What is HDMI 2.1? Everything you need to know

What is HDMI 2.1? Everything you need to know

Most people probably don’t give much thought to their HDMI cables. “If it ain’t broke, don’t fix it”, as the old adage goes. Your current cables, connecting your Blu-ray player to your television, projector or soundbar work perfectly well, and that’s all that matters, right?

But the HDMI Forum – the organisation that manages updates and information about cables – is already looking towards the future, with HDMI 2.1. This new standard has increased bandwidth, supports higher frame rates, and can carry not just 4K but up to 10K video from your source to your screen.

So while you won’t have to rip out your cables and rush down the shops for replacements just yet, you should be aware of what the future of television might well look like…

What does HDMI 2.0 do?

What does HDMI 2.0 do?

Image source: HDMI.org

For those that don’t know the specs of their current cable, let’s get up to speed. HDMI 2.0 dates from 2013, and its main party-piece is being able to pass 4K content at 60fps (frames per second) - that’s video of 3840 x 2160 resolution, refreshed 60 times per second.

That high frame rate is routinely utilised by 4K video games that need to track lots of different objects like whizzing bullets or speedy enemies - most films are made in 24fps, and television programmes are 25fps (or 30fps if the show is made in the USA).

A few years later a small update, HDMI 2.0a, made the link between televisions and players capable of carrying HDR (High Dynamic Range) information as well, with HDMI 2.0b coming soon afterwards with support for HLG (Hybrid Log Gamma). Until now, that’s been the top standard for most consumers.

MORE: How to set up your TV and get the best picture

What does HDMI 2.1 do?

Image source: HDMI.org

Image source: HDMI.org

Essentially, HDMI 2.1 has the capability to double-down on what HDMI 2.0a can manage. 2.1-standard cables will be able to easily outstrip the 4K limit, sending a maximum of 10K content at 120fps down the pipe.

All those extra pixels – six times that of standard 4K video – require greater bandwidth to send the information across. HDMI 2.1 cables are up to the task, with an upper limit of 48Gbps (Gigabits per second) rather than 18Gbps.

HDMI 2.1 will also be able to support Dynamic HDR. This allows the television to adjust its picture based on frame-by-frame information in the manner Dolby Vision and HDR10+ operate. Since a dark landscape might have different contrast requirements to that of a brighter scene, the ability to make instant adjustments should mean your movies and TV shows look their best.

The new standard has a few more improvements, too - it should, for instance, reduce the amount of time it takes to go from blank screen to content.

And for game consoles and virtual reality headsets, HDMI 2.1’s Variable Refresh Rate and Quick Frame Transport features should result in a smoother experience.

Finally, HDMI 2.1 is also ready to support eARC – an update to the ARC (Audio Return Channel) connection which will let you send DTS:X and Dolby Atmos soundtracks from your TV to your audio system, helping you get greater (and more convenient) audio excitement from compatible movies and shows.

MORE: HDR10 vs Dolby Vision: which is better?

Will I have to buy a new television?

Will I have to buy a new television for HDMI 2.1

Sharp's 70-inch 8K TV

Right now, you won’t. But you might have to in the future - it depends on what you’re looking to use HDMI 2.1 for. With regards to eARC, the HDMI Forum says it’s unclear whether your existing ARC connection will be able to work with it. That’s because it’s up to the manufacturers whether it will be available through a firmware update. We expect to hear more about this in due course.

In the FAQs on the Forum, it says “manufacturers can produce products that are compatible with both eARC and ARC. However, eARC is not defined to be backwards-compatible with ARC”.

Likewise, it’s possible Dynamic HDR will be available via a firmware update, but it looks like that’s down to the manufacturers too. Right now, we’ll just have to wait and see. But we expect televisions manufactured from 2019 onwards to start having HDMI 2.1 ports rather than HDMI 2.0.

In reality, the market is only just getting used to 4K, so we wouldn't be put off buying a new TV now because of what might arrive further down the line.

MORE: HDMI ARC and HDMI eARC - everything you need to know

Will I have to buy new cables?

Will I have to buy new cables that support HDMI 2.1?

Image source: HDMI.org

Yes you will, although not yet. You should wait for the relevant hardware and software to become available before the need to join it together becomes an issue. Beware that any cables currently on the market that claim 48GB capabilities have not yet been compliance tested.

The Ultra High Speed HDMI cable – currently in prototype, uncertified stage – will have the capacity to carry the 48GB bandwidth for uncompressed HDMI 2.1 feature support. 

It's looking likely that the cables will be optical rather than copper wire, too. At CES, Silicon Line, who designed Samsung's ultra-thin 'One Invisible' cable, discussed its development of an optical cable to carry the bandwidth, with its newly-designed chip allowing for a cable thickness of only 3mm, and an end price in-line with that of traditional wires. 

We spied a prototype, which was being demonstrated to carry an 8K signal between a source and 8K TV, and with practicalities in mind, it did seem more appealing than the chunky copper wires also on display at HDMI's show booth.

We'll have to wait to see what prevails, but it does look likely that optical is the most feasible option.

Naturally, the forthcoming 2.1-compliant cables will be backwards compatible with previous versions of the HDMI specification, so you won't need to ever unplug and plug cables depending on the source and content used (can you imagine?!)

MORE: 8K - everything you need to know

When can we expect to see these updates?

At CES 2019, a HDMI Forum spokesperson told What Hi-Fi? that the organisation was "close" to completing the full certification (apparently over 1500 pages long!) for HDMI 2.1. "It's not years away!", they said.

As for the hardware, while 8K TVs have been previewed at industry shows for over a year, only now are we starting to see pledged support for HDMI 2.1 in home cinema kit. 

At CES, some TV brands confirmed its 2019 sets would be HDMI 2.1 compatible. 

HDMI 2.1 support features across all LG’s 2019 OLED models (there's four of them on the LG OLED65C9 4K OLED) and some of its NanoCell LCD TVs. 

Samsung's current Q900R 8K TVs (such as the QE85Q900R and QE65Q9FN) don't have HDMI 2.1 inputs, but Samsung says they will when the standard is officially certified. As their HDMI inputs are housed in a separate One Connect Box, Samsung plans to simply swap it out for a HDMI 2.1-compliant version for free.

Sony's just-announced ZG9 8K TV will also receive a firmware update to enable HDMI 2.1, too. We'll have to wait and see whether Sony's new 4K A9G model is on the 2.1 roadmap too.

As everything in the video chain will need to be on the HDMI 2.1 bandwagon for the end user to benefit from its features, we're encouraged by confirmation of support in some home cinema amplification, too. 

Denon's 13.2-channel flagship AV receiver, the AVC-X8500H, won't support HDMI 2.1 straight out of the box, but you have the option to add it through a 'charged upgrade service'. It will be a similar case with the Marantz AV8805, the brand's first 13-channel preamplifier.

We'll be keeping our eyes and ears peeled for more HDMI 2.1 news in the coming weeks and months.

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