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How can I minimize input lag on fallout 4 ?

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Re: How can I minimize input lag on fallout 4 ?

Postby KKNDT » 13 May 2018, 02:08

RealNC wrote:
KKNDT wrote:But I still have a question. Wouldn't it cut the frame rate to half of the refresh rate due to the frame time being longer than a refresh cycle(Assuming the system is very powerful) ?

Nope. This only happens when the game takes longer than 16.7ms (with 60Hz vsync) to actually render the frame. The FPS halving only occurs when render times are too long, not when frame presention times are too long. An FPS limiter controls frame presentation times.

In other words, a game that is susceptible to this would experience FPS halving if it would, say, run at 50FPS uncapped. But if it would run with 60FPS or higher when uncapped but you use a frame limiter to artificially cap it to 50FPS, then there will not be any FPS halving; the game will simply run at 50FPS instead of 30, even with vsync ON.

This is because when using a frame limiter, the back buffer (the buffer that holds the frame to be displayed next) actually contains a frame that is ready. It's just being held back by the frame limiter. When the game is unable to reach the frame rate cap however, that means the back buffer is NOT ready yet - the game is taking too long to render the next frame and put it into that buffer. So since there's no frame in the back buffer, there's nothing to send to the monitor when the vsync signal occurs, and instead the front buffer is sent again to the monitor. That means the frames are displayed twice, and thus FPS is halved.


Thank you for the post.
So can I understand in this way?
If the game runs at 100 FPS uncapped,it takes ~10ms to render a frame. Now you give it a 50 FPS cap, it will still take 10ms to render a frame, but will hold back ~10ms before start to work on the next frame?
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Re: How can I minimize input lag on fallout 4 ?

Postby RealNC » 13 May 2018, 05:07

KKNDT wrote:Thank you for the post.
So can I understand in this way?
If the game runs at 100 FPS uncapped,it takes ~10ms to render a frame. Now you give it a 50 FPS cap, it will still take 10ms to render a frame, but will hold back ~10ms before start to work on the next frame?

Yes.
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Re: How can I minimize input lag on fallout 4 ?

Postby KKNDT » 13 May 2018, 10:54

RealNC wrote:
KKNDT wrote:Thank you for the post.
So can I understand in this way?
If the game runs at 100 FPS uncapped,it takes ~10ms to render a frame. Now you give it a 50 FPS cap, it will still take 10ms to render a frame, but will hold back ~10ms before start to work on the next frame?

Yes.


Thanks a lot.
For many games, it's really hard to maintain FPS approaching or exceeding the refresh rate. Now you have a 144HZ non-VRR monitor and can only run the game at ~80 FPS. If you simply turn on VSYNC, stutter is to be introduced. Is it a good way to cap the game to ~72 FPS?
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Re: How can I minimize input lag on fallout 4 ?

Postby RealNC » 13 May 2018, 13:34

KKNDT wrote:For many games, it's really hard to maintain FPS approaching or exceeding the refresh rate. Now you have a 144HZ non-VRR monitor and can only run the game at ~80 FPS. If you simply turn on VSYNC, stutter is to be introduced. Is it a good way to cap the game to ~72 FPS?

This results in micro-stutter because some vsync signals are missed. For this to work well, you need either 72Hz, or 144Hz with 1/2 vsync. On NVidia, you can use Profile Inspector and in the game's profile, choose "1/2" in the vsync setting. After you apply, you most probably need to reboot for this to actually apply when you start the game.

To verify whether it worked or not, disable any FPS cap, start the game, and see if it runs at 72FPS max even though you're on 144Hz. If yes, then the setting works.

Now you do the same FPS cap trick as before, except that instead of setting a cap of 0.01FPS below refresh rate, you set a cap of 0.01 below half the refresh rate. If your detect refresh was exactly 143.998 for example, and you would normally cap to 143.988, you instead cap to 71.989 (143.998 / 2 - 0.01).

The result is perfect 72Hz vsync even though you're running 144Hz. Also, input lag is lower than true 72Hz, because the monitor refreshes each frame at the speed of 144Hz, not 72Hz.

The same trick works for other refresh rates too, btw. You can use 1/2 vsync on 120Hz for example to run 60FPS games with lower input lag compared to 60Hz.

If you're on AMD, then I'm afraid you're out of luck. 1/2 vsync (called "double vsync" on AMD) was configurable using Radeon Pro, but that utility appears to be abandoned and no longer works on modern Windows versions and/or driver versions.
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Re: How can I minimize input lag on fallout 4 ?

Postby Chief Blur Buster » 14 May 2018, 12:48

RealNC wrote:The same trick works for other refresh rates too, btw. You can use 1/2 vsync on 120Hz for example to run 60FPS games with lower input lag compared to 60Hz.

If you're on AMD, then I'm afraid you're out of luck. 1/2 vsync (called "double vsync" on AMD) was configurable using Radeon Pro, but that utility appears to be abandoned and no longer works on modern Windows versions and/or driver versions.

I found out you can get a similar effect with AMD Enhanced Sync + RTSS 60fps cap.
In a sense, it effectively behaves as a low-lag 60Hz double-vsync mode.
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Re: How can I minimize input lag on fallout 4 ?

Postby KKNDT » 16 May 2018, 09:12

RealNC wrote:On NVidia, you can use Profile Inspector and in the game's profile, choose "1/2" in the vsync setting.


Very useful infomation. Allow me to ask more questions ;)

1. If the game can run ~140FPS, or ~200FPS, but you only have a 60HZ monitor. Is it good to cap the FPS to ~120(2x) or ~180(3x) to avoide the stutter when using Fastsync?

2. If you set MPRF to 3, with double buffer VSYNC, and fill up all the frame buffers. Are there 4 frames in total behand the front buffer waiting to be displayed? Are these frames all stored in the graphics memory?

3. Is MPRF only useful to VSYNC ON which doesn't drop old frames?
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Re: How can I minimize input lag on fallout 4 ?

Postby RealNC » 16 May 2018, 10:39

KKNDT wrote:1. If the game can run ~140FPS, or ~200FPS, but you only have a 60HZ monitor. Is it good to cap the FPS to ~120(2x) or ~180(3x) to avoide the stutter when using Fastsync?

Last time I checked, fast sync already does that on its own.

2. If you set MPRF to 3, with double buffer VSYNC, and fill up all the frame buffers. Are there 4 frames in total behand the front buffer waiting to be displayed? Are these frames all stored in the graphics memory?

I don't know for sure where they are stored. It's data that the GPU uses to render a frame, they're not rendered frames yet. So they're most probably in RAM. MPRF in general is a bad idea for applications like games.

3. Is MPRF only useful to VSYNC ON which doesn't drop old frames?

No. MPRF is something that is not tied to vsync. It has an effect with vsync off, fast sync, and g-sync.
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Re: How can I minimize input lag on fallout 4 ?

Postby Chief Blur Buster » 16 May 2018, 11:23

KKNDT wrote:1. If the game can run ~140FPS, or ~200FPS, but you only have a 60HZ monitor. Is it good to cap the FPS to ~120(2x) or ~180(3x) to avoide the stutter when using Fastsync?

Stutter does generate harmonic-stutter between framerate and refreshrate, so you will notice that Fast Sync stutter can increase/decrease as you pass these intervals. Capping 120fps on a 60Hz using Fast Sync, does seem to look smoother than capping 90fps at 60Hz, because it makes it easier for Fast Sync to round-off the refresh cycles. It's worth a try if you have overkill GPU power and only have a fixed-Hz 60Hz monitors, and you hate stutter, hate tearing, and hate input lag. So 120fps and 180fps Fast Sync actually does seem to provide relatively good motion quality.

Your results will be mixed depending on the game. For example, aiming may become wonky. But some will improve aiming. Some games actually look really nice capping at those multiples (ONLY for low fixed-Hz monitors, in conjunction with Fast Sync or Enhanced Sync) -- if (A) your game can run at ultra high frame rates consistently and (B) you're stuck with a low-Hz fixed-Hz monitor.

The better move is to upgrade your monitor obviously, but it can be a reasonable low-lag tearing-free status quo while saving up for a VRR monitor.
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