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The next generation of HDMI will support 8K video with HDR

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Posing the question: will we ever have enough pixels?


The industry body responsible for HDMI has announced a first draft of the standard’s next set of specifications, and oh boy: we are getting a lot of extra pixels. HDMI version 2.1 — which will be backward compatible with current HDMI devices — will support 8K video with HDR at a 60Hz refresh rate, or 4K video at a 120Hz refresh. For those interested in the raw numbers, 4K resolution is 3,840 x 2,160 or 8.3 million pixels, while 8K is 7680 x 4320 or 33 million pixels. As the HDMI Forum’s Technical Working Group puts it (with a just a little understatement) this new capacity will allow for “immersive viewing and smooth fast-action detail.”

Like all new A/V tech specs, what we’re seeing now is very much designed for the future. 4K content has only recently become relatively common, and 8K content is years and years away from hitting your screens. We are seeing the first 8K TVs and monitors enter the market, but they’re either prototypes or specialist products designed for photo and design professionals. And, as well as the displays themselves, to get HDMI 2.1 running at full whack you’ll also need new cables that can support up to 48Gbps bandwidth. Reading about a new tech spec is easy; you have to wait for the compatible hardware and content.

48Gbps: it’s this much more than 18Gbps.
HDMI Forum

(A brief side note: the industry presentation for HDMI 2.1 mentions support for “10K” resolution as well as 8K, but doesn’t explain what exactly this means. It’s possible that it’s a reference to an as-yet-undefined 16:9 ratio resolution that’s the next step after 8K, but, as noted by Ars Technica, it’s more likely to be a reference to a resolution comprised of multiple displays, or an ultrawide version of an 8K screen. Either way, don’t worry about 10K for now — we’ve barely scratched the surface of what we’ve already got.)

Putting aside the prospect of watching Planet Earth VII on a screen more detailed than reality itself, perhaps the most interesting part of the new HDMI spec is something called “Game Mode VRR,” which should, you guessed it, benefit gamers. Game Mode VRR supports a variable refresh rate and allows a graphics processor to display an image on screen “the moment it is rendered,” says the HDMI Forum.

This is an actual image from HDMI Forum’s industry presentation; this is what gamers look like.
HDMI Forum

For those not in the know, variable refresh rates (or “VSync,” as it’s often called) allows a monitor to change how often it refreshes the image on screen. This is important, as the speed with which a graphics processor can create an image can vary. So, if you’re in the middle of a game and suddenly everything within four feet of you blows up, your processor will slow down as it’s forced to render every bit of shrapnel in the immediate vicinity. Without a variable refresh rate this can lead to the image “tearing,” as your monitor and processor go out of sync. It’s possible to compensate for this by turning on a variable refresh rate, but that in turn usually means there’ll be some sort of input lag as your processor and display are fixed in lock-step.

With HDMI 2.1’s Game Mode VRR, some manner of variable frame syncing will be built directly into the HDMI specification. This isn’t entirely new, with alternate A/V standard DisplayPort offering something similar known as Adaptive Sync. But, given HDMI’s massive presence and industry-wide support, Game Mode VRR should have a sizable impact. At any rate, we’ll find out more when the specification is finalized later this year. The HDMI Forum suggests a release date of Q2 2017, so look forward to more bandwidth-and-pixels talk then.