60Hz Single Strobe VRR - M32Q Aim Stabilizer Sync Bug

[Discorz]

I was playing around with M32Q, disabled/enabled freesync and aim stabilizer sync a few times and noticed it bugged into single strobe VRR mode. Previously it was using high frequency PWM backlight fill to compensate brightness at lower refresh rates. Now it can single strobe within full 48-170 Hz/fps VRR range. BUT there is no PWM fill so brightness will change as framerate varies. Fortunately it doesn't toggle back to sample-and-hold mode below 75 fps as it used to.

Is it usable? Well not really. Its still too dark (approx. 100 nits), red decay is way too pronounced at low refresh rates, and since brightness is fluctuating any frame drops and stutters will look like flicker. Basically only good thing about it is MPRT staying perfectly consistent within VRR range.

Here is how I got it to work, pretty simple:
1. Disable Aim Stabilizer Sync and FreeSync
2. Enable Aim Stabilizer Sync
3. Enable FreeSync
Normally its intended to turn Freesync on first and Aim Stabilizer Sync second.

If you see some tearing in the videos that's because camera shutter is not perfectly matching monitor refresh rate. Freesync was working fine. I used 2-bar cascade sync track because my camera shutter is not very flexible.

Part 1 - variable flicker and brightness

phpBB [video]

Part 2 - frog pursuit

phpBB [video]

Normal mode: viewtopic.php?p=73457#p73457
As u can see below 120 Hz there is too much red ghosting and PWM fill actually nicely hides that in normal mode.
Speed: ∼1440 pps
Overdrive: Picture Quality


In this bugged mode M32Q can do classic fixed single strobe below 75 Hz. And since this requires FreeSync to be enabled any frame drops will appear as flicker. But I can work around this by keeping FreeSync enabled within monitor OSD but disabling it in AMD's control panel. So this way we get rid of both frame drop flicker and brightness fluctuation. Below are pictures of it. I'll leave it up to you to decide how it looks.

Classic fixed single strobe - 60 Hz middle screen


Fullscreen strobe crosstalk 60 Hz

Speed: 960 pps
Overdrive: OFF

I used amd gpu and can't know if it works for nvidia

[Chief Blur Buster]

Ideally, pulse width of VRR strobing should dynamically vary with frametime, to maintain brightness without PWM fill algorithms.

Also there should be additional settings by monitor manufacturers (currently being considered mandatory for future Blur Busters Approved strobed VRR)

- VRR Strobe Algorithm [PWM Backfill] [Single Strobe Always]
- VRR Strobe Pulse Width as Percentage of Refresh Cycle
- VRR Minimum strobe Hz for VRR range (where PWM backfill starts to kick in regardless)
- VRR Strobe Phase Offset Relative to previous VBI

(Mandatory-ness still TBD, and menu naming terminology still TBD)

Another possibility is concurrent pulse height (DC brightness) AND pulse width control, to maintain constant MPRT and brightness simultaneously, but that is a bit complicated and not supported by all backlight controllers, but may be presented as an option when backlight controllers don't have precise percentage-of-refresh-cycle variances.

[Discorz]

I'm wondering how did those old bugged g-sync monitors strobe with VRR?

VRR strobing as percentage of refresh cycle is probably the easiest to implement and most effective. Small MPRT fluctuation shouldn't be that noticeable. Optional algorithm for minimums would come in real handy since some users find low Hz flicker too strong.

If panel with ksf phosphor (more and more monitors use it) single strobes at low refreshes red ghost becomes real distracting. How do you manage to hide it without PWM, is it even possible?

[thatoneguy]

Another possibility is concurrent pulse height (DC brightness) AND pulse width control, to maintain constant MPRT and brightness simultaneously, but that is a bit complicated and not supported by all backlight controllers, but may be presented as an option when backlight controllers don't have precise percentage-of-refresh-cycle variances.

This is a thought I've had. In the future when MicroLED becomes mainstream we'll activate BFI/Rolling Scan and brightness will dynamically automatically boost accordingly to make up for it making it look at first glance like the option did nothing.
This would be as opposed to the user having to up the brightness manually after activating BFI.
Something like the user sets "100 nits" for SDR for example and the screen always makes sure that it's delivering an effective 100 nits of brightness to the viewer when on SDR no matter the setting.
I'm sure the Ambient Contrast Ratio that's been talked about would also complicate things a great deal further.

[Chief Blur Buster]

Personally, longer term, I'd like to see ultra high framerates at ultra high Hz instead. Using various kinds of frame rate amplification technology.

At some point, all the strobed VRR bandaids are so complex, that brute Hz and frame rate amplification techniques (e.g. 100fps -> 1000fps) then becomes easier.

But we are in the midst of GPU silicon shortages and next generation GPUs takes time to come out.

[Discorz]

Very true. As you said before real life does not flicker.