240hz on 60FPS games

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crossjeremiah
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240hz on 60FPS games

Post by crossjeremiah » 28 Feb 2018, 21:17

So this is my dilemma, I play Melee which is a very fast paced game. 120hz feels good, and 60hz feels the best but to play online with low input lag 120hz would be the best.
I made a reddit post about it, and I'm having small complaints about this may be all in my head kind of thing.
https://www.reddit.com/r/smashbros/comm ... h=7c540a44

The question is, would you notice any motion cadence or stutter on 240hz running at 60fps? I myself would think so because its displaying that same frame four times in that small window of 60hz

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Chief Blur Buster
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Re: 240hz on 60FPS games

Post by Chief Blur Buster » 28 Feb 2018, 22:19

There is no difference between perfect cadence at 60/120/180/240 at 60Hz.

This is because the same frame is repeated, so there's no difference in the frame appearance.

That's because multiple brief duplicate refreshes looks identical to one longer refresh -- when it comes to standard LCD monitors (which are sample-and-hold displays: They display a frame for the whole duration of the refresh cycle.

Assuming each frame is displayed 4 times, on a sample-and-hold display 60fps@240Hz looks exactly the same as 60fps@60Hz. Same for 60fps@480Hz. Same for 60fps@120Hz. In general, if all things are equal (e.g. monitor processing lag), higher Hz is less lag.

However, framerate aliasing (imperfect frame pacing) may mean the game may play 240fps with 5 frame repeats then 3 frame repeats, then 4 frame repeats, then 3 frame repeats, then 5 frame repeats, etc. Inconsistent number of repeats equals stutter.

Also, input lag is a very complex topic -- see my post here:
Chief Blur Buster wrote:in CS:GO, measured 12ms for VSYNC OFF at 1000 frames per second (last few bars). That's much less than Prad's monitor-only measurement -- and that was via our high speed video camera.

It's a "first-anywhere-on-screen" reaction methodology for that specific game, as eSports players often play with peripheral vision too -- and this methodology can produce dramatically lower numbers than "first-single-point" measurements or "VBI-to-photons" measurements.

Image

These numbers are the full chain, from mouse button to pixels, taken via high speed camera, in GSYNC 101 Part #3.

Image

Numbers for the full whole chain would naturally be higher than the monitor-only lag (if that is what prad.de is trying to measure).

Not saying their numbers are incorrect, but they need to document their input lag measuring methodology. I suggest that prad.de to fully document their lag measurement method to properly documenting HOW they measure lag -- it will help compare notes better.

Lag methodology will output different values for:
-- Lag from GPU-side to monitor pixels
-- Lag from monitor input to monitor pixels (excludes cable transmission overheads, e.g. +1ms)
-- Lag from mouse to monitor pixels
-- Lag from keyboard to monitor pixels

And screen location:
-- Lag from VBI to monitor top (ala VSYNC ON input lag)
-- Lag from VBI to monitor center (ala VSYNC ON input lag)
-- Lag from VBI to monitor bottom (ala VSYNC ON input lag)
-- Lag of pixel transmitted from GPU to corresponding pixel shown on monitor (more representative of VSYNC OFF input lag)

And how the lag tester starts the lag stopwatch:
-- Button press
-- Dongle on cable (VBI detector)
-- Black box (Leo Bodnar, etc)
-- API call (e.g. Direct3D Present() or OpenGL glutSwapBuffers)
-- etc.

And how the lag tester stops the stopwatch:
-- Photodiode on a specific location on screen (e.g. oscilloscope, Leo Bodnar, etc)
-- Differentials between two screens
-- First reaction anywhere on screen (e.g. high speed camera)

And how soon to stop the stopwatch
-- First GtG photons detectable
-- GtG 10% (recommended -- very human visible now by then)
-- GtG 50% (recommended)
-- GtG 90%
-- GtG 100% (artificially long, not recommended)
-- Undocumented (e.g. Leo Bodnar, ugh).

And other variables to keep in mind:
-- Lag of a specific Hz (varies from Hz to Hz)
-- Leo Bodnar Tester is lag of VSYNC ON 60Hz
-- SMTT 2.0 is lag-differential between two screens and runs 1000fps VSYNC OFF
-- Lag of VSYNC OFF is also very different from lag of VSYNC ON.

Also different behaviours:
-- VSYNC ON lag testers will have more lag at bottom edge than top edge for most screens
60Hz vs 240Hz have massive differences
-- VSYNC OFF lag testers (at high frame rates) will equalize lag throughout the screen, since VSYNC OFF is scanout-following
60Hz vs 240Hz have less differences, but due to frameslice lag gradients, MIN/AVG/MAX is tighter at 240Hz
-- VSYNC OFF adds a slight lag-randomization of (1/Hz)th of a second. Lag is lowest just right below a tearline. Lag is highest just right above a tearline. And because the lag jitter is a full refresh cycle due to the random tearline locations - this results in MIN/AVG/MAX becomes much tighter at higher Hz than lower Hz when using VSYNC OFF lag testers.
-- Etc.

240Hz displays currently have bad 60Hz lag numbers (worse at 60Hz lag than the best 60Hz monitors) but excellent 240Hz lag numbers. But that is different from 240Hz lag -- not everyone even bothers using 60Hz. Depending on methodology, naturally, some results will be better and some results will be worse.

And lag numbers are not comparable between different review websites.

That is normal and acceptable but insufficient disclosure of lag test methodology is a huge problem. During 2018 we will communicate with other websites to standardize this further.
Also there's not really technically a buffer lag anymore in many monitors -- but there's a scanout lag. Basically top edge is low lag but bottom edge is higher lag, when it comes to VSYNC ON. (However, for VSYNC OFF, top/center/bottom lag can get equallized).

Also, TomsHardware tests use an input lag test with a VSYNC ON bias, see this thread:
viewtopic.php?f=10&t=3780&start=20#p30821
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Chief Blur Buster
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Re: 240hz on 60FPS games

Post by Chief Blur Buster » 28 Feb 2018, 22:22

Should I get a GSYNC monitor?
G-SYNC will not help with netplay, in fact it will add even more input lag on top of it. What GSYNC does is that it syncs to your refresh rate and fps. So if the game runs at 60fps then the monitor will constantly be at 60hz, so in general you wouldn't get the low input lag you would get with 120hz.
This is, however, cherrypicked advice. Inaccurate for more than 50% of games -- likely over 90% if you use RTSS to help your 60fps framepacing perfection.

60fps on a 240Hz GSYNC monitor is much lower lag than 60fps on a 144Hz GSYNC monitor which is much lower lag than 60fps @ 60Hz VSYNC ON. This is not true for VSYNC OFF however. People are corret when sometimes 60fps looks better with 60Hz VSYNC ON but this isn't always true for all games. Also, there's a lot of lag.

You can fix framepacing using RTSS for MUCH-better looking 60fps on GSYNC, and it finally looks as good as 60Hz VSYNC ON (if you've configured correctly) -- while having much less lag than 60Hz VSYNC ON.

However, a game with POOR framepacing can play worse at 60fps on GSYNC than 60fps on 60Hz.
The art is in correctly configuring your monitor.

Frame pacing is important (e.g. consistent time between refresh cycles) to make 60fps on GSYNC look exactly the same as perfect 60fps@60Hz VSYNC ON.

This is because each frame are scanned out at maximum refresh cycle speed so the "60Hz" refresh cycle appears to the human eye in 1/240sec. (top edge appears at 0/240sec, middle of refresh cycle appears at 0.5/240sec, and bottom of refresh cycle appears at 1/240sec).

However, what is true is some games have flaws with VRR. However, low framerates on a high-Hz VRR monitor is always massively lower lag than low framerates on a low-Hz VRR monitor, or low framerates VSYNC ON -- because each refresh cycles are scanned-out at their maximum-Hz velocity regardless of its current fps/Hz during max-Hz VRR mode. (e.g. when running 30-240Hz range = each frame is scanned-out in 1/240sec regardless of how much time elapsed between the individual refresh cycles)
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Re: 240hz on 60FPS games

Post by Chief Blur Buster » 28 Feb 2018, 22:33

That said, you are very right for VSYNC ON:

Cadence is better at the multiples if you use VSYNC ON.
Motion looks much better 60fps@120Hz than 60fps@144Hz.

Also, when using VSYNC ON, it's definitely true that 120Hz is preferable to 144Hz.
60fps@120Hz VSYNC ON has less input lag than 60fps@60Hz VSYNC ON.
And less stutter than 144Hz.

However, if you're using VSYNC OFF, the answer often changes -- depending on the game.

120Hz vs 144Hz matters a whole lot less. In fact, sometimes the beat-frequency effects is better at other framerates. For example, 119fps@120Hz and 121fps@120Hz sometimes has 1 big stutter per second. While 120fps@144Hz has 24 smaller microstutters per second. But it depends on the game you play. If your game is good enough with good framepacing and stays consistent 120fps@120Hz, it can look good (except for a slow-moving scrolling tearline if you use VSYNC OFF). Tearline rolling speed and microstutters are often beat-frequency effects. If your game likes to vary its frametimes a lot (varying frametimes is practically the mathematical definition of stutter!) then the answer can change -- to the point where 144fps may actually have a "preferred feel" over 120fps. I've seen games that play better ~59-61fps@144Hz VSYNC OFF than ~59-61fps@120Hz VSYNC OFF because of rolling-tearline or the infrequent-but-jumpier-stutter effect. i.e. Watch out for the beat-requencies and harmonic-frequencies!

The answer is "It depends".
The answer can sometimes change for VSYNC ON versus VSYNC OFF versus GSYNC.
And the answer can change again when reconfigured (e.g. adding RTSS to GSYNC).

Also, worth studying is: http://www.blurbusters.com/1000hz-journey which is fully based on science.

It's not the same topic, but it helps understand that persistence (motion blur) equals frame visibility time -- so low framerates have more motion blur than high framerates -- when it comes to sample-and-hold displays (aka non-strobed). Which leads to why 60fps has the same amount of motion blur for the same panel tech regardless of refresh rate (60Hz, 120Hz, 240Hz).

You see, on sample-and-hold displays, painting a 2nd image has no visible effect.
It just looks like a longer refresh cycle instead of multiple shorter refresh cycles.

However, if you're using LightBoost (ie. ONLY when strobing is enabled), THEN there is an effect --

Image

60fps at 120Hz LightBoost = 2 images
40fps at 120Hz LightBoost = 3 images
30fps at 120Hz LIghtBoost = 4 images.

However, for sample-and-hold, persistence is frame visibility time.

Image
This assumes framerates equal refresh rate.

120Hz displays have 8ms persistence when running at full 120fps.
However, 240Hz displays also have 8ms persistence when running at 120fps too -- half framerates will have more motion blur.

So 120fps@120Hz and 120fps@240Hz has the same amount of motion blur and same amount of smoothness (assuming perfect cadence) -- stutter is caused by varying-number-of-repeats. No stutter occurs for constant-consistent-number-of-repeats.

You also see this at http://www.testufo.com -- double framerate has half motion blur.
The "120fps" UFO has the same smoothness and same blur on a 120Hz monitor and a 240Hz monitor -- assuming it's similar pixel response panel (Typical 1ms GtG TN panel).

But it doesn't matter (When non-strobed) how many repeat refreshes there are because repeat refreshes in sample-and-hold (NON-strobed, NON-LightBoost) look exactly the same as lone longer-displayed refresh.
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Re: 240hz on 60FPS games

Post by Chief Blur Buster » 28 Feb 2018, 22:46

Summary:
  • Stutter is not caused by repeat refresh cycles on sample-and-hold displays (non-strobed LCDs, no black periods)
  • Stutter can be caused by repeat black periods (same frame strobed multiple times: LightBoost/PWM dimming/etc)
  • Stutter can be caused by varying frame visibility times
  • Stutter can also have other causes too (e.g. hard disk accesses) which influences the above (e.g. varying frame visibility times)
  • For VSYNC ON, yes -- 60fps @ 120 Hz can look better than 60fps @ 144Hz
  • For GSYNC, games with good framepacing, 60fps at any GSYNC look exactly like 60fps @ 60Hz VSYNC ON
  • For GSYNC, games with terrible framepacing, 60fps at any GSYNC can be worse than 60fps @ 60Hz VSYNC ON
  • For GSYNC, RTSS can help fix framepacing issues
  • GSYNC at higher Hz is lower lag. 60fps @ 240Hz GSYNC has less lag than 60fps @ 144Hz GSYNC
  • For non-strobed, 60fps@60Hz and 60fps@120Hz and 60fps@240Hz and 60fps@(any Hz GSYNC/FreeSync) look identical (no stutter) provided game has perfect framepacing. Exact same grand totalled identical-frame visibility time, if the display is sample-and-hold (non-LightBoost).
  • During VSYNC OFF, many gaming monitors are now line-buffered (closer to a CRT). Cable scanout can be same as panel scanout, e.g. sub-frame latencies on a pixel-to-pixel basis. There's no full framebuffer lag when it comes to these monitors.
  • Assuming monitor processing the same, the higher GSYNC Hz, the lower lag versus VSYNC ON. 60fps @ 240Hz GSYNC has much, much less lag than VSYNC ON 60fps @ 60Hz
  • Different legitimate methods of input lag tests create very different results (e.g. SMTT versus Leo Bodnar versus TomsHardware approach) simply because they use different stopwatching (different stopwatch start trigger, and different stopwatch end trigger). Can't generalize based on just one lag test. Synthetic lag tests are often disconnected from actual real-world lag tests (e.g. high speed camera on VSYNC OFF CS:GO).
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crossjeremiah
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Re: 240hz on 60FPS games

Post by crossjeremiah » 01 Mar 2018, 00:11

Thank you so much for this response

crossjeremiah
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Re: 240hz on 60FPS games

Post by crossjeremiah » 01 Mar 2018, 10:28

I'm going to rewrite my reddit post with updated material.
So 240hz @ 60fps GSYNC has lower lag than 120hz @60fps VSYNC ON/OFF



So is Fast-Sync more useful than VSYNC-ON in 60fps situations? (I don't have a GSYNC monitor, I'm still running a XL2430T)

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Re: 240hz on 60FPS games

Post by RealNC » 01 Mar 2018, 11:18

crossjeremiah wrote:So is Fast-Sync more useful than VSYNC-ON in 60fps situations? (I don't have a GSYNC monitor, I'm still running a XL2430T)
Fast sync is for cases where your FPS can reach values that are multiples of your refresh. For 60Hz, fast sync starts being OK at about 180FPS, and really good at over 300FPS.

If you play a game that is able to go into 600FPS territory, fast sync becomes as good as g-sync.
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Re: 240hz on 60FPS games

Post by Chief Blur Buster » 01 Mar 2018, 14:46

crossjeremiah wrote:Thank you so much for this response
You are welcome!
Monitor engineering is so complicated. even monitor manufacturers learns from reading Blur Busters!
RealNC wrote:
crossjeremiah wrote:So is Fast-Sync more useful than VSYNC-ON in 60fps situations? (I don't have a GSYNC monitor, I'm still running a XL2430T)
Fast sync is for cases where your FPS can reach values that are multiples of your refresh. For 60Hz, fast sync starts being OK at about 180FPS, and really good at over 300FPS.

If you play a game that is able to go into 600FPS territory, fast sync becomes as good as g-sync.
Yep, during sample-and-hold operation...

As long as the mirostutter amplitudes are well below motion blur size length -- yes.

Basically, 600fps creates microstutter amplitudes of 1/10th the frame step, and motion blur is always a minimum of full frame step -- for 60Hz sample-and-hold. It pretty much literally looks like VSYNC ON 60fps when your framerates are so extremely high that Fast Sync microstutters are well below the noisefloor of the display motion blur...

However, I still see Fast Sync microstutter when enabling ULMB/LightBoost even at ~500fps+ territory. Framerate-locked VSYNC ON is still superior for strobed operation if targetting image-motion-quality-prioritization instead of lag minimization (those are sometimes contradictory goals).

If you're doing 600fps, you should be buying a 144Hz+ monitor (heck, 240Hz!) and taking advantage of the benefits of the higher framerate. :)
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crossjeremiah
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Re: 240hz on 60FPS games

Post by crossjeremiah » 01 Mar 2018, 16:46

Thank you again,
I'm gonna hold off on posting anything because I want to understand it more before I tell other people.

Is there any advantages to having a frame limiter and turning off vsync? Or does having vsync off defeat the purpose.
Would I set the limiter to 120hz (specific refresh rate) - 0.01 (and use 120hz)
or since its a 60fps game can I use 60hz(specific refresh rate) - 0.01 (and use 120hz)


Like having the least amount of input lag @120hz/144hz on a 60fps game.

The Melee community is filled with people who are sensitive to input lag, I literally feel like I'm not hitting my timings, and such so I have either increase the input lag or decrease it.
This is how input lag in melee basically works.
http://kadano.net/SSBM/inputlag/

theres alot of testing done also
https://docs.google.com/spreadsheets/d/ ... d=48074256

its hard to match up with these monitors

We use crt strictly only for tournament. LCD's are strictly banned from tournament play unless theres affordable monitors that can match a crt response time

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