HDMI 2.1 and Cables -- How not to Get Scammed

UPDATE as of 4/27/20: The article below was written in January, 2020. Since that time, HDMI Licensing has released a "generic compliance testing specification" for Category 3 cables, but this is NOT a functioning compliance testing spec. The conclusion given below still holds: there are still no certified Category 3 "Ultra High Speed" HDMI cables, and anyone who claims to have one is not telling the truth. At some point (When? We don't know yet!) this will change, and we'll let you know. Our original article follows:

Today (this piece was written on January 6, 2020) the HDMI Forum, which issues specifications for HDMI, announced that the upcoming Compliance Test Specification for Category 3 Cables (Ultra-High-Speed, often erroneously referred to as "HDMI 2.1 Cables") will require registration and special labeling (akin to, but not the same as, the labels used on cables carrying the "Premium" certification labeling). We'd like to help you understand what this means -- and in particular, to understand what it means if you have already purchased something that was described as an "HDMI 2.1 Cable" or an "Ultra High Speed HDMI Cable." It may be time to shake someone down for a refund.

So, here's the executive summary. As of today, there is still not a single legitimate cable certified to the HDMI 2.1 "Category 3" 48 Gbps specification. As of today, there is still no testing center equipped to issue a certification for such a cable. And a legitimate Category 3, "Ultra High Speed," 48 Gbps cable will have a sticker affixed to the package attesting to the certification -- but no such stickers have yet been issued, to anyone, for any product. So, while Ultra High Speed cables loom on the near horizon, if you've already bought one, you've been scammed.

The Specification and Certification Process:

For starters, it may be helpful to understand the specification and certification processes under the HDMI spec. HDMI is sort of the step-child of DVI, the original consumer parallel-digital-video standard. But DVI was characterized by considerable problems, and the way the spec was administered, there was nobody to police the spec and make sure that things that said "DVI" on them were compatible with other devices that said "DVI" on them, or to make sure that any of these devices actually conformed to the relevant specs. When HDMI was formed -- by some of the same companies involved in creating DVI -- the decision was made that this must not happen again. Products would require certification before they could use the HDMI trademarks, and certification could only come from an independent testing lab, NOT from the product vendor itself.

There are two principal layers to the HDMI specification. The first is the broad specification document -- hundreds of pages of technical requirements for sources, sinks (devices receiving HDMI signals) and cables. But that broad specification document, though it sets out technical requirements in general terms, doesn't specify how conformity to those requirements is to be measured -- and as anyone who knows his way around a spectrum analyzer can tell you, that's very important. If we're measuring impedance and impedance stability, for example, it makes a huge difference whether we're doing the measurement with a TDR (time-domain reflectometer) or with a signal generator and an oscilloscope.

That's where the next layer comes in: the Compliance Testing Spec. Where the main spec tells you things like what the signal frequency range is that the cable must accommodate, and how well it must perform in so doing, the Compliance Testing Spec is a document that sets out the exact measurement protocols. It tells you what kind of signal to generate, how to connect it to the cable, what kind of device to use to measure the output, and what criteria the resulting output must be judged against to generate either a "PASS" or a "FAIL" result.

As we've said, however, the HDMI specification (with minor exceptions not applicable here) does not allow "self-certification." If we at BJC develop a new cable and measure it, following the CTS faithfully, and conclude that it passes, we CANNOT issue ourselves a certification. To get a certification, we have to submit the cable to an HDMI ATC (Authorized Testing Center), and the ATC will run the tests and tell us whether we have passed or failed. We have done this repeatedly, getting certifications for standard and high-speed cables, and most recently, certifications for the Premium HDMI Cable program; we were the first vendor in the USA to have Premium-Certified HDMI Cables for sale.

What Happens "In the Wild":

Unfortunately, the consumer cable market has always been a bit of a dodgy place. Practically the moment any new specification comes out, there are vendors claiming to have the product. And there's money in that -- as soon as people hear that there's a new, better cable called for by HDMI 2.1, they start searching for an "HDMI 2.1 cable." And, sad to say, there are a lot of vendors who are happy to claim that this is exactly what they have.

HDMI 2.1 has had a rather long and slow arrival. The new version was announced at CES in January 2017, but there was neither a main spec nor a CTS available yet. Here we are on January 6, 2020, and guess what? There is STILL no CTS for cables, though we are told it is coming soon. So, for three years, unscrupulous vendors have been taking advantage of consumer eagerness to have the next big thing, selling "HDMI 2.1 cables," "Ultra High Speed Cables," or "48 Gbps cables."

What the Real Thing Is (or will be) and What it Will Look Like:

So, how can a person spot a real HDMI 2.1 cable? Well, that's a trick question, so first we'll fix the question, and then move on to the answer.

There is no such thing in the proper HDMI lexicon as an "HDMI 2.1 cable." If a vendor uses terms in that way, it's a red flag. The difficulty here is that all versions of HDMI accommodate older spec versions. An HDMI cable that was originally certified under the first certification program is STILL a certified HDMI cable under 2.1, no matter that the certification may be more than ten years old. And it would still pass certification today, but it would now bear the designation "Standard HDMI cable," the lowest data-rate specification of what, under HDMI 2.1, is a three-tiered system.

For that reason, and because of other deceptive practices we needn't get into here, the HDMI licensing authority does not permit HDMI cables to be labeled by version number. Such labeling is unhelpful at best, and confusing or misleading at worst. To be clear, it is fine to reference the specification (e.g. "this cable will support all features and protocols supported by HDMI 2.0"), but it's not a 1.3, 1.4, 2.0, or 2.1 cable.

Proper cable labeling is by bandwidth and presence or absence of the "ethernet channel." These days most cables have the ethernet channel, and few devices use it for anything, so that's almost always irrelevant. What you should be looking for is the specification level. In the spec these are called "Category 1" or 2 or 3, but they have corresponding names which are more often used: Standard, High Speed, and Ultra High Speed. A Standard speed cable is certified to handle the data rates required to support video to the level of 720p or 1080i. A High Speed cable is certified to handle 10.2 Gbps (total, between three data channels of 3.4 Gbps each). An Ultra High Speed cable is certified to handle 48 Gbps (total, between four data channels of 12 Gbps each, the clock pair having been converted to a regular data pair).

Beyond that, by the way, you're not looking for anything else, even if you think you are, and even if somebody is trying very hard to make you think you are. Vendors make long lists of features their cables will support: colorspaces, audio formats, specific resolutions and framerates, et cetera, but the fact is that cables do not provide feature-specific support; if the bandwidth of the cable is appropriate to the devices it connects, there being only these three bandwidth categories, it WILL support whatever features and protocols, colorspaces, color gamuts, color depths, resolutions, framerates, audio formats, and so on, and so on, which any other cable of the same bandwidth will support.

Correcting the Question...

So, there's no such thing as an "HDMI 2.1 cable." How do you tell if a cable is a legitimate Ultra High Speed cable?

This, fortunately, is about to be made easier than ever. In the old days, if one had a question about a vendor's certification, it was often impossible to drag the certificate out of him. And when one did, as often as not it would turn out that the certificate didn't encompass the cable being sold. We've had countless vendors send US certificates like this when trying to sell us cable -- we'll be interested in 24 AWG HDMI cable, and we'll find that the vendor has a certificate only for a six-foot-long 30 AWG cable, but is shipping all manner of HDMI cables of different designs, none of which have actually been ATC-tested.

Those types of shenanigans are over, at least for the new Ultra High Speed Cable, because today's announcement tells us that each and every individual UHS cable will be, and must be, accompanied by a hologram-marked, 3D barcoded tag which, if scanned, will guide one directly to the certification information for that cable. As long as the label, when scanned, matches the cable, you're good to go.

When Will Ultra High Speed Cables be Available?

We hope to have our own UHS cables available in the coming months; just as we were the first to bring a certified Premium HDMI cable to the US market, we'd like to be early in bringing a true Ultra High Speed Cable to the market as well. This is dependent, however, upon the CTS being issued, the ATCs tooling up for the testing, and development work with our vendors. Understand, though, that right now we aren't the only ones lacking Ultra High Speed cable. Nobody, anywhere, has such a cable at this date, despite the fact that some people have supposedly been selling them for almost three years now.

Yikes! I Bought One! What do I do?

If you've been scammed by a vendor claiming to have Ultra High Speed cables, you're not alone. We have been fielding questions for years now as to why we don't have these cables when other people do, and despite our efforts to clarify the topic, we have the impression that many people have come away thinking that we were simply behind the times and making up excuses for selling outdated product. We are sure that many of those people have gone on to buy from one or another of the fraudulent UHS cable sellers.

If this has happened to you, don't be afraid to ask for your money back. And when you're arguing with someone about it, have the HDMI press release (screenshot here) on this subject at hand.

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