Some questions about G-Sync and V-Sync

[Stahlmann]

Yesterday I played around with the 3D settings in my NVCP (Nvidia control panel) after reading about how to lower input lag. The main inspiration was this post:

 

 

Now, after playing around with the settings and testing a few games, I'm now more confused about how VRR works and what are the best settings to prevent tearing while also having the least possible amount of input lag.

 

The first thing that is always mentioned in these videos is to turn off V-Sync because it somehow magically increases input lag. AFAIK all V-Sync does is cap your framerate to your monitor's refresh rate, so it shouldn't result in more input lag than just manually enabling an FPS cap at 120 FPS in my case with a 120 Hz monitor. Is that fundamentally true or is there something else going on with V-Sync that impacts input lag, other than limiting your FPS?

 

I noticed that even with G-Sync enabled, I need to turn V-Sync on to prevent tearing. Turning off V-Sync and capping my FPS to 120 (my refresh rate) or even capping 1-5 FPS lower than that always results in visible and distracting tearing, even when the game is running under 120 FPS, so V-Sync shouldn't even kick in in this situation. Is V-Sync just an additional toggle needed to actually enable G-Sync in this case?

 

In general, the videos from the other post said that disabling v-sync and using the in-game fps cap to keep the GPU under 90% utilization produces the best input lag results. However, in my experience, this leads to awful tearing, even when the FPS is below my refresh rate, so it should be within the G-Sync VRR window.

 

So currently I ended up at these settings in NVCP that feel the best to me while also resulting in no tearing:

- Under G-Sync settings, enable it for 'fullscreen AND windowed applications'

- Under 3D settings, set preferred monitor technology to 'G-Sync (compatible)'

- Under 3D settings, set frame rate cap to 'off' (this one basically goes against the advice most people give)

- Under 3D settings, set ultra low latency mode to 'Ultra'

- Under 3D settings, set V-Sync to 'on'

- If supported by the game, set Nvidia Reflex to 'Boost'

[GuiltySpark_]

16 minutes ago, Stahlmann said:

I noticed that even with G-Sync enabled, I need to turn V-Sync on to prevent tearing. Turning off V-Sync and capping my FPS to 120 (my refresh rate) or even capping 1-5 FPS lower than that always results in visible and distracting tearing,

This is very odd. I've been using GSync since 2016 and always just set a global framerate cap 2-3fps below my max refresh in Nvidia Control Panel (now the Nvidia app). Currently on my C2 I have it set to 118fps and I haven't seen tearing in years. I've played with VSync also being on as the Blur Busters GSync 101 article has explained for years but I don't like the feel of it. 

 

TBH as long as you found something that works for you, might as well roll with it. I know I have.

[Agall]

15 minutes ago, Stahlmann said:

Yesterday I played around with the 3D settings in my NVCP (Nvidia control panel) after reading about how to lower input lag. The main inspiration was this post:

 

 

Now, after playing around with the settings and testing a few games, I'm now more confused about how VRR works and what are the best settings to prevent tearing while also having the least possible amount of input lag.

 

The first thing that is always mentioned in these videos is to turn off V-Sync because it somehow magically increases input lag. AFAIK all V-Sync does is cap your framerate to your monitor's refresh rate, so it shouldn't result in more input lag than just manually enabling an FPS cap at 120 FPS in my case with a 120 Hz monitor. Is that fundamentally true or is there something else going on with V-Sync that impacts input lag, other than limiting your FPS?

 

I noticed that even with G-Sync enabled, I need to turn V-Sync on to prevent tearing. Turning off V-Sync and capping my FPS to 120 (my refresh rate) or even capping 1-5 FPS lower than that always results in visible and distracting tearing, even when the game is running under 120 FPS, so V-Sync shouldn't even kick in in this situation. Is V-Sync just an additional toggle needed to actually enable G-Sync in this case?

 

In general, the videos from the other post said that disabling v-sync and using the in-game fps cap to keep the GPU under 90% utilization produces the best input lag results. However, in my experience, this leads to awful tearing, even when the FPS is below my refresh rate, so it should be within the G-Sync VRR window.

 

So currently I ended up at these settings in NVCP that feel the best to me while also resulting in no tearing:

- Under G-Sync settings, enable it for 'fullscreen AND windowed applications'

- Under 3D settings, set preferred monitor technology to 'G-Sync (compatible)'

- Under 3D settings, set frame rate cap to 'off' (this one basically goes against the advice most people give)

- Under 3D settings, set ultra low latency mode to 'Ultra'

- Under 3D settings, set V-Sync to 'on'

- If supported by the game, set Nvidia Reflex to 'Boost'

Since the beginning, which was a Nvidia DIY kit modded VG248QE way back in 2014, I've globally disabled V-sync in the control panel. Otherwise, the only other setting I set is the fullscreen+fullscreen windowed with regards to G-sync.

 

I'm particularly sensitive to changes in latency now a days after using my Neo G8's 4K 240Hz display. What I've found as the absolute best way to get the smoothest possible experience:

 

-3D v-cache CPUs

-Globally disable V-sync (turn off V-sync where possible, but it kind of doesn't matter)

-Unlock the framerate

 

The most noticeable part is when you get framerate dips, something 3D v-cache helps mitigate. But otherwise, your goal is to get the highest framerate possible so that when a dip occurs, the display can be ready to compensate. In games with those dips, the difference between locking at 240 and unlocking to allow 1.5-2x overdrive is massive.

[191x7]

13 minutes ago, Stahlmann said:

Yesterday I played around with the 3D settings in my NVCP (Nvidia control panel) after reading about how to lower input lag. The main inspiration was this post:

 

 

Now, after playing around with the settings and testing a few games, I'm now more confused about how VRR works and what are the best settings to prevent tearing while also having the least possible amount of input lag.

 

I just want to make it clear that in the following, I'm always talking about the Nvidia driver settings, NOT in-game graphics settings.

 

The first thing that is always mentioned in these videos is to turn off V-Sync because it somehow magically increases input lag. AFAIK all V-Sync does is cap your framerate to your monitor's refresh rate, so it shouldn't result in more input lag than just manually enabling an FPS cap at 120 FPS in my case with a 120 Hz monitor. Is that fundamentally true or is there something else going on with V-Sync that impacts input lag, other than limiting your FPS?

 

I noticed that even with G-Sync enabled, I need to turn V-Sync on to prevent tearing. Turning off V-Sync and capping my FPS to 120 (my refresh rate) or even capping 1-5 FPS lower than that always results in visible and distracting tearing, even when the game is running under 120 FPS, so V-Sync shouldn't even kick in in this situation. Is V-Sync just an additional toggle needed to actually enable G-Sync in this case?

 

So currently I ended up at these settings in NVCP that feel the best to me while also resulting in no tearing:

- Under G-Sync settings enable it for 'fullscreen AND windowed applications'

- Under 3D settings set preferred monitor technology to 'G-Sync (compatible)'

- Under 3D settings set frame rate cap to 'off'

- Under 3D settings set ultra low latency mode to 'Ultra'

- Under 3D settings set V-Sync to 'on'

 

The thing with v-sync is the buffering. If your refresh is 120 and your framerate falls below, at that moment the framerate is halved.

So if you have v-sync and your framerate drops below 120 it becomes 60 and 60 has double the latency of 120...

Triple buffering helps with that, instead of losing half you lose a fourth, it would drop to 90.

 

If you have tearing in your VRR range, that means VRR isn't working for you. Check your monitor driver, monitor settings, the connection (type) you use and the GPU bios and settings.

[Stahlmann]

4 minutes ago, GuiltySpark_ said:

This is very odd. I've been using GSync since 2016 and always just set a global framerate cap 2-3fps below my max refresh in Nvidia Control Panel (now the Nvidia app). Currently on my C2 I have it set to 118fps and I haven't seen tearing in years. I've played with VSync also being on as the Blur Busters GSync 101 article has explained for years but I don't like the feel of it. 

 

TBH as long as you found something that works for you, might as well roll with it. I know I have.

Basically the the long and short of it is that I found out that the manual frame rate cap isn't necessary once you also use V-Sync.

[GuiltySpark_]

1 minute ago, Stahlmann said:

Basically the the long and short of it is that I found out that the manual frame rate cap isn't necessary once you also use V-Sync.

Very true, and that's what the GSync 101 arcticle has explained for years. I just can't get over how it feels in FPS titles so I'm happy to just use the framerate cap instead. 

 

https://blurbusters.com/gsync/gsync101-input-lag-tests-and-settings/14/

[191x7]

Just now, Stahlmann said:

Basically the the long and short of it is that I found out that the manual frame rate cap isn't necessary once you also use V-Sync.

That's true, but it's also logical since v-sync is a buffer that holds a whole frame.

[Stahlmann]

1 minute ago, 191x7 said:

The thing with v-sync is the buffering. If your refresh is 120 and your framerate falls below, at that moment the framerate is halved.

So if you have v-sync and your framerate drops below 120 it becomes 60 and 60 has double the latency of 120...

Triple buffering helps with that, instead of losing half you lose a fourth, it would drop to 90.

 

If you have tearing in your VRR range, that means VRR isn't working for you. Check your monitor driver, monitor settings, the connection (type) you use and the GPU bios and settings.

In that case it should also look like 60 Hz once I drop below 120, shouldn't it? That's not how it behaves im my case. 100 fps feels and looks like 100, same with 90, 80, etc.

[Stahlmann]

3 minutes ago, GuiltySpark_ said:

Very true, and that's what the GSync 101 arcticle has explained for years. I just can't get over how it feels in FPS titles so I'm happy to just use the framerate cap instead. 

 

https://blurbusters.com/gsync/gsync101-input-lag-tests-and-settings/14/

That explains why V-Sync is needed to completely get rid of tearing, even when using G-Sync. Thanks, that was exactly what I was looking for.

 

Sadly, they still don't talk about the reasoning behind ALSO limiting framerate below the refresh rate.

Scratch that, it's talked about in the FAQ.

[191x7]

1 minute ago, Stahlmann said:

In that case it should also look like 60 Hz once I drop below 120, shouldn't it? That's not how it behaves im my case. 100 fps feels and looks like 100, same with 90, 80, etc.

Then you're not using v-sync. You might be using fast sync. V-sync always drops. And V-sync always halves the framerate. And even when you're above your refresh most of the time, even then it adds some latency due to how the tech works.

[Agall]

5 minutes ago, Stahlmann said:

In that case it should also look like 60 Hz once I drop below 120, shouldn't it? That's not how it behaves im my case. 100 fps feels and looks like 100, same with 90, 80, etc.

VRR is supposed to match or 2x/3x overmatch the framerate. The only exception to that was very early freesync which didn't below like 45 fps.

 

Its also possible the issues you're seeing aren't a g-sync issue but a CPU limitation or pixel response time limitation. Personally, I've used a wide range of G-sync displays, including a 2016 era ROG laptop with a 75Hz g-sync display that I overclocked to 100Hz. Even on that device, I would globally disable V-sync.

[GuiltySpark_]

1 minute ago, Stahlmann said:

That explains why V-Sync is needed to completely get rid of tearing, even when using G-Sync. Thanks, that was exactly what I was looking for.

 

Sadly, they still don't talk about the reasoning behind ALSO limiting framerate below the refresh rate.

Go here and click the questions. That question is specifically answered. 

 

https://blurbusters.com/gsync/gsync101-input-lag-tests-and-settings/15/

 

 

I've experienced this myself. Occasional tearing when the framerate overshoots the max refresh rate. The limit prevents that. Essentially you're attacking the problem from multiple angles. 

[GuiltySpark_]

TBH, this whole topic has a wide range of opinions, as you're seeing from this thread. Some are vehemently against VSync from an idealistic POV, myself included, however I think most overlook how when combined with GSync and a framerate cap, as the blurbusters article explains its the most "ideal" solution. 

 

[Stahlmann]

2 minutes ago, 191x7 said:

Then you're not using v-sync. You might be using fast sync. V-sync always drops. And V-sync always halves the framerate. And even when you're above your refresh most of the time, even then it adds some latency due to how the tech works.

 

Out of the FAQ @GuiltySpark_ posted earlier:

Quote

G-SYNC + V-SYNC “Off”:
The tearing inside the G-SYNC range with V-SYNC “Off” is caused by sudden frametime variances output by the system, which will vary in severity and frequency depending on both the efficiency of the given game engine, and the system’s ability (or inability) to deliver consistent frametimes.

G-SYNC + V-SYNC “Off” disables the G-SYNC module’s ability to compensate for sudden frametime variances, meaning, instead of aligning the next frame scan to the next scanout (the process that physically draws each frame, pixel by pixel, left to right, top to bottom on-screen), G-SYNC + V-SYNC “Off” will opt to start the next frame scan in the current scanout instead. This results in simultaneous delivery of more than one frame in a single scanout (tearing).

In the Upper FPS range, tearing will be limited to the bottom of the display. In the Lower FPS range (<36) where frametime spikes can occur (see What are Frametime Spikes?), full tearing will begin.

Without frametime compensation, G-SYNC functionality with V-SYNC “Off” is effectively “Adaptive G-SYNC,” and should be avoided for a tear-free experience (see G-SYNC 101: Optimal Settings & Conclusion).

 

Makes sense tbh.

[191x7]

3 minutes ago, Stahlmann said:

That explains why V-Sync is needed to completely get rid of tearing, even when using G-Sync. Thanks, that was exactly what I was looking for.

 

Sadly, they still don't talk about the reasoning behind ALSO limiting framerate below the refresh rate.

Scratch that, it's talked about in the FAQ.

In the G-sync range there should be no tearing if everything is working fine.

Going above that range one might experience tearing, and that is why people limit their framerates in games and/or use Fast Sync or Enhanced Sync.

I'll say once again - if you're having tearing in your VRR range something isn't working right.

[Stahlmann]

4 minutes ago, 191x7 said:

In the G-sync range there should be no tearing if everything is working fine.

Going above that range one might experience tearing, and that is why people limit their framerates in games and/or use Fast Sync or Enhanced Sync.

I'll say once again - if you're having tearing in your VRR range something isn't working right.

The tearing I was talking about earlier was technically in the VRR range, but towards the top, around 100-110 fps, which makes sense when looking at what blurbusters was writing about. And the tearing specifically happened when V-Sync was disabled and in the lower part of the display like blurbusters described, so that checks out.

 

7 minutes ago, Agall said:

VRR is supposed to match or 2x/3x overmatch the framerate. The only exception to that was very early freesync which didn't below like 45 fps.

Afaik what you're describing is LFC, so VRR can work way below the technical VRR range of a monitor by multiplying the frames. In the actual VRR range, this multiplication shouldn't happen.

 

7 minutes ago, Agall said:

Its also possible the issues you're seeing aren't a g-sync issue but a CPU limitation or pixel response time limitation. Personally, I've used a wide range of G-sync displays, including a 2016 era ROG laptop with a 75Hz g-sync display that I overclocked to 100Hz. Even on that device, I would globally disable V-sync.

I have never heard of CPUs being responsible for tearing. Pixel response times certainly aren't a problem since i'm on an OLED, and specifically an LG C2, which is officially G-Sync compatible certified.

[porina]

8 minutes ago, Stahlmann said:

In that case it should also look like 60 Hz once I drop below 120, shouldn't it? That's not how it behaves im my case. 100 fps feels and looks like 100, same with 90, 80, etc.

This case applies to when V-sync is on, and there is no VRR in play. Frame times usually vary a fair bit, and this is looking at individual frames, whereas fps is usually an average over time. If few enough frames drop into the lower effective fps region, you don't perceive it as being in that lower fps region. Maybe a little micro-stutter.

[Agall]

2 minutes ago, GuiltySpark_ said:

TBH, this whole topic has a wide range of opinions, as you're seeing from this thread. Some are vehemently against VSync from an idealistic POV, myself included, however I think most overlook how when combined with GSync and a framerate cap, as the blurbusters article explains its the most "ideal" solution. 

 

In the way I've configured my setups with v-sync disabled, I haven't seen tearing on my systems in nearly a decade. Any input latency concerns are handled by just having a well balanced system and settings that allow for a high and smooth framerate.

 

GN's video with that Nvidia engineer sort of demonstrates this, having your settings dialed in to where you're at a slight GPU limit, where too far in either way will either flood the frame buffer or have it always drained.

[GuiltySpark_]

2 minutes ago, Agall said:

In the way I've configured my setups with v-sync disabled, I haven't seen tearing on my systems in nearly a decade. Any input latency concerns are handled by just having a well balanced system and settings that allow for a high and smooth framerate.

 

GN's video with that Nvidia engineer sort of demonstrates this, having your settings dialed in to where you're at a slight GPU limit, where too far in either way will either flood the frame buffer or have it always drained.

I don't currently use VSync either and haven't since getting into GSync back with my PG348Q in 2016. I've tried to do as "little" as possible and simply run a framerate cap to stay within the GSync range and its worked great for me. One of those things that its working so I don't really need to mess with it. 

[PDifolco]

11 minutes ago, GuiltySpark_ said:

TBH, this whole topic has a wide range of opinions, as you're seeing from this thread. Some are vehemently against VSync from an idealistic POV, myself included, however I think most overlook how when combined with GSync and a framerate cap, as the blurbusters article explains its the most "ideal" solution. 

 

In my experience VSync massively reduces tearing in "fast moving" games 

Don't care much if it adds some couple ms input lag

[Agall]

1 minute ago, Stahlmann said:

The tearing I was talking about earlier was technically in the VRR range, but towards the top, around 100-110 fps, which makes sense when looking at what blurbusters was writing about. And the tearing specifically happened when V-Sync was disabled and in the lower part of the display like blurbusters described, so that checks out.

 

Afaik what you're describing is LFC, so VRR can work way below the technical VRR range of a monitor by multiplying the frames. In the actual VRR range, this multiplication shouldn't happen.

 

I have never heard of CPUs being responsible for tearing. Pixel response times certainly aren't a problem since i'm on an OLED, and specifically an LG C2, which is officially G-Sync compatible certified.

G-sync and OLED is more complicated since it can't just strobe the backlight to match framerate like a normal LED backlight. LTT recently talked about this, so they have to engineer ways around that 'limitation' by forcing a full refresh. The way I see it too, g-sync on an OLED doesn't make sense since it'll either duplicate frames or be able to neigh instantly refresh a new frame. So any latency you're seeing might just be a lack of framerate and you're getting periods of stale frames with poorly implemented G-sync.

 

I have a friend who has the 45" 1440p UW 240Hz OLED and keeps G-sync disabled since it wasn't well implemented.

[Stahlmann]

12 minutes ago, Agall said:

G-sync and OLED is more complicated since it can't just strobe the backlight to match framerate like a normal LED backlight. LTT recently talked about this, so they have to engineer ways around that 'limitation' by forcing a full refresh. The way I see it too, g-sync on an OLED doesn't make sense since it'll either duplicate frames or be able to neigh instantly refresh a new frame. So any latency you're seeing might just be a lack of framerate and you're getting periods of stale frames with poorly implemented G-sync.

 

I have a friend who has the 45" 1440p UW 240Hz OLED and keeps G-sync disabled since it wasn't well implemented.

Now that's just wrong. G-Sync was already working for years on ALL of my OLED displays. The only real question that came up was why I also need to enable V-Sync (which I also had enabled 24/7 in NVCP before, but never thought about why), why driver-side V-Sync is more desirable than in-game V-Sync and why we still need to manually cap fps below the refresh rate, even when already using V-Sync. All of these questions were answered on the G-Sync 101 @GuiltySpark_ linked.

 

It's not black magic. LG has had OLED TVs with an official 'G-Sync compatible' certification since their 2019 C9 lineup. I don't think Nvidia would give out a certification if they're barely able to utilize VRR.

 

Other than the occational flickers at extreme FPS fluctuations, which is what LTT described in their video, there are no inherent issues that mean OLEDs can't use VRR properly. These 'extreme fps variations' pretty much only happen during loading screens for example. Not in gameplay. It's not gonna start flickering because you dip from 240 to 140 FPS, but rather when you go from 240 to 10 FPS with big frametime spikes.

 

So your friend should really reconsider running G-Sync. I'm sorry he had to bother with tearing all this time.

[Agall]

3 minutes ago, Stahlmann said:

Other than the occational flickers at extreme FPS fluctuations, which is what LTT described in their video, there are no inherent issues that mean OLEDs can't use VRR properly. These 'extreme fps variations' pretty much only happen during loading screens for example. Not in gameplay. It's not gonna start flickering because you dip from 240 to 140 FPS, but rather when you go from 240 to 10 FPS with big frametime spikes.

So most likely you're getting a refresh of a black screen where no frame was available? 

[porina]

22 minutes ago, GuiltySpark_ said:

Very true, and that's what the GSync 101 arcticle has explained for years. I just can't get over how it feels in FPS titles so I'm happy to just use the framerate cap instead. 

 

https://blurbusters.com/gsync/gsync101-input-lag-tests-and-settings/14/

I hadn't seen this earlier. So their recommendation is:

Driver: G-sync enabled for full screen, V-sync ON

Games: Use fullscreen or exclusive fullscreen, not borderless fullscreen. Turn OFF V-sync. If fps exceeds refresh then limit below.

 

What I've ran, and largely haven't had problems with following general settings:

Driver: G-sync enabled for full screen, V-sync to application preference

Games: V-sync ON. I don't have game settings that exceed refresh rate where it matters. G-Sync Compatible TV I run full screen only. On G-sync monitor, I run borderless since it makes it a lot easier to move between multiple displays.

 

Some observations: I used to have G-sync also enabled for windowed content, but I found this has a weird effect in some software, where it feels like the responsiveness varies erratically, sometimes 60 Hz effective, sometimes native refresh. On the TV, it seemed to also cause it to shift between game mode (low latency) and normal mode a lot. This is really annoying as it blanks a short time with a popup when it does so.

 

The only game I've turned V-sync off is Cities Skylines II. It can run at low fps, like 20fps, and V-sync off does help responsiveness even at that framerate. I haven't noticed tearing.

[Stahlmann]

Just now, Agall said:

So most likely you're getting a refresh of a black screen where no frame was available? 

No it's not like an on/off flicker. It's just a dip in brightness because of the different voltages required at different refresh rates to reach a certain brightness. It's more like you get an occational frame with the wrong brightness during these situations, be it too bright or too dim. But it's not really bothersome, as it's really only during loading screens and you can get used to it pretty quickly.