RTSS Scanline Sync HOWTO

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Re: RTSS Scanline Sync HOWTO

Post by Chief Blur Buster » 22 Oct 2020, 06:16

Unwinder wrote:
22 Oct 2020, 06:10
Chief Blur Buster wrote:
14 Oct 2020, 18:23
IDEA! (Usability/Debugging):
A mode where a horizontally moving vertical bar is overlaid on game graphics (like this one) could be great for RTSS Scanline Sync. Make that a transparent overlay on top of RTSS, perhaps colored the same as the graph/framerate counter.
Done, it is implemented in upcoming RTSS beta.
https://forums.guru3d.com/threads/rtss- ... st-5845445
Fantastique!

Currently, I'm busy on the 8000Hz-mouse stuff with my 360Hz monitor (biggest project) but I definitely am going to revisit an improved/miniaturized RTSS Scanline Sync HOWTO with the new moving-bar tearing indicator.
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Digika
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Re: RTSS Scanline Sync HOWTO

Post by Digika » 25 Oct 2020, 16:04

Chief Blur Buster wrote:
24 Jun 2019, 13:05
The "3fps cap differential" advice is only for variable refresh (G-SYNC, FreeSync, VRR, VESA Adaptive-Sync).[/b

Chief Blur Buster wrote:
28 May 2019, 15:13
tygeezy wrote:Vsync and using rtss to cap ever so slightly below your monitors refresh rate?

It is lower lag than VSYNC ON without capping, but can still produce sawtooth latency effects.
Image
Lower latency, but a latency-sawtoothing artifact as the framerate cap slews past the refreshrate. It may take several seconds to complete a single sawtooth cycle though.


Okay so which one it is I'm getting mixed signals, cap. One post clearly states that using vsync + capping your framerate below refresh rate - has visible inputlag benefits, as per graph. Another one states that this only should be used for adaptive sync technology.
???

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Re: RTSS Scanline Sync HOWTO

Post by Digika » 25 Oct 2020, 16:18

furfoot wrote:
01 Feb 2020, 05:05
I think I'm missing something. So settings:

App detection low
Stealth off
Custom direct 3d off
Framerate limit 0
Scanline Sync value of 1
OSD On (Raster, Framebuffer)

My display is set to 120hz 1080p with no frame limit or VSYNC in place.

Start overwatch and my framerate doesn't seem to be limited to my refresh rate. I was under the presumption that scanline sync option actually limited frames to your refresh rate. What am I doing wrong?
having exactly same issue. Post here:
viewtopic.php?p=46428#p46428
states that enabling Scanlinesync essentially works as vsync i terms it limits your FPS to refresh rate. However, that is not true. Same config as above but before enabling it I've tested uncapped framerate. Enabling SS and adjusting tear does nothing to cap it, I need to also cap FPS.

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Re: RTSS Scanline Sync HOWTO

Post by Chief Blur Buster » 25 Oct 2020, 16:47

Digika wrote:
25 Oct 2020, 16:04
Okay so which one it is I'm getting mixed signals, cap. One post clearly states that using vsync + capping your framerate below refresh rate - has visible inputlag benefits, as per graph. Another one states that this only should be used for adaptive sync technology.???
To understand, check out:
Understand The Capping Differential (fps vs Hz)!
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Re: RTSS Scanline Sync HOWTO

Post by Digika » 25 Oct 2020, 17:15

I'm not sure how that is supposed to explain the issue of framerate not being capped to refreshrate with basic Syn setup:

Code: Select all

[Framerate]
Limit=0
LimitDenominator=1
LimitTime=0
SyncScanline0=1
SyncScanline1=0
SyncHotkeys=1
SyncPeriods=0
According to aforementioned post, sync cycle should be aimed to be fixed at scanline 1 (+/- jitter) and just like with VSCYNC on the framerate is capped to refresh rate (1000ms/refresh rate). But it isnt, there is no cap. With my 80HZ custom refresh rate (see attachment) I'm getting cosmic FPS value in Spelunky 2 and woken up neighbor form my GPU coilwhine.
Attachments
123.jpg
123.jpg (109.64 KiB) Viewed 849 times

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Re: RTSS Scanline Sync HOWTO

Post by RealNC » 25 Oct 2020, 22:19

Digika wrote:
25 Oct 2020, 16:04
Okay so which one it is I'm getting mixed signals, cap. One post clearly states that using vsync + capping your framerate below refresh rate - has visible inputlag benefits, as per graph. Another one states that this only should be used for adaptive sync technology.
???
-3FPS cap is for VRR. -0.01FPS cap is for normal vsync without VRR.
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Re: RTSS Scanline Sync HOWTO

Post by terry98 » 26 Oct 2020, 14:32

RealNC wrote:
25 Oct 2020, 22:19
-3FPS cap is for VRR. -0.01FPS cap is for normal vsync without VRR.
I wasn't aware of this.. if I'm using scanline sync then I have to set the screen refresh to 60Hz and set the refresh in the settings to 16.66944ms? (which would be for 59.99fps) or do I have to set it elsewhere?

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Re: RTSS Scanline Sync HOWTO

Post by Digika » 26 Oct 2020, 15:09

RealNC wrote:
25 Oct 2020, 22:19
-3FPS cap is for VRR. -0.01FPS cap is for normal vsync without VRR.
Okay, thanks.
I figured out my issue with scanline sync not limiting properly. Now, I have a few questions about some weird suggestions in the OP:
Chief Blur Buster wrote:
24 Jan 2019, 02:26
VSYNC OFF: Calibrate tearline offscreen
Fast Sync: Calibrate tearline to stay permanently above bottom edge
Enhanced Sync: Calibrate tearline to stay permanently above bottom edge
Why is it recommended to move tearline down, just above the bottom edge? Let's take basic VSYNC OFF setup, where we just move tearline away so we dont see it. We start at scanlinesync at 1, top. If we start to move scanline down, towards the bottom edge then we essentially gonna see mostly last frame. In this case, we greatly lower input latency (as a consequence), however we lose on frame data actuality (since it is mostly last frame). On the contrary, if we start to move scanline sync/tear up, we now mostly seeing last frame after sync, but in this case we take greater input latency hit.

So why did the how-to settle on these recommendation?

P.S. Dont take it personal, but I think the how-to in question written in a really confusing and poorly structured way. I think it really would be worth rewriting it properly, in more approachable way, with more situational explanations.

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Re: RTSS Scanline Sync HOWTO

Post by Chief Blur Buster » 26 Oct 2020, 15:57

I hear you. This is a very old HOWTO that does need to be rewritten, indeed.

But RTSS Scanline Sync is an airplane cockpit compared to other sync technologies and is very hard to explain without raster interrupts knowledge (beam raced tear lines). First, to understand how RTSS Scanline Sync was born: See Tearline Jedi.

Now the reason why if you’re using the other sync technologies instead of VSYNC OFF, is that tearline moves downwards on a time-bases, as it follows the Display Scanout (high speed videos).

Once you see the links. You begin to realize tearlines just above bottom edge will take less time to the end of refresh cycle. This is important for sync technologies that waits-til-end-of-refresh (like VSYNC or triple buffering) before showing new frames.

If the tearline is below bottom edge during VSYNC OFF, then turning on a sync technology can add one refresh delay as since it already missed the end of refresh cycle (last pixel row or first line of VBI), the enabled sync technology it waits until the end of the next refesh cycle before displaying the presented frame, because if the VSYNC OFF tearline is already below screen bottom edge, “the VSYNC is already missed!”, so +1 refresh lag penalty. Might as well turn off Scanline Sync and use plain jane VSYNC ON instead. So if you want less lag with a “non-VSYNC-OFF” RTSS Scanline Sync, you want the tearline as close to VBI (screen bottomedge) but still BEFORE in clock time, as seen in high speed videos at www.blurbusters.com/scanout ... Windows frame presentation triggers at the end of refresh cycle, before the VBI. It’s not the ideal way I want Windows to function, but this is an issue — I prefer that non-VSYNC-OFF technologies blocks until beginning of new refresh cycle and life would be a helluva lot simpler, and we’d already be getting Quick Frame Transport benfits. But we are fighting against the behavior of legacy design Present()-to-Photons black box.

RTSS Scanline Sync is more advanced, and hard to write an easy guide for.
- It’s like University versus Elementary School (VSYNC ON).
- Skill Level 40 versus Skill Level 2.
- Assembly Programming versus BASIC programming
- Pilot cockpit versus car dash

One computer may behave like a brand new Boeing 747 and another computer may behave like a defective Cessna, in how the tearline jitters, cycles, and how easy/stubborn it is to calibrate on different systems. Turning it to child’s play for some, and a hair pulling experience for others. It’s so unusually sensitive to imperfections. I even offered 300 Euros to someone technically literate to write an RTSS Scanline Sync HOWTO....and they failed. So guess I gotta do the dirty job myself, eh?

[Blur Busters is accepting cirriculum-vitae for highly technically literate freelance writers, that understands the Blur Busters concepts of GtG, MPRT, lag, and can branch to these. squad[at]blurbusters.com ...]

That’s the problem of RTSS Scanline Sync in writing easy guides for it.

But, yes, an easier guide will come sometime 2021.
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Re: RTSS Scanline Sync HOWTO

Post by Chief Blur Buster » 26 Oct 2020, 16:14

Digika wrote:
26 Oct 2020, 15:09
RealNC wrote:
25 Oct 2020, 22:19
-3FPS cap is for VRR. -0.01FPS cap is for normal vsync without VRR.
Okay, thanks.
Yep.

3fps cap differential for VRR
0.01fps cap differential for non-ScanlineSync Low Lag VSYNC ON
No differential needed for RTSS Scanline Sync (do not add one)

Differentials are needed for different reasons for different sync technologies.
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