Question before I buy LG C9 – does custom resolution + custom refresh rate + G-Sync work?

[Pabaisa]

Hi, I'm pretty much set on buying LG C9 55' as my pc ultrawide display but I am unable to find whether E9/C9/B9 accepts custom refresh rates and does G-Sync work with those custom refresh rates (I know it accepts custom resolutions)?
I will set it to ultrawide resolution - 3860x1600 (or 1440, no scaling obviously; will see what screen height my eyes will be comfortable with) but I would love to set a higher refresh (in accordance with my GPU HDMI 2.0 bandwidth limitations) and still use G-Sync. Thanks.

 

[kasakka]

You cannot get more than 3840x1600 @ 60 Hz unless you have a HDMI 2.1 GPU. With HDMI 2.1 GPU 3840x1600 @ 120 Hz should be possible.

You need to set it to use GPU scaling so the display will think it gets 3840x2160 output when really the GPU outputs 3840x1600 with black bars. The built-in display scaler does not support custom resolutions.

 

[Monstieur]

Custom resolutions generally do not work on modern TVs with low latency - their ASIC signal processors can only handle fixed resolutions, refresh rates, and colour formats. e.g. The C9 doesn't support 4K 120 Hz 8-bit YCbCr420 even though it's within HDMI 2.0 bandwidth, but the CX does. It probably won't support a custom resolution of 4K 90 Hz with any colour format either, though there is enough bandwidth. There are exceptions on some models, like a custom resolution of 1440p 120 Hz which the EDID didn't expose but was supported by the hardware.

Whenever someone claims a custom resolution works, it's actually the GPU silently using the nearest compatible resolution and cropping / scaling the image.

 

[kasakka]

Custom resolutions generally do not work on modern TVs with low latency - their ASIC signal processors can only handle fixed resolutions, refresh rates, and colour formats. e.g. The C9 doesn't support 4K 120 Hz 8-bit YCbCr420 even though it's within HDMI 2.0 bandwidth, but the CX does. It probably won't support a custom resolution of 4K 90 Hz with any colour format either, though there is enough bandwidth. There are exceptions on some models, like a custom resolution of 1440p 120 Hz which the EDID didn't expose but was supported by the hardware.

Whenever someone claims a custom resolution works, it's actually the GPU silently using the nearest compatible resolution and cropping / scaling the image.

With GPU scaling you can run pretty much any lower resolution, to the display it will show up as if it is getting 16:9 4K afaik. But since we don't have HDMI 2.1 GPUs yet, the max refresh rate with the C9 and CX is 60 Hz if you want to run say 3840x1600.