Every time you begin to display a program via HDMI, there is a handshaking process where basically the source asks the monitor “Are you authorized to display this content?” Then they agreed upon the resolution.

When this process goes haywire, this will be your display. I’ll bet you have a Samsung unit.

1) Try getting a better or shorter HDMI.
2) Turn everything off and on to force a new handshake.

A long-running story in the world of electronic security has been the reconstruction of on-screen data using RF interference from monitors or televisions. From British TV detector vans half a century ago to 1980s scare stories about espionage, it was certainly easy enough to detect an analogue CRT with nothing more than an AM broadcast radio receiver. But can this still be done in the digital age? It’s something [Windytan] has looked into, as she reconstructs images using leakage from HDMI cables.

It does however leave the tantalizing possibility of using this as a medium to wirelessly export data from a compromised machine, and it’s down this route she goes. She finally arrives on a scheme of encoding data as lines of individual colors that look like interference patterns over a desktop, and from there can send and retrieve files. It works for digital audio streams, and as shown in the video below, even an MJPEG video stream, hidden in the noise from a video signal. That’s impressive work, by any standard!

Using HDMI radio interference for high-speed data transfer
https://www.windytan.com/2023/02/using-hdmi-radio-interference-for-high.html

This project was made possible by at least C++, Perl, SoX, ImageMagick, liquid-dsp, Dear Imgui, GLFW, turbojpeg, and v4l2!

HDMI on erinomainen standardi, joka on vallannut video- ja audiosignaalin siirron olohuoneissa ja työpöydillä. EU:n sähköturvallisuusviranomaisten tekevä testi kuitenkin osoittaa, että HDMI-kaapelien laadussa on paljon toivomisen varaa.

Testistä vastasivat neljän maan sähköturvallisuusviranomaiset: Elsäkerhetsverket Ruotsissa, Bundesnetzagentur Saksassa, BAKOM Sveitsissä ja Agentshap Telecom Hollannissa. Testissä oli mukana kaikkiaan 30 kaapelia eri valmistajilta ja peräti 27 näistä reputti eli ei täyttänyt vaatimuksia.

Testissä kävi ilmi, että yhdeksän kymmenestä HDMI-kaapelista ei täytä EMC-vaatimuksia. EMC -häiriöt tarkoittavat, että signaaleja vuotaa. Tämä voi häiritä muita lähellä olevia laitteita. Testissä käytiin läpi myös antennikaapelien EMC-ominaisuuksia ja vuoden 2012 testiin perusteella antennikaapelin laatu on heikentynyt.

Viranomaisten mukaan kaapelin hinnasta ei voi suoraan päätellä sen laatua. Joissakin tapauksissa kalleimmat kaapelit vuosivat eniten.

HDMI-liitäntästandardi on ehtinyt versioon 2.1. Sen myötä väylän datansiirtokyky kasvoi 2.0-standardin 18 gigabitistä 48 gigabittiin sekunnissa. Tämän mahdollistaa se, että 2.1-standardissa jokaisen johtimen läpi viedään dataa kaksinkertainen määrä eli 12 gigabittiä. Lisäksi kellosignaaleille varattu neljäs johdin otetaan datan käyttöön. Tällä päästään standardin määrittelemään 48 gigabittiin sekunnissa.

Käytännössä HDMI-kaapelin yli voidaan siirtää ruudulle 60 kertaa sekunnissa virkistyvää 8K-kuvaa tai 120 kertaa virkistyvää 4K-kuvaa. Markkinoilla 2.1-versio on edelleen marginaalisessa asemassa.

Technology moves quickly these days as consumers continue to demand more data and more pixels. We see regular updates to standards for USB and RAM continually coming down the pipeline as the quest for greater performance goes on.

HDMI 2.1 is the latest version of the popular audio-visual interface, and promises a raft of new features and greater performance than preceding versions of the standard. As it turns out, though, buying a new monitor or TV with an HDMI 2.1 logo on the box doesn’t mean you’ll get any of those new features, as discovered by TFT Central.

HDMI 2.1 aimed to deliver multiple upgrades to the standard. The new Fixed Rate Link (FRL) signalling mode is the headline piece, providing up to 48 Gbps bandwidth, a major upgrade over the 18 Gbps possible in HDMI 2.0 using Transition Minimised Differential Signalling, or TMDS. TMDS remains a part of HDMI 2.1 for backwards compatibility, but FRL is key to enabling the higher resolutions, frame rates, and color depths possible with HDMI 2.1.

Thanks to FRL, the new standard allows for the display of 4K, 8K, and even 10K content at up to 120 Hz refresh rates. Display Stream Compression is used to enable the absolute highest resolutions and frame rates, but HDMI 2.1 supports uncompressed transport of video at up to 120 Hz for 4K or 60 Hz for 8K. The added bandwidth is also useful for running high-resolution video at greater color depths, such as displaying 4K video at 60 Hz with 10 bit per channel color.

Also new is the Variable Refresh Rate (VRR) technology, which helps reduce tearing when gaming or watching video from other sources where frame rates vary. Auto Low Latency Mode (ALLM) also allows displays to detect if a video input is from something like a game console. In this situation, the display can then automatically switch to a low-latency display mode with minimal image processing to cut down on visual lag.

When HDMI 2.1 Isn’t HDMI 2.1 – The Confusing World of the Standard, “Fake HDMI 2.1” and Likely Future Abuse
https://tftcentral.co.uk/articles/when-hdmi-2-1-isnt-hdmi-2-1

HDMI on erinomainen standardi, joka on vallannut video- ja audiosignaalin siirron olohuoneissa ja työpöydillä. EU:n sähköturvallisuusviranomaisten tekevä testi kuitenkin osoittaa, että HDMI-kaapelien laadussa on paljon toivomisen varaa.

Testistä vastasivat neljän maan sähköturvallisuusviranomaiset: Elsäkerhetsverket Ruotsissa, Bundesnetzagentur Saksassa, BAKOM Sveitsissä ja Agentshap Telecom Hollannissa. Testissä oli mukana kaikkiaan 30 kaapelia eri valmistajilta ja peräti 27 näistä reputti eli ei täyttänyt vaatimuksia.

Testissä kävi ilmi, että yhdeksän kymmenestä HDMI-kaapelista ei täytä EMC-vaatimuksia. EMC -häiriöt tarkoittavat, että signaaleja vuotaa. Tämä voi häiritä muita lähellä olevia laitteita. Testissä käytiin läpi myös antennikaapelien EMC-ominaisuuksia ja vuoden 2012 testiin perusteella antennikaapelin laatu on heikentynyt.

I’d be curious to see how commercial AV cables (Extron, Kramer, Crestron, etc) compare.
I basically only buy consumer cables as a last resort because of how expensive and variable quality they are.

We told you we’d do it, and here it is! Testing a whackload of HDMI 2.1 and 2.0 cables to find out if you’ve been wasting your money on cables for no good reason.

Viewer comments:

I don’t even need new HDMI cables but I feel like buying new HDMI cables…

I bet so many dodgey companies that make hdmi cables are pissed as hell at you right now. Thanks for the information Linus, another video to add to my education playlist grievous cough

It would be nice to put the failures into consumer terms. For example, “This cable works with 1080p, but not 4K.” “This cable won’t carry ethernet data, but otherwise works.” “This cable simply doesn’t carry video at all.” In other words, when there is a continuity fault, what applications are impacted?

My test is see if it’s reliable providing a 120hz 4k hdr signal from my PC, but that’s the application I care about, and most probably don’t need a cable that passes that spec anyways. Almost any cable should be able to do 1080/1440p 60hz or 4k30, which for the average user is probably the highest they’re going to use.

I seriously love this! This is one of those fields where getting a “quality” cable is never verifiable.

nstaller tester here, from the hundreds of cables that I’ve bought, tested & used, 2 brands have stood out for me with value for money and performance for price : For passive cables- Cable Matters premium certified 2.0 cables the 3M & under will do most HDMI 2.1 functions and all 2.0b functions.

Active Cables: Monoprice Cabernet series. Have used these on 15M runs and they always work (chroma is 4:2:0) they meet in wall fire ratings, will do all HDMI 2.0.

Thanks for the video, HDMI cables was definitely not one I knew much about, and your explanation (plus spending a grand on the massive assortment) gave me (and I assume others) a good background on what to look for!

Very interesting and informative. I would like to see more cable testing on a more granular basis like which length cable brand is best.

I was seriously expecting Linus to test that THOUSAND dollar HDMI cable that he bought several years ago. He literally said that he wanted to use an oscilloscope to see the tiny gain in conductivity of something like that. THE CABLE CAME IN A CARRYING CASE WITH AN AUTHENTICITY CERTIFICATE!!!

Linus: buys a cable tester
The entire cable industry: I’m in danger! * chuckles *

Thank you for this really helpful video. Reliable information on cables is hard to find. I was recently worrying about what type and brand to buy for when I buy new devices so this explanation and testing video is extremely helpful.