4k,120hz + G-Synch over 30 meters - HDMI optical does not behave!


Novice Member
Hi there,

I would like to connect my gaming system from the office room with the tv from the living room. In perspective, the cable should be hidden in the wall, hence the necessary length of 30 meters. For this I tried somewhat expensive cable from Jenving (SUPRA - HDMI 2.1 AOC (optical) 8k/HDR 30 Meter cable).

The components used for testing always had the latest firmware or driver version.
LG OLED 77 C9PLA, Firmware 05.00.10
Gigabyte NVIDA RTX 3080 Gaming OC, 461.09

Within the HDMI 2.1 specification I intend to run 3840x2160p in 10 bit + VRR /G-Synch over the 30 meters distance. Unfortunately, I cannot operate the components with the 30 meters Supra cable (but it works with a cheapo 3 meter Hdmi cable).

I tried several settings with the 30-meter super cable, of which the following settings worked:
1920x1080p @ 120 hz, RGB 10 bit
1920x1080p @ 120 hz, RGB 12 bit
2560x1440p @ 60 hz RGB, 8 Bit, G-Synch
3840x2160p @ 60 hz, 4:4:4 with G-Synch – 8 bit
3840x2160p @ 60 hz, 4:2:0 with G-Synch – 10 bit
3840x2160p @ 50 hz, RGB with G-Synch – 8 bit
3840x2160p @ 30 hz RGB - no G-Synch - 10 bit

The following settings did not work with the 30 meters Supra cable:
3840x2160p @ 50 hz, RGB with G-Synch – 10 bit
3840x2160p @ 60 hz, 4:4:4 G-Synch – 10 bit (screen flickers rarely for one second before going black)
3840x2160p @ 60 hz, 4:4:4 no G-Synch – 10 bit
3840x2160p @ 60 hz, 4:2:2 no G-Synch – 8 bit
3840x2160p @ 100 hz, 4:2:0 no G-Synch 8 bit
3840x2160p @ 120 hz, 4:2:0 no G-Synch 8 bit
3840x2160p @ 120 hz, 4:2:0 with G-Synch 8 bit

Variance of testing:
All tests have been made with and without LGs Instant Gaming Response / VRR / G-Synch and with and without LGs Ultra HD Deep Color enabling option.
I tested the cable in the rolled-in state as well as in the unrolled state, in case there should be any differences. Kinks or other damage are not visible.

When I applied the desired settings (3840x2160p @ 120 hz, 10 bit RGB) for the first time with the Supra cable, the TV flickered for several seconds and the picture appeared partly. After that, the picture was no longer displayed. In subsequent attempts, the flickering never occurred again, the picture remained permanently black for those settings. Only the previously listed settings work reliably.

The settings that were the most closely aligned with the desired target, using the Supra cable were:
3840x2160p @ 60 hz, 4:4:4 with G-Synch – 8 bit
Interestingly for 3840x2160p @ 60 hz, 4:4:4 with G-Synch –10 bit the picture flickers for 1 second and then the screen goes black sometimes.

For reference, a no name HDMI 2.1 cable in 3 meters I got from Amazon for 16 € works at the following desired settings.
3840x2160p @ 120 hz, 10 bit RGB with working G-Synch
I assume that it also works for outputs with a lower bandwidth.
All components support DSC (if necessary?)

For the record, both the graphics card and the TV support HDMI 2.1 and the supra cable was used in the correct orientation. No other devices were connected to the TV while testing. Multiple HDMI ports of the devices were used during testing, although every single port supports HDMI 2.1 at 48 Gbit/s.

The Supra cable requires a voltage of 5 volts from the HDMI port for operation. So far, I could not find any data whether the RTX 3080 also provides this. I wonder if a too low output voltage means that only the signals with a high bandwidth are not transmitted.

Does anyone have a tip or approach to this?


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Joe Fernand

Distinguished Member
AVForums Sponsor
'Does anyone have a tip or approach to this?' - move the PC :)


Otto Pylot

Active Member
5V/50mA output is standard for all HDMI ports as it is part of the HDMI hardware specifications. 30m (90') is very long for any cable, regardless of their marketing or product claims. I'm sure you know this but active cables are directional so the orientation, source to sink is critical. You won't damage anything but you also won't get a picture.

For in-wall installations, the use of a conduit (1.5"- 2.0" diameter) is highly recommended. That is the ONLY way to future proof your cabling as it makes for installing the cable much easier and safer. And it is easier to control bend radius. Video technology will always outpace connection technology so you need a plan to easily upgrade/swap your cabling out when the time comes, and it will. A single cable, source to sink, with no wall plates, adapters, extenders, etc in-between is the most reliable connection.

You can try a voltage inserter. They are a little USB-powered dongle that goes between the cable and the source (usually) and provides a consistent 5v/500mA of output current to the cable independently of the the HDMI port. Some folks have implied that there may be a slight loss of pq because it is a "break" in the HDMI chain but I never saw anything in my testing. However, at 30m you have distance working against you. It's worth a try and even good ones are relatively cheap. They are not a guarantee to correct your issues but some have found that they worked. You just need an USB power source either from the the tv/receiver's USB port of thru the supplied wall adapter. There is a 17" or so USB cable so you do have some room to connect to an outlet. You can also use a 1m USB 3.0 adapter cable if you need a little extra length.

Ruipro 8k, Gen-3b or c is what we recommend, and Ruipro supplies a voltage inserter in case you need one. There were quite a few reports of issues with the first release of some of the 3080/3090 Nvidia GPU, possibly due to inadequate QA/QC testing. To that end, Ruipro has tweaked their proprietary chipsets for better compatibility with the LG C9/CX and their 8k cable (hence Gen-3b, 3c). It's not a guarantee that they will work, especially at 30m, but they are actively and continually improving their cables for better compatibility across the board with the new HDMI 2.1 devices coming to market. Unfortunately, gamers are the beta testers for the HDMI 2.1 option sets as HDMI 2.1 doesn't really offer anything for the non-gamers yet. You also have to keep in mind that HDMI 2.1 is a set of options. They are not really standards so the device mfrs can implement those options however they choose. 40Gbps instead of 48Gbps for example. That results in compatibility issues that the cable mfrs are trying to overcome. Even with a hybrid fiber cable, distance is still your enemy.

As @Joe Fernand mentions, move your equipment closer together (a lot closer together) if possible. If not, you'll always be fighting the distance monster.


Distinguished Member
Agree with Joe and Otto but I would also add how are you going to control the PC.

Are you going to introduce any lag into the controllers. No point having VRR at up to 120Hz if there is 500ms delay in the input and will be shot/crash etc before you can react.


Novice Member
The mouse-delay with a 30 meter usb 3.0 cable is surprisingly not noticeable. With wireless gaming mice (short cable to transmitter) like the logitech G502, I noticed more delay.

Unfortunately, it is not possible to move the PC and the TV closer together. Alternatively, a second PC would be necessary, which costs much more than a (very expensive) hdmi cable.

The voltage inceptor lowers the signal to hdmi 2.0. as far as no 2.1 injectors exist, right?, But i guess the problem is and remains the length.

I will lay empty tubes for the future during the current renovation and lay a cable as soon as products emerge with which a reliable connection is possible.

Thx for the help guys

Otto Pylot

Active Member
The voltage inserter just provides a constant 5v/500mA current. It has nothing to do with the HDMI option sets other than it introduces a "break" in the HDMI chain. Voltage inserters are not HDMI version specific so don't go looking for an "HDMI 2.1 voltage inserter" because they don't exist, and neither do "HDMI 2.0" ones for that matter.

Ruipro is coming out with a newer hybrid fiber cable up to 50m (150') but eARC will only be available to about 33m (100'). CORRECTION: Ruipro is coming out with the new Gen-3c cable which has better compatibility but the cable I just mentioned is for the HDMI 2.0 option sets and will be called the Ruipro-X cable. Sorry about that.

Installing a 1.5" - 2.0" is a good idea because that's the ONLY way to future proof your cabling because you will be swapping out your cables probably sooner than later.
Last edited:

Joe Fernand

Distinguished Member
AVForums Sponsor
Note the size of HDMI hoods (esp. the length of Fibre hoods) when selecting the correct size of conduit and avoid any tight bends.



Active Member
Just wanted to add to this that the Ruipro 8k Gen 3C cable works perfectly at 15m and is 'meant' to work fine up to 100m so I guess 30m should be sweet. :)

The mouse-delay with a 30 meter usb 3.0 cable is surprisingly not noticeable. With wireless gaming mice (short cable to transmitter) like the logitech G502, I noticed more delay.

Which extension cable did you use? I tried a 10m USB 2.0 extender cable and it wouldn't provide power to a Logitech unifying USB dongle. :(

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