Ghosting/high response time improvement for a laptop?

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jayloofah
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Joined: 24 Mar 2021, 09:48

Ghosting/high response time improvement for a laptop?

Post by jayloofah » 24 Mar 2021, 09:57

First time posting here!

There are well known ghosting issues with some of the recent panels used by Lenovo for their Thinkpad series. They're basically on the edge of what is passable for modern hardware response rates and have pretty severe ghosting as a result.

I was wondering if there is any way to modify/hack the display driver of a laptop to potentially reduce this response time. I'm quite new to this but from browsing some of this forum, it looks like it might be a possibility? Thanks!

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Re: Ghosting/high response time improvement for a laptop?

Post by Chief Blur Buster » 24 Mar 2021, 16:37

Overdrive can provide significant ghosting reductions to many laptop LCDs but can consume huge amounts of battery power.
Normally it is done in the monitor panel, but it can be done as a GPU shader.
Many laptop panels omit overdrive to save battery power.

On the market?
No easy options at all, unfortunately, other than upgrading to a higher Hz laptop LCD. Extra Hz can compensate for lack of improved overdrive. Some panels skip overdrive to save battery power. For example, 240 Hz laptop LCDs will have about one-quarter the ghosting of 60 Hz laptop LCDs, even for "inferior overdrive versus inferior overdrive". (Even though desktop 240Hz and desktop 60Hz is sometimes slightly clearer relative to their laptop equivalents, due to better overdrive, a 120Hz laptop screen will have less ghosting than a 60Hz desktop screen. So purchasing extra Hz for a laptop screen can be done for ergonomic purposes too -- a Razer 240 Hz laptop is a pleasure to do browser scrolling on, for example -- with half the motion blur of a 120Hz iPad!).

Theoretically?
Assuming the GPU has enough power, it's possible to implement overdrive as a GPU shader. But it has to be done as refresh-cycle-processing, rather than frame-processing. Meaning a virtual display driver, not a frame presentation hook (like RTSS or SweetFX etc). Meaning even if the game frame rate is only 20fps, overdrive processing should only be done between adjacent refresh cycle pairs (i.e. the last refresh cycle of a previous frame, and the first refresh cycle of a new frame). Frame-based overdrive processing doesn't work well. There's a discussion thread about this. Be noted that LCD overdrive can be algorithmically complex yet otherwise simple as a lookup table for a fixed-Hz screen at a known temperature (such as 20C).
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