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CONFIRMED: G-SYNC includes LightBoost sequel. (nVidia sanctioned, no hack)

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Mark Rejhon

Senior member
Dec 13, 2012
273
0
71
Good news for people who want "LightBoost" style strobing at other refresh rates, to reduce GPU requirements (85fps @ 85Hz) or to reduce input lag (144fps @ 144Hz).

G-SYNC's optional superior sequel to LightBoost (optional fixed-rate strobe mode) actually supports strobing at 85Hz and at 144Hz (at least), in addition to existing LightBoost modes (100Hz and 120Hz).

Clues:

  1. The G-SYNC upgrade datasheet has 85Hz added.
  2. AndyBNV suggested on NeoGAF the low-persistence mode is superior to LightBoost.
  3. The YouTube video of John Carmack at G-SYNC launch, was very suggestive.
  4. Many articles mentions 85Hz as a CRT frequency that stops flickering for many people.
  5. The pcper.com livestream suggests a very high fixed refresh in low-persistence mode.

Upon analysis, both 85Hz and 144Hz are available strobed modes with G-SYNC, in addition to 100Hz and 120Hz.
You heard it first from me.
 

BrightCandle

Diamond Member
Mar 15, 2007
4,762
0
76
I am kind of disappointed that the low persistence mode is based on a fixed refresh rate. I appreciate there are many challenges in making it work well at variable refresh but I hope in a future release we see them try to do that. Low persistence, high frequency and variable refresh is a combination of technologies that has real potential to remove the problems with LCDs in high speed motion.

I don't think the combination of clues confirms 85 and 144hz for lightboost, they haven't yet said much on the topic at all. The 85hz from the datasheet might very well just come from their module, which basically overrides the entire input (it takes display port in). They may have just added 85hz as there was a big gap. But If that is all they have done to enhance over lightboost I am a surprised that they considered that vastly better. Based on Tom's comments its more than that, I sure hope it is.
 

Mark Rejhon

Senior member
Dec 13, 2012
273
0
71
I am kind of disappointed that the low persistence mode is based on a fixed refresh rate. I appreciate there are many challenges in making it work well at variable refresh but I hope in a future release we see them try to do that. Low persistence, high frequency and variable refresh is a combination of technologies that has real potential to remove the problems with LCDs in high speed motion.

I don't think the combination of clues confirms 85 and 144hz for lightboost, they haven't yet said much on the topic at all. The 85hz from the datasheet might very well just come from their module, which basically overrides the entire input (it takes display port in). They may have just added 85hz as there was a big gap. But If that is all they have done to enhance over lightboost I am a surprised that they considered that vastly better. Based on Tom's comments its more than that, I sure hope it is.
It's more than that, from what I can gather from limited information. I'm very, very good at analyzing LCD motion blur technologies.
I correctly predicted blur-free LCD's was now scientifically possible mid-2012 using a scanning/strobed backlight, before LightBoost became popular, and embarked upon the project before discovering LightBoost.

There are so many, many ways to improve on LightBoost:
-- Easily enabled via OSD or NVIDIA utility
-- More refresh rates available
-- Better color
-- No gamma bleach
-- Calibrated for direct view 2D, not calibrated for tint of 3D glasses
-- More brightness (brighter strobes)
-- Adjustable persistence (shorter and longer strobes than LightBoost)

I hope they allowed persistence to be adjustable all the way down to 0.25ms or 0.5ms. It's technically possible with a LED edgelight, as the LED phosphor of white LED's was measured to be only about 0.1ms-0.2ms, when people use an oscilloscope+photodiode on a LED backlight. It shows in the TFTCentral oscilloscope measurements. (Note: If using RGB LED's, you can theoretically get down to 1 microsecond persistence on a strobe-backlight LCD on modern panels that can complete GtG's in total darkness between refreshes)
 
Last edited:

bystander36

Diamond Member
Apr 1, 2013
5,154
132
106
Strobe modes adds an average of half a frame of input lag, when looking closely at the high speed video: http://www.youtube.com/watch?v=hD5gjAs1A2s

With a strobe mode, the LCD is refreshed in total darkness, so the flash only happens at the end of the refresh. That means the top of the screen has a full frame of input lag, the center of screen has half a frame of input lag, and the bottom edge of screen has unchanged input lag. Confirmed with my prototype Blur Busters Input Lag Tester.

But, strobe mode actually improves human reaction time (for eye-tracking use cases, such as circle strafing, high speed helicoptor flybys, and other fast panning that requires fast reaction times) because of the lack of motion blur, greatly outweighing the ~4ms of added average input lag, allowing people to score better. You can think of it as a fair tradeoff: In exchange for increasing input lag by half a frame, it decreases human brain lag by more than that.
As I mentioned before, if you do count the time the backlighting is dimmed, then ya, there is some extra delay. The pixels change color the same.

And how you perceive the delay is definitely different.
 

looper

Golden Member
Oct 22, 1999
1,654
10
81
Good stuff. They're finally really promoting a strobe backlight mode now!
I've been trying to reach nVidia. Since Blur Busters is the reason for LightBoost 2D popularity:

[SHAMELESS-PLUG]
If any nVidia employees are reading this, can they refer me to nVidia's PR? I'd like to put Blur Busters on the blogger reporter invite list to future nVidia launch events. Being located in Toronto, Chief Blur Buster is within driving distance of Montreal. Blur Busters would love to attend future launches similar to G-SYNC.
[/SHAMELESS-PLUG]
You deserve it , Mark. You have been very helpful on this topic for a long time.
 

Whitestar127

Senior member
Dec 2, 2011
397
24
81
Good news for people who want "LightBoost" style strobing at other refresh rates, to reduce GPU requirements (85fps @ 85Hz) or to reduce input lag (144fps @ 144Hz).

G-SYNC's optional superior sequel to LightBoost (optional fixed-rate strobe mode) actually supports strobing at 85Hz and at 144Hz (at least), in addition to existing LightBoost modes (100Hz and 120Hz).

Clues:

  1. The G-SYNC upgrade datasheet has 85Hz added.
  2. AndyBNV suggested on NeoGAF the low-persistence mode is superior to LightBoost.
  3. The YouTube video of John Carmack at G-SYNC launch, was very suggestive.
  4. Many articles mentions 85Hz as a CRT frequency that stops flickering for many people.
  5. The pcper.com livestream suggests a very high fixed refresh in low-persistence mode.

Upon analysis, both 85Hz and 144Hz are available strobed modes with G-SYNC, in addition to 100Hz and 120Hz.
You heard it first from me.
Call me when 60fps @ 60Hz is supported. ;)
But seriously, 60fps is the sweetspot for many games. It's not just that this would reduce GPU requirements, but many games are in fact locked at 60Hz.

Can G-sync reduce blur when games run at 60fps or below? Or does it only eliminate stutter?
 
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