1/2 Refresh Rate - inconsistent input lag?

Everything about latency. Tips, testing methods, mouse lag, display lag, game engine lag, network lag, whole input lag chain, VSYNC OFF vs VSYNC ON, and more! Input Lag Articles on Blur Busters.
Post Reply
Finnen
Posts: 3
Joined: 04 Nov 2019, 16:32

1/2 Refresh Rate - inconsistent input lag?

Post by Finnen » 04 Nov 2019, 16:49

Sometimes, when I can't maintain stable 60 FPS in games, I tend to lock them at 30 FPS for more consistent experience. I play mostly RPGs / TPP games, so it's not really a problem for me. I vastly prefer "flat-line" 30 FPS than fluctuating 40-50. To do that and minimize the input lag, I use the following method:

- disable in-game VSync
- force "1/2 Refresh Rate" standard VSync through NVIDIA Inspector
- set the maximum pre-rendered to 1
- lock the frame rate to 0.01 FPS below the half of my refresh rate in RTSS (59.99Hz / 2 = 29.995Hz, so I lock to 29.98)

This trick always worked fine. It gave me very consistent 30 FPS with heavily minimized input lag (though, in my opinion, still higher than some console games like Horizon, which is quite bizzare).

Sadly, this "trick" is hard to pull recently. I am using Windows 10 (1903). I started to notice that input lag is not as low as it used to be when doing the above procedure. What's most important, the input lag became inconsistent. I can actually feel that it's changing while playing the game - sometimes it's higher, sometimes it's lower.

The most bizzare thing, however, is that when I launch the game the input lag is a bit high. Then I press ALT+TAB and go back to the game. Suddenly, input lag is much lower (as it used to be long ago when I used this trick before), it works fine for several seconds, and then it rises again and the game clearly feels less responsive. The same "switch" of latency can happen even after opening/closing in-game menus or, for example, going through the loading screen when reloading save game or switching zones.

Has anyone encountered such phenomenon? It's almost as if the RTSS was losing focus on the game or something? Though not completely, because when I completely disable RTSS or set the framerate limiter to 0, I can feel even higher input lag. I tried disabling full screen optimizations in Windows 10, game bar, setting the compatibility to Windows 7 (to disable all kinds of enhancements Windows 10 might be adding), enabling/disabling HPET in BIOS, changing maximum pre-rendered frames, setting the latest Ultra Low Latency Mode. Nope, nothing, absolutely the same results in all cases.

Tested on games on Origin (for example, Kingdoms of Amalur at 4K res) and from Xbox Game Pass (The Outer Worlds) and Steam (for example, Skyrim Special Edition). Can install more games and test more, if needed.

Spec: i5-4440, GTX 970, 16GB RAM, latest NVIDIA Drivers (fairly fresh installation of Windows 10, the same thing happened in two previous NVIDIA driver versions)

User avatar
RealNC
Site Admin
Posts: 3069
Joined: 24 Dec 2013, 18:32
Contact:

Re: 1/2 Refresh Rate - inconsistent input lag?

Post by RealNC » 07 Nov 2019, 09:01

Did you test for your actual refresh rate? Most monitors are not 60.0Hz. They're somewhere near 59.94 so you'd need to cap to 29.96FPS. Test here:

https://www.testufo.com/refreshrate

Make sure your browser has hardware acceleration enabled.

Also, you might want to try RTSS scanline sync x/2. If that works for your game, it provides the lower input lag.
SteamGitHubStack OverflowTwitter
The views and opinions expressed in my posts are my own and do not necessarily reflect the official policy or position of Blur Busters.

QaisyarNazwan
Posts: 1
Joined: 06 Jul 2020, 00:45

Re: 1/2 Refresh Rate - inconsistent input lag?

Post by QaisyarNazwan » 06 Jul 2020, 00:47

Finnen wrote:
04 Nov 2019, 16:49
Sometimes, when I can't maintain stable 60 FPS in games, I tend to lock them at 30 FPS for more consistent experience. I play mostly RPGs / TPP games, so it's not really a problem for me. I vastly prefer "flat-line" 30 FPS than fluctuating 40-50. To do that and minimize the input lag, I use the following method:

- disable in-game VSync
- force "1/2 Refresh Rate" standard VSync through NVIDIA Inspector
- set the maximum pre-rendered to 1
- lock the frame rate to 0.01 FPS below the half of my refresh rate in RTSS (59.99Hz / 2 = 29.995Hz, so I lock to 29.98)

This trick always worked fine. It gave me very consistent 30 FPS with heavily minimized input lag (though, in my opinion, still higher than some console games like Horizon, which is quite bizzare).

Sadly, this "trick" is hard to pull recently. I am using Windows 10 (1903). I started to notice that input lag is not as low as it used to be when doing the above procedure. What's most important, the input lag became inconsistent. I can actually feel that it's changing while playing the game - sometimes it's higher, sometimes it's lower.

The most bizzare thing, however, is that when I launch the game the input lag is a bit high. Then I press ALT+TAB and go back to the game. Suddenly, input lag is much lower (as it used to be long ago when I used this trick before), it works fine for several seconds, and then it rises again and the game clearly feels less responsive. The same "switch" of latency can happen even after opening/closing in-game menus or, for example, going through the loading screen when reloading save game or switching zones.

Has anyone encountered such phenomenon? It's almost as if the RTSS was losing focus on the game or something? Though not completely, because when I completely disable RTSS or set the framerate limiter to 0, I can feel even higher input lag. I tried disabling full screen optimizations in Windows 10, game bar, setting the compatibility to Windows 7 (to disable all kinds of enhancements Windows 10 might be adding), enabling/disabling HPET in BIOS, changing maximum pre-rendered frames, setting the latest Ultra Low Latency Mode. Nope, nothing, absolutely the same results in all cases.

Tested on games on Origin (for example, Kingdoms of Amalur at 4K res) and from Xbox Game Pass (The Outer Worlds) and Steam (for example, Skyrim Special Edition). Can install more games and test more, if needed.

Spec: i5-4440, GTX 970, 16GB RAM, latest NVIDIA Drivers (fairly fresh installation of Windows 10, the same thing happened in two previous NVIDIA driver versions)




Have u found a fix yet? Me too are having the same problem

deama
Posts: 162
Joined: 07 Aug 2019, 12:00

Re: 1/2 Refresh Rate - inconsistent input lag?

Post by deama » 06 Jul 2020, 05:26

Finnen wrote:
04 Nov 2019, 16:49
Sometimes, when I can't maintain stable 60 FPS in games, I tend to lock them at 30 FPS for more consistent experience. I play mostly RPGs / TPP games, so it's not really a problem for me. I vastly prefer "flat-line" 30 FPS than fluctuating 40-50. To do that and minimize the input lag, I use the following method:

- disable in-game VSync
- force "1/2 Refresh Rate" standard VSync through NVIDIA Inspector
- set the maximum pre-rendered to 1
- lock the frame rate to 0.01 FPS below the half of my refresh rate in RTSS (59.99Hz / 2 = 29.995Hz, so I lock to 29.98)
Disabling in-game vsync is good, but then using it via nvidia won't do you any good unless you're running in fullscreen exclusive mode, even then I hear windows 10 doesn't play well with that so that might not even work.
The reason for this is that from windows 7, microsoft introduced the dwm, it adds about a refresh cycle's worth of input lag, but keeps everything pretty much tear free, kinda like having vsync always on, even on desktop. Back in windows 8 they made it hard to disable it, and in windows 10 it can break some stuff if you disable, e.g I heard you won't be able to use nvidia control panel.
Anyway, disable all vsync and just use RTSS's scanline or scanline x/2 (for half refresh rate).

Changing the pre-rendered frames or the "latency mode" won't do anything unless you push your GPU to 97%+ usage, it may actually increase input lag, so I recommend you always keep it on off, and never go beyond 70% gpu usage (higher gpu usage increases input lag, but it gives diminishing returns at about below 60-70%).

You're better off using the scanline sync feature as it will properly sync with your monitor because like RealNC mentioned, your monitor's refresh rate won't actually be 120hz if it says so, it'll be 119.8hz, or 120.3hz, and this changes everytime you reboot your PC, or even restart your monitor, or can even change if you switch from fullscreen exclusive to normal.

Trying to fix this might be a doosy, but I guess we can start from the bottom.
Download something called presentmon.exe
https://github.com/GameTechDev/PresentMon/releases
run it, it will tell you the latency delay of one part of the whole input lag chain (forgot which one lol, something about how long GPU takes to get a finished frame to the monitor).
After running it, run a game and set it to windowed mode, push the window over to the side so you can see the presentmon.exe window and while trying to play the game normally, look at what the latency it says, and also, look at how much it fluctuates.
Report here your results and from that point we can get a better picture of what the problem might be.

Post Reply