Talk about NVIDIA G-SYNC, a variable refresh rate (VRR) technology. G-SYNC eliminates stutters, tearing, and reduces input lag. List of G-SYNC Monitors.
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Post by Bulsac » 20 Jan 2020, 02:15

Hello everybody,

I have had the LG C9 for a week and use it as a monitor on my PC.

The current firmware is also installed and this brings VRR over HDMI.

However, the picture flickers when GSync is activated.

I monitor the frame times using RTSS. The flickering correlates with small frame time spikes. However, these are not so strong that e.g. the GSync range of the TV is undershot (40-120 Hz).

I have tested different HDMI cables, different resolutions, color depths, picture options etc.

You can hardly see the flickering. The flickering is most noticeable in dark scenes. With the cell phone camera, however, the flickering can be seen much more strongly with a 60 fps recording.

The problem seems to be most severe with UE4 games. Tested SW Fallen Order and Insurgency Sandstorm.

PC Specs: RTX 2080 1700X @ 3,9 16 GB RAM and 2 TB Intel 660p NVME

Youtube Link:
GSync is on for the first 10 seconds of the video.
GSync is off in the last 10 seconds.

Is the TV broken or is the flickering normal?

Thank you for your help

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Re: LG OLED 55 C9

Post by Chief Blur Buster » 20 Jan 2020, 14:32

Flicker behaviour during dramatic framerate changes is often an artifact on some (not all) VRR displays.

For LCDs, primary reason is the behaviour of LCD pixels slowly fading (i.e. to white, the default unpowered color on most panels) during longer intervals between refresh cycles. So the pixel color difference may be bigger during short intervals between refresh cycles — versus long intervals between refresh cycles.

For OLEDs, I’m not sure what the flicker mechanism is, but it is possible that there is a very similar mechanism — OLED pixels fading a few percent towards black (default unpowered state) during longer intervals between refresh cycles.

Even a sample-and-hold display is not always perfectly ‘holding’ the static refresh cycle, and the refresh cycle will slightly fade to white or fade to black (Depending on screen technology) during the longer intervals between refresh cycles.

The flicker behaviour would not manifest itself during smooth framerate changes, but during dramatic framerate changes, such as bringing a menu up, or a major spike in

This is normal if the flicker is relatively faint (~1-2%). It would be nice if the flicker behaviour did not exist, but is considered quite subtle.
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       To support Blur Busters:
       • Official List of Best Gaming Monitors
       • List of G-SYNC Monitors
       • List of FreeSync Monitors
       • List of Ultrawide Monitors

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Joined: 20 Jan 2020, 02:02

Re: LG OLED 55 C9

Post by Bulsac » 21 Jan 2020, 01:55

Thank you for the feedback.

I know the behavior of some VRR displays that you described.

In this model, however, it seems extremely pronounced. It gets even worse as soon as HDR is activated in Windows. Here is a 60 fps cell phone camera recording with activated Windows HDR:


However, since no other owner of the LG C9 OLED complains, I have to rule out a defect.

I have now ordered another HDMI cable (although the current should support 48 GBit) and will also test a different graphics card and a different mainboard.


I have now tested the TV on another PC to rule out all possible software and hardware influences.

2nd PC: nVidia 1660, Intel CPU, SATA SSD, 16 GB RAM

I also tested a 48 GBit HDMI "2.1" cable, an HDMI 2.0 cable and some other "unkown" ones. Additionally I tested the VRR at 1080p, so bandwidth shouldn't be a problem for any cable.

The flickering still occurs. I even tested other sockets. I must therefore assume that the television is defective, since no one else is reporting these problems.

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