HDMI 2.1 explained: Everything you need to know in one place

HDMI 2.1 is on the way: Here’s everything you need to know

Still trying to get used to HDMI 2.0b and the 4K HDR content that the standard is made for? Brace yourself for a new wrinkle: The group behind the specification announced in late November the advancement of HDMI 2.1. Many questions have arisen as a result of this announcement. Some folks are worried about whether their new 4K TV or 4K Ultra HD Blu-ray player is already out of date or concerned that they’ll soon need to purchase a bunch of new HDMI cables. Then there are the questions surrounding what HDMI 2.1 brings to home entertainment systems: What’s new, how does it work, and when is it coming?

With 8K TVs already in stores, these questions are more relevant than ever. We’ve got all the answers right here, and while the subject matter is a little technical, we’ve made every effort to break it down in a way that is meaningful to both the average Joe and the hardcore A/V enthusiast. We’ll start by answering the questions we get asked most often on various forums and social media.

Is my new TV about to become obsolete?

Absolutely not. If your TV supports 4K UHD resolution and High Dynamic Range (HDR) — or even just 4K — it is far from obsolescence.

If you bought your TV within the past couple of years, you’re good to go for a while.

It’s true that HDMI 2.1 opens up a wealth of new possibilities, which we’ll get into shortly, but we’re years from even our first glimpse of most of those potential features, and even then, it will be years more until specs like 8K TV resolution and 4K at 120Hz are anywhere close to mainstream.

Bottom line: If you bought your TV within the past couple of years, you’re good to go for a good while. What if you’re on the verge of buying a new TV now, you ask, and thinking about waiting until HDMI 2.1 comes out? Don’t. You’ll be waiting for a while for it to come out in the first place, and the benefits of HDMI 2.1 will come in as a trickle, not a steady stream.

Does HDMI 2.1 require new HDMI cables to work properly?

Yes. As you’ll learn in the specs-oriented tech explanation of HDMI 2.1 below, the new standard nearly triples the amount of data that can fit down an HDMI cable at once. That being the case, to take full advantage of HDMI 2.1, the use of a new Ultra High-Speed HDMI cable will be required. In some rare instances, it may be possible to use an existing high-speed HDMI cable with a newer HDMI 2.1 device, but since the amount of information being crammed down this digital pipeline is increasing at a rapid rate, it will be wise to buy new Ultra High-Speed HDMI cables at the same time any devices supporting HDMI 2.1 are purchased.

Note: Nothing is changing about the size or connection type of the HDMI cable ports and jacks. The new Ultra High-Speed HDMI cables will fit perfectly into older devices.

Is HDMI 2.1 backward compatible?

Yes. You will be able to connect any HDMI-enabled device supporting any older version of the HDMI standard, and it will work just fine on a new HDMI 2.1-enabled TV or display. For instance, if in the future you want to connect your then-archaic Xbox One to your shiny new 8K TV with HDMI 2.1, that won’t be a problem at all.

Can my HDMI 2.0b devices be firmware upgraded to HDMI 2.1?

In theory, this is possible, but it is highly unlikely. Jeff Park, director of technology at HDMI LA, informed us that while there are premium chips out there which can be firmware upgraded, they are extremely expensive and rarely used by manufacturers. Chances are, your TV or 4K Ultra HD Blu-ray player doesn’t have one of those rare chipsets built into it.

Why do we need a new HDMI version?

Believe it or not, consumer-level home entertainment devices can already approach the 18Gbps bandwidth limits of HDMI 2.0b. Take a 4K Ultra HD Blu-ray disc, for instance (heck, take the best 4K Ultra HD Blu-ray discs!): 4K image resolution on its own is a big bandwidth hog, but then add 10-bit color, 4:4:4 color sampling, 60 FPS content, Dolby Atmos and DTS:X multi-channel surround sound, HDR metadata, and all the other little bits that need to get from a 4K Ultra HD Blu-ray player to a TV, and you get close to maxing out that 18Gbps limit. How do you improve products if you’re already running out of space on the digital highway that carries all this video and audio information? You don’t. You have to pave a new highway, and that’s exactly what the HDMI organization has done with HDMI 2.1.

Beyond the high resolution and increased frame-rates Hollywood and game studios would like to use, more lines of communication needed to be opened up between devices sitting on either side of an HDMI cable. Right now, your Blu-ray player or game console can talk to your TV, but only tiny bits at a time. They spit words at each other, but they can’t have a conversation in real time. By changing the way HDMI jacks and HDMI cables are structured, the HDMI organization was able to not only handle more traffic on the digital entertainment highway, but also to route that traffic in a smarter way so that more communication could be passed among the traffic.

In other words, if HDMI 2.0b is our existing, choked-up freeway system, then HDMI 2.1 is a mega-highway filled with autonomous cars driving themselves, immune to bottlenecks, and instantly adapting to traffic fluctuations. So what does that mean for you and your entertainment system?

What can HDMI 2.1 do that HDMI 2.0b can’t? What’s new?

As you’ve gathered by now, HDMI 2.1 can handle lots more information, and it’s easy to understand how that could translate into higher video resolution. High-resolution numbers like 8K and 10K get all the attention, probably because they are significantly larger than the 4K we see on our TVs now and that seems meaningful. But high-resolution capability is the least exciting part about HDMI 2.1 in our opinion, so while we’ll start with resolution specs, stick with us for the rest because HDMI 2.1 enables a more beautiful picture and an easier-to-use system than ever before.

  • Resolution: HDMI 2.1 allows for higher resolutions at higher frame rates than before. With HDMI 2.1, we can get 4K at 120Hz, 8K at 60Hz, and right up to 10K resolution for industrial and commercial applications. The resolution increase isn’t such a big deal on its own for TVs and projectors — we’re already close to maxing out the limit of detail our eyes can see at typical viewing distances — but adding higher framerates is great news for gamers. The HDMI organization says some Hollywood directors are eager to migrate to 120Hz native filming and want for that high-framerate content to make it into viewers’ homes as well as theaters.
  • eARC: HDMI ARC already allows us to share audio back and forth between a TV and an A/V receiver or soundbar, but limited bandwidth means that audio is often compressed and reduced down to stereo. With eARC, we can now get uncompressed, full-resolution audio over HDMI 2.1 connections. This will simplify system setups dramatically because it means users can connect everything to their TV and then run a single HDMI cable to their receiver or soundbar without losing sound quality. Fewer cables, less mess, better sound!
  • Dynamic HDR: High Dynamic Range is already the best improvement to TV picture quality since 1080p HD, but it can be better. If you’re at all familiar with Dolby’s version of HDR, Dolby Vision, then you likely know the reason some reviewers consider it superior to other formats is that it is a dynamic HDR medium. In other words, Dolby Vision makes changes to the dynamic range of an image as the image itself changes. The result is a more accurate, vibrant, and … well, dynamic picture. The only hangup with Dolby Vision is that it is a proprietary technology and not every electronics manufacturer wants to pay licensing fees to use it. HDMI 2.1 brings dynamic HDR performance to other flavors, including the dynamic version of HDR10, HDR10+ (though, it should be noted that Director of Panasonic Media Alliance Office, Paul Williams, claims that HDMI 2.ob can support HDR10+) and others, which should bring better HDR experiences to more TVs and more formats.
  • Variable Refresh Rate: Gamers will be happy to learn that true 4K gaming with no lag or stutter will mean fluid, smooth gameplay at high resolutions.
  • Quick Frame Transport: This will also reduce latency for no-lag gaming. First-person shooter games will be transformed, and virtual reality will break into new levels of real-time interactivity
  • Quick Media Switching: You know that blank, black screen you get sometimes when you switch sources or from games to streaming apps? That’s going away forever.
  • No more lip sync issues: Currently, it can be a hassle to sync up the video from your TV with the audio from your receiver or soundbar. This is because the TV may be using a heavy amount of processing, while the audio system’s processing takes far less time than the video processing. The result is a delayed output of a video signal relative to an audio signal, or the reverse effect — either way, your sound doesn’t match the timing of your picture. HDMI 2.1 will make it possible for TVs to talk in real time to A/V receivers, soundbars, Blu-ray players, game consoles, and other source devices to ensure your video and audio are in perfect sync, all of the time.

That’s our rundown of HDMI 2.1. As you can see, the new standard opens up a wealth of new possibilities. Now, it’s time for manufacturers to decide how they take advantage of the new spec and turn possibilities into real-life benefits. As has always been the case in the tech world, sometimes watching the change happen is just as fun as experiencing the change itself.

Visit this page at HDMI.org to learn more about HDMI 2.1 specs.

Special thanks to Jeff Park at HDMI LA and Chris Heinonen of Wirecutter and Reference Home Theater for providing deep technical background for this article.

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