I got the ROG Swift (PG278Q) -- my tests

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

Re: I got the ROG Swift (PG278Q) -- my tests

Postby Chief Blur Buster » 02 Aug 2014, 09:48

RealNC wrote:
mello wrote:
Chief Blur Buster wrote:And what about triple buffering ? How does it affect input lag in the best case scenario (VSYNC ON) that you just desribed ?

Tripple buffering will always increase lag by at least one frame. The kind of triple buffering the Chief is talking about, which actually reduces lag, is not used anymore in games. It was last used about 15 years ago or so. These days, triple buffering means just one more render-ahead buffer compared to double buffering.

This isnt true. What happened is it became non-obvious how to turn it on.
Today, it is more confusing how to turn it on, because it is more obscure.

This is the lag-reducing triple buffering: http://www.anandtech.com/show/2794

It is still possible to do it today, if you use utilities to configure the drivers, but it is tricky to confirm sometimes. Moe easy to do is use windowed mode. The old style of triple buffering occurs when you use windowed+VSYNC OFF, since the compositing layer grabs only the latest frame, once a refresh. You do not see tearing during VSYNC OFF, yet input lag is reduced in windowed mode! However, the compositing layer sometimes adds two frames of lag on some GPUs, so it behaves like a double buffer stacked in series with 'proper' triple buffering, so you get 1 frame of extra lag (but better than 2 frames lag) However, on GPUs and Windows drivers that only add 1 frame for compositing, then it becomes equal to old-fashioned proper triple buffer (and no penalty over true intentional 'proper' triple buffers of yesterday yore). In all cases, you get less lag than VSYNC ON windowed mode, but no tearing!

Games that have "full screen windowed mode", turn that on. You see lag increase. Now, turn off VSYNC. You see lag decrease, but no tearing.

Also, I wish all GPUs would keep compositing fast and minimum depth, only 1 frame shallow where possible, by doing just-in-time compositing in-GPU during VSYNC. Then it has no lag penalty over proper triple buffer. Memory bandwidth is fast enough to finish compositing in just a few hundred microseconds, so compositing can be done just-in-time in GPUs. Manufacturers that do not, need to get with that ball already being done in some GPUs, and optimize compositing to be as shallow as possible. Then, there is only the double buffer style lag penalty, and reduced by VSYNC OFF and compositing becomes the defacto proper triple buffer. Some say it is 'emulated', but it is a duck (it looks like a duck, it quacks like one, it reduces lag without tearing). It is a real proper triple buffer occuring, then potentially tape-delayed a bit again by inefficient compositing! (But still less lag than double buffering in windowed mode on same GPU!)

Min you, double-buffer is better for strobe motion quality in the best case scenario (perfect framerate-refreshrate sync). But if you hate input lag and/or get stutters or framerate slowdowns, 'proper' triple buffer is better.

This may be an interesting test to do at some point.
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Re: I got the ROG Swift (PG278Q) -- my tests

Postby RealNC » 02 Aug 2014, 12:08

Chief Blur Buster wrote:
RealNC wrote:Tripple buffering will always increase lag by at least one frame. The kind of triple buffering the Chief is talking about, which actually reduces lag, is not used anymore in games.

This isnt true. What happened is it became non-obvious how to turn it on. Today, it is more confusing how to turn it on, because it is more obscure.

This is the lag-reducing triple buffering: http://www.anandtech.com/show/2794

It is still possible to do it today, if you use utilities to configure the drivers, but it is tricky to confirm sometimes.

I'd love to know how to do that. D3DOverrider's "triple buffer" option only adds an additional buffer to the queue. (or so it seems.) And the Windows desktop compositor has more lag than fullscreen vsync.
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Re: I got the ROG Swift (PG278Q) -- my tests

Postby nimbulan » 02 Aug 2014, 15:37

RealNC wrote:I'd love to know how to do that. D3DOverrider's "triple buffer" option only adds an additional buffer to the queue. (or so it seems.) And the Windows desktop compositor has more lag than fullscreen vsync.

I've always found the desktop compositor to significantly increase stutter as well. I can't even play high frame rate videos smoothly without setting my video player to exclusive fullscreen mode and have never been able to get accurate results from the UFO tests because of this.
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Re: I got the ROG Swift (PG278Q) -- my tests

Postby spacediver » 02 Aug 2014, 19:22

is desktop compositor disabled when I play quakelive fullscreen? (I think I have the desktop compositor enabled because I'm using aero)
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Re: I got the ROG Swift (PG278Q) -- my tests

Postby RealNC » 02 Aug 2014, 20:47

spacediver wrote:is desktop compositor disabled when I play quakelive fullscreen? (I think I have the desktop compositor enabled because I'm using aero)

In fullscreen mode, Aero is always temporarily disabled.
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Re: I got the ROG Swift (PG278Q) -- my tests

Postby spacediver » 02 Aug 2014, 21:47

cheers, that's what I remember reading, but wasn't sure.
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Re: I got the ROG Swift (PG278Q) -- my tests

Postby Chief Blur Buster » 02 Aug 2014, 22:27

nimbulan wrote:I've always found the desktop compositor to significantly increase stutter as well. I can't even play high frame rate videos smoothly without setting my video player to exclusive fullscreen mode and have never been able to get accurate results from the UFO tests because of this.

What GPU and driver version are you using?
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Re: I got the ROG Swift (PG278Q) -- my tests

Postby nimbulan » 02 Aug 2014, 23:03

Chief Blur Buster wrote:
nimbulan wrote:I've always found the desktop compositor to significantly increase stutter as well. I can't even play high frame rate videos smoothly without setting my video player to exclusive fullscreen mode and have never been able to get accurate results from the UFO tests because of this.

What GPU and driver version are you using?

This has been true since Windows 7 was released, with a GTX 260 and a 760, across every driver version I've used in that time. I've always found windowed mode in games useless because of it (even more useless now that G-sync requires fullscreen.) It feels like the compositor can't handle a framerate more than 30 or so in realtime and I find it hard to believe that I'm the only one when it's behaved identically on two different systems, though both Intel/nVidia systems with multiple monitors. When I first bought the VG248QE, I couldn't even get 24/30 fps video to play smoothly but it slowly fixed itself over the course of a week or two.
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Re: I got the ROG Swift (PG278Q) -- my tests

Postby Papagaj » 05 Aug 2014, 01:34

Anyone tried Diablo 3 with G-SYNC ? The game has a lot of stuttering with V-SYNC and a lot of tearing without V-SYNC so i guess G-SYNC is the way to go there ...
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Re: I got the ROG Swift (PG278Q) -- my tests

Postby nimbulan » 05 Aug 2014, 01:56

Papagaj wrote:Anyone tried Diablo 3 with G-SYNC ? The game has a lot of stuttering with V-SYNC and a lot of tearing without V-SYNC so i guess G-SYNC is the way to go there ...

There's a thread about that actually: http://forums.blurbusters.com/viewtopic.php?f=5&t=362

Long story short: There was an update that broke something so G-sync would only work with vsync enabled in the game options, but that also limited the framerate to 60. It used to work fine with vsync off in the game options. I have no idea if that was ever fixed.

On the plus side the last time I played it seemed like they had finally fixed the horrendous dynamic data loading stuttering bug that existed since launch so G-sync might actually be beneficial.
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