G-Sync and ULMB at the same time is in fact possible!

Motion blur eliminating strobe backlights found in gaming monitors. This includes NVIDIA LightBoost, Ultra Low Motion Blur (ULMB), EIZO Turbo240, ToastyX Strobelight utility, etc.

Re: G-Sync and ULMB at the same time is in fact possible!

Postby cskippy » 05 Apr 2017, 02:29

Just to check, this only works with the Dell Gsync monitors and Benq Gsync monitors? I've tried on my Acer XB270HU and it doesn't work, but it's firmware limits ULMB to 100Hz not 120.
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Re: G-Sync and ULMB at the same time is in fact possible!

Postby Chief Blur Buster » 09 Apr 2017, 21:47

AFAIK, it is not certain which monitors can be hacked to do strobing and GSYNC at the same time. Probably only the 120Hz+ ones.
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Re: G-Sync and ULMB at the same time is in fact possible!

Postby RealNC » 20 Apr 2017, 16:30

Just tested on a ViewSonic XG2703-GS. It works with +5 VT. I added +5 to the existing resolutions (2560x1440 at 120Hz and 100Hz) to test.

The monitor single-strobed down to 38Hz (RTSS 38FPS cap). Huge flicker at that refresh rate, obviously. From 37Hz and below, it starts to double-strobe and the flicker goes away. But there's a double-image effect, obviously.

The lower the Hz get, the more severe the crosstalk gets. Also, crosstalk is higher than non-hacked ULMB at the same refresh. Meaning G-Sync+ULMB @ 85Hz has more crosstalk than stand-alone ULMB 85Hz. But it's not too bad at 85 and up. At 60Hz, it's too severe to be usable. Maybe this is tweakable?

The brightness is mostly stable, but sometimes a black frame will "flash" in when FPS fluctuates.

So even though it works, it's not that useful in games that can't keep rock-solid frame times. If there's a spike or dip, a black frame appears.
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Re: G-Sync and ULMB at the same time is in fact possible!

Postby hammelgammler » 20 Apr 2017, 18:03

Can you tell me how you got it to work RealNC? I have an Acer XB271HU, it maybe works the same like on your ViewSonic. I would love to try that out.
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Re: G-Sync and ULMB at the same time is in fact possible!

Postby RealNC » 20 Apr 2017, 18:26

hammelgammler wrote:Can you tell me how you got it to work RealNC? I have an Acer XB271HU, it maybe works the same like on your ViewSonic. I would love to try that out.

First, switch to a refresh rate other than 120Hz. Like 144 or 100. Then:

  1. Then run CRU. Find the entry for 2560x1440@120Hz. It's probably in the extension block (the box at the bottom.) Double click the extension block entry. Once you find the 2560x1440@120Hz entry, double click it. A dialog will open that looks like this:
    https://www.blurbusters.com/wp-content/ ... astyx.jpeg
  2. Click the "Total" radio box (the "round button" that says "Total" next to it.) Then in the second column (labelled "Vertical" at the top), add 5 to the number you see there. If for example it's 1525, make it 1530. Whatever it is, just add 5.
  3. Click OK on everything until CRU closes.
  4. In the NVidia panel, disable G-Sync. Close the NVidia panel.
  5. In the CRU directory, run "restart.exe".
  6. Open the nvidia panel and select 120Hz.
  7. In the monitor's OSD, enable ULMB.
  8. In the nvidia panel, enable G-Sync.
  9. In the "3D settings" in the nvidia panel, make sure the "preferred refresh rate" setting is "application preference", otherwise games will automatically switch to 144Hz where this hack doesn't work.
That's it. You should now still be in ULMB mode even though you enabled g-sync. If you start a game and make sure 120Hz is used, you should get G-Sync+ULMB.

Once you've had your fill and discovered that this mode is a cool hack but rather useless ( :mrgreen:), reset everything back to normal by running "reset-all.exe" and reboot the computer. You'll be back to normal.
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Re: G-Sync and ULMB at the same time is in fact possible!

Postby Chief Blur Buster » 20 Apr 2017, 19:18

RealNC wrote:The lower the Hz get, the more severe the crosstalk gets. Also, crosstalk is higher than non-hacked ULMB at the same refresh. Meaning G-Sync+ULMB @ 85Hz has more crosstalk than stand-alone ULMB 85Hz. But it's not too bad at 85 and up. At 60Hz, it's too severe to be usable. Maybe this is tweakable?

This is quite a shame that strobe phase isn't ideally aligned. Or it's the variable overdrive that GSYNC uses -- that wreaks havoc with strobe crosstalk.

I imagine this is a hidden "beta mode" of the monitor that NVIDIA left in, for experimentation. If only there were hidden settings to tweak the variable overdrive to be more strobe-friendly.

Is strobe crosstalk still bad if you adjust the ULMB Pulse Width down -- to half it was?

RealNC wrote:Once you've had your fill and discovered that this mode is a cool hack but rather useless ( :mrgreen:), reset everything back to normal by running "reset-all.exe" and reboot the computer. You'll be back to normal.
Not useless -- just extremely finicky.

A range of 85-120Hz is really tight for comfortable GSYNC strobing. It'd be far more useful if it was a 240Hz strobe mode with a 60Hz-240Hz VRR range, or some kind of a fade-to-nonstrobing algorithm (like the ones I wrote about in 2013).

In theory, it is also a very useful 60Hz single-strobe ULMB mode, if you use an emulator.

It's one of the only ways to get "60Hz single-strobe ULMB". It's occasionally a challenge to trick things like emulators to run in GSYNC mode, but several of them work that way -- and this ULMB+GSYNC trick is in theory good way to get 60Hz single-strobe ULMB.

Also if you simply treat this ULMB+GSYNC as a 120Hz strobe mode that doesn't stutter when framerates dip down to ~100fps or ~85fps, this can be useful.
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Re: G-Sync and ULMB at the same time is in fact possible!

Postby RealNC » 21 Apr 2017, 02:21

Chief Blur Buster wrote:It's one of the only ways to get "60Hz single-strobe ULMB". It's occasionally a challenge to trick things like emulators to run in GSYNC mode, but several of them work that way -- and this ULMB+GSYNC trick is in theory good way to get 60Hz single-strobe ULMB.

Black frame insertion is superior in this case. 60FPS MAME + 120FPS BFI + 120Hz strobe works better. It's somewhat dim (since you lose brightness twice), but you get zero crosstalk.

It's like viewing this:

http://www.testufo.com/#test=blackframes

on 120Hz ULMB. The bottom UFO is super-clear, but quite dim. You need 100% brightness + 100% ULMB pulse width. If your monitor has a strong backlight (fortunately, many monitors do), it's quite usable.

What I'm REALLY looking forwards to now is OLED + G-Sync, given the initial results in the Dell thread. Good things are coming!
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Re: G-Sync and ULMB at the same time is in fact possible!

Postby hammelgammler » 21 Apr 2017, 09:08

RealNC wrote:
hammelgammler wrote:Can you tell me how you got it to work RealNC? I have an Acer XB271HU, it maybe works the same like on your ViewSonic. I would love to try that out.

First, switch to a refresh rate other than 120Hz. Like 144 or 100. Then:

  1. Then run CRU. Find the entry for 2560x1440@120Hz. It's probably in the extension block (the box at the bottom.) Double click the extension block entry. Once you find the 2560x1440@120Hz entry, double click it. A dialog will open that looks like this:
    https://www.blurbusters.com/wp-content/ ... astyx.jpeg
  2. Click the "Total" radio box (the "round button" that says "Total" next to it.) Then in the second column (labelled "Vertical" at the top), add 5 to the number you see there. If for example it's 1525, make it 1530. Whatever it is, just add 5.
  3. Click OK on everything until CRU closes.
  4. In the NVidia panel, disable G-Sync. Close the NVidia panel.
  5. In the CRU directory, run "restart.exe".
  6. Open the nvidia panel and select 120Hz.
  7. In the monitor's OSD, enable ULMB.
  8. In the nvidia panel, enable G-Sync.
  9. In the "3D settings" in the nvidia panel, make sure the "preferred refresh rate" setting is "application preference", otherwise games will automatically switch to 144Hz where this hack doesn't work.
That's it. You should now still be in ULMB mode even though you enabled g-sync. If you start a game and make sure 120Hz is used, you should get G-Sync+ULMB.

Once you've had your fill and discovered that this mode is a cool hack but rather useless ( :mrgreen:), reset everything back to normal by running "reset-all.exe" and reboot the computer. You'll be back to normal.


Dude thanks, I got it to work via the Control Panel, no need to use CRU. Works as intended in Overwatch.

But there's some severe flickering, even when having MIN FPS of 0.1% = 110, 1% = 160, AVG = 240. I limited the FPS to 115, but there's still some flickering which isn't that nice on the eyes. Any way to reduce that, or is it the variable Overdrive that got mentioned? This mode would be extremely nice without that "black-flicker-flash"-thing.

Do we need a complete 100% stable 115 FPS without any variation (114-116 or so) to get no artifacts?
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Re: G-Sync and ULMB at the same time is in fact possible!

Postby Chief Blur Buster » 21 Apr 2017, 10:40

Wow, more displays are being confirmed.
"Strobed VRR Hack" aka "ULMB+GSYNC" confirmations:

Confirmed ULMB+GSYNC Hack:
-- Dell SD2716DG
-- Acer XB271HU
-- ViewSonic XG2703-GS

Any other displays that are confirmed? I tried this trick (both the Resolution-off-by-a-few trick, and VT-off-by-5 trick) on the ASUS ROG PG278Q to no success, but I suppose this is a hidden feature inside newer GSYNC monitors.

Being an "early beta" unrefined strobe with a tight usable range (overdrive not optimized, strobe phase not optimized, too much flicker at lower end, and slams against the 120Hz limit) it probably is only useful for games that "usually runs near 120fps, but you don't want stutters in the occasionl drops to 85fps-100fps range" situations.

I will be writing a new BlurBusters HOWTO on the ULMB+GSYNC trick, but we need more confirmations.
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Re: G-Sync and ULMB at the same time is in fact possible!

Postby Chief Blur Buster » 21 Apr 2017, 10:41

hammelgammler wrote:Do we need a complete 100% stable 115 FPS without any variation (114-116 or so) to get no artifacts?

Not 100% stable. Just smooth modulations between framerates. Reportedly, Dell SD2716DG (at least) doesn't flicker if it smoothly modulates from 115fps->114->113->112->111->110->111->112->113->114->115fps as an example. Sudden framerate modulations will flicker and show artifacts, however.

It is very game-dependant, and MAY also be monitor-dependant.

It's probably most useful in situations where you're using ULMB/LightBoost anyway and have a consistent maximum framerate 90% of the time, but you want to improve that "other 10% of time" situation -- and the game has very smooth consistent frametimes that doesn't modulate too erratically too often. A single stutter (ULMB only) is a lot more noticeable than a brief drop to 119fps-118fps (ULMB+GSYNC), so you simply use ULMBZ+GSYNC for your "ULMB" situations (high-consistent framerates) rather than your "GSYNC" situations (low & hugely varying framerates). Used properly, some are saying ULMB+GSYNC looks good -- at least on certain monitors.

Helps a lot if you have a lower-latency SSD (especially the new PCI Express variants, such as M.2 NVME ones) and nothing significant runs in the background -- you need those HDD-access stutters lowered to the absolute minimum. Mondoo memory for caching (16GB, 32GB DRAM etc) and games installed on SSD. Things like turning against a wall to detailed scenery usually as smooth framerate modulations -- but a single HDD access will give you sudden framerate changes. Eliminate that, and the unoptimized ULMB+GSYNC becomes more bearable.

This will get better in future, as there's flicker-elimination logic found in NVIDIA's patents not yet currently used with this ULMB+GSYNC hack.
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