Articles and whitepapers

So, You Think You Don't Need HDMI? (3/5/2007)

By Ben Jamison, VizionWare

By now it should be apparent to anyone that has been considering the purchase of new display and electronics equipment that the age of high-definition television is here. According to several industry sources, the sales of 1080p-capable displays have gone from less than 5% of total displays purchased just six months ago to over 30% in March 2007.

We now have two new high-definition DVD formats in Blu-ray and HD-DVD that are capable of outputting 1080p video resolutions and multichannel high-resolution lossless digital audio. Two of the three new gaming platforms on the market have high-definition playback and storage options. And finally, downloadable high-definition content is currently available for purchase online through several different merchant sites with the promise of more to come.

But this increased new digital picture and sound performance comes at a price. High definition places dramatically increased demands on the cables and interconnects that link these systems together in order to deliver the best possible quality of the new digital formats.

Enter HDMI - the missing link

HDMI (High Definition Multimedia Interface) was developed as a high-performance digital interconnect standard specifically designed for high-def video and audio applications. It provides extremely high-bandwidth capabilities that can deliver the best information available on a single wire, reducing the number of wires needed and dramatically simplifying installation complexity. It also provides a link between source and display components, allowing them to communicate with each other to transfer the best possible sound and picture formats and resolutions. HDMI is currently the only A/V interconnect standard other than DVI, that incorporates HDCP (High Definition Copy Protection) to enable high-def content to be delivered in its maximum supported resolution.

Like any good new standard, HDMI continues to evolve. Since its introduction in 2002, the standard has continually been upgraded to take advantage of the increases in display and source technology developments, providing increased performance features. The latest update to the specification, HDMI 1.3, has been bifurcated into two classifications; Category 1 and Category 2, to ensure maximum compatibility and incorporate support for the latest advances in processing standards and capabilities.

Considering all of that, it is no surprise that HDMI has become the industry standard interconnect for digital display transmission in just a few short years. By 2011, over 278 million HDMI ports will be incorporated into almost every type of consumer electronics A/V component.

So what's the rub?

With such a compelling value proposition for the consumer, why is there still so much confusion about HDMI? This is a more complex question than it may seem on the surface. We are in a highly transitional phase in the migration from legacy analogue and SD (Standard Definition) digital audio and video formats to newer and much more demanding HD (High Definition) standards that are emerging in the marketplace.

Adding to this confusion are articles and blog threads that seem to support the notion that all HDMI cables are the same. Would you believe that all 1080p displays are the same? Or that all DVD players are the same? Of course you wouldn't. Anyone considering investing in the latest high-def video and audio technologies should be no less interested in understanding the link that will connect all of this technology together than they would any of the other components in their system. If you don't, then you are not realizing the potential of what real high definition can look and sound like.

Other complaints about HDMI range from bad picture quality to cables that don't work at all. Silicon Image, one of the founders of HDMI and the 'gatekeeper' of the HDMI specification, founded Simplay HD Labs whose charter is to test all HDMI components to ensure compatibility and compliance to HDMI specifications. These testing programs are designed to help consumers know that the digital entertainment devices that they purchase work according to specifications aimed at maximizing the delivery of HD content.

It is important to note that while Simplay HD testing guarantees a 1080p signal, it does not guarantee the picture will be free of interference. Bit errors and other undesirable artefacts are not uncommon, even in some of the more expensive passive HDMI cables, particularly at lengths beyond 7m. HDMI 1.3 Category 2 increases this data significantly from 4.4Gb/s (1080p/60Hz at 8-bit colour) to as much as 6.68Gb/s (1080p/60Hz at 12-bit colour) and beyond. Most of these passive HDMI cables however, were not designed to handle such data rates over any significant distances.

Artefacts introduced into image using passive HDMI cable longer than 7m

Educate yourself

There are many so-called HDMI cables out there that do not meet HDMI specifications. Just because a cable has an HDMI label on it, doesn't necessarily mean it passes the latest specifications for HDMI performance and compliance. If you are planning to use 1080p, be sure your HDMI cable is at least 1.3 Category 1 compliant. Earlier versions of HDMI were only designed to support resolutions up to 1080i. Performance can vary widely from cable to cable, especially in lengths of more than 5-7m.

Carefully consider your needs and look at all of the available options that can best address your installation requirements.

Most of today's notable interconnect suppliers continue to apply the same passive cabling technology that has been used for over a decade in analogue audio and video interconnects such as S-Video and component analogue. But the continually increasing data rate demands of today's HD digital video and audio are several times higher than what these cable manufacturing techniques were originally designed for. Despite many attempts to improve their performance by using more conductive metal conductors and more extensive shielding materials, traditional passive cabling solutions now face severe physical and material property limitations that limit their performance and can compromise installation flexibility in today's demanding HD home theatre environments.

Several different cabling accessories have been designed to overcome many of the limitations of today's passive interconnect technology. External in-line signal amplifiers and discrete equalizers are available from several manufacturers and are designed to compensate for the loss of performance in passive HDMI cables in certain situations. These solutions are expensive and many times produce only marginal improvements in overall performance.

Another new and radically different approach to consider uses active signal conditioning electronics in both ends of the interconnect to provide an optimised link between the source and the display, and deliver HDMI 1.3 compliant theatre quality video and studio quality audio over very long distances.

Conclusion

No matter what electronics components you choose to purchase for your particular home theatre experience, HDMI digital interconnects are the best and ultimately the only logical choice for your high-definition components if you want to get the most from your home theatre system. Give them the same weight and importance as you do the other components of your system and you will find the investment will pay you back in spades.

Ben Jamison is vice president of sales and marketing at VizionWare, and has over twenty-five years' experience in consumer electronics, professional video sales and marketing, and broadcast television. VizionWare is a Texas-based audio and video digital interconnect manufacturer.

www.vizionware.com