Re-Defining HDMI Performance

What can be done to cure connectivity issues? The solution is very simple.

Re-Defining HDMI Performance
Jeff Boccaccio · September 16, 2011

Wire and cable products are the lifeblood between electronic devices. There is a true engineering science behind wire and cable, and without its advancements new technologies could never exist. In today’s products, multiple types of wires are necessary to carry multiple types of signals. This not only includes analog and digital signals, but also AC/DC power supply voltages and grounding methodologies.

Poor performance within the analog ecosystem can be caused by distortions, poor signal levels, crosstalk and more. But the same holds true for digital signaling, except that there is one very big difference: defining digital performance.

Case in point: You can talk about HDMI cable performance until you are blue in the face, yet never answer the most obvious question of how do they differ? Many believe “digital is digital,” and that no matter how you slice it, if enough HDMI data arrives to each device, the picture quality will look the same. So what are the cables’ differences? This is where the so-called experts fail to report on an obvious answer.

Mention HDMI to almost any person in the CE pro community, and usually you will get a negative response, like “plug and pray.” The ire has nothing to do with the way the picture looks! On the very rare occasions at DPL Labs that we might hear about a picture quality issue, it does not concern the cable.

There has not been any distinction between performance in quality vs. performance in reliability. It is the reliability that has so many integrators upset, not the quality. Yet both always seem to be lumped into the same category of performance.

Are there differences in HDMI cables? You bet. DPL Labs has examined countless cable designs and has found through exhaustive testing why some work and why some don’t. But we don’t justify the outcome by watching video on a TV set and assume it qualifies as a test standard - how absurd and barbaric. How many times have you installed systems that fail to operate, and by just swapping out the display or the source for a different device the problem corrects itself?

So how can anyone justify characterizing a testing sequence by using a television! Oh, I can see us now, writing an engineering report using sparkles as a unit of measurement. Maybe it could go something like, “Unit has 62 sparkles, DPL thinks that’s good.” That would go over like a lead balloon.

If one were to examine just the video alone, its operating range has only a 900mv window, about 10dB. Breach that window and you’re in trouble. Those that are low in that window do not necessary complement other products with similar integrity. It’s the matchup that can kill you.

Why is it that some systems work with one set of products while others don’t? You can mix and match these all day long and they will work somewhere, but not necessarily everywhere.

The cure to all this from a wire and cable perspective is very simple. Manufacturers have to adhere to the rules in the science behind cable transmission lines. Whether it is video, software, voltage or timing, if a manufacturer will just keep its performance meter no less than 50 percent, then everyone will have a “plug and play” day.

  About the Author

Jeff Boccaccio is president of DPL Labs. Jeff can be reached at [email protected] Have a suggestion or a topic you want to read more about? Email Jeff at [email protected]

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