Hardware support: The LG OLED CX does not work properly with the RTX 3080. It chroma subsamples at 4k 120Hz. G-Sync is completely broken

The LG OLED CX does not work properly with the RTX 3080. It chroma subsamples at 4k 120Hz. G-Sync is completely broken
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The LG OLED CX does not work properly with the RTX 3080. It chroma subsamples at 4k 120Hz. G-Sync is completely broken

Posted: 20 Sep 2020 06:58 AM PDT

Hi,

This post is for everyone who has considered buying an OLED 4k TV from LG to game on with the RTX 3080. I'm not trying to get tech support here but rather try to get attention for this issue so LG or Nvidia will fix this.

I have recently bought an 48" LG OLED CX for the 4k 120Hz HDR gaming experience on the RTX 3080. Since I haven't been able to get a RTX 3080 yet, a friend of mine brought his Zotac RTX 3080 over to my house to test and experience the 4k 120Hz TV. Well... it's been a pretty big disappointment. We experienced the following.

The LG CX will automatically chroma subsample at 4k 120Hz, meaning you will get 4:2:2 instead of 4:4:4. Everything is fine at 4k 60Hz. But at 4k 120Hz we noticed something is wrong with the colors. The chroma subsampling is clearly evident when looking at the borders of dark text. This is not some small issue because it pretty much ruins the 4k 120Hz experience once you notice it.
4k 60Hz, 1440p 120Hz seem to be 4:4:4 with no subsampling.
We researched online and there are numerous reports confirming this chroma subsampling issue at 4k 120 Hz. (sources: https://www.avsforum.com/threads/2020-lg-cx%E2%80%93gx-dedicated-gaming-thread-consoles-and-pc.3138274/page-74, https://hardforum.com/threads/lg-48cx.1991077/page-103) Apparently only the CX models are affected, for the C9 models 4k 120 Hz 4:4:4 is working fine. I couldn't find a single piece of evidence that the LG CX is capable of 4k 120Hz 4:4:4 with an HDMI 2.1 input.
Since other TV models are not affected I doubt this is Nvidia's fault. It more points toward LG's side. When reading through the forums, it looks like this internal downsampling issue of an 4:4:4 input to 4:2:2 has been an issue for months, nothing has been done yet to fix it . It is even questionable if LG is aware of this and whether they will ever fix this.
If this is a software bug and is fixable by LG, this might get fixed if we bring enough attention to it. However, if this is a hardware bug (meaning the LG CX has never been capable of 4k 120Hz 4:4:4 with HDMI 2.1) I highly doubt this will get fixed before PS5 release and release of Cyberpunk 77 (or ever). I have yet to see a single piece of evidence that the LG CX is even capable of 4k 120 Hz 4:4:4 ...
G-Sync is completely bugged. We were forced to turn it off.

Until this issue and the Gsync issue (which is most likely on Nvidia's side and will be fixed with the new driver update) is resolved, do not buy the LG CX if you are expecting a true 4k 120Hz 4:4:4 experience, it is not acceptable with the 4:2:2 issue and you should not spend 1.5k or even 2k+ USD/Euro on this TV until LG has fixed this.

I have found a real image of a LG CX monitor with this issue from another forum that really shows how much a problem the chroma subsampling is (4k 120Hz 10bit, all pictures taken by Sixi82 from the avsforum, I am not taking any credit for them and solely using them to help resolve this issue):

no subsampling:

https://www.avsforum.com/attachments/4k60-jpg.3038320/

https://www.avsforum.com/attachments/img_4723-jpg.3038322/

https://www.avsforum.com/attachments/4k60_1-jpg.3038325/

with subsampling:

https://www.avsforum.com/attachments/4k120-jpg.3038326/

https://www.avsforum.com/attachments/img_4724-jpg.3038327/

https://www.avsforum.com/attachments/4k120_1-jpg.3038328/

credit: https://www.avsforum.com/threads/2020-lg-cx%E2%80%93gx-dedicated-gaming-thread-consoles-and-pc.3138274/post-60110685

You will especially notice this in PC mode when you play a game with text. The text just becomes a blurry, smeary mess at close distance, it's like having the wrong prescriptions for your glasses. At this price point 1.5k - 2.5k USD/Euro this is just unacceptable. There is no point of using this TV as gaming monitor if text becomes smeary at 4k 120Hz and even 100Hz and every other framerate other than 60Hz according to some in the forums.

Apparently LG decided to cut the HDMI 2.1 transfer rate from 48 Gbits/s to 40 Gbits/s. But still 40 Gbits/s is still enough for 4k 120Hz 4:4:4 HDR.

EDIT:

I just want to clarify why this issue should not be considered some small inconvenience for LG and Nvidia but rather an important issue that might decide over massive future revenues:

The LG OLED CX will be a groundbreaking and a class definiting "monitor": first TV to support 4k 120Hz AND 4:4:4AND G-Sync AND HDR. This has never been done before. Unlike other 4k OLED models this makes the LG CX perfect for gamers.
Gaming on the LG OLED CX is from another world. Breathtaking colors, strong contrasts, low input lag. And all with features tailored towards gamers (G-Sync, high refreshrate). When i first tried the LG CX it opened my eyes. I had a matrix moment where I decided that I take the truth pill. I cannot ever go back to a non-OLED display. If you have never experienced that, you must try it, it is nothing like you have ever experienced.
If this chroma subsampling issue and G-Sync issue is not resolved, this will definitely break the LG CX for gamers, it is nothing more than an ordinary OLED TV then.
LG and Nvidia might potentially lose a huge market. I can totally imagine a future where gamer enthusiast's first monitor choice is an OLED monitor with G-Sync because it offers everything an IPS monitor has but with better colors, contrast, HDR and so on.
The revenue and profit margins on the OLED monitors will be probably much higher than the current IPS/TN/VA monitors and might lead to a significant revenue stream for Nvidia and LG.

EDIT 2:

Things I have/others have tried to fix it:

Switch HDMI cables. I have tried with 2 different HDMI 2.1 cables (50 Euro each) that support up to 8k 60Hz
Switch between all kinds of different modes: SDR/HDR, PC Mode, 8 bit, 10 bit, done nearly everything.
G-Sync seem to work again when going back to an older driver version with RTX 2000 or older series.
Chroma subsampling primarily (or only) affects the LG OLED CX and becomes noticable at 4k 120Hz, 100Hz and 1080p 120Hz. 1440p 120Hz is fine.

I just hope we bring enough attention towards these 2 issues. They will either make or break the OLED gaming monitor. If this issues persist the OLED gaming monitor market will probably die in its infancy and will never recover.

Although the B9 and C9 models do not have the chroma subsampling issues (don't take my word for it), the current model and only not discontinued model, the CX, has this issue which makes it quite important to fix it quickly with all the new RTX 3080 owners who want to upgrade soon with Cyberpunk 77 and other game releases

EDIT 3:

John Archer just covered these issues on Forbes

https://www.forbes.com/sites/johnarcher/2020/09/20/lg-oled-tvs-having-issues-with-latest-nvidia-rtx-30-graphics-cards/#513a5d57267a

EDIT 4: To counterclaim that the HDMI cable is the issue (https://twitter.com/BigJohnnyArcher/status/1307760577775915008) : I think the strongest argument against that is that C9 has no subsampling whereas the CX subsamples with the same HDMI cable (DP to HDMI 2.1 adapter) and setup:

(see people who testet that: /u/kasakka1, https://www.avsforum.com/threads/2020-lg-cx%E2%80%93gx-dedicated-gaming-thread-consoles-and-pc.3138274/post-60113799 , https://www.avsforum.com/threads/2020-lg-cx%E2%80%93gx-dedicated-gaming-thread-consoles-and-pc.3138274/post-60113596 , https://twitter.com/Sixi82/status/1307761189951336450)

" I own both a CX 48 and C9 65. Using the Club3D DP 1.4 + DSC -> HDMI 2.1 adapter on v1.03 firmware with a 2080 Ti:

C9 is ok at 4K 60 Hz, 4K 120 Hz in both SDR and HDR. Full RGB, no issues.
CX is ok at 4K 60 Hz SDR/HDR.
CX is ok at 1440p 120 Hz SDR/HDR. For some reason. The res/refresh rate combo is listed separate in the display EDID, no other 120 Hz resolution is shown like this.
CX is ok at 1080p 60 Hz.
CX is not ok at 1080 120 Hz.
CX is not ok at 4K 120 Hz SDR. It downsamples to 4:2:2.
CX is not ok at 4K 120 Hz HDR. It looks fine but there is something off about the colors when looking at the Rtings.com test pattern, colors look more muted somehow but in normal use the difference is hard to see. There seems to be a very slight difference in sharpness compared to 4K 60 Hz." by laxu

" Its not cable related. Atleast not for me. Tested 3 "8K" "4k120" UltraHighSpeed HDMI 48GBps Cables from different. All with the same result, as described in the article. therefor i believe the signal is transported as it should be from GPU to OLED. " Sixi82 Twitter

It also doesn't seem like that people who supposedly got the LG OLED CX to work have gotten any special kind of HDMI cable: https://twitter.com/TheTechChap/status/1307743408732209164.

submitted by /u/Dogegoblin
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