RTSS Scanline Sync HOWTO

Everything about latency. Tips, testing methods, mouse lag, display lag, game engine lag, network lag, whole input lag chain, VSYNC OFF vs VSYNC ON, and more! Input Lag Articles on Blur Busters.
User avatar
RealNC
Site Admin
Posts: 3741
Joined: 24 Dec 2013, 18:32
Contact:

Re: RTSS Scanline Sync HOWTO

Post by RealNC » 21 Mar 2021, 12:54

hl3.exe wrote:
21 Mar 2021, 11:49
All the frames are nicely paced! But when I checked my performance profile I noticed that 1 thread is running unusually high load when Scanline Sync is toggle on.
That's normal. RTSS will limit FPS in the game by blocking the thread and waiting in a loop until enough time has passed. This loop actually counts as CPU use. However, it doesn't really calculate anything other than checking if enough time has passed. So you see high CPU load on the affected core, but there's no raised power consumption. CPU temperature for example stays low.

See this comment by the RTSS developer: https://forums.guru3d.com/threads/limit ... st-4443926
SteamGitHubStack Overflow
The views and opinions expressed in my posts are my own and do not necessarily reflect the official policy or position of Blur Busters.

User avatar
SixelAlexiS
Posts: 26
Joined: 05 Mar 2021, 04:02

Re: RTSS Scanline Sync HOWTO

Post by SixelAlexiS » 27 Jul 2021, 12:55

Can anyone help me eliminating tearline with scanline sync x/2 on a 60HZ signal? I've tried -30, -60, -90 etc. but still get it and I'm confused about the SyncFlush since the guide doesn't talk specifically about the scanline sync x/2 method. Thanks :)

User avatar
RealNC
Site Admin
Posts: 3741
Joined: 24 Dec 2013, 18:32
Contact:

Re: RTSS Scanline Sync HOWTO

Post by RealNC » 27 Jul 2021, 13:00

SixelAlexiS wrote:
27 Jul 2021, 12:55
Can anyone help me eliminating tearline with scanline sync x/2 on a 60HZ signal? I've tried -30, -60, -90 etc. but still get it and I'm confused about the SyncFlush since the guide doesn't talk specifically about the scanline sync x/2 method. Thanks :)
SyncFlush should be 1 by default I think. If you can't stabilize the tear line, then you could try SyncFlush 2, though it might hurt more than help.

Also, make sure you didn't do some silly mistake like having another FPS limit active. Make sure you set RTSS FPS limit to 0.
SteamGitHubStack Overflow
The views and opinions expressed in my posts are my own and do not necessarily reflect the official policy or position of Blur Busters.

User avatar
SixelAlexiS
Posts: 26
Joined: 05 Mar 2021, 04:02

Re: RTSS Scanline Sync HOWTO

Post by SixelAlexiS » 27 Jul 2021, 13:54

RealNC wrote:
27 Jul 2021, 13:00
SixelAlexiS wrote:
27 Jul 2021, 12:55
Can anyone help me eliminating tearline with scanline sync x/2 on a 60HZ signal? I've tried -30, -60, -90 etc. but still get it and I'm confused about the SyncFlush since the guide doesn't talk specifically about the scanline sync x/2 method. Thanks :)
SyncFlush should be 1 by default I think. If you can't stabilize the tear line, then you could try SyncFlush 2, though it might hurt more than help.

Also, make sure you didn't do some silly mistake like having another FPS limit active. Make sure you set RTSS FPS limit to 0.
I want to specify that I'm using it on a Vulkan application (Cemu emulator) without RTTS cap and no cap inside Cemu.

I've just find out from your post on guru3d forum that flush 2 works on Vulkan too, I've tried it but it didn't change anything, I've put it like this by modifying the Cemu.exe.cfg :

[Framerate]
Limit=0
LimitDenominator=1
LimitTime=0
SyncScanline0=-90
SyncScanline1=0
SyncPeriods=1
LimitTimeDenominator=1
SyncLimiter=0
SyncFlush=2

There was no "SyncFlush" at all before so I've put it under framerate like I've read on a guide.

The tearline I get isn't constant btw, it manifest every time i move the camera around and it's like "walking" from top to bottom of the screen and then it disappear, this is why I don't know how to "hide" it even by changing the negative values of s-sync.

Is there any trick to use in my case? Thanks again :)

User avatar
RealNC
Site Admin
Posts: 3741
Joined: 24 Dec 2013, 18:32
Contact:

Re: RTSS Scanline Sync HOWTO

Post by RealNC » 27 Jul 2021, 15:22

SixelAlexiS wrote:
27 Jul 2021, 13:54
I want to specify that I'm using it on a Vulkan application (Cemu emulator) without RTTS cap and no cap inside Cemu.
Emulators have never been a good target for FPS capping, unfortunately. They need to time their frame presentation to match that of the machine they emulate. So this is probably what causes the tearline to drift so much. In essence, the frame timing that needs to be emulated is an FPS cap in itself. Disabling it is usually not an option, because that would change the game speed.

I believe your only option is to switch to vsync or fast sync and use scanline sync x/2 on top of that to get a low-latency cap that gets rid of most vsync lag (but not all of it.)
SteamGitHubStack Overflow
The views and opinions expressed in my posts are my own and do not necessarily reflect the official policy or position of Blur Busters.

User avatar
Chief Blur Buster
Site Admin
Posts: 11647
Joined: 05 Dec 2013, 15:44
Location: Toronto / Hamilton, Ontario, Canada
Contact:

Re: RTSS Scanline Sync HOWTO

Post by Chief Blur Buster » 27 Jul 2021, 20:04

Depending on how the emulator caps its framerate, and how configurable the emulator is, you can get an emulator to sync well to RTSS Scanline Sync system pretty reliably.

It works very well with certain emulators, but you may need to cherrypick driver settings, emulator, emulator settings, before RTSS Scanline Sync works reliably.

The big problem is how two nearby-caps can badly interact with each other. However, many emulators ARE configurable to speedup/slowdown to match VSYNC, e.g. a 59Hz or 61Hz display will run an emulator imperceptibly slow or fast. Those emulator settings that syncs emulator to VSYNC, will usually be easiest to enable RTSS Scanline Sync.

Tinker Route: A good "tinkering route" is use 50Hz temporarily for a 60Hz emulator, or use 60Hz temporarily for a 50Hz emulator. Tinker the emulator settings (before you even touch RTSS) to get the emulator to run perfectly slow (low pitch sound + perfect panning) or perfectly fast (high pitch sound + perfect panning). This is the "sync to VSYNC" feature of some emulators, or the "Run as fast as possible + VSYNC" equivalent settings.

Once you successfully configure the emulator to "sync to VSYNC" (rather than to a fake refresh rate clock), activate RTSS and tinker RTSS. It then is very easy to get RTSS Scanline Sync working. Now the emulator will sync properly to a precise cap driven by RTSS Scanline Sync.
Head of Blur Busters - BlurBusters.com | TestUFO.com | Follow @BlurBusters on Twitter

Image
Forum Rules wrote:  1. Rule #1: Be Nice. This is published forum rule #1. Even To Newbies & People You Disagree With!
  2. Please report rule violations If you see a post that violates forum rules, then report the post.
  3. ALWAYS respect indie testers here. See how indies are bootstrapping Blur Busters research!

MrBonk
Posts: 11
Joined: 27 Mar 2015, 03:55

Re: RTSS Scanline Sync HOWTO

Post by MrBonk » 29 Jul 2021, 22:41

RealNC wrote:
27 Jul 2021, 15:22
SixelAlexiS wrote:
27 Jul 2021, 13:54
I want to specify that I'm using it on a Vulkan application (Cemu emulator) without RTTS cap and no cap inside Cemu.
Emulators have never been a good target for FPS capping, unfortunately. They need to time their frame presentation to match that of the machine they emulate. So this is probably what causes the tearline to drift so much. In essence, the frame timing that needs to be emulated is an FPS cap in itself. Disabling it is usually not an option, because that would change the game speed.

I believe your only option is to switch to vsync or fast sync and use scanline sync x/2 on top of that to get a low-latency cap that gets rid of most vsync lag (but not all of it.)
Not necessarily. If you are disabling the internal framerate limiting in an emulator they will usually just run everything unchecked. I've been able to successfully use SS in lieu of the internal limiting on a few emulators to solve problems (Such as the 59.94hz vs actual display refresh issue)without much issue. (And the few issues I have had relate to mixed framerate titles when the emulator doesn't just duplicate 30hz games to a 60hz output. Or issues that don't exist when trying to use vsync normally. For example in PCXS2 in some games using Vsync in the OpenGL back-end or using Scanline Sync in DX11 or OGL, having the Multi Threaded VU or Instant VU hack will cause significant slowdown under 60FPS in some games in scenes that without some form of Vsync run upwards of 100-200FPS. I don't know why this is. Sadly disabling those hacks in a game like Xenosaga fixes the issue in cutscenes as it can run full speed in those well. But then during gameplay there will be scenes where without the speed hack it can't reach full speed.)
I haven't tried Cemu personally with SS. But in PCSX2 and PPSSPP haven't had disabling the internal limiter cause a problem. Usually you have to disable the internal limiter otherwise Scanline Sync doesn't seem to work properly.

For what it's worth though Cemu might be a different case because how the game itself is limiting framerate as well.(Since games on that era of hardware would have limited framerates differently than games of older generations that probably just based the limiting and synchronized on a per scanline basis on output?) And as far as I remember Cemu doesn't output duplicated frames for 30hz games. So you would *have* to use 1/2 SS for those games, as long as they aren't a mixed framerate game. (IE: 60fps in menus)
Just my anecdotal experience.

ysenojftw
Posts: 56
Joined: 17 Feb 2021, 23:53

Re: RTSS Scanline Sync HOWTO

Post by ysenojftw » 13 Oct 2021, 01:13

What would be the best way to set this up for 360hz for csgo. I’m running a 3070 gpu, interested in trying to see what this would look and feel like.

User avatar
Chief Blur Buster
Site Admin
Posts: 11647
Joined: 05 Dec 2013, 15:44
Location: Toronto / Hamilton, Ontario, Canada
Contact:

Re: RTSS Scanline Sync HOWTO

Post by Chief Blur Buster » 13 Oct 2021, 01:27

ysenojftw wrote:
13 Oct 2021, 01:13
What would be the best way to set this up for 360hz for csgo. I’m running a 3070 gpu, interested in trying to see what this would look and feel like.
For 360Hz, I instead recommend G-SYNC instead of RTSS Scanline Sync. At 360Hz, the lag penalty of VRR is able to be tweaked to be negligible, especially if your framerate range of your game is completely fitting inside the VRR range and never hits your cap.

RTSS Scanline Sync is mainly best for games that can do framerate=Hz with only 50% GPU load. It's kind of hard to do 360fps 360Hz while keeping GPU load 50% or less. Also, the VBI at 360Hz is too tiny to hide the VSYNC OFF line accurately. You could do 240Hz+QFT timings on a 360Hz monitor, to have a VBI large enough to hide very jittery tearing.

However, I know at least one person loved RTSS Scanline Sync for CS:GO at 240Hz, so YMMV.

Feel free to give it a try anyway, as framerate=Hz really enhances fluidity in many games.
Head of Blur Busters - BlurBusters.com | TestUFO.com | Follow @BlurBusters on Twitter

Image
Forum Rules wrote:  1. Rule #1: Be Nice. This is published forum rule #1. Even To Newbies & People You Disagree With!
  2. Please report rule violations If you see a post that violates forum rules, then report the post.
  3. ALWAYS respect indie testers here. See how indies are bootstrapping Blur Busters research!

Unwinder
Posts: 10
Joined: 08 Oct 2020, 06:12

Re: RTSS Scanline Sync HOWTO

Post by Unwinder » 16 Oct 2021, 05:31

I see no mentions of hybrid scanline sync mode, which was introduced in RTSS about a half year ago. Here is some basic info about it, which can be useful in context of this HOWTO thread:

https://forums.guru3d.com/threads/msi-a ... st-5951576

Post Reply