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HDMI 2.1 TV: why the new cable standard matters

HDMI 2.1 cable
(Image credit: Shutterstock)

What is HDMI 2.1? The new standard for HDMI connectors has arrived in full force on new 2021 TV ranges, with plenty of HDMI 2.1 TVs releasing where there had been only a small handful previously.

HDMI 2.1 is a game-changer, quite literally. It allows you to pass more information from games consoles, AV receivers and the like – upping the potential resolution and refresh rate for more detailed pictures and better-looking games. In a world of PS5 and Xbox Series X consoles, that's a big deal, and it's clear that TV makers are trying not to miss out on demand for the next-gen gaming machines.

It's easy to forget, though, that when High Definition Multimedia Interface (or HDMI) first arrived on the scene, it similarly shook up the AV industry. Everyone rejoiced at no longer having to use bulky SCART connectors, or those confusing component video cables, ever again. Instead HDMI offered high definition video with a connector that was just a little bigger than a standard USB plug. 

Over the years the HDMI standard has seen continuous improvement, with extra features being added as the needs of televisions have changed. HDMI 2.1 is just the next step in that process. 

The headline feature here is support for 8K content at 60fps, but there are also a number of minor features that add up to a much more capable standard such as support for Variable Refresh Rate (VRR), Dynamic HDR, and Quick Media Switching, which should make it faster than ever to change between the devices attached to your television. 

Here's a rundown of everything that's due to arrive with the new standard.

HDMI 2.1 resolution and refresh rates

HDMI 2.1 connection

HDMI 2.1 'lays the pipe' for the TV and VR industries

The new HDMI 2.1 cables will allow faster refresh rates, including 8K resolution video at 60 frames per second and 4K at 120 frames per second – and it's that second feature that will be the real selling point for gamers and home cinema geeks, at least at first.

"We've increased resolutions and frame rates significantly," Jeff Park, Director of Marketing at HDMI Licensing, told TechRadar, adding that "NHK [Japan's national public broadcaster] is going to push 8K120 as an actual broadcast stream, and many consumer electronics manufacturers want to hit that target, so we're laying the pipe to give the industry flexibility. It's practical stuff."

Although it's about keeping HDMI at the bleeding edge, HDMI 2.1 can actually go ever further, supporting resolutions as high as 10K at 120Hz – though that kind of capability is a while away from being supported on commercial sets.

HDMI 2.1: a saviour for gaming?

Best Dolby Xbox Series X games

(Image credit: Shutterstock/Miguel Lagoa)

HDMI 2.1's biggest potential may be in the world of gaming – and anyone gunning for a next-gen games console like the PS5 or Xbox Series X will almost certainly be looking for a TV that support HDMI 2.1.

Why's that? HDMI 2.1 covers a number of technologies, including capability for 4K gaming at 120Hz, or 8K gaming at 60Hz – both of which are set to be visually impressive if you have the hardware and cables to support them.

8K gaming is a while off still, but HDMI 2.1 means you soon won't have to choose between 4K resolution and high refresh rates, being able to experience both together.

HDMI 2.1 also enabled VRR (variable refresh rate), which helps to keep games looking smooth by switching up the refresh rate on the fly to best suit how much is happening onscreen. That means less image lag, stutter and frame tearing similar to the effect achieved by FreeSync and G-Sync.

This is great news for gamers, because HDMI 2.1 will enable a 3D graphics processor to render and display images in real time, which will result in more fluid gameplay and greater detail.

HDMI 2.1: what is eARC?

It's not all about TVs, either; soundbars, AV amplifiers and other audio equipment will also benefit from HDMI 2.1 – though it will mean upgrading all of your equipment.

For the last few generations, HDMI cables have had an Audio Return Channel (ARC), which means audio can be sent both ways between a TV and audio gear. This essentially enables a display to send its own audio – perhaps from a built-in Netflix app – to a soundbar or surround sound system, bypassing its own speakers.

AV amplifiers and other audio equipment will also benefit from HDMI 2.1 – although it will mean upgrading all of your equipment.

Enhanced Audio Return Channel (eARC) is nothing more than a simple update to keep pace with changes in audio codecs, specifically to include the new object-based audio codecs, Dolby Atmos and DTS:X.

"eARC ups the bandwidth significantly,” says Park. “Previously you were limited to two-channel PCM or legacy Dolby Digital or DTS audio, but with eARC that reverse channel can now support much higher bandwidth audio including Dolby True HD, DTS HD, Dolby Atmos, DTS:X and other object-based audio at much higher bandwidths."

HDMI 2.1: what is a 48G cable? 

HDMI 2.1 cable

Incoming HDMI 2.1 cables will cope with 48Gbps (Image credit: Shutterstock)

This is about defining a new specification of a HDMI cable's speed, with so-called 48G cables (for now just a working title) offering 48Gbps bandwidth for sending uncompressed 8K video, with HDR, over a HDMI 2.1 cable.

So why do we need a 48G-rated cable? "Because we're carrying so much data now – we've gone from 18Gbps in HDMI 2.0 to 48Gbps in HDMI 2.1," says Park. "Today we have 'standard speed' and 'high speed' HDMI cables, and 48G will be related to that."

Ditto the compliance tests that each HDMI 2.1 cable will have to pass in order to be labelled as such. Backwards-compatible with earlier versions of the HDMI specification, and able to be used with existing HDMI devices.

HDMI 2.0 cables are all really the same, despite what some manufacturers will try to tell you with their branding – but an HDMI 2.1 cable with 48Gbps will be necessary to experience the technology's capabilities, and you'll need a compatible HDMI 2.1 port on any connecting hardware (TVs, soundbars) too.

HDMI 2.1 TV: what screens are out there?

Sony AG8 OLED

(Image credit: Sony)

2021 is the year that HDMI 2.1 goes mainstream. The standard only received piecemeal support last year on a handful of high-end sets, often with only one HDMI 2.1 port with two or three HDMI 2.0 ports alongside.

That's still the case with some manufacturers (the Sony A90J OLED will feature a mix of 2.1 and 2.0 inputs), while others are going all-in on HDMI 2.1 ports on their premium TV ranges. Both LG and Samsung are in this latter camp, and you can expect up to four HDMI 2.1 ports on select sets.

Sony was surprisingly slow to incorporate the standard, given it was also behind the PS5 consoles, only bringing HDMI 2.1 to two Sony TVs last year – through an over-the-air firmware update – though support is set to be better this year.

LG was a big early adopter, with the LG CX OLED featuring four HDMI 2.1 ports – though at 10-bit 4K/120Hz passthrough rather than the full 12-bit. This shouldn't really affect your picture onscreen, given that the CX only has a 10-bit panel anyway, though it's worth noting that there are other LG TVs that support the full 12-bit HDMI, such as the ZX OLED.

Jamie Carter originally contributed to this article.