line is completly gone. Even at 120fps, hitting the 144hz ceilling rarely, I can´t spot the tearline.

If you're seeing a tearline at any point, you're actually getting reduced input lag when you see it. There can't be an increase in input lag with visible tearing, it would be the other way around; the input lag would increase (if only slightly) when you didn't see the tearing.

The noticeable increase in input lag with VRR only occurs when you hit the VRR ceiling when paired with V-SYNC "on," at which point it reverts to standalone V-SYNC behavior.

The -3 FPS limit with VRR + V-SYNC "On" is for avoiding standalone V-SYNC behavior by staying within the VRR range.

The -3 FPS limit with VRR + V-SYNC "Off" is only to stay in the VRR range, and prevent reversion to standalone V-SYNC OFF. In this scenario, the FPS limit does not prevent V-SYNC latency, because V-SYNC is off.

Something else is going on. Which did you test with, G-SYNC + V-SYNC "Off" or "On" in the control panel? Also, have you read my article? Because you really need to grasp the basics of VRR to troubleshoot this effectively, and understand what is and isn't to be expected with VRR functionality.

That's said, it's possible that Nvidia's software implementation for this G-SYNC to FreeSync driver isn't behaving properly, or at least behaving the same way standalone G-SYNC or FreeSync does.

Again, early days; I'm honestly surprised Nvidia offered this at all.
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Re: New Nvidia driver Gsync support - Gsync Ceilling problem

Postby Notty_PT » 16 Jan 2019, 00:04

I don´t know then, maybe something else is triggering the added input lag, but I have no idea. What I can assure you is that once I turn Gsync OFF the difference in input lag is night and day; in both cases with Vsync OFF. But once I drop to 120fps I notice no difference between Gsync ON and OFF. So something is defo happening, that is causing increased input lag when too close from the ceilling.

Also anything higher than 120fps will create a tear line when Vsync is OFF.
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Re: New Nvidia driver Gsync support - Gsync Ceilling problem

Postby jorimt » 16 Jan 2019, 00:37

Yeah, I couldn't offer much more at this point without testing this feature myself with a supported FreeSync monitor, something I don't have access to currently.

Good news is, it looks like the Chief plans on doing some general input lag and basic functionality tests on this over the coming months, at which points things should become clearer.

There's always the chance some other outlets will eventually test it as well.
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Re: New Nvidia driver Gsync support - Gsync Ceilling problem

Postby Luckbad » 16 Jan 2019, 01:00

For what it's worth:

My normal shooter monitor is the Dell S2716DG (G-Sync).

I tested Overwatch today on a Dell S2419HGF with G-Sync compatibility enabled. 141 FPS set in Overwatch.

It felt just as good as always. I tore up with McCree. Snappy, crisp, no tearing, no blanking. I saw the FPS reading on the monitor fluctuating above 144 like you describe, but Overwatch and NVIDIA's overlay reported otherwise and the feel never went bad.
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