Best approach for getting 4k@120hz from PC to an LG CX from a distance of 15m

[RodKing]

My 15m HDMi cable only has enough bandwidth for 4k@60hz. Is it possible to get 4k@120hz from an HDMi cable or what other method could make this possible? An extender? Is HDMi 2.1 required? Fiber optic? Some other cables with adapters? 

Not sure if any of this could work but I don't even know if it's possible

[Aereldor]

HDMI is digital, the signal doesn't degrade with cable length. The cable just has to be thick enough to physically support the amount of data being carried. I found that regular ass Amazon Basics HDMI 1.3 cables were good enough for 2.0, I doubt the cables would bottleneck 4k@120.

[Biomecanoid]

12 minutes ago, Aereldor said:

HDMI is digital, the signal doesn't degrade with cable length. The cable just has to be thick enough to physically support the amount of data being carried. I found that regular ass Amazon Basics HDMI 1.3 cables were good enough for 2.0, I doubt the cables would bottleneck 4k@120.

HDMI is not analogue to degrade over distance and show artifacts but instead it stops working completely if you go over the supported distance.

[mariushm]

You're both incorrect. 

 

The cable is still cable, the copper wires have resistance and therefore voltage drop. The longer the cable, the higher the losses, which makes individual bits harder to decode, makes the signal more "fuzzy"... at that high bandwidth each bit "takes" a much shorter time on the cable, and there's higher chances of bits to be corrupted and that can cause drops in HDCP encryption or bad blocks in the image.

 

At longer lengths and high resolutions and refresh rates (more bandwidth), the cable quality matters more. 

 

46 minutes ago, Aereldor said:

Amazon Basics HDMI 1.3 cables were good enough for 2.0, I doubt the cables would bottleneck 4k@120.

They worked fine because your resolution and refresh rate was long  small, as was the distance. your cable was probably 1.8-3m (10ft) long, not 15 meters. 

Also, 4K 120 hz is 2 x 4K 60 hz bandwidth, or ~ 8 x 1080p 60 Hz bandwidth ... so quite a difference. 

 

Optical fiber cable would be the ideal choice, as long as the chip in the cable can actually recognize and work with 4K AND 120 Hz. Some may be picky about it. 

Regular hdmi cables with signal amplifier chips in the middle should be cheaper and should work fine. 

 

[Aereldor]

16 minutes ago, mariushm said:

You're both incorrect. 

 

The cable is still cable, the copper wires have resistance and therefore voltage drop. The longer the cable, the higher the losses, which makes individual bits harder to decode, makes the signal more "fuzzy"... at that high bandwidth each bit "takes" a much shorter time on the cable, and there's higher chances of bits to be corrupted and that can cause drops in HDCP encryption or bad blocks in the image.

 

At longer lengths and high resolutions and refresh rates (more bandwidth), the cable quality matters more. 

 

They worked fine because your resolution and refresh rate was long, as was the distance. your cable was probably 1.8-3m (10ft) long, not 15 meters. 

Also, 4K 120 hz is 2 x 4K 60 hz bandwidth, or ~ 8 x 1080p 60 Hz bandwidth ... so quite a difference. 

 

Optical fiber cable would be the ideal choice, as long as the chip in the cable can actually recognize and work with 4K AND 120 Hz. Some may be picky about it. 

Regular hdmi cables with signal amplifier chips in the middle should be cheaper and should work fine. 

 

10 meters IIRC. 

[Stahlmann]

I've also been trying to do this for months. I need a 10m cable between my 3080 and C9, but all optical cables are not only expensive, but incompatible somehow. I've tried ALL optical HDMI 2.1 48Gbits/s cables on amazon germany and have not found a single one that worked. I tried it with a shorter standard copper cable to see if it works at all, and it did. So i have no dead HDMI ports on my devices.

26 minutes ago, mariushm said:

Optical fiber cable would be the ideal choice, as long as the chip in the cable can actually recognize and work with 4K AND 120 Hz. Some may be picky about it. 

Regular hdmi cables with signal amplifier chips in the middle should be cheaper and should work fine. 

Can you point me in the direction of a 2.1 cable with a signal amp? I've never seen one of these.

[Stahlmann]

1 hour ago, Aereldor said:

HDMI is digital, the signal doesn't degrade with cable length. The cable just has to be thick enough to physically support the amount of data being carried. I found that regular ass Amazon Basics HDMI 1.3 cables were good enough for 2.0, I doubt the cables would bottleneck 4k@120.

4K 120Hz needs some serious bandwidth when you don't want to use chroma or only 8bit. 48Gbps to be exact. Unsurprisingly most 2.0b cables and lower cannot handle this much data and will only display a black screen instead. Sadly even most 8K 60Hz or 4K 120Hz marketed cables don't even support it. And yes, the signal will degrade over longer distances. That's the reason why the HDMI 2.1 certified cables only include up to 3m long cables right now.

 

Pretty much the only options for longer range HDMI are optical fiber cables which are extremely expensive ($100+ for 10m or more) and have compatibility issues with the NVIDIA RTX 3000 GPUs.

 

It's extremely frustrating to own both a 3080 and a C9 OLED TV, but being bottlenecked to 4K 60Hz 8bit because i just can't find a cable that can transfer a HDMI 2.1 signal over 10m.

[circeseye]

9 hours ago, Stahlmann said:

4K 120Hz needs some serious bandwidth when you don't want to use chroma or only 8bit. 48Gbps to be exact. Unsurprisingly most 2.0b cables and lower cannot handle this much data and will only display a black screen instead. Sadly even most 8K 60Hz or 4K 120Hz marketed cables don't even support it. And yes, the signal will degrade over longer distances. That's the reason why the HDMI 2.1 certified cables only include up to 3m long cables right now.

 

Pretty much the only options for longer range HDMI are optical fiber cables which are extremely expensive ($100+ for 10m or more) and have compatibility issues with the NVIDIA RTX 3000 GPUs.

 

It's extremely frustrating to own both a 3080 and a C9 OLED TV, but being bottlenecked to 4K 60Hz 8bit because i just can't find a cable that can transfer a HDMI 2.1 signal over 10m.

sigh...hdmi 2.1 is new...hell theres hardly any certified for short distances. later in the year im guessing more will show up but for 6' and under...anything over 6' will take longer and im guessing pricey

it sucks for some of us that need that distance...but even optical hdmi 2.0 are pricey unless you go generic

[Ahoy Hoy]

My only thought would be using professional hdmi cables.
The company which springs to mind is Belden they make HDMI cables for the events industry. They have some high end HDMI cables like the Belden Perfect Path 700 can do 4k to over 50 meters but I couldnt verfiy if they would manage the 120Hz. So maybe its worth sending them a email and asking if they have a product which does it. (but it may be expensive a 10m cable is over £100)