How does HDMI extender work over one wire?

[skillz22]

I saw this video from LTT: 

 

and they didn't bother to explain how the product actually worked.

 

I had a look on the website, and it seems to say that you usually need two wires to get the sender and receiver to work. They show Linus' video on the website proclaiming that Linus even got this to work with one wire, but it works better with two.

 

My question is, how does this product actually work? Two wires make sense to me, one to tie the grounds together and the other to send data, but how did Linus get this one wire configuration working? Furthermore, how does adding a second wire help the signal if one wire works fine?

[Loote]

They compress the HDMI signal, so for 1080p it goes down from 3 gbit/s to much less, with less data you need less accuracy, so you get bigger distance, or can use worse 'cable', HDMI itself has 3-4 data channels, but it could use just 1 of them at 1/3(1/4) resolution(hdmi 2.1 could do 4k 30Hz on 1 Data channel if it only depended on bandwidth).

Basically their converters do two things: 1. lower the data rate 2. are very good at handling poor signal.

[skillz22]

23 hours ago, Loote said:

They compress the HDMI signal, so for 1080p it goes down from 3 gbit/s to much less, with less data you need less accuracy, so you get bigger distance, or can use worse 'cable', HDMI itself has 3-4 data channels, but it could use just 1 of them at 1/3(1/4) resolution(hdmi 2.1 could do 4k 30Hz on 1 Data channel if it only depended on bandwidth).

Basically their converters do two things: 1. lower the data rate 2. are very good at handling poor signal.

I get that the device compresses the signal, what I meant was I do not understand how you can send data over a single wire. You need a closed circuit to send any sort of current (and thus a signal)... right?

 

In Linus' video, both the sender and receiver were floating, and there was no way for the two devices' grounds to be tied together. How did he get a video signal over the single wire?

[Loote]

One cable comes with signal, so the receiver can detect the difference between signal and neutral, it doesn't need to have neutral provided by another cable, I think the second cable provides the second line of data, not neutral either.

My guess it can smartly adjust what it considers 0 and 1, depending on the quality of the signal, it doesn't have to be for example 5V and -5V, they might as well work with 1V and 7V

[harryk]

5 hours ago, slickboss21 said:

In Linus' video, both the sender and receiver were floating, and there was no way for the two devices' grounds to be tied together. How did he get a video signal over the single wire?

I suspect the devices are using a floating ground reference. Essentially using the chassis ground as reference and relying on the ambient environment to dissipate any charge difference. For signals with very small current flow this will work as long as there aren't any strong electric fields around.

[skillz22]

14 hours ago, harryk said:

I suspect the devices are using a floating ground reference. Essentially using the chassis ground as reference and relying on the ambient environment to dissipate any charge difference. For signals with very small current flow this will work as long as there aren't any strong electric fields around.

Thanks for the info! I did not know that this was possible.