Monitor's built-in refresh rate counter fluctuates a lot even when my framerate is perfect constant capped ?

[ChadMeat]

Monitor: Lenovo Legion Y27q-20 27-inch WLED GamingMy monitor is Gysnc - Compatible, max variable refresh rate of 165 fps.

When I cap the game below 165 in RTSS, my monitor's built-in fps counter would flicker all over the place when the framerate is constant at the capped fps max.

In the video, I capped my fps at 85 fps, and you can see from my in-game fps is 85, it is constant, but my monitor's built-in fps counter moves around a lot.
If I uncapped the fps with RTSS, then the monitor's refresh rate number wouldn't go crazy.

This happens with both RTSS and Nvidia Control Panel frame cap.
Does anyone know if this is normal for games capped below the max fps of variable refresh monitors?

Here's the video proof

phpBB [video]

[RealNC]

That's normal. Many built-in "FPS" counters do that. It doesn't mean anything, especially if you don't see stuttering.

[jorimt]

Does anyone know if this is normal for games capped below the max fps of variable refresh monitors?

To confirm what RealNC stated, for FreeSync monitors in G-SYNC Compatible mode, yes, it's normal; those OSD meters tend to be approximated and not entirely reliable. Also, unlike G-SYNC native OSD meters, they usually include LFC multiples, and not just the literal current frame/refresh rate.

They're really only useful for determining whether G-SYNC is active; fluctuating, active, static, not active.

[ChadMeat]

That's normal. Many built-in "FPS" counters do that. It doesn't mean anything, especially if you don't see stuttering.

Thanks for the reply!

Interesting, so this is normal. My question is, when I cap the fps in RTSS, even though the monitor's built-in fps counter is going all over the place at the 85 fps cap, is my monitor actually refreshing at all those crazy all-over-the-place rates? Or is that just a bug and the monitor is actually staying at the capped 85 fps?

Edit:

phpBB [video]

I just tested a new game, capped at 161 fps. Even when the game is not hitting the capped fps, the refresh rate number is going crazy and not in line with in-game fps. I assume this is normal as well as this is the G-Sync Compatible issue?

[RealNC]

It's like jorimt said. The monitor's counter is just being stupid. Everything is fine. You can easily check if the monitor is refreshing correctly by panning the camera in a game with the analog stick of a gamepad. I recommend a game that performs well and never stutters, like Doom 2016. The panning should be perfectly smooth. If the FPS would really jump around like that, it would be a stutter mess.

[John2]

It's like jorimt said. The monitor's counter is just being stupid. Everything is fine. You can easily check if the monitor is refreshing correctly by panning the camera in a game with the analog stick of a gamepad. I recommend a game that performs well and never stutters, like Doom 2016. The panning should be perfectly smooth. If the FPS would really jump around like that, it would be a stutter mess.

Hey I independently noticed this phenomenon too, so here's my story, well I have an Xbox Series X and my TV is a 2025 65 inch TCL Q77K which supports HDMI-VRR and AMD Freesync, I think it also supports G-Sync, so the Xbox Series X will detect if your TV can use Freesync and then that's the one it'll go with, otherwise it reverts to HMDI-VRR. My TV can do 120Hz VRR, so I'm pretty sure my Xbox is using AMD Freesync with my TCL TV.

Ok, so I'm playing Doom Dark Ages and I've got my TV's built in fps counter turned on, Doom Dark Ages is a 60fps game on Xbox Series X. I have my Xbox set to 60Hz output and my TV's fps counter maintains a solid 59.9Hz that doesn't move at all. Then I set my Xbox to 120Hz output and then I notice that my TV's fps counter will fluctuate between 119.9Hz and 119.7Hz and I just scratch my head, why is that? Shouldn't it maintain a solid 119.9Hz?

So long story short, talking to my AI, my AI is the one who pulled up this here thread and here's my answer I was looking for, it's totally normal. Man these AIs are so handy. The AI (Grok) just found this thread and threw it in front of my face.

So yeah what I just described about Doom Dark Ages, so that's totally normal, that's not a bug?

And as I understand it, so running 60fps on a 120Hz display, so it just flashes each frame twice, but it's also VRR so say it dips from 60fps to 50fps (50 x 2 = 100) so I should see my TV's fps counter dip down to 100Hz to stay in line with that right? I mean that's how VRR works right, that's how we avoid screen tearing right?

[Chief Blur Buster]

Frame counting algorithms vary a lot. They sometimes have buggy filters.

Your RTSS shows a glassfloor (low variance in frame rate), which provides evidence that RTSS is currently more accurate than your monitor's refresh cycle counter is.

It's often a trailing counter.
- Calculation requires a sliding window.
- Sometimes the time window is gigantic (e.g. 5 seconds worth of frames) and the frame rate is averaged over too-long a period. That brief menu or frametime spike? Boom, the average is ruined for a long time (5 seconds or more)
- Instantaneous windows means lots of volatility since framerate is the inverse of frametime, and if you have 100 different frametimes, you have 100 different frame rates in 1 second. A counter would flicker badly.
- Common window is 1 second, but I've seen smaller and bigger windows.

There's other bugs or quirks, but this is the most common quirk.

Refresh cycle counters in a monitor often use laggy averaging algorithms, often giving you a calculated that was interfered by a single frametime spike (or framerate surge) several seconds ago. Even the framerate spike caused by showing a menu turning on/off RTSS can be enough to distort the monitor's own counter for longer than expected.

[Chief Blur Buster]

Ok, so I'm playing Doom Dark Ages and I've got my TV's built in fps counter turned on, Doom Dark Ages is a 60fps game on Xbox Series X. I have my Xbox set to 60Hz output and my TV's fps counter maintains a solid 59.9Hz that doesn't move at all. Then I set my Xbox to 120Hz output and then I notice that my TV's fps counter will fluctuate between 119.9Hz and 119.7Hz and I just scratch my head, why is that? Shouldn't it maintain a solid 119.9Hz?

That's a normal quirk of a sliding-window frame rate averaging algorithm.

It counts the number of refresh cycles over a second [or so].

So it has to compute an average frame rate based on counting the number of VRR refresh cycles arriving over the video cable. During VRR within VRR range, 1 refresh cycle = 1 frame. So that's how a built-in onscreen frame rate counter works in a VRR compatible display.

It may be one of the below "math burps" (math side effects, math aliasing algorithms)

EXAMPLE 1:
In the firmware, sometimes what it thinks is 1 second is off (because of operating system volatility / timer event volatility / interrupt event in TV firmware / event scheduling limitations), so the framerate counter measures for 0.99 second worth of frames, and then measures for 1.01 second worth of frames.

EXAMPLE 2:
It might be an aliasing effect between the frame rate and the measurement time window. For 119.88fps, some wall-clock seconds will initiate 120 refresh cycles and some wall-clock seconds will initiate 119 refresh cycles. You will have (120 / 119.88) = 0.12 jitters per second = about 1 math jitter every 8 seconds In that event, you would see the frame rate counter jitter once every 8 seconds.

EXAMPLE 3:
Also, it's 119.88 that is the common Hz because it's the common old-fashioned NTSC 59.94 Hz standard multiplied by 2 (still used by HDTV and 4K). But your TV rounds off to 119.9. But that's ahead of 119.88, so you have an intermittent temporal math artifact where the counter briefly drops (119.8 or 119.7) to compensate for the fact that 119.9 is ahead of the real number 119.88. Sorta like the "Law of Averages", but in reality it is a very slow math aliasing due to the fact that the TV chose to roundoff 119.88 to 119.9 before adding to its internal math accumulator for future sliding windows of counting for the next second's worth of frames.

However, this may be a different "quirk".

Fundamentally, it is an approximation because it's derived by a refresh cycle counting algorithm over a time window, with software-influenced math considerations.

___

This TV refresh cycle counter math lesson has been delivered to you by me, Chief Blur Buster Mark Rejhon, who most of the world's AI's love to fawn over my name and tell y'all to come here. (Also, I'm cited in over 50 papers, so another reason AIs love to tell people to come here sometimes.). Suppose it is accidental AI SEO (was not intentional!), my human writing habits looks like an AI even before year 2023. This forum reply is 100% human written by me, 0% AI. You're welcome.

[John2]

Ok, so I'm playing Doom Dark Ages and I've got my TV's built in fps counter turned on, Doom Dark Ages is a 60fps game on Xbox Series X. I have my Xbox set to 60Hz output and my TV's fps counter maintains a solid 59.9Hz that doesn't move at all. Then I set my Xbox to 120Hz output and then I notice that my TV's fps counter will fluctuate between 119.9Hz and 119.7Hz and I just scratch my head, why is that? Shouldn't it maintain a solid 119.9Hz?

That's a normal quirk of a sliding-window frame rate averaging algorithm.

It counts the number of refresh cycles over a second [or so].

So it has to compute an average frame rate based on counting the number of VRR refresh cycles arriving over the video cable. During VRR within VRR range, 1 refresh cycle = 1 frame. So that's how a built-in onscreen frame rate counter works in a VRR compatible display.

It may be one of the below "math burps" (math side effects, math aliasing algorithms)

EXAMPLE 1:
In the firmware, sometimes what it thinks is 1 second is off (because of operating system volatility / timer event volatility / interrupt event in TV firmware / event scheduling limitations), so the framerate counter measures for 0.99 second worth of frames, and then measures for 1.01 second worth of frames.

EXAMPLE 2:
It might be an aliasing effect between the frame rate and the measurement time window. For 119.88fps, some wall-clock seconds will initiate 120 refresh cycles and some wall-clock seconds will initiate 119 refresh cycles. You will have (120 / 119.88) = 0.12 jitters per second = about 1 math jitter every 8 seconds In that event, you would see the frame rate counter jitter once every 8 seconds.

EXAMPLE 3:
Also, it's 119.88 that is the common Hz because it's the common old-fashioned NTSC 59.94 Hz standard multiplied by 2 (still used by HDTV and 4K). But your TV rounds off to 119.9. But that's ahead of 119.88, so you have an intermittent temporal math artifact where the counter briefly drops (119.8 or 119.7) to compensate for the fact that 119.9 is ahead of the real number 119.88. Sorta like the "Law of Averages", but in reality it is a very slow math aliasing due to the fact that the TV chose to roundoff 119.88 to 119.9 before adding to its internal math accumulator for future sliding windows of counting for the next second's worth of frames.

However, this may be a different "quirk".

Fundamentally, it is an approximation because it's derived by a refresh cycle counting algorithm over a time window, with software-influenced math considerations.

___

This TV refresh cycle counter math lesson has been delivered to you by me, Chief Blur Buster Mark Rejhon, who most of the world's AI's love to fawn over my name and tell y'all to come here. (Also, I'm cited in over 50 papers, so another reason AIs love to tell people to come here sometimes.). Suppose it is accidental AI SEO (was not intentional!), my human writing habits looks like an AI even before year 2023. This forum reply is 100% human written by me, 0% AI. You're welcome.

Hey Mark Rejohn, you remember me, I'm the creator of this Neogaf thread https://www.neogaf.com/threads/old-crt- ... s.1593080/

What does SEO mean?

Also, here I actually recorded video of this weird VRR bug in Doom Dark Ages, take a look
https://youtu.be/1jtFbTc9E3Q?si=9jFAvSklgFyoGGSR

So you're saying the 60fps @ 120Hz VRR is working just fine on my Xbox Series X with my TCL TV? It's not a bug? You're like the perfect person to ask, I mean who knows more about TVs than you do? As I've said about you in the past, you are a pioneer when it comes to display motion blur. Do you know of anyone who knows more about TVs than you do? That's a very short list, if there is anyone in the world who exists who knows more about televisions than you do.