Stutter Stutter or Smooth as Butter

[jimortality]

Brands Hatch especially, even in practice screen stutter. I think it's not just me and maybe down to the unreal engine? I've tried all different things so if you're smooth as Butter, please post your settings and how you're eliminating it. Thank you.

Acer Predator X34p
I 7-6700k
Nvidia 1080ti
16gb Ram a lam.
And not forgetting my brand new Master Cooler 212 Evo

 

[Noctam]

Thanks again for all this information.

Yes, the range of the monitor is a small 48-75Hz.

Your explanation for the 144hz is great, I love the drawing.
So I understand the idea of the shorter hence quasi-invisible tearing but just to go a bit deeper: if the monitor isn't VRR, v-sync ON would be at 144fps only on a 144Hz screen?
So for heavy games you would always run with vsync off, is that right?
Wouldn't a 60fps screen be better in a way if you play mostly heavy games (and do not have the option of a VRR screen)?

This PC will one day be running a glorious RTX Nvidia card but for the moment it's an humble 1660 Super.

@RasmusP I can't see your video, it seems private.

 

[RasmusP]

Thanks again for all this information.

Yes, the range of the monitor is a small 48-75Hz.

Your explanation for the 144hz is great, I love the drawing.
So I understand the idea of the shorter hence quasi-invisible tearing but just to go a bit deeper: if the monitor isn't VRR, v-sync ON would be at 144fps only on a 144Hz screen?
So for heavy games you would always run with vsync off, is that right?
Wouldn't a 60fps screen be better in a way if you play mostly heavy games (and do not have the option of a VRR screen)?

This PC will one day be running a glorious RTX Nvidia card but for the moment it's an humble 1660 Super.

@RasmusP I can't see your video, it seems private.

Video should be visible now. Wrong checkbox...

About the monitors:
All monitor support a few different hz settings.
144 hz monitors can mostly run at:
50/60/85/100/120/144 hz so your question is kinda irrelevant hehe.

But to answer it:
Vsync only means that the gpu will hold back the new frame until the next refresh cycle (scan out) will happen.
So you can always display a frame either:
1 refresh cycle long
2 refresh cycles
3 refresh cycles etc.

So when you activate vsync and the fps drop to 120 fps for example, that one frame that took longer to render will be displayed until the next frame is ready.
2 refresh cycles, 3 refresh cycles.. Until the gpu got the next one ready!

It's easier to think about this in frame times. So 1000/144 = 6.94ms

Every 6.94ms a new frame from the gpu could be displayed.
If the gpu takes 8ms to get the next frame ready (or the cpu took longer, ofc), the current frame will be displayed for another refresh cycle.

Dropping the current fps to 72 fps.
And then causing an input lag of (2x 6.94ms - 8ms = 5.88ms to the next refresh cycle /new frame).

If the gpu takes more than 2x 6.94ms, the current frame will be displayed a third refresh cycle. Dropping the fps to 48 fps.

Also important to know:
With vsync, there's always at least 1 frame cached to keep things smooth!
However if you limit the fps a tiny bit below the refresh rate of the monitor, this buffer will slowly be emptied and the input lag at least feels a lot shorter. There's sadly no real info about this out there and we couldn't really test it scientifically here on rd ).

Low Latency set to "ultra" kinda does this. But it's stuttering visibly since the limit is too far below the hz.

Anyway, with vsync the fps will always drop to half/third/quarter etc of the hz.
With vrr, the fps will only drop to the actual delay in frame time.

So instead of "144/144/72/72/144", you'll have: "144/144/139/137/144".
But ofc it would be 141, as we would limit the fps 3 fps below the hz value with vrr


With Nvidia, you can run the "Nvidia inspector". Little Programm that shows more options than the standard driver menu.
There you can actually set the vsync to full, half, 1/3.
So limiting the fps to 72 on a 144 hz monitor without issues.

I'm not sure how well a fps limiter at 72 fps work.
It would drop the vsync to 72 fps automatically but I'm not sure if it would sync correctly or run asynchronous and therefore cause a hiccup every now and then, when it becomes so far off that a frame needs to be displayed a 3rd time.

Hope that slowly clears up the fog haha

 

[Noctam]

The video works now, it's clearly visible!

Thanks a lot for the clarification. So in the end I should just never again buy a non VRR screen, as simple as that!

One last question, if I understand the idea of using a limiter under the refresh rate for VRR, I'm a bit lost about the concept of a limiter just under the limit for "classic" vsync, shouldn't this trigger a drop to 30fps?

 

[RasmusP]

Thanks a lot for the clarification. So in the end I should just never again buy a non VRR screen, as simple as that!

Exactly

One last question, if I understand the idea of using a limiter under the refresh rate for VRR, I'm a bit lost about the concept of a limiter just under the limit for "classic" vsync, shouldn't this trigger a drop to 30fps?

Yes. But to understand this you need to understand the idea of the frame buffering that happens with vsync.

It's not like the fps will lock to 30 fps, when you set the limit to 59 fps. Instead you will only display 1 frame a second time, once per second.
That's because there is a frame buffer that starts being full and becomes empty over that one second.

But imagine it like this:
with vsync, the GPU will always have a frame ready in the buffer that the monitor will grab the frame from but also another frame cached in another buffer.

So there will always be one full frame ready when the monitor will grab the next one.

This causes input lag, which is definitely noticeable! When you drive through a quick chicane, you'll notice the virtual wheel lagging behind.
Or when you would play a shooter, you'll notice the mouse to be sluggish, like pudding.

Now if you limit the fps below the refresh rate, for example 59, there will be 1 frame missing after 1 second.

So once per second, you will have a "buffer re-fill lag".
Like "60/60/60/60/60/60/60/60/60/60/30/60/60/60/60/60"

And if you limit the fps at 59.5 fps, this will happen every 2 seconds.

In theory the input lag ("How fresh is your next frame"), would vary from:
"the same as without the limiter"
to
"no input lag at all"

But from my experience, the input lag will be low and consistent.
I don't understand this...

From my experience the input lag will become lower, the further you go below the refresh rate. But the stutter will be less visible, the closer you stay at the refresh rate.

So 60 Hz + 59 fps = low input lag, visible stutter
60 Hz + 59.99 fps = higher input lag, no visible stutter

I personally always use -0.03.
So 60 Hz = 59.97 fps limit.

My tv is 60.0000000001 Hz according to vsync tester.

 

[Noctam]

I think I get it thanks to your explanation. So basically we are triggering a very short mis-sync in order to emtpy the buffer?

 

[Noctam]

I'm not sure how well a fps limiter at 72 fps work.
It would drop the vsync to 72 fps automatically but I'm not sure if it would sync correctly or run asynchronous and therefore cause a hiccup every now and then, when it becomes so far off that a frame needs to be displayed a 3rd time.

This might be the answer (quote of a post by RealNC on guru3D):

If you are using double or triple vsync (setting "vsync" in NVidia Profile Inspector to "1/2" or "1/3"), then your cap needs to be 0.01 below half your refresh rate. So for a 119.982Hz monitor, you'd cap to 119.982 / 2 - 0.01 (for 1/2 vsync) or 119.982 / 3 - 0.01 (for 1/3 vsync.)

 

[RasmusP]

I think I get it thanks to your explanation. So basically we are triggering a very short mis-sync in order to emtpy the buffer?

Yeah that would be one way to describe it.
Although it's not "mis-synced". It's just that the cache starts full and goes empty. And when it's empty, one frame gets displayed twice on the monitor. Meanwhile the cache gets re-filled.

But you won't see tearing, the actual frame buffer to the monitor will always stay synced.

 

[Case_]

BTW, I recently did get a 75 Hz Freesync monitor, also doubting if it's even worth it on this low refresh rate. It absolutely is if you care about input lag (I do a fair bit). It gives you by far the easiest, most convenient and more importantly most consistent way of achieving the lowest input lag possible, and, at least with the nVidia G-Sync "emulation", if you activate G-Sync for windowed and borderless windowed mode, it also seems to somehow be able to work around the added input lag in borderless mode, which as far as I know is not possible to do any other way. Tear free image is a nice bonus, of course, but that can be achieved without VRR in several different ways, so not that big of a deal.

(Not that it helps with the terrible ACC input lag all that much, but it helps a bit, at least )