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30fps method: half-refresh nvidia option + refresh rate / 2?

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30fps method: half-refresh nvidia option + refresh rate / 2?

Postby aweigh0101 » 30 Oct 2018, 22:12

Is that the "best" method right now?

Should i substract 0.01 after dividing the refresh rate by 2? (using refresh rate number from UFO site).

the website tells me my refresh rate is 80.002, so i divided by 2 then substracted 0.01 and using that number inside RTSS frame cap option field.

in nvidia control panel i have half-refresh selected.

(yes... i know 80/2 is not 30fps)
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Re: 30fps method: half-refresh nvidia option + refresh rate

Postby Chief Blur Buster » 30 Oct 2018, 23:04

There are many workflows possible to pull this off but if you are trying to do perfect half-framerate capping using RTSS, try this:

1. Use VSYNC ON along with NVIDIA Fast Sync or AMD Enhanced Sync

2. In RTSS, enter exactly half the number you get in http://www.testufo.com/refreshrate

There will be potential stutter-smooth-stutter-smooth cycling but the logic in NVIDIA Fast Sync / AMD Enhanced Sync helps this to an extent -- while keeping input lag low.

NOTE: If you're getting too much smooth-stutter-smooth-stutter cycling, try slightly lowering the cap a bit -- by approximately ~0.01 increments -- until the stutter cycling stops. This difference is explained at the HOWTO Low-Lag VSYNC ON
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Re: 30fps method: half-refresh nvidia option + refresh rate

Postby aweigh0101 » 30 Oct 2018, 23:21

thank you for the reply.

i tried it out and indeed lowering refresh rate / 2 result by -0.01 each time did indeed reduce the smooth->smooth->stutter!->smooth again cycle.

it's incredible how predictable and obvious the smooth-stutter cycle is! Once you notice it there is no going back, ever, you will never be able to NOT feel it...

i ended up substracting 0.01 three times for a total of: 80.002 / 2 - 0.03

the smooth-stutter cycle is ALMOST perfect right now. ALMOST. Question though: what about Scanline sync x/2 though? should i use that in addition to also setting a cap? or should one option be used instead of the other?

I have it OFF right now which is Scanline sync "0" on the GUI.
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Re: 30fps method: half-refresh nvidia option + refresh rate

Postby Chief Blur Buster » 30 Oct 2018, 23:46

As far as I know -- scanline sync is not supported for half-framerate capping. There might be custom settings that permits this to happen, but I am not familiar with them right now.

Scanline sync is good for automatic perfect Hz-to-fps capping with no differentials needed. But it only works well for fps=Hz and fps=(Hz x 2) capping.

Though used for tearingless VSYNC OFF, there's also a clever way to calibrate scanline sync with NVIDIA Fast Sync and AMD Enhanced Sync (the use of large negative scanline offset, first visually calibrated to have a tearline hovering permanently above bottom edge of screen, never touching bottom, in VSYNC OFF before enabling FastSync/EnhancedSync), if you prefer the occasional rare microstutter over the occasional rare tearline.
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Re: 30fps method: half-refresh nvidia option + refresh rate

Postby RealNC » 31 Oct 2018, 08:05

Scanline sync x/2 does cap to half your refresh rate. You get 40FPS in this case. You still need GPU headroom left for it to work. Also note that scanline sync is a cap in itself. The FPS value you enter in the "framerate" field has no effect when scanline sync is non-0. Finally, you need vsync OFF for scanline sync to work correctly.

I noticed you use the nvidia control panel for half refresh. That means you're using adaptive vsync. That will not work correctly when frame capping. You need to use nvidia profile inspector and set "1/2 vsync" instead. If you use adaptive 1/2 vsync instead of 1/2 vsync, you will see random tearing when capping your frame rate.
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Re: 30fps method: half-refresh nvidia option + refresh rate

Postby Chief Blur Buster » 31 Oct 2018, 14:52

Thanks for the correction.

So combining RTSS scanline sync with NVinspector 1/2 vsync -- provides this solution?
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Re: 30fps method: half-refresh nvidia option + refresh rate

Postby RealNC » 31 Oct 2018, 16:43

Chief Blur Buster wrote:Thanks for the correction.

So combining RTSS scanline sync with NVinspector 1/2 vsync -- provides this solution?

Nope. Vsync must be OFF when using scanline sync. You can use fast sync with normal scanline sync, but with scanline sync x/2, fast sync will have judder.

So use either 1/2 vsync in inspector + RTSS cap to half Hz - 0.01, or use scanline sync x/2 with vsync OFF. If the GPU is fast enough for scanline sync x/2, that's the best solution, as it completely gets rid of vsync lag.
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Re: 30fps method: half-refresh nvidia option + refresh rate

Postby Amoda154 » 06 Dec 2018, 17:39

Please can someone help me with this.
I play Assassin creed odyssey on (4k 60hz Tv).
My resolution is set to 2160p 4k. So it will be very demanding so i play at 30 fps. So my question is can someone help me in detail how to set rtss scaline x/2 to play at 30 fps? Because i tried the steps recomended for x/2=-30 but i realized that the screen is still refreshing at 60hz so when fps dip below tearing will start to be visible. Should i set monitor screen to 30 hz and use scaline x=-30 instead of x/2 or am i missing someting?
To summarize i want 30 fps for this game using rtss scaline sync.
Please any help will be appreciated.
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Re: 30fps method: half-refresh nvidia option + refresh rate

Postby RealNC » 06 Dec 2018, 19:58

x/2 scanline sync will give you 30FPS at 60Hz.
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Re: 30fps method: half-refresh nvidia option + refresh rate

Postby Amoda154 » 07 Dec 2018, 05:44

Yeah i know
But tearing happens randomly in the game, like in assassin creed odyssey which is a demanding game, tearing occurs in dense areas. I tested gpu usage which stays below 60%.
What is the cause of random tearings happening?
It seems like same behavior as adaptive sync , tearing occurs in dense areas where system cannot sustain certain fps.
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