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RTSS now has new automatic Low-Lag VSYNC ON (raster based)

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Re: RTSS now has new automatic Low-Lag VSYNC ON (raster base

Postby alexander1986 » 18 Jan 2019, 04:51

So I have some amazing results with scanline sync when playing fortnite on my lightboosted 120 hz monitor @ 120 fps, no tearing no stutter and no motion blur + very low input lag if any compared to just 120 fps limit,

just have a question, in my case, should i set SyncTimeout to 0,1, or 8333 for best result ?


If I understand it correctly, setting it to 0 will not disable synchronization if framerate falls below monitor refreshrate, traditional vsync with low input lag? (but if framerate drops below 120 at any point, it will still synchronize and that can have negative effect on input perhaps is my thought?)

setting it to 1 will calibrate timeout automatically and RTSS will benchmark or monitor framerate and disable the sync if framerate drops below refreshrate? (does this take up resources though? like cpu/gpu time and add load or delay maybe?

and setting it to 8333 will be kind of like adaptive vsync with low inputlag for 120 hz, allowing tearing and disabling sync if framerate drops below refreshrate, in this case 120 hz/8.33 ms? (feels like this is best idea in my case?)

Is this correct or I understood it wrong? Ive been reading about the timeout value here in beginning of this post:

viewtopic.php?f=2&t=4173

and am not really sure what would be best in my case for the lowest input lag and/or best setting to have it on in those rare cases my framerate drops below 120 or frametime exceeds 8.33 ms, I presume its best to set it so that it disables the sync if framerate falls below refreshrate, since in my case its used for competitive play in a FPS, my FPS is at 120 fps for a large majority of the time but if/when it drops, I wonder what the timeout should be set to for best effect :p

hope this makes sense, thanks !
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Re: RTSS now has new automatic Low-Lag VSYNC ON (raster base

Postby MonarchX » 18 Jan 2019, 15:22

jorimt wrote:
MonarchX wrote:I have them like this now for NVidia Forced V-Sync + G-Sync on 165Hz display

Why are you using Scanline sync with G-SYNC?

Scanline sync is, as far as I'm aware, user controllable tearline steering, which means it isn't technically a form of V-SYNC at all, but a V-SYNC OFF method that mimics the look of traditional V-SYNC, but without the lag.

It's not intended to be used in conjunction with VRR, but to be used standalone if, for instance, your display doesn't have VRR capabilities.


Got it! Do you know about ENB FPS limiter? How does it compare to RTSS, NVidia Inspector/Drivers, and in-game FPS limiters?

BTW, does it make sense to set FPS limiter 3fps below or should the number be even? I figured that for 144Hz, 140fps/hz would be easier for the system to keep smooth than 141fps/hz? no?
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Re: RTSS now has new automatic Low-Lag VSYNC ON (raster base

Postby RealNC » 18 Jan 2019, 16:00

MonarchX wrote:BTW, does it make sense to set FPS limiter 3fps below or should the number be even? I figured that for 144Hz, 140fps/hz would be easier for the system to keep smooth than 141fps/hz? no?

141FPS means RTSS is using a 7.09ms scanout interval. 140FPS means it's using a 7.14ms interval. There's no reason why 7.14ms would be better than 7.09ms. Or any other time interval.
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Re: RTSS now has new automatic Low-Lag VSYNC ON (raster base

Postby jorimt » 18 Jan 2019, 16:05

MonarchX wrote:Got it! Do you know about ENB FPS limiter? How does it compare to RTSS, NVidia Inspector/Drivers, and in-game FPS limiters?

I haven't tested the ENB limiter, so I can't say. What I can say, is that the RTSS limiter only has higher input lag than most in-game limiters, and only by 1 frame, at most.

When compared to uncapped at the same framerate, even within the G-SYNC range, the RTSS limiter can actually have less lag, so at worst, it is neutral in that regard (which is about as good as you can get for an external limiter), and it also does a good job of steadying frametime (as the long as the framerate is limited by it), since that's how it limits to the desired average framerate.

MonarchX wrote:BTW, does it make sense to set FPS limiter 3fps below or should the number be even? I figured that for 144Hz, 140fps/hz would be easier for the system to keep smooth than 141fps/hz? no?

Limiting FPS in even numbers with G-SYNC would only be for OCD purposes. Since VRR effectively adjusts the refresh rate to the GPU render rate, there are no ill effects of "odd" number delivery. Though if it bothers you that much, -2 FPS is what I used in all my tests, which was found to be the minimum needed to stay within the G-SYNC range.
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Re: RTSS now has new automatic Low-Lag VSYNC ON (raster base

Postby Chief Blur Buster » 24 Jan 2019, 01:55

RealNC wrote:
MonarchX wrote:BTW, does it make sense to set FPS limiter 3fps below or should the number be even? I figured that for 144Hz, 140fps/hz would be easier for the system to keep smooth than 141fps/hz? no?

141FPS means RTSS is using a 7.09ms scanout interval. 140FPS means it's using a 7.14ms interval. There's no reason why 7.14ms would be better than 7.09ms. Or any other time interval.

Let's be careful as "scanout interval" is confusing terminology.

The refresh cycle's scanout duraton is constant on a VRR monitor, only the interval between the scanout starts changes.
For a 144Hz VRR monitor, 7.09ms frametime = 6.94ms(1/144sec) scanout time + 0.15ms VBI time.
Assuming that 7.09ms frametime is within the VRR range (which it is).

(High speed videos of refresh cycle scanout & info in article).
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Re: RTSS now has new automatic Low-Lag VSYNC ON (raster base

Postby RealNC » 24 Jan 2019, 13:32

Chief Blur Buster wrote:
RealNC wrote:141FPS means RTSS is using a 7.09ms scanout interval. 140FPS means it's using a 7.14ms interval. There's no reason why 7.14ms would be better than 7.09ms. Or any other time interval.

Let's be careful as "scanout interval" is confusing terminology.

The refresh cycle's scanout duraton is constant on a VRR monitor, only the interval between the scanout starts changes.

Uh, that's exactly what I said :P
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Re: RTSS now has new automatic Low-Lag VSYNC ON (raster base

Postby mist » 05 Feb 2019, 14:13

Hello! :)
Why scansync not works on some modern games.
Scansync work perfect in ut99 But i cant control tearline in Quake Champions and Unreal Tournament 4. Tearline in this games have random position. Why? Can you explain me. What i am do wrong?

Thanks.

ps win7x64, AMD rx570
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Re: RTSS now has new automatic Low-Lag VSYNC ON (raster base

Postby Chief Blur Buster » 05 Feb 2019, 15:03

mist wrote:Hello! :)
Why scansync not works on some modern games.
Scansync work perfect in ut99 But i cant control tearline in Quake Champions and Unreal Tournament 4. Tearline in this games have random position. Why? Can you explain me. What i am do wrong?

It's the game, not the RTSS scanline sync.

Precise raster-controlled tearline position require ultra-precise timing -- like a "raster interrupt" which is what RTSS Scanline Sync is essentially doing. At 1920x1080 144Hz the monitor is running at 160 kilohertz scanrate. (160,000 pixels rows per second transmitted sequentially over the video cable). That means a 1/160,000second delay means the tearline moves downwards by 1 pixel. Modern games don't have perfect enough framepacing to allow such ultra tearline-control precision.

To enable RTSS to do ultra-precise scanline control your 0.1% worst frametimes must not exceed a refresh cycle. If you are running at 144Hz, that means your game must absolute never drop below 144fps for 99.9% of the time! That is how demanding RTSS scanline sync is, for giving your dream lagless VSYNC ON.

Adjust your refresh rate (lower it), game detail (lower it), upgrade GPU, do everything you can, until your worst frametimes almost never take longer than a refresh cycle. THEN RTSS scanline sync will work very well. That's why it is amazing for older games but crap for newer games.
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Re: RTSS now has new automatic Low-Lag VSYNC ON (raster base

Postby mist » 05 Feb 2019, 17:48

Thanks for quick reply :)

I have 60hz monitor. And stable 60fps in modern games, but some times it drops to 58-59fps. And this modern games not fully smoothed like old games. Why? Because i am not have 100% 60fps? But even in times then i have stable 60fps my picture not 100% smooth and clear, i see some semitearing at position that i set in RTSS.

ps Why Hotkeys(ctr+shift+up/down or shift+up/down) not work?
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Re: RTSS now has new automatic Low-Lag VSYNC ON (raster base

Postby Chief Blur Buster » 05 Feb 2019, 23:18

mist wrote:ps Why Hotkeys(ctr+shift+up/down or shift+up/down) not work?

You have to edit your RTSS config file to enable the hotkeys.

You can also try increasing SyncFlush -- use SyncFlush=1 -- to see if the tearline tames a bit.

Yes, you essentially need to be fully 60fps all the time with Scanline Sync. Even 59.99fps or 59.98fps will cause tearline movement. So disabling certain features like shadows and lowering AA may be needed to get Scanline Sync to work well.

Another alternative is to simply combine Scanline Sync with Fast Sync / Enhanced Sync -- but it requires some special calibration of the tearline first (see HOWTO)
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