HDMI 2.1: What You Need to Know

Time to Get New Cables?

The HDMI Forum released the HDMI 2.1 standard for video cables and connections last November, and that means upgrades are on the horizon. The current wave of TVs, game systems, and media streamers will remain untouched for most of the coming year, but after the HDMI Forum's press conference on HDMI 2.1 at CES 2018, we have an idea of what the new standard will bring. Before you scramble for new cables, here's what you should know.

Faster, Better 4K

The HDMI 2.1 standard is faster than HDMI 2.0, the current connection used by modern home entertainment devices. It nearly triples the bandwidth of HDMI 2.0, defining a maximum speed of 48Gbps compared with 18GBps. For 4K TVs, that means an HDMI 2.1 connection can handle 4K video at up to 120 frames per second. That's natively transmitted video, not the motion processed, interpolated 24, 30, and 60fps video current TVs with 120Hz refresh rates can display. That means smoother action that looks much less artificial.

These faster speeds mean wider support for dynamic high dynamic range (HDR) video. Yes, that's two dynamics in one term, but there's a reason. HDR expands the dynamic range of video, which determines how dark, bright, and colorful each pixel can get. Most current HDR content is static, defining a set range with HDR10 or adjusting levels based on individual TVs with profile metadata. These levels stay constant through the movie or show you're watching.

Dynamic HDR makes the dynamic range variable instead of static. Additional metadata for each scene or frame tweaks the dynamic range of the picture to best fit the content. These adjustments let dark scenes show more shadow detail and bright scenes show more highlight detail by giving the video more flexibility and control within the light and color ranges of each scene.

8K Enabled

HDMI 2.0 was the real step that enabled 4K video to gain momentum. HDMI 1.4 supported 4K resolution at up to 30 frames per second, but HDMI 2.0's 4K60 compatibility set the standard for watching 4K content on a 4K TV. HDMI 2.1 skips the 30fps step for 8K (7,680 by 4,320) and jumps straight to enabling the new, much higher resolution at 60fps. Technically, the standard supports up to 10K resolution in terms of sheer bandwidth, but 10K hasn't actually been defined beyond approximately 10,000 horizontal pixels. On paper, 8K120 and 10K120 are also possible through HDMI 2.1, but they present entirely new questions about media format and transmission outside of cable speed.

Don't worry about rushing to get an 8K TV, though. Your 4K screen will remain valid and eye-catching for several years (though if you still have a 1080p HDTV, you should consider upgrading). According to the HDMI Forum, only 400,000 8K TVs are expected to ship worldwide in 2018, and they'll almost entirely be released in China. That number will move up to 900,000 in 2020, with approximately half spread across Europe and North America and the rest in China. That's not a lot of 8K TVs for the next three years.

8K is still a fledgling technology on the consumer side, with no significant media distribution or TV manufacturing presence yet. It will be several years before 8K TVs become the new high-end, flagship standard, and at least a year or two after that before prices reach a level reasonable for normal consumers.

New Cables and Devices

TVs, media streamers, and game consoles will need to be built with HDMI 2.1 in order to use it rather than receive a firmware upgrade to enable it, since the much higher bandwidth will need faster hardware connections to support it. This means HDMI 2.1 won't be found on your current devices at any point; it's strictly a new standard for new hardware to be released from 2018 onward.

HDMI 2.1 will require new HDMI cables, which will be labeled Ultra High SpeedHDMI Cables. They'll look and function similarly to older HDMI cables, and use HDMI A, C, and D connectors (standard HDMI, mini HDMI, and micro HDMI respectively). Like HDMI 2.0 and HDMI 1.4, cables will be backward compatible to a point, so HDMI 2.1 devices will work just fine with HDMI 2.0 cables for showing 4K60 content.

When Will It Matter?

Don't worry about getting new HDMI 2.1 devices and cables for now. It won't even be an option for most of this year, and widespread consumer adoption won't get rolling until 2019. In fact, the HDMI Forum won't finish publishing its HDMI 2.1 compliance testing specification, which is required to certify HDMI 2.1 products, until Q3 2018.

More importantly, that backward compatibility I mentioned means your TV, Blu-ray player, and other devices won't suddenly stop working when everything else has HDMI 2.1. The HDMI 2.0 devices you've bought in the last few years will still handle up to 4K60 video, and even when you get something new with HDMI 2.1, it'll still work just fine with everything else in your home theater. It just won't support 8K60Hz.