Adaptive VSync vs Adaptive Vsync + FPS limit

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Meylink
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Adaptive VSync vs Adaptive Vsync + FPS limit

Post by Meylink » 11 Jul 2021, 08:45

Hello,

I'd like to know if there's any difference between using Adaptive Vsync alone, and Adaptive Vsync with an FPS lock ( refresh rate + 1 ).
I tried it on Horizon Zero Dawn and the frametime graph is a smooth line compared to no fps lock where there's a lot of fluctuations.

I'm using Adaptive VSync on all my games except online ones as the input lag doesn't bother as much as the awful tearing. So is there any performance impact with adding fps lock on top of Adaptive Vsync
Thanks!

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Re: Adaptive VSync vs Adaptive Vsync + FPS limit

Post by RealNC » 11 Jul 2021, 17:22

Some people refer to VRR as adaptive sync. Can you clarify whether you mean actual adaprive sync (which is normal vsync that gets disabled if the game drops FPS below Hz), or do you mean VRR (meaning g-sync or freesync.)
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Re: Adaptive VSync vs Adaptive Vsync + FPS limit

Post by Meylink » 11 Jul 2021, 18:47

Yes, I mean adaptive sync as in the normal vsync.

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Re: Adaptive VSync vs Adaptive Vsync + FPS limit

Post by RealNC » 11 Jul 2021, 19:18

Capping your FPS when using vsync provides lower input lag. Normally you'd cap to about 0.01 below your refresh rate. However, this probably won't work for adaptive vsync because it would always tear. So in that case, you should cap to exactly the refresh rate and then raise it slightly until it stops tearing.

So if your refresh rate is, say, 59.95Hz, cap to that. If it tears, cap to 59.96FPS next. Keep raising it by 0.01 until it stops tearing.

You can measure you real refresh rate here:

https://www.testufo.com/refreshrate

Obviously use RTSS to cap FPS, as it provides fractional FPS capping.
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Meylink
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Re: Adaptive VSync vs Adaptive Vsync + FPS limit

Post by Meylink » 11 Jul 2021, 19:33

Thanks for your answer! I tried capping below the refresh rate and I get tearing as you mentioned.
So I should be capping above the refresh rate with adaptive vsync.

Out of curiosity, why does capping fps with adaptive vsync performs better than adaptive vsync alone?
Thanks again!

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Re: Adaptive VSync vs Adaptive Vsync + FPS limit

Post by RealNC » 11 Jul 2021, 19:48

Meylink wrote:
11 Jul 2021, 19:33
Out of curiosity, why does capping fps with adaptive vsync performs better than adaptive vsync alone?
Same reason as with normal vsync. It reduces vsync backpressure. I posted about it here:

https://forums.guru3d.com/threads/the-t ... st-5380262
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Re: Adaptive VSync vs Adaptive Vsync + FPS limit

Post by Meylink » 11 Jul 2021, 20:11

So it would perform better if you can maintain the fps. What if it drops below your refresh rate would there be any difference or does that only apply to vsync low lag method?

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Re: Adaptive VSync vs Adaptive Vsync + FPS limit

Post by RealNC » 11 Jul 2021, 20:21

If the game does not reach the FPS cap, then nothing happens. It's as if there is no FPS cap.
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Re: Adaptive VSync vs Adaptive Vsync + FPS limit

Post by Meylink » 15 Jul 2021, 17:32

I followed the Vsync low lag method, and I found out that it works perfectly for my use case. I've got a question tho, when the framerate drops below the refresh rate, is the fps shown on screen actually 30 fps or is it whatever value like 40 50 fps etc ?

From what I understood, Vsync for it to work drops to the next divisor of your refresh rate if you can't keep up with it but with this method is it actually the same?

At first, I thought that Adaptive Vsync would be better cause it doesn't introduce that but after trying this method I no longer get any kind of screen tearing even if I drop below the refresh rate. And the performance is actually the same (?)

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Re: Adaptive VSync vs Adaptive Vsync + FPS limit

Post by RealNC » 15 Jul 2021, 20:35

Meylink wrote:
15 Jul 2021, 17:32
From what I understood, Vsync for it to work drops to the next divisor of your refresh rate if you can't keep up with it but with this method is it actually the same?
The FPS limiter doesn't change anything in that case. Whether or not your FPS will drop to 30 depends on each game. If a game does that, you can use this method with fast sync instead of vsync. There is a possibility that fast sync with this method could introduce some jitter, but I haven't tried it extensively (since I use g-sync, which pretty much deprecates all of that.) Try it out I guess and see if it's OK.

There's always RTSS scanline sync as well. When it works, it gives really good results. You run the game with vsync OFF (meaning you have zero lag) and scanline sync then makes sure there's no tearing. Scanline sync is kind of "the poor man's g-sync". It's really nice when it works.
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