Discussion about Phosphor Fade Simulation / Rolling-Scan Software BFI

[Chief Blur Buster]

Simulate CRT 60Hz phosphor decay in LCD strobe 60Hz is good for less flicker, but undesirable for motion quality, panning in CRT 60Hz a white moving object in a fullscreen black background, cause a long trail WhiteToBlack behind the white object. This same test in XG270 SingleStrobe 60Hz with strobe fast WhiteToBlack, for sure leave much less trail, but with heavy blink

The solution can be set a long strobe lenght at 60Hz for compensate, trade Flicker with MotionBlur.

We'd need 1000 Hz LCDs to more accurately emulate phosphor decay -- since phosphor decay can't be emulated accurately at 16.7ms granularity at 60Hz (stepped fade effect with LCD-like ghosting effects). Phosphor decay ideally needs to be emulated at millisecond, even sub-millisecond granularity. One could implement a software-based rolling-scan BFI, e.g. theoretical 4-segment BFI for 60fps at 240Hz with gamma-corrected alpha-blended zones between segments, an equivalent of phosphor decay emulation.

[AddictFPS]

We'd need 1000 Hz LCDs to more accurately emulate phosphor decay -- since phosphor decay can't be emulated accurately at 16.7ms granularity at 60Hz (stepped fade effect with LCD-like ghosting effects). Phosphor decay ideally needs to be emulated at millisecond, even sub-millisecond granularity. One could implement a software-based rolling-scan BFI, e.g. theoretical 4-segment BFI for 60fps at 240Hz with gamma-corrected alpha-blended zones between segments, an equivalent of phosphor decay emulation.

For 100% emulation is the only way, all screen pixels as a different decay "start time" and "end time". But currently, the XG270 backlight can be programmed to make the strobe lenght, Off-On close to instantaneous, and On-Off a progressive fullscreen decay ? a OSD "Under 75Hz mode" setting to apply this behavior with current PureXP+ strobe lenght levels.

Scanout speed 240Hz 4.16ms -> all pixels have the signal to change color
GTG máx time (100% transition) +9ms (like ACER XV273X with same panel) -> at 13.16ms all pixels has the stable color
From 13.16 to 16.66, the are 3.5ms to play with this decay without crosstalk, it could work ?

You'll still have to rely on software BFI + 120 Hz in your favourite emulators.

Anyone know software BFI that work with GPU drivers, in order to make BFI+120Hz in DirectX OpenGL and Vulkan games capped at 60FPS ?

[Chief Blur Buster]

Fade emulation on strobe backlights will only go part way.

The problem with flicker perception is that strobing is global, while CRT is rolling scan.

CRTs feel like they flicker less because something is being illuminated somewhere all the time.

If you see a high speed video of a CRT, you will see a phosphor dot or bar at all times.
The total amount of light hitting human eyes remain relatively constant over the milliseconds

If you see a high speed video of a strobe backlight, you will see some moments that a screen is completely black.
The total amount of light hitting human eyes varies wildly over the milliseconds

This cannot be emulated very easily with sample-and-hold displays at current refresh rates, unless there's an expensive FALD scanning backlight. See this thread -- Scanning Backlight Via a FALD

[Chief Blur Buster]

I have opened discussion threads at a few emulator forums, to highlight this potential, as a "Temporal HLSL":

http://forum.arcadecontrols.com/index.p ... 926.0.html

https://github.com/mamedev/mame/issues/6762

This is probably a long-term incubation, but I will probably create a TestUFO CRT Emulator in the coming years, as it's relatively simple for me to create.

I'd likely make it a Hz-agnostic CRT emulator, and use gamma-corrected alphablend on the overlapping areas of the rolling-scan segments.

[thatoneguy]

Congrats Chief on finally launching your electron beam temporal simulator!!!
Didn't know where else to post so... sorry for necrobumping.

[xenphor]

Could this tech be used with VR headsets? I tried VR for the first time with a Quest 3 and my eyes couldn't tolerate the flickering. I think a lot more people could tolerate VR if the image didn't flicker.

[thatoneguy]

Could this tech be used with VR headsets? I tried VR for the first time with a Quest 3 and my eyes couldn't tolerate the flickering. I think a lot more people could tolerate VR if the image didn't flicker.

Counter-intuitive
The rolling scan behavior would be much more noticeable on VR

I haven't heard too many people complain about flicker with VR
That said, the plan for VR is likely high hertz(+480hz at least) and asynchronous reprojection

[Supermodel_Evelynn]

Don't we have to wait for 1000HZ OLED first?

CRT was like OLED it didn't have all these bad backlight bleed and off center tinting of an image as CRT could activate individual pixels like OLED

LCD tech is just bad even at 1000HZ I wouldn't touch that after experiencing my QD-OLED

I really wish we could see this tech in OLED a full 100% emulation of CRT full works even with VRR enabled what a dream that would be.

[William Sokol Erhard]

Could this tech be used with VR headsets? I tried VR for the first time with a Quest 3 and my eyes couldn't tolerate the flickering. I think a lot more people could tolerate VR if the image didn't flicker.

Counter-intuitive
The rolling scan behavior would be much more noticeable on VR

I haven't heard too many people complain about flicker with VR
That said, the plan for VR is likely high hertz(+480hz at least) and asynchronous reprojection

This is an interesting subject. I've been an XR software developer for years and I've dove pretty far down the AR and VR display temporals rabbit hole and I can only hope that you're right. Whether there's even a plan at all for display temporals in VR is another question but let's talk technicals.

Humans are absolutely capable of noticing strobing rates above 90Hz. The flicker fusion threshold is a relatively fluid and multivariable equation and most people stop noticing flicker in most circumstances at around 90Hz but a significant proportion can still notice it up to 120Hz in some circumstances. https://en.wikipedia()org/wiki/Flicker_fusion_threshold

Fluorescent lighting with strobing at 100Hz or 120Hz is associated with often subconscious discomfort as found by a variety of studies. DOI: 10.1080/001401398186928

Especially in VR, higher brightness with HDR displays as well as increased FOVs, duty cycle characteristics, and even the wavelengths of light can make flicker significantly more noticeable than a phone display or computer monitor.

Most VR headsets unfortunately run at 90Hz; even recently released high end headsets like the Apple Vision Pro, Bigscreen Beyond, and MeganeX 8K. Those devices, as well as the Quest 2 & 3, often run below that rate for various types of content.
The quest often runs at 72Hz for natively rendered content and that's well within the flicker range.

strobed-display-image-duplicates.png (155.68 KiB) Viewed 609 times

Even with high refresh rates and reprojection, temporal issues remain. 480Hz with strobing and reprojection on 60FPS content for example would be a big improvement over PSVR running at 120Hz with 60FPS content but both systems would exhibit multiple projection artifacts like those shown above.

Ultimately the solution is going to have to be either or both a high framerate input and interpolation/extrapolation.
Without interpolation, if a 60FPS input is fed into a full persistence (un-strobed) 1000Hz VR display with the best depth reprojection and disocclusion filling, camera movement will be essentially artifact free but any non-camera object movement will be stuck with all the artifacts of 60FPS/Hz.

I don't see any application of CRT emulation in VR outside of recreating a virtual living room (where only the virtual CRT would have it) or for artistic/experimental purposes.
That said, there's definitely applications on flat displays even outside of those use cases.