Explain FPS under Vertical Sync?

[Netherspark]

I'm actually kind of confused about how FPS is supposed to behave with Vertical Sync enabled -- what everybody says is that if you have V-Sync with a 60Hz screen, when the frame rate drops below 60 it immediately cuts to 45, and then 30, then 15.

But this is not what happens. When I drop below 60 FPS it goes down naturally and smoothly to any number - it could be 54 FPS, or 48, or 42, or anything else. So why do people say it's only supposed to be 60-45-30-15? How exactly is it supposed to work?

[Svisalith]

You'd get a new frame every 16.67ms (1/60'th of a second) with a 60hz vsync lock

If any frame is slower than that, it can't be displayed until the next window which is 2x 16.67ms (1/30'th of a second)

Vsync only cares if there is a new frame ready for the next refresh but your FPS meter is averaging a time period that is 60x longer. If you got no frames at all for half a second it would still say 30fps even though you had 0 frames for the first half of the second and 30 frames in the second half, that's not very representative of in-the-moment smoothness.

On a frame by frame basis a single slightly missed frame would appear and feel like having 60fps, suddenly "30fps" for one frame and then 60fps again with no in between

If you count all of the frames in the last second then there will have been 59 frames - 58 of them came at "60fps" and the last one at "30fps". The FPS meter will say 59.

With Vsync each frame can only be displayed on a new refresh so the effective frametime for each individual frame has to be a factor of the refresh rate. At 60hz the most relevant ones are 1/60'th of a second (every refresh), 1/30'th of a second (every second refresh), 1/20'th of a second (every third refresh) and 1/15'th of a second (every fourth refresh). The gap between 60 and 30 when you slightly miss a 60hz refresh is the most brutal.

[Wramp]

some people seem to get a better experience from setting the refresh rate to 59 Hz instead of 60 (if your monitor supports it) when using Vsync. but overall the above post explains the math involved. I, personally, would not use Vsync

[Netherspark]

So it IS cutting to 45/30/15, but only so briefly that its unnoticeable?

What's confusing me is that people say this is choppy and stutters the game, but it looks perfectly smooth to me. The actual impact of this on the game is no differerent than playing with V-sync turned off.

some people seem to get a better experience from setting the refresh rate to 59 Hz instead of 60 (if your monitor supports it) when using Vsync. but overall the above post explains the math involved. I, personally, would not use Vsync

Well without V-sync I get screen tearing and rough-looking gameplay.

[Svisalith]

^A lot of people use FPS limits slightly below refresh rate. Having an FPS limit below the screens refresh rate, even slightly below (like 60hz with a 59.99fps limit) prevents the buffer from building up and adding the huge vsync input lag but it's awkward at best to use with a static refresh rate screen https://www.blurbusters.com/howto-low-lag-vsync-on/

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So it IS cutting to 45/30/15, but only so briefly that its unnoticeable?

What's confusing me is that people say this is choppy and stutters, but it looks perfectly smooth to me. The actual impact of fluctuating FPS on the screen is no differerent than playing with V-sync turned off.

60/30/20/15

It should be very much noticable, frames suddenly taking twice as long as before. Those smoothness and input lag spikes are particularly huge but there are even changes to things like motion blur as well

If you're using windows 8 or 10, make sure that you're playing in exclusive fullscreen - not windowed or windowed fullscreen. Those modes force vsync on all of the time regardless of what you have set ingame; a slightly different implementation of vsync but still vsync.

[Netherspark]

60/30/20/15

It should be very much noticable, frames suddenly taking twice as long as before. Those smoothness and input lag spikes are particularly huge but there are even changes to things like motion blur as well

It looks perfectly smooth to me. I have no discernable input lag either. Frame rates go up and down the same as it would without V-sync.

If you're using windows 8 or 10, make sure that you're playing in exclusive fullscreen - not windowed or windowed fullscreen. Those modes force vsync on all of the time regardless of what you have set ingame; a slightly different implementation of vsync but still vsync.

I play pretty much everything in windowed fullscreen and I can turn V-sync on & off no problem.

[Svisalith]

It looks perfectly smooth to me. I have no discernable input lag either.

What can i say, you have low standards

I play pretty much everything in windowed fullscreen and I can turn V-sync on & off no problem.

not the desktop compositor vsync on win8/10 or some of the win7 themes

[Netherspark]

What can i say, you have low standards

Let me rephrase: it IS perfectly smooth. There are no jumps, chops or stutters of any kind. Frame rate falls and climbs almost one-by-one (60-59-58-57-56-55-54 and so on).

not the desktop compositor vsync on win8/10 or some of the win7 themes

When I turn it off in-game, the frame rate is unlocked, climbs to 90+ and screen tearing occurs. V-sync is most certainly not active.

[potis]

Let me rephrase: it IS perfectly smooth. There are no jumps, chops or stutters of any kind. Frame rate falls and climbs almost one-by-one (60-59-58-57-56-55-54 and so on).




When I turn it off in-game, the frame rate is unlocked, climbs to 90+ and screen tearing occurs. V-sync is most certainly not active.

Triple Buffering needs to be enabled for the whole "60-30" etc etc to happen, some games have this locked with Vsync, most dont.

And at the same time you need to have such horrible random FPS drops to experience it, it wont happen instantly below 60 FPS, things are smarter than that.

Problem with Vsync used to be that it tended to bug out sometimes and cause problems in multiple games WoW had something similar at a point where as example, 100 FPS-->Raid combat -->50 FPS-70, Vsync on 60 FPS-->Raid combat 40-30 FPS at least for me in many different PCs, used to play without Vsync then, dont remember when and what fixed it, had Vsync back up after that again.

Ignore the children that cant understand, what you are experiencing is normal, i play with Vsync on 24/7 for years now for the very same reason, screen tearing is unbearable and i dont have the money to upgrade to 144Hz to get rid of both 60hz and tearing </3.

[Netherspark]

Triple Buffering needs to be enabled for the whole "60-30" etc etc to happen, some games have this locked with Vsync, most dont.

And at the same time you need to have such horrible random FPS drops to experience it, it wont happen instantly below 60 FPS, things are smarter than that.

So this will only happen with both Triple Buffering active and very severe FPS drops? That makes more sense.

The reason I'm really asking is because I'm going to be upgrading both my PC and monitor soon, and I'll be going for a 144Hz screen but may not be able to maintain 144+ FPS. And from what so many people are saying i would really be getting just 72 FPS with V-sync on.

So what I really want to know I guess, if I'm running a game at say 125 FPS with V-sync on and Triple Buffering off (without GSync/Freesync), will I actually get 125 FPS or 72?

[coprax]

So what I really want to know I guess, if I'm running a game at say 125 FPS with V-sync on and Triple Buffering off (without GSync/Freesync), will I actually get 125 FPS or 72?

You will have 125 unique frames then, but with uneven frame-pacing in between (some frames will have double the refresh time between each other). But since the refresh rate is 6.94ms it will be less noticable than on a 60hz screen.

[Denpepe]

If you have an nvidia card, you could always use the adaptive sync setting in the nvidia control panel which gives you a g-sync like feature iirc.

[Netherspark]

You will have 125 unique frames then, but with uneven frame-pacing in between (some frames will have double the refresh time between each other). But since the refresh rate is 6.94ms it will be less noticable than on a 60hz screen.

So it should still look smooth during gameplay?

[teamkiller]

So this will only happen with both Triple Buffering active and very severe FPS drops? That makes more sense.

The reason I'm really asking is because I'm going to be upgrading both my PC and monitor soon, and I'll be going for a 144Hz screen but may not be able to maintain 144+ FPS. And from what so many people are saying i would really be getting just 72 FPS with V-sync on.

So what I really want to know I guess, if I'm running a game at say 125 FPS with V-sync on and Triple Buffering off (without GSync/Freesync), will I actually get 125 FPS or 72?

With a 144hz panel, you should not need V-sync so honestly don't worry about that detail. At that refresh rate, you should not ever get tearing unless you are playing an esports game or a really old game. If you end up upgrading your GPU to a 1000 series card, I highly recommend fast sync in the nVidia panel.

[Afrospinach]

It looks perfectly smooth to me. I have no discernable input lag either. Frame rates go up and down the same as it would without V-sync.

The input lag scenario is not a rule, if you get input lag drop it to 59hz. The only games I can recall having an issue with is Rage and Dead Space.

[potis]

So this will only happen with both Triple Buffering active and very severe FPS drops? That makes more sense.

The reason I'm really asking is because I'm going to be upgrading both my PC and monitor soon, and I'll be going for a 144Hz screen but may not be able to maintain 144+ FPS. And from what so many people are saying i would really be getting just 72 FPS with V-sync on.

So what I really want to know I guess, if I'm running a game at say 125 FPS with V-sync on and Triple Buffering off (without GSync/Freesync), will I actually get 125 FPS or 72?

I have been playing on 144Hz screens, 3 different ones practically daily for the last 2 years (Net cafe) compared to my 60Hz at home.

WoW in raids drops to 40-50 FPS 24/7, i dont see a difference on the screen, tearing and quality of it when it does, versus when i stand there with 100 FPS.

Same with any other game, the quality of the screens overall is much better than a 60Hz and as i said, Triple Buffering is required to be enabled to cut your FPS in half when it goes below.

Vsync exists to make the tearing disappear when your monitor cant catch up to your GPU, with 144Hz that problem is completely evaporated, along with the new nvidia staff for any other situation, Adaptive and Fast Sync exist for that.

[Lathais]

It looks perfectly smooth to me. I have no discernable input lag either. Frame rates go up and down the same as it would without V-sync.




I play pretty much everything in windowed fullscreen and I can turn V-sync on & off no problem.

Some people actually can not see any difference at all above 30FPS. I know I can. It is night and day difference to me. My best friend and his wife, absolutely can not.

[Kagthul]

Same with any other game, the quality of the screens overall is much better than a 60Hz and as i said, Triple Buffering is required to be enabled to cut your FPS in half when it goes below

... yeah, except that isnt remotely what triple buffering does. At all.

https://www.anandtech.com/show/2794/2

Triple buffering will smooth out frame drops, not cause them to be more severe. If youre using Vsync, you should ALWAYS be using Triple Buffering if your GPU has the grunt to enable it without a performance hit.

[potis]

... yeah, except that isnt remotely what triple buffering does. At all.

https://www.anandtech.com/show/2794/2

Triple buffering will smooth out frame drops, not cause them to be more severe. If youre using Vsync, you should ALWAYS be using Triple Buffering if your GPU has the grunt to enable it without a performance hit.

No one said it doesnt smooth are frame rates supposedly as a technology i said what it actually does, it has been proven that

1)most games dont support it properly.
2)It does exactly as i said, makes the 60-30 jump whenever the frames drop below 60 suddenly, it was and is useless, at least in Blizzard games, i rememeber observing similar behavior in many games before 2010-12 but cant really prove it.

Either way, what TB does on the background is irrelevant with the result at the front, there was a period that completely made WoW unplayable if it was enabled, not sure when it was fixed, havent enabled it since forever, ever.

Just some games, have TB locked with Vsync and its very obvious to experience, some others dont have it at all, or as a choice.

Here, from a post that explains it:

"Without triple buffering, if your system cannot generate frames in 16ms of time on a consistent basis, your FPS will drop to near half. Normally, if your frames take 20ms to generate, you'd get 50 FPS, and they'll be displayed as soon as they are created, but with V-sync and a two buffer system, the GPU cannot start rendering a new frame until the previous one is displayed. That means every frame will end up taking 33.3ms before they are displayed, resulting in 30 FPS.

The near 30 FPS issue when you can't get 60 FPS is rare. EXTREMELY rare today, but 10 years ago, it happened all the time."

Basically as i remember,problem evaporated with the much faster GPUs it seems.

It is supposed to keep shit at 60, but with it enabled i jumped to 30 all the time, could just be the ancient stuff, who knows, if its fixed now, it should be on.

Here: this post from 3 years ago explains what i was experiencing years back and why i am wrong with TB, but right at the same time :

http://www.mmo-champion.com/threads/...uffering/page2