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[Thread Superseded] G-Sync 101 w/Chart (WIP)

Talk about NVIDIA G-SYNC, a variable refresh rate (VRR) technology. G-SYNC eliminates stutters, tearing, and reduces input lag. List of G-SYNC Monitors.

Re: G-Sync 101 w/Chart (WIP)

Postby Sparky » 22 Nov 2016, 13:46

jorimt wrote:
Sparky wrote:Let's call the threshold 36fps for now, it may be monitor specific, because as far as I know we only have a sample size of one. That gives us a 20.7ms window to play with(1/36 of a second - 1/144 of a second). so 10 above, 10 below, or maybe they got clever and made the centering of it depend on how quickly and in which direction framerate is changing.

It's not quite possible to have a framerate below zero. The tearing can happen anywhere in the 0~36 range, the issue is how fast it's changing. Say one frame is 31ms(32fps), so the monitor will throw in an extra refresh, say it starts that self refresh at 14ms. If the next frame finishes between 14ms and 21ms(48~71fps), or between 41ms and 48ms(21~24fps), you'll get a tear or delay(depending on v-sync setting), but if instead the next frame is between 7 and 13ms(72~144 fps), or 49 and 70ms(14~20fps), you wouldn't get that tear/delay, because the monitor would have completed its self refresh by then. Also, if the framerate slowly creeps down over many frames, you won't get tearing because the monitor has time to adjust when it does the additional refresh.

I too thought the minimum number may vary by monitor, but after seeing that both the official and unofficial source stated an almost identical number, we're just to have to assume it's the correct one.

I see, so the way I have it split into three sections now ("Below G-Sync Range," "Within 1ms Polling Range," "Exceeds 1ms Polling Range") is redundant, seeing as one behavior is causing all instances.

Basically, it tears when it misses the frametime window with V-Sync off, and suspends with V-Sync on. I'll have to carefully rearrange and word all of this to make it digestible to the average G-Sync user.

Just to confirm, this happens so quickly, there is no way it is adding additional input latency with G-Sync + V-Sync on, unless of course you hit the G-Sync ceiling (where this doesn't occur anyway), correct?

Appreciate the input, as always.
Yes. I'm not exactly sure what happens at the ceiling with vsync on, but I suspect Nvidia put a framerate cap somewhere in their driver.
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Re: G-Sync 101 w/Chart (WIP)

Postby jorimt » 22 Nov 2016, 14:00

Barring any inaccuracies in my previous camera tests, it does appear they are limiting the framerate when it hits the ceiling, maybe even by only 0.5 frames. I should be seeing at least a 2-3 frame difference between G-Sync ceiling and fps cap, but I've done several tests, and the difference is usually about 1 frame, give or take a couple ms, even with G-Sync and V-Sync disabled.

It would be interesting to see if the results are the same with a more accurate setup. Hopefully someone will test it sometime.

Edit: Or my tests aren't accurate enough. Forgot about this, but his tests show about three frames when it hits the ceiling:
Image
https://www.youtube.com/watch?v=F8bFWk61KWA
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Re: G-Sync 101 w/Chart (WIP)

Postby Chief Blur Buster » 22 Nov 2016, 14:28

Excellent work, jorimt!

Would you like to provide an article (Word, HTML, etc) for publication on the main Blur Busters website?
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Re: G-Sync 101 w/Chart (WIP)

Postby jorimt » 22 Nov 2016, 14:45

Chief Blur Buster wrote:Excellent work, jorimt!

Would you like to provide an article (Word, HTML, etc) for publication on the main Blur Busters website?

Wow, Uhm, yes.

As @Sparky just pointed out a couple posts ago, however, a few of my conclusions aren't 100% there.

I'm currently working on the chart and the post to reflect that instead of the 1ms polling rate, the anomalies (tearing with V-Sync off, etc) are actually being caused by frametime variances that miss the VRR window in instances just below the G-Sync ceiling and during frametime spikes. I'd also like to gather more data on framerate limiters and input latency just below the G-Sync ceiling; which I don't currently have the equipment for. Until then, the fps limit suggestions in my "Optimal G-Sync Settings" section, while probably very close to the truth, are still speculative.

That said, I would love to work my way up to a full article once I feel confident that everything is fully confirmed.

If you have any input or corrections to offer along the way, again, I'm all ears :)
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Re: G-Sync 101 w/Chart (WIP)

Postby Chief Blur Buster » 22 Nov 2016, 14:59

The artwork provided is really impressive.

You can write a "Caveats" paragraph section for the article, to cover these uncertainities/unknowns.

If you need anything to speed up this or make it easier (e.g. improved test components), let me know! For this quality of BlurBustersForum content, I would offer spare electronics parts to provide, even a spare Arduino if it helps a test, etc. Send me a PM or email squad[at]blurbusters.com if you are missing something that is hampering or slowing down your testing ability.

[EDIT: This offer goes to anybody who's posted lots of tests here in this forum -- "Cleaning Up The Blur Busters Closet" to give out excess spare parts -- goes for anyone here who has already posted lots of tests to the Blur Busters audience, like your post! Available while spare parts lasts. Posted November 2016.]
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Re: G-Sync 101 w/Chart (WIP)

Postby jorimt » 22 Nov 2016, 15:01

Thanks! I'll pm you with more details.
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Re: G-Sync 101 w/Chart (WIP)

Postby kandor1978 » 27 Nov 2016, 16:33

Hi there,

I have a Acer Predator z35 monitor
And when I enable the screen fps display which basically displays the hz the screen is running in realtime I can see it actually go down to even 1-2hz

This does of course not happen in games as I don't have games that will run that bad :)

But some windows software engage the gsync and will show this effect
and sometimes in games while it loads the level for example in Battlefield 1 I have seen the counter go down to under 10hz

Also what I have found at least on this screen is I can see tearing with vsync off even with gsync enabled and fps limited to 120fps when its run in 144hz mode

It is factory overclockable to 200hz but I find the overdrive feature really bad in 200hz mode
I use it in 144hz and extreme in Overdrive settings and everything looks good

Anyway just wanted to share what I have found with this screen

Best,
Kandor
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Re: G-Sync 101 w/Chart (WIP)

Postby lexlazootin » 27 Nov 2016, 21:26

It is factory overclockable to 200hz but I find the overdrive feature really bad in 200hz mode
I use it in 144hz and extreme in Overdrive settings and everything looks good


Good work!

Sorry to bother you, but does 'extreme' fix the overdrive, or was it simply you 'retriggering' overdrive after you overclocked it? For example, overclock to 200hz and then turn OD to off or extreme and then back to 'normal'.

Also does the colours get worse when you overclock? there might be a 'fast gaming' profile you can use to fix the colours.
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Re: G-Sync 101 w/Chart (WIP)

Postby jorimt » 27 Nov 2016, 21:50

kandor1978 wrote:Also what I have found at least on this screen is I can see tearing with vsync off even with gsync enabled and fps limited to 120fps when its run in 144hz mode

I have no doubt the required fps limits to eliminate tearing with G-Sync + V-Sync off may vary by display, which is why I include the disclaimer in both my OP and chart stating "1ms Polling Range” chart sections and FPS limits are currently speculative, and may not apply to all games."

I'm in the process of testing these issues further, and will eventually include input latency tests between the various methods and framerate limits. I hope to prove that G-Sync + V-Sync off isn't necessary at all, and that the only difference between it and G-Sync + V-Sync on, is that G-Sync + V-Sync off has tearing.

Again, G-Sync is V-Sync. They can't be applied on top of each other; it's either a variable refresh rate or fixed refresh rate. G-Sync simply reverts to V-Sync behavior with V-Sync on if it hits or exceeds its maximum range. Still, some have gotten it into their heads that G-Sync + V-Sync on is inferior to G-Sync + V-Sync off, and insist on using the latter over the former.
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Re: G-Sync 101 w/Chart (WIP)

Postby kandor1978 » 28 Nov 2016, 09:43

About the overdrive
It just either does too little or too much in 200hz mode on this screen
In 144 in extreme it seems to have been very optimized for it

About colours and display quality it self, I cant say I see any difference between 200hz and 144hz mode so they did a good job at overclocking just they did not consider the overdrive settings needs to be different

About gsync and vsync off

At some version of drivers before I would not get any tearing as long as I was under the screen hz in fps but then they updated the driver and it messed up that
I am 100% sure of this as I remember it very clearly
Dont know what version it was, and kind of don't care as I want to run latest driver

About vsync off and vsync on even when under screen hz, I find that it has lower input lag than vsync on but this part is probably placebo
At least maybe :) as I dont have any way to actually measure it
Would have been nice to try and actually make out if it really is a difference or not

Also found out that you can kind of get the smoothness of GSYNC with ULMB but with 1 line of constant tear
What I do is set everything to ULMB as I would normally do
Then set the game in question to run in windows border less mode and setup in that specific profile for that game to run the game with gsync instead of ULMB
This has worked for me, games feels a lot nicer how things move (csgo and battlefield are only ones I tried)
But that constant tear is very annoying so I am not using it.

I really would have loved to run the clearity of ULMB and GSYNCs smoothness

Sorry for going into different subjects here
also I find games run even smoother with even gsync if I change timer resolution to 0.5 ms instead of standard 1ms of my computer
I do this with SetTimer resolution tool

Best,
Kandor
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