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HDMI 1.4: Clearing Up Confusion

Several times a day during last month’s CEDIA EXPO in Atlanta, DPL Labs president Jeff Boccacio presented his very well-attended seminar, “How to Do More with HDMI One Dot Four,” where he taught integrators and installers how to take full advantage of the expanded capabilities that this new AV cable revised specification offers. Through his HDMI testing and verification program in Ormond Beach, Florida, Boccacio has learned a thing or two about HDMI. Here’s what he shared with RS, after getting back from Atlanta.

What are the biggest misconceptions still facing the HDMI 1.4 technology?
No question about it, it’s the announcement of the inclusion of Ethernet within the spec. This sounds so significant that people have come to believe that the cable interface has undergone a major change and is no longer fully compatible. This is simply incorrect. The Ethernet addition has no influence on the cable or the interface. In order to add Ethernet capability, HDMI took advantage of an unused pin in the original interface and uses it in conjunction with another existing wire within the design to add the Ethernet signal. The only difference is the way the cables are constructed. Other than this one minor change, Rev 1.3 cables are the same and HDMI 1.4 cables are fully compatible with HDMI 1.3 installations (minus the Ethernet capability, of course).
Jeff Boccaccio lectures to a packed house at the Ethereal booth during CEDIA EXPO 2009 in Atlanta.

What about other features, such as an audio return channel and the 4k by 2k resolution standard on the new spec?
As far as the new 4K by 2K resolution capability, there is a lot of confusion over questions pertaining to the system’s bandwidth. Again, many of these people have been erroneously told that the bandwidth in HDMI 1.4 was increased. Under Rev 1.3, the bandwidth per channel was 3.4 Gbps. Under Rev 1.4 the bandwidth remained at 3.4 Gbps. The big difference here is that 4K by 2K’s frame rate was reduced from 60Hz to 30 Hz, which cuts the overall bandwidth in half, allowing it to just squeak by the 3.4 Gbps upper limit.

You just got back from CEDIA EXPO where you led several seminars on the subject.
How was the turnout?

That is a great question, Jeremy. This year I will have performed better than 75 HDMI presentation and workshops with incredible attendance. Given all of the negative conjecture about attendance in advance of this EXPO, I was not really sure what to expect. However, our turnout ended up just as fantastic as the others. Especially our events on the main floor, each of which turned out to be standing room only. Great turnouts. There is such a hunger for real information on advanced digital signaling solutions such as HDMI.

What sorts of questions seemed to come up again and again during Q&A at your sessions?
Without a doubt the biggest area of confusion, and even fear, has been centered on the issue of High-Bandwidth Digital Content Protection (commonly known as HDCP.) I can understand this concern, because the process of HDCP is very complex with many instructions taking place continuously while the system is running. It doesn’t take much of a hiccup to cause HDCP-related problems. The next most prevalent issue [relates to] HDMI over Cat-5/6 installations.

The popularity of HDMI over Category cable–commonly called baluns–is sweeping over the install sector like a tidal wave. Baluns open the door to longer cable runs, often needed in sophisticated installations. But perhaps even more importantly, by using a balun solution, installers regain the ability to field-terminate their cables as they have always been able to do with analog installations. However, baluns are not impervious to HDCP issues either. Unless the balun has some kind of HDCP recovery capability, capacitive loading can really cause some problems on the Cat-5 over longer distance runs.

Please tell me that this is the last HDMI revision for a while.
On the one hand, I think it is safe to say that the newly announced Rev. 1.4 is going to be around for a while as the industry adapts to its many new capabilities, which will take quite a while to implement. On the other hand, that is a very analog comment.

To really understand the power of HDMI, don’t think of it as just a cable in the analog sense of a static specification–essentially a dumb pipeline that inevitably will become a limiting factor to technological advancement. Rather, think of HDMI as an active and dynamic interface. HDMIs specification revisions cause many to chafe as they have to adapt to the new parameters–but what is really going on is the interface is growing, expanding the possibilities such that the technology at each end of the interface, source units and displays, can advance technologically as well.

HDMI will always change so that it does not limit industry technological advances. It is a smart system and extremely adaptable…more adaptable than the people using it unfortunately.

As an engineer, we hope there will be many revisions. These revisions, and past ones, have brought us much greater capability such as higher resolution, much greater color depth for more accurate high-definition pictures, and now wonderful new capabilities such as Ethernet and audio return, which reduce cable clutter and opens new doors to simplified installations.

Sure, it will be more challenging as we move into newer and better options, but like a wise man once told me “the most successful people are the most adaptable.” Plus, from a business standpoint, just think of all those wonderful goodies yet to be sold.