A commonly asked question from anyone looking to buy a premium 4K Ultra HDTV today is “will it be compatible with the new HDMI 2.1 input standard.”

Experts in the field of home theater installation, and AV testing and calibration technologies who attended last Sunday’s TV Shoot Out at custom home theater specialty retailer Value Electronics of Scarsdale, N.Y. advise not to worry about.

Unfortunately, compliance testing protocols and procedures for HDMI 2.1 certification have not been announced yet for many product categories, meaning that it’s very unlikely that any 4K Ultra HDTVs available this year will carry the HDMI 2.1 connector.

But two of the experts who designed and implemented the set-up logistics at the shootout told the audience comprised of AV enthusiasts, calibrators, manufacturers representatives and the technology media not to worry about it.

The following is a transcript of a brief presentation by custom electronics specialist Brent McCall, of Metra Home Theater Group and Matt Murray, AVPro Store VP, a supplier of technical video testing and set-up gear for professional electronics installers, explaining why the purchase of a TV today will be an investment that will pay dividends for years to come, without having full HDMI 2.1 capability.

McCall: “The world’s still safe for you to go out and buy [today’s premium TV] products. You don’t have to panic with HDMI 2.1 coming down the pipe. But there are some changes to be aware of.

Right now, HDMI, as you know it, is three channels. Red, Green and Blue, or D0, D1 and D2.

Since day one of HDMI 1.0 there have been four high-speed channels built into the interface. That fourth high-speed channel will be turned on for the first time as a legitimate high-speed channel with 2.1. Up until this point it has just been a clock ticking along syncing up the Reds, the Greens and the Blues. It hasn’t had to do much.

Where you will move into some challenges moving forward is if you have some cable infrastructures in place that don’t treat that channel the same as One, Two and Three (or D0, D1, D2). When that occurs, you will have failures.

Other than that, the feature sets [of HDMI 2.1] are vastly available right now from a lot of the manufacturers. eARC, or Enhanced Audio Return Channel, will bring the ability to pass through Dolby Atmos from your display panel back into your AV receiver or sound bar over the HDMI cable.

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It is an incredible feature set. It will take us a lot farther down the road to enjoying the audio part of all of the work these. guys put in. That’s the coolest feature in the world and you don’t need 2.1. You just need a current TV set that has an HDMI 2.0b connection

But do you know how much bandwidth is necessary for 4K, 60 frames per second, 4:4:4 chroma sub sampling and 10-bit? It is not 18.2 Gbps [the maximum bandwidth for the HDMI 2.0 spec]. What most people don’t see is that little tiny word `or’ that ought to be on package. 4K/60fps, 4:4:4, 10-bit actually requires between 22.5 and 23.5 Gbps.

What is the bandwidth for HDMI 2.0 anything? 18.2 Gbps. So be careful with the bandwidth numbers. The number doesn’t tell you the truth unless it’s in context.

But what really tells the story is what you see and what you hear. What gets down that pipe.”

Murray: “What is important from my standpoint are the problems that TV enthusiasts, calibration experts and people who really understand this stuff are facing, because these are people really driving the next generation of everything.

If I’m out there making products and not thinking about these people, then obviously there are going to be some major disconnects.

This is the third year that we’ve done High Dynamic Range (HDR) Ultra HDTVs [in the TV Shoot Out]. It is incredibly complicated and thankfully there are people willing to put their necks out there to do this and share with the world what we are doing.

The first year we couldn’t really calibrate [for HDR], the next year we could calibrate a little and this year everyone has got controls so we can set these things up really well.

Not to get too crazy with HDMI 2.1, but 48 Gbps [the full bandwidth of the HDMI 2.1 spec] is the number that everyone sticks in their mind. But I think it is really going to be a while before we get there.

We went from about 20 formats that we needed to manage to 130-plus optionally supported formats. We have to start thinking about that, because there are going to be a number of content creators and people who want to do amazing new things.

The HDMI Forum sets minimum compliance tests but where HDMI 2.0 had a list of things that would be required, HDMI 2.1 for the first time brings in digital compression — it allows for built-in compression in the spec. So if we are at 6 Gbps per lane, when we add a fourth channel we are at 24 Gbps. So, we are talking about the ability to pass 4K/120 using compression and as long as you can support 4K/60fps 4:4:4 or 8K 4:4:4, you are able to call yourself HDMI 2.1.

Where this is all going to is fixed-rate lanes. That’s why you see a lot of these things including a lot of different bit depths inside of one item. Hopefully, this will work in such a way where we [connect] a device and we communicate with a TV. The TV sends back a message saying effectively, `Here’s my level.’ Then it will open up everything within that level to the source device. The source device can then decide what it is going to do.

Right now with HDMI 2.0, we’ve learned that it’s very hard when you have 11 Gbps one day, 14 Gbps the next day and 17 Gbps the day after that.”

McCall: “The other issue we are seeing with AVRs and switching devices, unless you’ve got a very, very good programmer, there is a very limited range of resolutions they will support. Anyone who has tried to support a PC through an AVR has been down that road. Yes, it’s supported by the HDMI interface but [whether or not the desired resolution will pass] it’s like going to a Chevy or Ford dealership and trying to buy a car, and [the buyer must decide] `Do you want power door looks, power windows, auto up?’

All of these are options that are not obligations in a standard. So yes these are all great features, but the product manufacturer will decide if he is going to spend the time and the money to enable it in any given product.

So, the short and the long of it is, you really don’t need to panic [about whether a TV you are considering today supports HDMI 2.1] as we move forward. [The most important factor is] the picture quality is just incredible today.”


By Greg Tarr


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