Discorz wrote: ↑23 Nov 2021, 06:46
Can VTs be pushed further at 240Hz? If yes would it make any difference compared to factory 240 VTs?
Successful large VTs at max Hz is very rare on any panel.
This is because large VT (QFT) simply pushes low-Hz to max-Hz scanout velocity (e.g. 120Hz refresh cycles scanned out in 1/240sec).
The fastest a refresh cycle can occur on a XG2431 is approximately 4ms scanout. The XG2431 scaler/tcon is capable of refreshing 270000 pixel rows per second (270KHz horizontal scan rate). So it can refresh one refresh cycle in 1080/270000ths of a second -- that's 0.004 second -- 4 milliseconds (a little under 1/240sec). This is based on a 1080-pixel row signal in a 1125-pixel-row signal transport (1080 visible, 45 blanking). QFT modes with Large Vertical Totals simply allows a lower-Hz to have the scanrate of max Hz.
Not all pixels on an LCD refresh at the same time, it takes 4ms from the first pixel to last pixel to refresh. That's much faster than a 60Hz LCD, as filmed in high speed video at
www.blurbusters.com/scanout
The fastest you can scanout the Innolux 240Hz panel is about 1080/270000ths of a second, regardless of Hz and QFT mode you create. So that's your essential theoretical maximum. So you can have a 4ms scanout at any Hz with the best possible QFT mode. For example, 4ms scanout at 60Hz means your LCD has lots of time to finish LCD GtG pixel response between refresh cycles. But at 240Hz, you literally only have less than 0.2 milliseconds of headroom between refresh cycles, unlike about ~13 milliseconds of headroom between refresh cycles at 60Hz, and ~8.5 milliseconds of headroom between refresh cycles at 120Hz.
Thus, that's why strobe crosstalk decreases more, the lower Hz you can go. You've got more headroom to create a larger blanking interval (pause between refresh cycles).
The world's first perfect zero-crosstalk strobed LCDs were only finally achieved recently; not a single faint duplicate image. With a full tuning, the XG2431 manages to have less crosstalk than NVIDIA LightBoost (a gold standard in low-crosstalk strobing), when tuned to the maximum with QFT and Strobe Utility, combined with a 120Hz-or-less mode. And do it without the color degradation of LightBoost. Even a CRT-like color gamut is preserved (with the exception of poorer blacks of LCDs versus CRT). Zero crosstalk at screen center, and ultra faint crosstalk at top/bottom that disappears the lower Hz you go.
Stock 60 Hz can't go zero crosstalk this because it's not a QFT mode, it slow-scans in (1080/1125)ths of 1/60sec (pretty much a bit above 16ms to scanout). But using QFT 60Hz (Vertical Total 4500) goes perfect zero crosstalk top/center/bottom after a good Strobe Utility tuning session at
www.blurbusters.com/xg2431
Incidentially, it is also how Quest 2 VR LCD and a Valve Index VR LCD does it; it does an accelerated low-latency scanout at low-Hz (like a large vertical total). It is likely a ~240Hz-ish LCD being underclocked to 72Hz, but now has a 90Hz and 120Hz mode via firmware update (with improved strobe tuning that made higher Hz possible).
Modern 1ms LCDs (IPS and TN) with approximately a 3:1 refresh rate headroom (e.g. 240Hz LCD underdriven at 75Hz) can go perfect zero crosstalk top/center/bottom better than LightBoost, with proper tuning.
With QFT modes, crosstalk can fall far below 1% and become perfect zero crosstalkless.
The XG2431 achieves less than 1% crosstalk when you use Strobe Utility + QFT Mode + Refresh Rate Headroom + Framerate=Hz. You have to combine all the possible tricks documented at
www.blurbusters.com/xg2431 in order to pull off the perfect crosstalkless strobed LCD mode that you cannot achieve on any other gaming monitor.
Generaly this occurs in the 60Hz-80Hz region, but 100Hz-120Hz can get under 1% crosstalk for screen centre if you warm up for an hour first and tune expertly on a VT2250 QFT mode (120Hz) or VT2700 QFT mode (100Hz), there will still be faint crosstalk (typically under ~10%) for top/bottom that completely disappears at ~80Hz and less.
Choose your refresh rate headroom based on how quality-priority strobing you want to do.
In my opinion, if your game can do above 60fps, then using 120Hz is the sweet spot, but 100Hz can make it easier to do framerate=Hz in more games.