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G-Sync - Double Buffer Issue

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.

G-Sync - Double Buffer Issue

Postby Nemesis2K » 19 Feb 2019, 05:54

I recently built a new PC and have been using it to play a windows store game (Sea of Thieves)

My PC specs are:
    Intel Core i9 9900K @ 5GHz
    Asus Z390 Formula XI Motherboard
    2x8GB Trident Z 4000MHz DDR4
    NVidia RTX 2080TI FE
    AOC AGON AG352UCG6 G-Sync Monitor (OC @ 120Hz)
    Corsair RM850i PSU
    Samsung 970 EVO 500GB V-NAND M.2 PCI-E (which game and windows are installed on)

Getting my head around G-Sync has been a bit of a challenge but upon finding the blur busters guide, everything was good. Except with Sea of Thieves.

So far I have used the website to determine my actual refresh rate, then subtracted 3 frames from that total. I am using RTSS to limit my FPS. Although If I used double buffering V-Sync, with G-Sync enabled, the game regularly drops to 60fps then jumps back up to 117 again. If I change it to triple buffering its almost perfect. Everywhere I have seen so far echo's the idea that triple buffering should not be used in conjunction with G-Sync but I am unable to play a smooth game with double buffering. As the drops are too much. Is there something I may be missing?

This is my first post and I am sure I have missed out on some pertinent information, so forgive me. If you need to know anything to help then just let me know.

Thanks
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Re: G-Sync - Double Buffer Issue

Postby jorimt » 19 Feb 2019, 09:39

Going only by the info you have provided, to start:

1. Make sure G-SYNC is actually functioning in the game (Nvidia Control Panel > [top menu bar] > Display > G-SYNC Indicator).
2. Do not use in-game V-SYNC. Disable it, and enable V-SYNC in the Nvidia Control panel.

The fact you're experiencing a double buffer half refresh lock tells me G-SYNC is not working in that game for you, for whatever reason. The behavior you describe is not possible with G-SYNC in any configuration, and can only occur with standalone double buffer V-SYNC.
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Re: G-Sync - Double Buffer Issue

Postby Nemesis2K » 19 Feb 2019, 11:13

I have everything set up as above post. VSync is enabled in the NVidia options and Vsync in game is disabled. Gsync is active as it is giving me the label at the left side. Yet every so often my frames dip to 60 then straight up again.

Edit: although even though Vsync is off in game, if I change the option in sea of thieves menu from double to triple buffering it stops the drops locking to 60fps. Could this just be an issue with the game? I don’t see anyone else talking about it.
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Re: G-Sync - Double Buffer Issue

Postby jorimt » 19 Feb 2019, 12:18

I own Sea of Thieves, and play it regularly with G-SYNC on the setup in my sig. I have not experienced this issue, so it must be specific to your setup.

When you say it "locks" to 60 and back, is the FPS ever between 60 and 117? If so, you're not getting double buffer half refresh lock behavior, your FPS is just dropping periodically.

And if G-SYNC truly is active, then I have no clue why triple buffer would be reducing your drops in this instance, unless you're just mistaking the "improvement" for areas that simply perform better, regardless of the in-game double/triple buffer setting (as opposed to like-for-like testing between the two settings in the identical areas).

However, if you're seeing a repeated drop from 117 FPS (your RTSS limit) directly down to 60 FPS and back, and aren't seeing any "in-between" FPS, then that is indeed double buffer half refresh lock, which yes, triple buffer would fix...but only if G-SYNC isn't active in that case.

The NVCP's G-SYNC indicator isn't full-proof either, so even if it says G-SYNC is active, sometimes it still isn't. I would say you should enable your display's built-in refresh rate meter and make sure it's fluctuating to ensure G-SYNC is active in the game, but I checked the documentation for your model, and it doesn't have one.
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Re: G-Sync - Double Buffer Issue

Postby Nemesis2K » 19 Feb 2019, 12:51

No it drops directly to 60 for all of a second then climbs back up to 117. It’s never in between. With triple buffer enabled and Vsync off in game then it will fluctuate between 117 and around 100 on islands.

I’m all out of ideas, is there anything else I could be missing?
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Re: G-Sync - Double Buffer Issue

Postby jorimt » 19 Feb 2019, 13:04

When you say "climbs," do you mean it gradually raises the FPS from 60 to 117, or does it just jump from 60 to 117? If it's the latter, then G-SYNC doesn't appear to be functioning for you in that game currently.

Also, what are you using to monitor the FPS? The in-game setting, MSI Afterburner + RTSS, standalone RTSS?

To start:

- Under Windows 10 Settings > Gaming, what do you have "Game bar," "Captures," and "Game Mode" set to?
- Have you disabled "fullscreen optimizations" globally via a regedit? (this could possibly mess with G-SYNC support for Windows Store games, which use a hybrid borderless/exclusive fullscreen mode at default)
- Do you have G-SYNC set to "Enable for full screen mode" or "Enable for windowed and full screen mode" in the NVCP?
- What happens with G-SYNC enabled + in-game & NVCP V-SYNC off?
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Re: G-Sync - Double Buffer Issue

Postby Chief Blur Buster » 19 Feb 2019, 13:08

Try jorim's suggestions. That said...

Some games just really doesn't want to co-operate with G-SYNC.

Some games have some "additional" frame rate logic that has very bad interactions with GSYNC. It's possible that the game has its own double-VSYNC behaviour built into it, and it's "falsing" pretty badly. You may want to experiment with a cap very far away from 117 such as 100fps cap, but only for this particular game. It's possible the game has some unwanted logic that automatically caps 60Hz everytime it detects a specific frametime (e.g. exactly 1/120sec, a 117fps cap may still have frametime fluctuations that includes a 1/120sec frametime).

Also try temporarily GSYNC+VSYNC OFF, the game might be using blocking-detection to automatically switch to a different framerate cap; frametimes that are quicker than a refresh cycles may cause a framebuffer blocking behaviour that the game detects, causing the game to incorrectly assume it's in a throttled VSYNC ON mode, and then try some internal framepacing trick that creates an unwanted behaviour. Some games try to be too clever for their own good.

Drivers (often) won't necessarily be doing this "one game is framepacing weird with GSYNC" so it's often logic in the game that doing some unwanted behaviours.

It's probably an issue with the game.

Does the problem disappear if you use a 100fps cap?
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Re: G-Sync - Double Buffer Issue

Postby Nemesis2K » 19 Feb 2019, 13:18

Thanks for the super fast replies and support, it’s appreciated. I’m not at home at the moment but will report back with findings shortly. I took a video a few months back showing this, I now use RTSS to track FPS and frametimes since the video was recorded, but you get the idea.

https://youtu.be/kT9G2stmNxU
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Re: G-Sync - Double Buffer Issue

Postby jorimt » 19 Feb 2019, 13:22

Chief Blur Buster wrote:It's probably an issue with the game.

That's what I would think if I didn't play it, but I do, regularly.

With the below settings, I have no such double buffer lock issue:

Image

I average anywhere between 80 - 120 FPS (everything set to "Mythical" under "Graphics Settings").

I have a 144Hz monitor, so if I were having this issue, my FPS would currently be locked to 72 FPS, but as the in-game meter is showing, I'm at 113.

This leads me to believe his issue is system specific, and that G-SYNC simply isn't working in this game for him for some specific reasons, or he's mistaking another/unrelated issue for double buffer lock.

@Nemesis2K, on top of the questions I asked in my last post, what in-game "Display Mode" are you using?

EDIT:

Nemesis2K wrote:I took a video a few months back showing this

Hmm, that looks more like frametime spike-induced drops from periodic background asset loading or in-game network activity to me. Have you tried that same test in that same scene/scenario with both G-SYNC and V-SYNC completely off?
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Re: G-Sync - Double Buffer Issue

Postby Nemesis2K » 19 Feb 2019, 13:53

I have it set to full screen and windows gsync. I haven’t changed any registry settings as it’s a new build. I have game dvr, game bar on but game mode is off. I haven’t tested without gsync and Vsync yet.
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