HDMI explained: What you need to know and what is the best HDMI cable?

Demystifying the AV world’s most complicated connection

HDMI explained: Best HDMI cables
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Since HDMI sockets and cables first appeared in 2002, they haven’t half caused some trouble. They’ve been responsible, for instance, for generations of AV equipment going suddenly and unceremoniously out of date. They’ve led to untold numbers of cable breakages due to their flimsy attachments.

Different HDMI sockets on different devices have bamboozled consumers by supporting different features. People trying to run long HDMI cable runs have sometimes found they get no picture.

Last but not least, ever increasing data demands placed on HDMI cables means they now come in three different grades that you actually need to have at least a rudimentary understanding of.

Despite all these issues, though, HDMI connections have endured. Mostly because for all their issues, they’ve remained almost endlessly upgradable, keeping pace with not just the demands of the AV world but, as we’ll see, the world of the smart home, too.

It’s also true, of course, that HDMI cables were designed with the best of intentions: to provide a single-cable digital video and audio solution.

Nonetheless, it’s clear that plenty of HDMI nonsense has happened along the way. So here we attempt to pick through the HDMI myths to provide only the facts that you really need to know.

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4k hdmi cable

Why aren’t all HDMI connections the same?

HDMI ports deal in digital data. And since the demands placed on digital data change much faster than things did in the analog age, HDMI connections and cables keep having to evolve too.

So quickly has HDMI had to adapt, in fact, that there a number of different generations of HDMI port are simultaneously playing a key part in today’s AV world. In fact, sometimes a single product can carry multiple generations of HDMI.

The main HDMI generations you need to concern yourself with if you’re thinking of buying a new AV product now are v1.4, v2.0, and v2.1. Let’s look at each in turn.

HDMI V1.4

HDMI v1.4 was a big deal when it debuted in 2009 because it was the first HDMI platform with enough data bandwidth for 4K picture resolutions. It can, though, only shift enough data to support 4K at up to 30 frames a second.

Similarly, while it supports high dynamic range playback, that support is restricted with 4K to 8-bit color quality, rather than the 10 or 12 bit support offered by later HDMI versions.

Many devices (such as cable boxes, the original PS4, most projectors and many relatively affordable TVs) still carry these relatively affordable ports.

HDMI v1.4 also introduced the HDMI Ethernet Channel (HEC). This allows two connected devices to share a wired Internet connection - potentially very handy for smart home installations.

Finally, v1.4 HDMIs support Audio Return Channel technology, which enables HDMI ports and cables to be used as both an AV input and an audio output.

So you can use an HDMI port to, say, pass a digital audio track out from a TV to an external ARC-capable audio device such as a soundbar (the Sonos Arc, for example) or AV receiver, even if that HDMI port is also receiving video and sound.

HDMI V2.0

The v2.0 HDMI provides much more bandwidth - chiefly so that it can better handle 4K video.

Its 18.0 gigabits per second throughput is enough to support 4K at frame rates of up to 60Hz, as well as high dynamic range video up to the wide ‘Rec 2020’ color space with 10/12-bits of color resolution.

Also introduced with HDMI 2.0 is support for up to 32 audio channels at a high 1536kHz sampling frequency, and as many as four simultaneous audio streams and two simultaneous video streams.

HDMI 2.0b additionally added playback of the new Hybrid Log Gamma format already used by the BBC and expected to be taken up by other broadcasters soon.

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Since 2019, one or two brands have been able to squeeze one or two features associated with the HDMI 2.1 standard we’re coming to next into HDMI 2.0 bandwidths. Sony, for instance, has managed to get eARC lossless sound technology working over HDMI 2.0 (see the HDMI 2.1 section for more on this), while Samsung has managed to support the AMD Freesync variable refresh rate gaming system without needing a 2.1 HDMI port.

This has led to some confusion over the usual HDMI naming/numbering conventions, with essentially 2.0 HDMIs getting referred to in terms of HDMI 2.1 features they might support.

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HDMI V2.1

Formally launched on November 28 2017, the v2.1 HDMI is the single biggest step forward for HDMI technology to date, with its massively increased 48Gbps maximum data rate opening up the potential for exceptional picture and sound quality, as well as innovative new features.

Unfortunately, though, it has also become by far the most complicated HDMI generation to date, thanks to a combination of displays ‘running ahead’ with some 2.1 features and claims before they’ve been fully ratified, and the potential for HDMIs of widely differing specs to be called HDMI 2.1.

Looking at the sort of new features HDMI 2.1 supports, as well as handling 4K images at frame rates of up to 120Hz, it can play video resolutions of up to 10K at lower frame rates (including 8K at 60Hz), paving the way for the next generation of 8K-resolution TVs.

It also supports so-called Dynamic HDR, where extra scene by scene information is provided to displays to help them show their HDR pictures better. Though dynamic HDR technologies such as Dolby Vision and HDR10+ have already been available via some HDMI 2.0 and even (in Dolby Vision’s case) HDMI 1.4 connections.

HDMI 2.1 introduces some key gaming features, such as variable refresh rate support to tackle image lag, stuttering and frame tearing; quick frame transport to help screens display images faster; and an Automatic Low Latency Mode feature that can trigger displays to automatically switch into their fast-response game modes when a game is detected.

These features are all expected to be supported by the PS5 and Xbox Series X, and have actually already arrived on Nvidia’s RTX 30 graphics cards.

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HDMI 2.1 also improves the HDMI Audio Return Channel feature. Its ‘eARC’ version supports bandwidths big enough to carry lossless (uncompressed) object based sound formats, such as the purest versions of Dolby Atmos and DTS:X carried on Blu-ray and 4K Blu-ray discs.

The trouble with HDMI 2.1 is that its implementation has become very fragmented between different displays, with different TVs and TV brands claiming support for various HDMI 2.1 features, rather than everyone just using a single HDMI 2.1 standard that covers ALL HDMI 2.1’s potential capabilities.

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Much of this potential confusion is down to manufacturers deciding to support different data rates with their various HDMIs, where the data rate can dictate the level of HDMI 2.1 features that can be supported.

The upshot of this is that you if you see a TV claiming to carry one or more HDMI 2.1 sockets (it’s common, just to confuse you more, for TVs to carry different HDMI ‘generations’), don’t assume that it will necessarily provide all the features HDMI 2.1 is capable of. Look for some sort of itemised breakdown of which specific HDMI 2.1 features it can deliver.

HDMI Overlap

As noted in passing while looking at each HDMI generation, there can be some feature fluidity between HDMI generations. For instance, the Dolby Vision dynamic HDR system has actually worked on every HDMI since v1.4.

Samsung has managed to get some HDMI 2.1 features (auto game mode, variable refresh rate support, support for other non-Dolby dynamic HDR formats) working on its current HDMI 2.0 TV connections. And Sony has been offering eARC support over HDMI 2.0 since 2019.

HDMI and CEC

One potentially useful trick of HDMI cables for smart home applications is CEC. Short for Consumer Electronics Control, CEC lets you control multiple devices connected via HDMI using only one remote control. So, for instance, if you connect a CEC-enabled Blu-ray player to a CEC-enabled TV, you will get extra menu options that let you use your TV remote to control Blu-ray playback.

Since the arrival of HDMI 2.0, CEC has had the potential to drive up to 15 devices via a single remote control.

CEC can currently be clunkily implemented or hard to follow on many devices, though - and many consumers don’t even know it exists. A concerted industry-wide push of CEC technology would likely help CEC realise its full smart home potential.

HDMI explained: What you need to know and what is the best HDMI cable?

HDMI cables: What you need to know

As with HDMI connections, different HDMI cables can carry different amounts of data. So if you just buy the cheapest HDMI cable you can find, it may not give you all the features you want. For instance, if an HDMI cable can’t carry at least 40Gbps of data, it won’t be able to support 4K at 120Hz gaming.

To try and make life easier, the HDMI.org has established three HDMI ‘standards’ for you to look out for when trying to buy an HDMI cable.

Basic ‘category 1’ HDMI cables are not designed to carry the 18Gbps data rates associated with today’s HDMI 2.0 4K/HDR connectivity. As a result, while they can cost mere pennies, they’re probably best avoided now if you have any interest in 4K/HDR picture quality, or HDMI’s latest CEC ‘smart home’ capabilities.

Category 2 HDMI cables - also known as High Speed HDMI cables - are designed to handle the 18Gbps required to unlock HDMI v2.0 features. Category 2/High Speed cables should be labelled as such on their retail information.

The newest HDMI 2.1 format depends on data rates far higher than HDMI 2.0’s 18Gbps. In fact, it needs as much as 48Gbps. So to cater for this you’ll need what’s called an Ultra High Speed HDMI cable capable of handling such huge amounts of data.

Should you buy Premium Certified/Ultra Certified HDMI cables?

While all HDMI cables should tell you at point of retail whether they are basic, High Speed or Ultra High Speed cables, that doesn’t mean that they’ve all been formally assessed by the HDMI Licensing group as definitely delivering all the features they promise. In fact, the vast majority will not have received official certification.

Uncertified High Speed and Ultra High Speed cables should all work fine, to be clear - but if you want absolute 100% peace of mind, you could look out for cables that have officially passed the official High Speed and Ultra High Speed compliance tests established by HDMI Licensing.

Looking out for officially certified cables is particularly recommended if you need a relatively long cable run (5m or more).

The ‘Premium Certified’ badge for HDMI cables was created by the HDMI Licensing Group to show that a cable has passed the organisation’s internal 18Gbps tests. The Ultra Certified Cable badge was created to show where a cable has passed the organisation’s internal 48Gbps tests.

Officially certified cables are allowed to show the HDMI Licensing group’s certification logo, complete with QR code, at point of retail (such as on their Amazon web pages).

Note that while Premium Certified cables have been widely available for some time, it was only in September 2020 that the first Ultra High Speed HDMI cable was officially certified - the best part of three years after the first Ultra High Speed HDMI cables went on sale.


What are Active HDMI cables?

Most HDMI cables are passive, and can pass their signals in either direction. Active HDMI cables, though, only send their signals in one direction. Why? Because they contain power boosters that amplify the signal coming from your source as they send it on its way.

For most HDMI cable runs an active HDMI cable won’t be necessary. However, if you need to use a really long cable run (likely 30 feet or more), an Active HDMI cable may make the difference between a data-intensive signal making it or not, as HDMI cables generally become less reliable the longer they are.

Active HDMI cables are potentially more likely to be useful for smart home applications based on CEC technology than typical video set ups.


Are expensive HDMI cables worth it?

You can spend thousands of pounds even on quite short HDMI cables. But there’s doesn’t seem to be any compelling reason to do so.

Unlike the analogue world, where higher quality analogue cables can deliver superior audio or picture results, HDMI’s digital nature essentially means that cables either carry enough zeroes and ones from one end to the other to deliver a signal, or they don’t.

Some relatively expensive cables can offer handy tricks such as extra-strong mounts, or smart home-friendly flat cable profiles for running under carpets. Also, if you’ve got a very long cable run and a 4K or even 8K screen to feed, it is possible that a relatively expensive cable will carry all that signal bandwidth more consistently/successfully. Cables that have received official certification from the HDMI Licensing group may cost a little more, too.

None of these premium options, though, need to cost hundreds or thousands of pounds.

The best HDMI cables to buy

Belkin Ultra High Speed HDMI Cable

Belkin Ultra High Speed HDMI Cable (2m)

$19.99, Amazon

Can handle HDMI 2.1 48Gbps data flows, and is approved by Apple for the distribution of 4K video and object-based sound.

AmazonBasics High Speed 2.0 cable

AmazonBasics High Speed 2.0 cable (1.8m)

$6.99, Amazon

The ultimate proof that you don’t need to spend much money at all to get even a decent ‘category 2’ high speed HDMI cable.

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QualGear High Speed Long HDMI 2.0 Cable (50ft)

$17.95, Amazon

This active 4K HDMI cable is again proof that you don’t have to spend a fortune to get a reliable cable even for long cable runs. This cable is available in much longer versions, too, without the price ever becoming painful.

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Monoprice Certified Premium High Speed HDMI Cable (25ft)

$35, Amazon

If you want a fairly long running cable with the extra peace of mind of Premium Certification, this is an impressively affordable option.

HDMI explained: What you need to know and what is the best HDMI cable?

True HQ Ultra High Speed HDMI cable 3m

$19, Amazon

No officially certified Ultra High Speed/Category 3 cables have yet gone on sale. But if you’re looking for a relatively long cable to meet that spec right now, this 48Gbps-capable 3m option from True HQ is probably the most credible option we’ve seen so far.
It explicitly lists compatibility with all of the latest gaming-related features you’d hope that a 48Gbps cable would cover, and crucially is already in the queue for the HDMI.org's official new certification process.

best hdmi cables

Ugreen high speed 270-degree angle plug (2m/6ft)

$14.99, Amazon

A great example of some of the installation innovations available in the HDMI cabling world. As well as using a flat cable arrangement, this Ugreen cable features a ‘right angle’ connection for close to wall installations.

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