LFC and freesync/gsync broken after monitor wakes up or when power cycling the monitor

Talk about AMD's FreeSync and VESA AdaptiveSync, which are variable refresh rate technologies. They also eliminate stutters, and eliminate tearing. List of FreeSync Monitors.
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christizzz
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LFC and freesync/gsync broken after monitor wakes up or when power cycling the monitor

Post by christizzz » 10 Oct 2020, 13:19

So after 2 threads on nvidia and on monitors. and several testing with other users... I can confirm that LFC IS broken on the LG- 27GL850.

LFC will break after power cycling the screen or waking the screen from sleep.So LFC is Low Frame Compensation... It is a solution for freesync monitors ( gsync compatible monitors) to get smooth experience when the Frames drops below the refresh rate range of the monitor. it is implemented in the driver.

The LG 27GL850 has range of 48Hz-144Hz

A practical example like the videos i provided: https://drive.google.com/file/d/14TlVhy ... sp=sharing

another video this time showing tearing https://drive.google.com/file/d/15CoMyz ... sp=sharing



When LFC is working correctly:
  • 40FPS will make the screen refresh at 80Hz: smooth and No tearing

    50Fps will make the screen refresh at 100Hz: smooth and No tearing

    70Fps is already smooth so LFC will disable and the screen will refresh at 70Hz: smooth and No tearing
When LFC is NOT working correctly ( in this case after power cycling the monitor OR waking the monitor from sleep, the driver of GPU breaks LFC)
  • 40FPS will make the screen refresh all over the place like in my video : Not smooth and visible tearing

    50Fps will make the screen refresh at 50Hz: smoothish and No tearing

    70Fps will refresh at 70Hz: smooth and No tearing
you can see that dropping below the 48FPS ( which is the limit of the monitor)..it no longer activate LFC...

The only way to solve this is to reboot OR to change the refresh rate of the screen from 144 to 120 and then back 144...

the LFC will be broken again as soon the monitor will power cycle or go to sleep.

I saw a lot of forums with this problem and thats a freesync + nvidia issue... not specific to my monitor but specific to gsync compatible monitors in general. I confirmed with several users on discord.

https://www.reddit.com/r/ultrawidemaste ... nc_issues/

https://forums.eagle.ru/showthread.php?t=230498

https://www.nvidia.com/en-us/geforc...- ... rced-to-r/



it doesnt have a lto of coverage because the Gsync will be working but not as intended with the LFC...

when LFC breaks , stutter and tearing will appear when out of range.


like in one of the threads, i created a BAT file that cyclce the refresh rate from 144 to 120 and back to 144 in order to reset the LFC and make it work again without rebooting the PC..


Maybe some users with 10XX can test this if they have a gsync compatible monitor...
thanks




regards

Christian
Last edited by christizzz on 15 Oct 2020, 07:37, edited 4 times in total.

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jorimt
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Re: LFC and freesync/gsync broken after monitor wakes up or when power cycling the monitor

Post by jorimt » 10 Oct 2020, 14:27

christizzz wrote:
10 Oct 2020, 13:19
Hello,

i got the LG monitor recently.
Monitor model?
(jorimt: /jor-uhm-tee/)
Author: Blur Busters "G-SYNC 101" Series

Display: Acer Predator XB271HU OS: Windows 10 Pro MB: ASUS ROG Maximus X Hero CPU: i7-8700k GPU: EVGA GTX 1080 Ti FTW3 RAM: 32GB G.SKILL TridentZ @3200MHz

christizzz
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Re: LFC and freesync/gsync broken after monitor wakes up or when power cycling the monitor

Post by christizzz » 10 Oct 2020, 14:34

oops sorry...its the LG 27GL850-B

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jorimt
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Re: LFC and freesync/gsync broken after monitor wakes up or when power cycling the monitor

Post by jorimt » 10 Oct 2020, 14:44

christizzz wrote:
10 Oct 2020, 14:34
its the LG 27GL850-B
Hmm, it is on the official G-SYNC Compatible support list. So it rules out any issues due to that.

I was going to recommend you roll back a couple driver versions, as there were some G-SYNC Compatible driver issues recently, but then you've mentioned you've gone back four, which should be plenty (FYI, that particular model was first supported on the 430.86 driver if you want to try that one just to rule the driver out).

So either the issues you are experiencing are specific to your monitor model (be it from undocumented OS or GPU driver quirks), or you possibly have a faulty unit (doubt it). Although I will say if this is only occurring when you power cycle the monitor during G-SYNC operation in a supported app, the use case is relatively fringe; how many users would actually do this on a regular basis? Possibly a reason this bug hasn't been caught.

Does this also happen when it power cycles/sleeps on the desktop? And does it happen when the monitor goes into standby on its own, or only when you manually power it on and off?

Hopefully other users with the same monitor model will chime in and report back so you can compare. You should also send a driver bug report to Nvidia if you haven't already:
https://docs.google.com/forms/d/e/1FAIp ... A/viewform
(jorimt: /jor-uhm-tee/)
Author: Blur Busters "G-SYNC 101" Series

Display: Acer Predator XB271HU OS: Windows 10 Pro MB: ASUS ROG Maximus X Hero CPU: i7-8700k GPU: EVGA GTX 1080 Ti FTW3 RAM: 32GB G.SKILL TridentZ @3200MHz

christizzz
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Joined: 14 May 2020, 07:52

Re: LFC and freesync/gsync broken after monitor wakes up or when power cycling the monitor

Post by christizzz » 11 Oct 2020, 13:08

Thank you for your reply... i tried the old first driver that added freeesync compatibility... it didnt help :(
searching the internet...i found a lot of problems regarding to gsync not working properly on freesync monitors after the monitor wake up from sleep ( not windows just the monitor)... i already sent mails to nvidia but still no replies whatsoever... this needs to be escalated somehow...

to be precise... power cycling the monitor will not break Gsync... it will break LFC....

on a fresh boot, the pendulum test at 40 FPS will show me 80Hz --> gsync indicator On
power cycling the monitor, the pendulum test at 40FPS will show refresh rates all over the place 49-144hz --> Gsybc indicator is ON ( forcing 50Fps..will show 50Hz so gsync is defintely working but the LFC got broke)

the only way i found that takes less time than a reboot is i wrote a BAT fil that chnages the refresh rate from 144 to 120 abd back 144,,,this will fix the LFC until the monitor sleeps again...

I saw another thread with an MSI monitor and Asus monitor both Gsync COmpatible... i dont know how to esacalte this to nvidia..

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jorimt
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Re: LFC and freesync/gsync broken after monitor wakes up or when power cycling the monitor

Post by jorimt » 11 Oct 2020, 14:03

christizzz wrote:
11 Oct 2020, 13:08
i dont know how to esacalte this to nvidia..
The Display Driver Feedback Form I linked is the closest you can get to contacting Nvidia directly regarding this.

Alternately, Manuel Guzman, a rep for the Nvidia driver team, regularly monitors the pinned threads on the below forum, so you can try to make a post about that in one of those existing threads there:
https://forums.guru3d.com/forums/videoc ... ection.21/

Beyond that, I have no direct contacts at Nvidia, and while I understand your issue, there's probably no user-side fix possible, and it would have to be addressed on the driver-side by their team.
(jorimt: /jor-uhm-tee/)
Author: Blur Busters "G-SYNC 101" Series

Display: Acer Predator XB271HU OS: Windows 10 Pro MB: ASUS ROG Maximus X Hero CPU: i7-8700k GPU: EVGA GTX 1080 Ti FTW3 RAM: 32GB G.SKILL TridentZ @3200MHz

Armadillo
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Re: LFC and freesync/gsync broken after monitor wakes up or when power cycling the monitor

Post by Armadillo » 12 Oct 2020, 13:23

christizzz wrote:
10 Oct 2020, 13:19
Hello,

i got the LG 27GL850-B monitor recently. the monitor is good but i noticed some weird behavior regarding refreah rate. So the monitor has a range of 48-144. LFC triggers sooner on the monitor, around 60fps (120hz). When power cycling the monitor this LFC range drops to 48 and doesnt seem to work correctly...when FPS drops below 48..it doesnt double. so when fps lets say is 40 the refresh rate will be like 65 or so.

Testing methodology:

I did the tests in some games but mainly in the Pendulum test of Nvidia:

*restart pc

*Start pendulum and force the fps to 50fps: VRR will show 110Hz

*Turn screen off and then back on VRR will show 50Hz and Gsync is broken ( tearing will appear)

*Turn Gsync off and then On (in nvidia control panel) The VRR will show 110Hz again and no tearing will appear


Someone with this monitor can try the steps i wrote above and pls confirm this ?

I tried the last 4 nvidia drivers with DDU... GPU: evga gtx 1070 ftw tried 2 different display ports cables

LFC and freesync are still broken since the first freesyc drivers.... waking the screen up break gsync...

i made a video: https://drive.google.com/file/d/14TlVhy ... sp=sharing
Not the monitor, must be a driver bug.


I don't have a solution, but the exact same thing happens on my monitor (Acer XV253QP).

It's not on the official compatablity list yet, but is validated in 456.71 (list on Nvidia's site doesn't go up to that driver yet). Anyway it behaves exactly the same.

After first boot, lfc is working fine and engages at 60fps and starts doubling the hz. After the monitor goes to sleep and wakes back up, lfc stops working. G-sync is working fine, only lfc breaks.

Turning G-sync off, then back on in control panel will make lfc work again, until another power cycle.

The behaviour has been consistent since I got the monitor across mulitple driver versions. I never bothered to chase it, I just assumed it was a quirk of the monitor and I don't really use lfc as most of the time my fps is >60.

Don't have a fix, just thought I'd let you know, it's not the monitor, must be a driver bug.

christizzz
Posts: 12
Joined: 14 May 2020, 07:52

Re: LFC and freesync/gsync broken after monitor wakes up or when power cycling the monitor

Post by christizzz » 13 Oct 2020, 11:32

thanks...i came here after i saw your thread on reddit... yes i think it is a driver issue witht he pascal cards... a user with a 3090 said it is working with him... and another with a 2070s saisd it is also working...i dont know how to escalate this to nvidia... i wrote to support ...but its still the same standard answers...

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