Zace wrote: ↑30 Nov 2021, 17:51
do you need qft on 240hz too?
Easy Answer:
Quick Frame Transport (QFT) is optional. It is useful for reduced input lag and reduced crosstalk for below maximum refresh rates (below 240Hz). For example, getting a 60Hz or 120Hz mode with the low input lag of 240Hz. QFT is not needed for full 240Hz.
Due to panel temperature / lottery / variances, you can still get strobe quality improvements (better than factory) via Strobe Utility without using QFT. Just remember to warm up your monitor for at least 30-60 minutes before using Strobe Utility. Warmer LCDs have faster LCD GtG pixel response than cold LCDs, especially in the winter.
(end of easy answer)
Long Advanced Answer:
Quick Frame Transport (QFT) refers to the speed of frame transmission on the video cable (which is also synchronized to scanout velocity on an Innolux 23.8" panels).
It is mainly better for below-max-Hz mode, because QFT accelerates a low-Hz mode to deliver refresh cycles at max-Hz velocity (e.g. 120Hz refresh cycles transmitted over the video cable in 1/240sec). In general, don't bother with QFT at 240Hz -- it mainly benefits less-than-240Hz modes. A 240Hz refresh cycle can't refresh faster than 1/240sec, but the XG2431 supports refreshing any low-Hz mode (e.g. 120Hz) at max-Hz velocity of 1/240sec.
Faster refreshing per refresh cycle creates a longer idle time between refresh cycles, to more easily hide LCD GtG pixel response in total darkness between refresh cycles, to make possible crosstalk-free strobing at low Hz. The world's first zero-crosstalk LCD operation needs to use these technique to hide real-world LCD GtG100% in a super-long VBI. Very few LCDs on the market can do this, such as Valve Index VR LCD, Oculus Quest 2 VR LCD, and the ViewSonic XG2431 LCD (via <120Hz + QFT + Strobe Utility re-tuning).
QFT means a 120Hz refresh cycle can be painted onto the XG2431 panel in just 1/240sec (about 4ms). This means the panel can idle for 4ms between refresh cycles in total darkness before the strobe backlight flash. This is long enough to let most pixels reach GtG100% for zero-crosstalk strobing, hiding LCD GtG limitations away from human eyes. Lower Hz allows more idle time between refresh cycles, so lower Hz will be easier go crosstalk-free.
It is not possible to create QFT modes via GMT, CVT, CVT-R timings formulas. QFT requires a custom EDID formula, that monitor manufacturers currently usually do not use (yet), but is now possible via a Custom Resolution Utility. Eventually I hope to convince future manufacturers to add a "Quick Frame Transport ON/OFF" setting in monitor menus (EDID swap behavior, similar to FreeSync ON/OFF), so people don't have to use ToastyX or Custom Resolutions to create QFT modes. This would be 100% true plug-and-play QFT.
But today, for now, QFT requires the creation of a Custom Resolution (same visible resolution, but much bigger blanking interval).
(end of long advanced answer)