Blur Busters Forums

Who you gonna call? The Blur Busters! For Everything Better Than 60Hz™ Skip to content

G-Sync + V-Sync input lag confusion

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.

G-Sync + V-Sync input lag confusion

Postby MonarchX » 29 Dec 2018, 21:02

I recently re-read the G-Sync review and technology explanation, but I was still confused regarding input lag addition/increase when comparing G+Sync + V-Sync (double buffering) and V-Sync-only (double-buffering) with G-Sync disabled entirely.

AFAIK, in fullscreen exclusive mode, at 60fps/hz, enabling V-Sync (double buffering) adds 16ms of input lag and at 120fps/hz, it adds about 8ms. Does the same apply to enabling V-Sync on G-Sync-capable displays with G-Sync enabled?

I thought that G-Sync, by itself (with V-Sync disabled), barely adds any input lag or doesn't add any at all andwhen V-Sync is added to G-Sync, then input lag is increase by some 1-2ms, not 16-8ms at 60-120hz...

If V-Sync does add that much input lag, even with G-Sync, then Borderless Windowed mode is still superior for input lag, even though there a slight decrease in FPS.
MonarchX
 
Posts: 59
Joined: 23 Feb 2014, 20:07

Re: G-Sync + V-Sync input lag confusion

Postby RealNC » 29 Dec 2018, 21:14

MonarchX wrote:AFAIK, in fullscreen exclusive mode, at 60fps/hz, enabling V-Sync (double buffering) adds 16ms of input lag and at 120fps/hz, it adds about 8ms.

It add much more than that. Sometimes 4 more frames of lag, which is 66ms.

Does the same apply to enabling V-Sync on G-Sync-capable displays with G-Sync enabled?

Almost, yes. It seems to be slightly less worse than just vsync, but not by much. This is why you using a frame limiter with g-sync is so helpful. It completely prevents the vsync lag from happening when using g-sync + vsync.

I thought that G-Sync, by itself (with V-Sync disabled), barely adds any input lag or doesn't add any at all andwhen V-Sync is added to G-Sync, then input lag is increase by some 1-2ms, not 16-8ms at 60-120hz...

Only when using a frame limiter. Uncapped g-sync + vsync will be pretty much as bad as just vsync.

If V-Sync does add that much input lag, even with G-Sync, then Borderless Windowed mode is still superior for input lag, even though there a slight decrease in FPS.

Nope. G-Sync with a -3FPS frame cap is superior.
TwitterSteamGitHubStack Overflow
The views and opinions expressed in my posts are my own and do not necessarily reflect the official policy or position of Blur Busters.
User avatar
RealNC
 
Posts: 2736
Joined: 24 Dec 2013, 18:32

Re: G-Sync + V-Sync input lag confusion

Postby Chief Blur Buster » 29 Dec 2018, 22:28

MonarchX wrote:I recently re-read the G-Sync review and technology explanation, but I was still confused regarding input lag addition/increase when comparing G+Sync + V-Sync (double buffering) and V-Sync-only (double-buffering) with G-Sync disabled entirely.

MonarchX wrote:AFAIK, in fullscreen exclusive mode, at 60fps/hz, enabling V-Sync (double buffering) adds 16ms of input lag and at 120fps/hz, it adds about 8ms. Does the same apply to enabling V-Sync on G-Sync-capable displays with G-Sync enabled?

Traditional VSYNC doesn't exist on a G-SYNC monitor until the G-SYNC framerate reaches maximum (e.g. individual frametime faster than a refresh cycle).

The lag of VSYNC ON or VSYNC OFF becomes applicable once the VRR monitor is maxed out and the refreshing is falling back to another sync behaviour.

NOTE: Sometimes framerate caps aren't perfect. A 143fps cap may fluctuate, e.g. some frametimes are 1/140sec and some frametimes are 1/145sec. One of those two would be faster than a refresh cycle, and begin to trigger a different sync behaviour.

MonarchX wrote:If V-Sync does add that much input lag, even with G-Sync, then Borderless Windowed mode is still superior for input lag, even though there a slight decrease in FPS.

Borderless windowed mode with VSYNC OFF is roughly akin to Exclusive fullscreen mode with NVIDIA Fast Sync / AMD Enhanced Sync -- aka low-lag variant of triple buffering (rather than a 3-framebuffer queue).

However, native G-SYNC is lower lag than that.

Cheers,
Head of Blur Busters - BlurBusters.com | TestUFO.com | Follow @BlurBusters on Twitter

       To support Blur Busters:
       • Official List of Best Gaming Monitors
       • List of G-SYNC Monitors
       • List of FreeSync Monitors
       • List of Ultrawide Monitors
User avatar
Chief Blur Buster
Site Admin
 
Posts: 6319
Joined: 05 Dec 2013, 15:44

Re: G-Sync + V-Sync input lag confusion

Postby MonarchX » 29 Dec 2018, 22:46

I think I got it. V-Sync + G-Sync input lag is bad only if FPS reaches max refresh rate? On 144Hz display at 1440p, even with GTX 1080 To and max graphics settings, in demanding games, its a very unlikely scenario. Most games have FPS limiters these days, but I heard they aren't as good as those that limit FPS on some micro level.

Going back to Borderless Mode. Since it does provide triple buffering, wouldn't it be smoother with VSync, GSync, and FPS limiter than Fullscreens Exclusive with same VSync and GSync conditions?

I also noticed the advice is to force NVidia V-Sync in NVCP, but games can still overwrite that.

Some side questions:
- Did Blur Buster's ever analyze, why, unlike Free Sync displays, GSync ones do not do well with postprocessing that often comes with monitors. The same exact panels that can offer color postprocessing and sharpness adjustment features through OSD controls cannot do the same if GSync is integrates. Is it due to some "direct passthrough" requirement?
- Have there been any ideas as to why ULMB can't use G-Sync?
MonarchX
 
Posts: 59
Joined: 23 Feb 2014, 20:07

Re: G-Sync + V-Sync input lag confusion

Postby RealNC » 30 Dec 2018, 00:23

MonarchX wrote:I think I got it. V-Sync + G-Sync input lag is bad only if FPS reaches max refresh rate?

Yes. That's why with g-sync, you get the best results if you use the game's FPS limiter, or something like RTSS is the game does not have a limiter, to cap your FPS to 3FPS below your current refresh rate. At 144Hz, that means a 141FPS cap will completely prevent vsync lag.

On 144Hz display at 1440p, even with GTX 1080 To and max graphics settings, in demanding games, its a very unlikely scenario. Most games have FPS limiters these days, but I heard they aren't as good as those that limit FPS on some micro level.

For g-sync, the game's own limiter is usually better. Unless it has too much microstutter, in which case you can use RTSS. The in-game limiters are not good when used with just vsync (no g-sync.) In that case, RTSS is the best solution because of it's accuracy for normal vsync.

Going back to Borderless Mode. Since it does provide triple buffering, wouldn't it be smoother with VSync, GSync, and FPS limiter than Fullscreens Exclusive with same VSync and GSync conditions?

No. You don't need triple buffering when using g-sync. Triple buffering was invented to solve a problem with normal vsync. G-Sync does not have that problem.

I also noticed the advice is to force NVidia V-Sync in NVCP, but games can still overwrite that.

I have not seen a game yet that can override it. If you set vsync to ON in the NVCP and vsync to OFF in the game's settings, the game will not override the NVCP setting. Although setting the in-game vsync to OFF is not needed, it's still recommended so that the game does not activate any hidden vsync-related settings. When using g-sync, it's best when the game thinks it is running with vsync OFF.

Have there been any ideas as to why ULMB can't use G-Sync?

Because it's difficult to do :P You can tweak some monitors to use ULMB and g-sync at the same time, but the results are not that good, as there can be too much flicker. See:

viewtopic.php?f=4&t=2883
TwitterSteamGitHubStack Overflow
The views and opinions expressed in my posts are my own and do not necessarily reflect the official policy or position of Blur Busters.
User avatar
RealNC
 
Posts: 2736
Joined: 24 Dec 2013, 18:32

Re: G-Sync + V-Sync input lag confusion

Postby Chief Blur Buster » 31 Dec 2018, 13:30

MonarchX wrote:- Did Blur Buster's ever analyze, why, unlike Free Sync displays, GSync ones do not do well with postprocessing that often comes with monitors. The same exact panels that can offer color postprocessing and sharpness adjustment features through OSD controls cannot do the same if GSync is integrates. Is it due to some "direct passthrough" requirement?

There is no such limitation.

And there is already an answer -- a very simple one at it:

The reason G-SYNC monitors don't have much post processing in G-SYNC mode is monitor manufacturers actually give the prototype monitors to NVIDIA to add G-SYNC to it. Therefore the monitor manufacturers aren't able to add as many fancy post-processing features to G-SYNC modes.

On the other hand, G-SYNC monitors have been well known for excellent overdrive. Many eSports player find that the G-SYNC monitors are often lower lag in non-G-SYNC mode thanks to NVIDIA's latency calibration, excellent overdrive tuning, excellent frameskip debugging, ULMB strobe tuning, and all the services that NVIDIA does for your favourite monitor manufacturer -- to make it worth the G-SYNC premium. That's why G-SYNC monitors cost more; it's NVIDIA getting a cut for all the work they do.

On the other hand, it can mean G-SYNC monitors sometimes tend to be like cloned purebred horses; while they are a high pedigree, it means they are relatively consistently high quality but will not ever have specific characteristics (e.g. no spots or stripes on the horse). In other words, not as many manufacturer-specific specializations such as adding a Sharpness adjustment that works during VRR mode.

FreeSync 2 is similiarly "rigorous" testing now albiet early FreeSync monitors can be quite all over the map -- manufacturers add FreeSync themselves, and some manufacturers were worse than others. Then again the manufacturer do have the freedom to add other fancy features (like a sharpness adjustment (like realtime Photoshop filters) that works realtime during VRR mode) that NVIDIA may not have added to G-SYNC.

Pros and cons. Many times, the G-SYNC premium can certainly indeed be worth it (even if you don't do G-SYNC). The great thing is that it's wholly up to the user to decide what monitor to buy -- you can buy FreeSync, G-SYNC, 60Hz, 144Hz, 240Hz -- and shop which one has a great FreeSync implementation as well as also a sharpness adjustment.
Head of Blur Busters - BlurBusters.com | TestUFO.com | Follow @BlurBusters on Twitter

       To support Blur Busters:
       • Official List of Best Gaming Monitors
       • List of G-SYNC Monitors
       • List of FreeSync Monitors
       • List of Ultrawide Monitors
User avatar
Chief Blur Buster
Site Admin
 
Posts: 6319
Joined: 05 Dec 2013, 15:44


Return to G-SYNC

Who is online

Users browsing this forum: Google [Bot] and 1 guest