HDMI Explained

At QED we positively embraced HDMI. Why? because of the technical elegance of the cable itself. For an HDMI cable to perform perfectly it requires precision conductor geometry, equally precise construction and of course, the highest quality materials. All these played to our strengths and expertise; after all, our cables have been exceeding our customer’s expectations for 35 years.

Oh, and the superb finish and styling?

Frankly, they’re not strictly necessary, but with a company like QED, with decades of near obsessive attention to detail, it just comes naturally.

HDMI is a demanding cable to get right, but that doesn’t mean that it has to be a complicated cable to understand, use and enjoy.

HDMI combines audio, video and control in just one connection, that’s the most important thing to remember. Everything between your Blu-ray and your flat-screen TV is carried by one cable. Simple, clean, magic (well almost). At QED our goal is to ensure you have the cable you need with the performance you expect. More than that, we want to help you through the tangle of cable options with clear explanations and guidance. We are here to help you make some simple choices.

HDMI – it’s fast.
You don’t need to know what’s going on inside the cable, that’s our job. But to give you some idea of the task, here’s some insider information. HDMI is digital. The information reaching the cable from the player is digital and the information the TV is expecting is digital. But cables don’t deal with digits, they deal with real-world analogue signals that are used to represent those digits. That means the cable has to deal with a very low level signal, a very high level signal and changing rather quickly from one level to the other. All the fuss, all the concern, all the worry about which HDMI cable to choose comes down to its ability to carry these highs and lows, separately, individually and cleanly from one end of the cable to the other.

When we say rather quickly, perhaps we’re understating that a bit too much. HDMI is currently specified to carry up to 10.2 Giga bits of uncompressed video, multi-flavoured audio and control signals every second. That’s the equivalent of 700 simultaneous HDTV broadcasts, 1,000 parallel high-speed broadband connections or the music from 7,500 CD players side by side, all playing at once. So actually, it’s very fast indeed.

We measure the effectiveness of our cables’ ability to change from high to low speed using what are called ‘eye diagrams’, like the one shown in Figure 1. Think of this as a photograph of a fast moving skipping rope which has been caught both in its ‘up’ and its ‘down’ position. If we make the skipping rope go up and down slowly, then the resulting ‘eye’ shape will be large and open (enough to jump through).

As we speed up the skipping movement, the opening will begin to close, eventually coming to a point where it is no longer big enough to jump through. HDMI cables need this ‘eye’ to be open, so that it is easy to determine the difference between when the rope is ‘up’ and when it is ‘down’. Increasing the speed of the digits and/or increasing the length of the cable, also reduces the size of the ‘eye’. Measuring poorer quality cables already reveals they produce a smaller ‘eye’. So, as the digit rate increases, the ‘eye’ of poorer cables gets smaller to the point where ‘up’ and ‘down’ are indistinguishable and the receiving equipment cannot understand the information (the digits) that are being sent.

HDMI – it’s more than just home cinema.
The HDMI interface is a whole bundle of wires and connections held within one outer sheath. Each needs to be individually constructed to fit its purpose. Three sets of wires are used to pass the high definition information (the digits) between source and destination, with a fourth set used for timing.

Having reduced the whole of the high-definition audio and video experience down to these four sets of wires, the end result is a ‘clock’ and three ‘streams’ of 1s and 0s (highs and lows, ups and downs). But these aren’t the only signals. The second part of the story is the existence of additional ‘control lines’ (over and above the wires discussed so far). These are used to keep the sending and receiving equipment, at either end of the cable, successfully talking to each other. Although they conduct much slower signals than the main wires, without these ‘control line’ connections there would be no pictures or sound. In effect, these control lines constitute the private ‘hot-line’ between the sending and receiving devices.

Devices communicate picture size, content protection, presence, status and all sorts of other things. Although slower, care still needs to be taken to ensure these signals arrive cleanly at the other end. Needless to say, QED takes that care.

Describing HDMI
Choosing the right HDMI cable for you needn’t be complicated. Yes, it’s true an inferior cable, one that was used for yesterday’s equipment, (particularly a long cable) may not be capable of carrying the signals from today’s high-speed, high definition products, but that doesn’t mean buying your HDMI cable should be a either a lottery or a risk. We have been closely observing industry reports and analysing future trends and there has been a lot of chatter about faster and faster HDMI needs and ever changing specifications. However QED aims to cut through all the jargon, enabling you to simplify your purchasing decision. It doesn’t really make sense to talk about Gbps (Giga bits per second) or other specifications if the equipment you wish to connect doesn’t communicate its requirements in a similar way. Do you know if your TV does 3Gbps or 4Gbps? Do you (or indeed anyone) actually care?

We are all familiar with the introduction of ‘HD Ready’ televisions. Then came ‘Full HD’, and now we have ‘Deep Colour’. These are terms the industry is now using and everyone can embrace.

The latest HDMI 1.4 specification describes just four types of cable; Standard Speed, Standard Speed with Ethernet, High Speed and High Speed with Ethernet. At QED we recognise it is our responsibility to research and understand the technical specifications which underpin the above terms. We then design and produce cables which not merely conform, but comfortably out-perform those specifications in every situation in which a QED customer will use their cable.

But for those that need something more ‘under the hood’ here is what they mean:

HDMI Cable Spec	High Street Term	Picture Size	Pictures per second	Bits per colour channel
Standard Speed	HD Ready	1080i/720p	30/60	8
-	Full HD	1080p	60	8
-	Deep Colour	1080p	60	12
High Speed	Full Deep Colour	1080p	60	16

If you see these words on your television or on your movie player then it’s easy to match them with the words used on the QED HDMI cable packaging, but more about that later.

Pitfalls
Not all HDMI cables are the same. True it may be currently possible to find a short cheap cable that appears to work for the equipment available today, but here are some things to consider.

Real world variation and tolerances may mean that a cable produced to simply ‘meet’ the specification on paper, may not actually comply every time in production. Similarly, both electronic display and source equipment will experience some variation in production and may also suffer some degradation of their performances over time. This means it’s not enough for a cable to merely meet the required specifications, it always needs to exceed them.

Unfortunately, these are not the only factors that contribute to poor performance. Poor choice of materials, imprecise control of cable geometries during manufacture, as well as physical imperfections and construction tolerances are all sources of error which can degrade performance, even after the original design has been passed as adequate.

To use an analogy, if someone fires a gun at you, there are some who would argue that being missed by just one inch is exactly the same as being missed by a mile. However, when the gun is being fired as often as it is in an HDMI cable, and in addition, being fired from a hand that is shaking (however minutely) I personally would feel a lot happier if I was confident the bullet would miss by a mile!

What about the HDMI system’s own ability to correct errors? QED’s response to that question is simply: “Why introduce errors in the first place? Isn’t it better to accurately receive every last detail of the uncompressed image, exactly as it was transmitted, instead of what the error correction thinks it should have been?”

Another hidden headache is, even if the cable achieves perfect transmission of the audio and video; a fault in the important ‘communication’ wires, can still stop the picture appearing. To be successful on every occasion, the cable designer must ensure the control lines are correctly maintained for all cables and for all lengths.

Conversely, if the communication lines are clean, but the cable cannot cope with the highest resolutions needed, then the two connected devices will tell each other that a higher resolution is possible and switch to that mode, again resulting in a blank screen!

Solution
At QED we firmly believe you should not be required to find your own solution to what is clearly not your problem.

We have analysed the requirements and produced that solution.

Every single cable in QED’s flagship ‘Signature’ range, comfortably exceeds the maximum specifications in place today (known as High Speed) without fault or failure, even at its maximum colour resolution of 16 bits per pixel. We refer to this specification as ‘Full Deep Colour’ in the table above, because it carries a full-size, 1080p, completely uncompressed picture. This is true of every Signature cable, from the very first one off the production line to the last (as backed by our Lifetime Guarantee).

We know every QED cable is fully up to the job because that’s the way we design them. Each one conforms to our described geometry and, from inside to out, is carefully crafted from our chosen materials. QED doesn’t use anyone else’s cable; and we don’t make cables for anyone else.

A range of choices
The QED ‘Signature’ is a range of unrivalled, truly aspirational models, which boast superior ability and performance headroom. They are the correct choice for someone who not only wants the very best now, but also doesn’t want the bother of having to upgrade to another cable in the future.

However, if you feel ‘Signature’ is just beyond your reach, then the ‘Reference’ range may be best for you. The whole Reference range, at minimum, exceeds the exacting standards required to support 12bit Deep Colour 1080p. Prior to 2008 it was nearly impossible to find any equipment that could send or receive these advanced signals, but such products are appearing in larger numbers now. If you think you will ever wish to take advantage of this Deep Colour experience then choose cables from the Reference range.

If, on the other hand, you simply want a cable to optimise the performance of the proliferation of today’s high definition products, then try the Performance Range. Every cable in the Performance Range, at minimum, exceeds today’s Full HD resolution 1080p needs and depending on length even reaches the High Speed standard of its more expensive brother.

Conclusion – To infinity and beyond….
There isn’t a single product, commercially available today, which even begins to worry the cables in the Signature Range. When tomorrow’s products come, you will have the satisfaction of knowing that all your Signature cables exceed the maximum specification that even those products could hope to achieve.

To help you match our cables to your needs you will see distinctive insignia on the packaging for each individual cable.

So, the complexity is removed. We’ve handled the complication and what remains is only the reassurance you need to make a simple choice.

Click here to return a list of QED HDMI cables.