THE PRO PERSPECTIVE: AUGUST 2009
Take It, Or Leave It
HDMI is rapidly becoming a standard interface in the pro AV industry, although not one that’s being greeted with much enthusiasm.
In case you hadn’t noticed lately, there’s been a big change in the connector panel of your new projectors, monitors, and video interfaces. Along with the usual composite, S-video, component, and 15-pin VGA jacks, you’re more likely to find an HDMI connector these days than a DVI connector.
“When did that start happening?” you ask. Oh, about three years ago, when display manufacturers decided to retain all of the connections used by the professional versions of their consumer LCD and plasma TVs. And interface manufacturers said, “Guess we should be supporting those formats, too” and began adding HDMI inputs and outputs to scalers and processors.
So, what happened to the good ol’ DVI format? That seemed to work reasonably well, and indeed you’ll still find ‘em on quite a few pro displays and projectors. But it’s obvious that display manufacturers would like to jettison DVI completely and switch to HDMI instead, particularly when you consider the latter’s ability to carry multiple channels of digital audio.
Is this a bad thing? Maybe not, particularly if you have single-monitor applications that use the monitor’s built-in speakers. Having all that video and audio transport capability in a single cable is appealing. And if you are installing a high-end consumer TV in a conference room or classroom, and you want to drive it with an upscaling red laser DVD players or a Blu-ray player, you’ll need to include HDMI connections in the mix.
But what if you are just switching and distributing digital video? Isn’t DVI good enough for that?
The answer is an emphatic “yes!” DVI is indeed good enough for the application, and in fact can do anything HDMI can do, sans audio. DVI also has one big advantage over HDMI, and that is its mechanically secure connection, which will hold up under just about any mounting or environmental conditions.
HDMI, on the other hand, is designed for easy connection and disconnection on consumer electronics equipment. The connector does not lock per se, and only requires about three pounds of pull before it pops out. That would make installation in a high-vibration environment inadvisable, and it would also seem to preclude unusual mounting schemes that would result in additional strain on the connector.
At least two companies have made attempts to secure HDMI connections. PPC of East Syracuse, NY ( http://www.ppc-online.com/) unveiled a locking HDMI connector at CES that works with existing HDMI jacks. It uses the small detents in HDMI jacks to more securely engage the plug and raises the “pull” force for disconnection to 12 pounds. Hey, that’s a start!
Another company, Blue Echo (http://www.blueechosolutions.com/), has a come out with the hd EZ lock, an adapter that works to secure existing HDMI connectors by fitting around them and using a set screw to prevent the plug from migrating. This approach is a bit more secure than the PPC connector, but it does require additional tools during installation and removal.
The obvious problem here is that outside manufacturers are being tasked to fix a problem that was created with the original HDMI specifications several years ago. Silicon Image, who is the “gatekeeper” for HDMI, didn’t incorporate a locking connector design in the original specification, and has yet to introduce one in subsequent updates.
Even the proposed v1.4 specifications, released on April 24, make no mention of a locking connector — only that a new, smaller connector using 19 pins is under consideration. (A smaller HDMI connector has been proposed before, but this is the first time it’s been part of a proposed spec upgrade.)
Other problems with HDMI have been legion, such as blank screens when switching HDMI sources, and resolution conundrums when connecting more than one display. But those are being addressed by using writeable EDID buffers within switchers and repeating or simulating valid EDID when switching from one video source to another, so as to prevent computers and DVD players from shutting down or going to sleep.
The real problem here is that the dominance of the consumer display industry is forcing AV systems integrators to deal with a whole host of interfacing issues they really shouldn’t have to worry about. But the issue has been forced by the ever-accelerating transition away from analog signal interfaces. For now, HDMI is about all there is, and DVI is largely disappearing from the consumer marketplace.
What about DisplayPort? The original DisplayPort 1.1 specification was released last year by the Video Electronics Standards Association (VESA) and is slowly winding its way through the display electronics world. As of this writing, only a few products have incorporated DisplayPort connectors (most recently, Dell’s Adamo notebook PC) and I have yet to see it show up on a single commercial AV interface.
The nice thing about DisplayPort is that it was designed by consensus, and as a result is likely to catch on in the world of desktop and notebook computing without too many “bumps.” That means we should be seeing monitors and projectors that incorporate DisplayPort eventually — but not any time soon.
One big advantage that DisplayPort has over HDMI is its support for direct-drive monitor (DDM) designs, or display panels that eliminate lots of internal video processing electronics. In theory, this could simplify monitor design considerably, not to mention cut down on weight and cost. The panel is simply driven directly from the computer’s video card, or a server. (Take note, digital signage designers!)
What about interoperability and adapters? On March 12, VESA issued an Interoperability Guideline for DisplayPort cable adapters, primarily aimed at you-know-who.
To quote from the press release, “…There is industry interest in establishing a means for achieving interoperability between DisplayPort Devices and DVI 1.0/HDMI compatible Devices. (You think?) For example, it is desirable to have the ability to connect a cable between a DisplayPort Source Device and a DVI 1.0/HDMI Sink Device (or vice versa) and have the devices interoperate. This interoperability cannot currently be accomplished at the specification level, but can be accomplished at the product level for products that are compliant with DisplayPort 1.1a and either the DVI 1.0 or HDMI specification.”
Well, good luck with that. I’m sure you are familiar with the list of “big lies,” which include “The check is in the mail” and “We’re from the government, and we’re here to help.” The term “simple interface” has been used numerous times before with regard to marrying HDMI and DisplayPort signals. It might turn out to be a strong candidate for the list!
Long story short, we’re stuck with HDMI, and it’s not going away. So learn to live with it, and make sure any video signal distribution electronics you have in your system are EDID-friendly. And maybe if we’re lucky, someone will design a true professional HDMI connector that locks securely in place and won’t fall out, even if you pound on it. Cross your fingers…
This article appears in the July August issue of Pro AV magazine.
