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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 RealNC » 26 Jul 2018, 12:59

Have you disabled g-sync and vsync? You need both of them disabled.

With that being said, since you have g-sync, why do you even want to use this? This is only useful for people without a VRR monitor.
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Re: RTSS now has new automatic Low-Lag VSYNC ON (raster base

Postby 7bhsq » 26 Jul 2018, 13:47

I'm pretty sure I was in ULMB mode only with V-sync disabled when I tried it. I'll have to give this another go later in the day. I was trying this technique out of curiosity, since I may not necessarily be using a G-sync monitor later down the line.
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Re: RTSS now has new automatic Low-Lag VSYNC ON (raster base

Postby 7bhsq » 27 Jul 2018, 01:22

Tested again. Made sure I was in 144hz, ULMB only with V-sync off. Remade the profile for EtG.exe just in case. Uncapped framerate is just over 300fps. Once I activated Scanline sync by setting it to -50, framerate was capped to 60.

Would any advanced options (if there are any) in the profile .cfg file make any difference?
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Re: RTSS now has new automatic Low-Lag VSYNC ON (raster base

Postby RealNC » 27 Jul 2018, 10:42

Probably not. I don't know what the issue is. Maybe you can ask the RTSS author here:

https://forums.guru3d.com/threads/rtss- ... -1.412822/
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Re: RTSS now has new automatic Low-Lag VSYNC ON (raster base

Postby Chief Blur Buster » 27 Jul 2018, 14:06

7bhsq wrote:Tested again. Made sure I was in 144hz, ULMB only with V-sync off. Remade the profile for EtG.exe just in case. Uncapped framerate is just over 300fps. Once I activated Scanline sync by setting it to -50, framerate was capped to 60.

Let's try one more thing before reaching out (Helps to keep his tech support load down on this utility he gives away for free -- gives him more time to do his fun programming on RTSS and less time trying to help 100's of users on a solution that I already know).

I think it might have to do with the SyncTimeout setting.
Find out what your configuration file says currently (does it have a SyncTimeout value) and let us know.
Then edit the SyncTimeout setting:

Try this too:
SyncTimeout=0

Or this:
SyncTimeout=2

Let's see if SyncTimeout is behaving in a pesky way...
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Re: RTSS now has new automatic Low-Lag VSYNC ON (raster base

Postby 7bhsq » 27 Jul 2018, 21:43

SyncTimeout is supposed to go under [Framerate] right? It's not present by default on a freshly generated profile.

SyncTimeout=0 didn't seem to do anything. It still caps at 60 FPS.
SyncTimeout=2 caps framerate at 120 instead.

Just to make sure I'm not misunderstanding what Scanline sync is supposed to do, I'll write down what think I understand. Please correct me if I'm wrong.

What Scanline sync is supposed to do is cap your framerate at your monitor's refresh rate while giving you control over where the tearline will appear with V-sync disabled. What this does is effectively give you tearless V-sync off.
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Re: RTSS now has new automatic Low-Lag VSYNC ON (raster base

Postby Chief Blur Buster » 30 Jul 2018, 11:02

7bhsq wrote:What Scanline sync is supposed to do is cap your framerate at your monitor's refresh rate while giving you control over where the tearline will appear with V-sync disabled. What this does is effectively give you tearless V-sync off.

Yes.

In the ideal situation. It works well in some games, but not in others.

This new RTSS feature makes tearlines as stationary as possible.

When you use negative scanline offsets, the tearline is moved above the top edge of the screen, hiding it completely.

In some games, the tearline won't stay stationary (keeps vibrating or shifting around a lot) and won't be permanently hidden. On other games, the tearing is permanently hidden.

So you end up having a tearingless VSYNC OFF -- or one of the most lagless VSYNC ON you can get without game modifications. (There's still minor framerate-capping lag but a lot less than traditional VSYNC ON). The similar feature in graphics cards is NVIDIA Fast Sync and AMD Enhanced Sync -- but this is done in a different way by RTSS as a tearing-controlled VSYNC OFF mode that can sometimes completely hide tearlines. ]

SyncTimeout=0 is disabled, and may trigger some alternative logic thats causing a 60 cap. I don't fully understand this myself (just yet..) but yes SyncTimeout=2 is likely the better setting for you.
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Re: RTSS now has new automatic Low-Lag VSYNC ON (raster base

Postby Eregoth » 28 Sep 2018, 12:14

Still trying to wrap my head around this stuff and have a couple of questions:
Am I correct in assuming that it's impossible to hide both tearlines when doubling the framerate to 120FPS on a 60Hz monitor?
Do the different SyncFlush values have different amounts of input delay? I'm guessing it's best to disable flushing if the tearline is stable already?
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Re: RTSS now has new automatic Low-Lag VSYNC ON (raster base

Postby Chief Blur Buster » 02 Oct 2018, 15:45

Eregoth wrote:Do the different SyncFlush values have different amounts of input delay? I'm guessing it's best to disable flushing if the tearline is stable already?

Use the lowest SyncFlush you can get with a stable tearline.

SyncFlush=2 gives you the most stable tearline but consumes a lot more GPU (50%)
SyncFlush=1 gives you less stable tearline but consumes a lot less GPU
SyncFlush=0 will give you almost no tearline stability (tearline jitters all over the place) unless super lightly loaded

Bigger SyncFlush values may slightly increase GPU load that add frame latency -- e.g. longer rendertimes = more rendertime lag. BUT this penalty can be saved by eliminating the 1-frame penalty of trying to use lowlag triplebuffering (FastSync/EnhancedSync) in combination with RTSS ScanLine technique (see below). So say, SyncFlush might add +1-2ms lag but then save -8ms at 120Hz during FastSync/EnhancedSync, leading to overall less lag. But it must be done correctly.

Eregoth wrote:Still trying to wrap my head around this stuff and have a couple of questions:
Am I correct in assuming that it's impossible to hide both tearlines when doubling the framerate to 120FPS on a 60Hz monitor?
Do the different SyncFlush values have different amounts of input delay? I'm guessing it's best to disable flushing if the tearline is stable already?

To understand RTSS scanline capping works, one needs to understand how tearlines and scanout latency work.

Did you know? Screens have a latency gradient due to the top-to-bottom scan. Not all pixels refresh at the same time, the monitor refreshes the top edge first. VSYNC OFF allows interruptions with fresher frames on the fly to this scanout. The frameslice area right below a tearline is always lowest lag, while the frameslice area above a tearline is always highest lag. The frameslice is an input-lag-gradient. At 120Hz (8ms refresh cycles), the vertical latency gradient of a 1/2 screen height frameslice is [+0ms...+4ms]. More frameslices, lower lag. Now, if you use VSYNC ON, the latency gradient becomes full screen [+0ms..+8ms]. Higher Hz (e.g. 240Hz) means the lag gradient is lower e.g. [+0ms...+4ms]. That's unavoidable if you want to eliminate all tearlines, you just have to live with the latency gradient. You can at least, still avoid a lot of framebuffer queue latency though. And, if you got a 240Hz monitor, the scanout latency gradient can be practically be a nonissue for most. VSYNC ON can have a few frames of input lag above-and-beyond the scanout latency.

You can combine the trick with NVIDIA FastSync and AMD Enhanced Sync to make both tearlines disappear.

But you must:

1. Enable Force flushing level 2 and stick to games that rarely exceeds roughly ~50% GPU when capped.

2. Use RTSS scanline capping at 2x framerate with two rasters.
Calibrate the tearlines so that tearline #1 is middle of screen and tearline #2 is always above bottom edge of screen.

3. THEN turn on NVIDIA Fast Sync and AMD Enhanced Sync to make both tearlines disappear.

The red colored text is so particularly super-important to have stutterless ultralow-lag triple buffering.

Technical programmer/raster scan line explanation: This is because Direct3D Present() and OpenGL glutSwapBuffers() will flip the buffer when raster hits bottom of screen (beginning of VBI). Tearline is the raster scan line position. If bottommost tearline is below bottom edge of screen during VSYNC OFF, it adds a 1 frame input lag penalty when enabling FastSync/EnhancedSync/TripleBuffered. If bottommost tearline jitters above/below bottom edge of screen during VSYNC OFF, it will erratically stutter when enabling FastSync/EnhancedSync/TripleBuffered. That's why you should always visually calibrate scanline offsets if you ever plan to combine scanline capping with FastSync/EnhancedSync/TripleBuffered for flawless stutterless low-lag operation. Therefore, always move that "tearline" to be essentially as close to the bottom edge of screen but permanently above it. THIS IS AN ADVANCED MANOEVERE THAT REQUIRES UNDERSTANDING OF DISPLAY SCANOUT. NOT FOR NEWBIES/INTERMEDIATES.

Then you can get a new kind of low-lag "VSYNC ON" that is even more resistant to tearlines, though because of earlier scanline offsetting, it may be ~0.5ms more laggier than using VSYNC OFF (but far lower lag than VSYNC ON, and does not require capping framerates below Hz like the easier low-lag VSYNC ON echnique)
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Re: RTSS now has new automatic Low-Lag VSYNC ON (raster base

Postby Eregoth » 06 Oct 2018, 08:39

Thank you for the detailed post! Going to try the Fast Sync method tonight in some less demanding games like CS:GO and Rocket League and see how it goes.
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