HDMI, or High Definition Multimedia Interface, was at its core, designed to satiate Hollywood's concerns over piracy and copyright management. As the concept needed to be sold to the average consumer, the benefits were (are) presented as easier and simplified connectivity, while potentially offering superior performance. Like so many things in this industry, the design and goals of the system are steeped in good intentions, and the results can be great, but there are some issues surrounding this subject that still perplex many. Certainly, companies that manufacture low-cost cabling, along with partner organizations and websites that sell it, may gloss over some issues that need to be addressed.
The first issue is cost of an HDMI cable, relative to its goals. Cost can be a factor of many things, whether it's distribution, packaging, associated marketing budgets, etc. HDMI however is victim to an interesting phenomenon that afflicts many digital cables out there--the idea that "if it's digital, the signal either gets there or it doesn't."
Well kids, it ain't that easy.
The first of many quasi-technical terms one may encounter along this research journey is "eye pattern". This is the pattern that one sees when viewing the "pattern" a signal generates while traveling over the cable. Example:
OK, so the cable passes the test. All we need to know, right? Not so fast. Admittedly, the eye pattern test is the fastest and best cursory test for whether an HDMI cable passes muster. Over certain distances (and this is where many consumers think they have to be really good guessers or engineers to know this) the center of the hexagonal shape in the center of the eye pattern gets smaller. If the red "box" in the middle touches the purple hexagon, the cable fails. This manifests itself by something called the "cliff effect." This addresses a scenario whereby a signal on an HDMI cable has a very specific distance it can travel, before one starts to see "sparklies" in the image. Seeing these artifacts means that you are very close to seeing nothing at all--over the cliff's edge, in other words. Cheaply-manufactured cables may proclaim that they produce products that "meet HDMI spec", but if a cable that passes a rudimentary eye pattern test under certain conditions fails under real-world conditions, the consumer shouldn't be expected to shoulder the burden. The catch is, how does one know how much money is required before they can avoid this issue?
The solution here is easier than one may think. Gauge and manufacturer make all the difference when making a purchase determination. The HDMI consortium use place-holder terms like "high speed" to make consumers at-a-glance understand what they're looking at. This can actually confuse the issue, since looking at the physical cable in the package may not yield much apparent difference. Here is what that type of terminology means:
- Standard (or “category 1”) cables have been tested to perform at speeds of 75Mhz, which is the equivalent of a 1080i signal.
- High Speed (or “category 2”) cables have been tested to perform at speeds of 340Mhz, which is the highest bandwidth currently available over an HDMI cable and can successfully handle 1080p signals including those at increased color depths and/or increased refresh rates. High-Speed cables are also able to accommodate higher resolution displays, such as WQXGA cinema monitors (resolution of 2560 x 1600).
Today, high-speed is not "necessary" given most applications, especially in what I call "rack-lengths" which are typically three to six feet. Where it makes total sense is in scenarios where perhaps a room is being remodeled and new cabling is being pulled. It's a good idea to ensure some semblance of "future-proofing" the wiring as much as possible, and pulling a high-speed HDMI is part of that prescription. Remember, HDMI can carry uncompressed 7.1 channel audio, plus 1080p video. This is an enormous amount of data. Two CAT-5 ethernet cables would have to be run to equal one HDMI cable. Sure, high-speed costs more, but probably less than having an installer come back and pull another cable a few years down the road.
So again, the rule of thumb is this: Purchase from reputable companies that either source from established cable manufacturers, or are well-known themselves for their own house products. Extremely inexpensive HDMI cables, while tempting, are a recipe for frustration, especially if they are installed in a semi-permanent environment, such as a sealed wall or ceiling. Do it right the first time, so you can look forward to technical updates instead of being frustrated by them.
Posts
