May/100
Commercial HDMI Cable Installs Issue
HDMI is quickly making headway into commercial A/V with the proliferation of HDMI interfaces on displays and source devices including laptops, Blu-ray disc players, and digital satellite and DVRs.
End users of commercial A/V systems, well aware of HDMI in home A/V, are asking integrators to implement HDMI in commerical A/V installations. As a result, the industry is quickly transitioning toward digital video and adopting HDMI as well as DVI, DisplayPort, and SDI.
Integrators working with HDMI in commercial A/V face essentially the same challenges as residential custom installers – maintaining signal integrity, ensuring compatibility between devices, and working with HDCP.
However, there are special considerations for addressing these challenges in professional A/V integration, due to the much larger scope and complexity of commercial systems compared to a home system. Here, we tackle three major issues.
Signal Integrity
In a commercial A/V environment, audio and video signals typically have to travel much longer distances than in a residence. Cables usually have to be installed in tight, limited spaces, and integrators want to be able to terminate them easily. Transmission requirements can range from as little as 25 to 50 feet, to several hundred feet, and even up to several miles when sending A/V signals between corporate or university campuses. Standard HDMI cables may be sufficient in applications with relatively short distance requirements, but will not be adequate for longer distances, for which other mediums including twisted pair and fiber optic cable should be considered.
To help ensure signal integrity in short-range applications, select high quality 2 metres HDMI cables rated by the manufacturer for the distance required. When using long HDMI cables to cover distances significantly beyond 50 feet, a cable equalizer may be necessary, especially at high resolutions including 1920×1080.
A cable equalizer attaches to the end of a long cable run and restores HDMI signals by compensating for cable losses. To provide for advanced HDMI features and capabilities such as deep color and 3D, high-speed 2 metres Mackuna HDMI cable should be selected if there is a potential for future system expansion or upgrades.
For distance requirements exceeding around 100 feet, an alternative to standard HDMI cables is a transmitter and receiver set that sends signals over twisted pair cable. Twisted pair is a proven medium for extending digital video signals, and integrators often prefer twisted pair cable since it is inexpensive, easy to pull through conduit, and can easily be field-terminated to custom lengths. When very long transmission distances are necessary, fiber optic cable and fiber optic A/V devices are the solution. A/V signals can travel for miles over fiber with negligible loss.
Device Compatibility
HDMI and other digital video formats utilize EDID (Extended Display Identification Data) communication, originally developed for use with analog VGA ports. EDID communication is a two-way data exchange that allows a display to convey its operational characteristics, such as its native resolution and refresh rate, to the source device, which then generates the necessary video characteristics to match the needs of the display.
This automates and optimizes compatibility between the source and display, without requiring the user to configure them manually. In pro A/V applications where computers are the most common source devices, EDID communication can save significant time and effort in system setup.
EDID was intended for a single connection between one source and one display. The situation becomes considerably more complicated when a signal needs to be split or routed. Distributing a signal to multiple displays may not be a problem if they are identical, but what if they are different, at various native resolutions? An integrator may select one display to establish EDID communication with the source, and then roll the dice on the others.
With either approach, the switching or distribution device always maintains EDID communication with all connected sources, even with a signal switch or split. An HDMI matrix switcher may include more sophisticated EDID management, due to the fact that separate EDID communication is required for each input / output tie.
Content Protection
The first is that all devices in the system, from source to display, must be HDCP-compliant. That may seem obvious to a residential integrator, but commercial A/V integrators may not be fully aware that just a single, non-HDCP compliant device, such as a simple HDMI switcher, can disable Blu-ray disc playback for the entire system.
Second, commercial system designers need to be aware that HDCP rules allow for a maximum of 127 devices downstream from the source, with up to seven levels of repeaters allowed. A residential installation is not likely to approach these limits, but system designers may be concerned if they’re working on a large commercial project that calls for HDCP compliance throughout. Certain source devices including Blu-ray disc players have been known to allow for much less than 127 downstream products, often even less than 16.
Some residential and commercial A/V integrators have decided to work around the issues related to HDCP by deploying analog-based video signal routing. This is a temporary solution, since the ability to deliver to analog high definition video output may be impacted in the future by the AACS-mandated “analog sunset,” and possibly other content protection provisions that could limit or disable analog output on HDMI-equipped devices.
Sep/090
HDMI Cable Scam, Fight for the best
If you have purchased a new HDTV set recently, you are already familiar with HDMI cables. If you are thinking about purchasing an HDTV anytime soon, you are about to be initiated. The problem is that HDMI cables have become a popular way to scam customers. If you know about this scam, you will be able to save yourself a lot of money.
So let’s start at the beginning. When you own an HDTV, you need to have a way to get a high definition signal onto the screen. The signal can come from a cable box, a DVD or Blueray player, a video game console or a satellite antenna. The easy, high tech way to carry that signal from the video source to the screen is a piece of wire called an HDMI cable.
An HDMI cable truly is an innovation. It carries all the video information to the screen in digital form, plus it carries all the sound information. Just a few years ago it took five or more cables to carry all this information and it wasn’t digital, meaning that it could degrade along the way. With HDMI it is all in one slim cable. It couldn’t be easier to connect things like cable boxes to a new HDTV.
So where’s the scam? You can find the scam by going to any big box electronics retailer and looking in the cable aisle. There you will find HDMI cables priced as low as $25 or $30 (if not, definitely head toward your local discount retailer for better prices). But you will also find HDMI cables priced above $100. And if you talk to a sales person, he will definitely be steering you toward the most expensive model. That is the scam. You can understand the scam if you understand how an HDMI cable works and what it does.
Let’s begin by going back in history to the birth of really expensive cables. It started with speaker wire. When you connect a normal speaker to a normal stereo system, you are sending both a signal (in the form of an oscillating wave) and a lot of power (potentially hundreds of watts) through the speaker cable. Someone realized that to send a lot of power, a thick cable would cause less distortion. Thus, mega cables were born. And they were expensive.
But with an 10m HDMI cable, you aren’t sending any oscillating analog waves, nor any power. What you are sending is a low-power digital signal. The digital signal is either on or off, and it is impossible to distort it without ruining it. The great thing about a digital signal is that, even if there is a little noise in the cable (and there always is, no matter how good the cable), the TV will clean it up when it interprets the digital signal. The whole beauty of moving to a digital world is that it eliminates distortion completely.
What this means to you is that there really is no such thing as a “better” HDMI cable. Either an HDMI cable works or it does not. If it doesn’t work, you will immediately know it. Your screen will freeze, or it will skip frames, or it will show big square blocks instead of a picture. It will be completely obvious that there is a problem. In that case you need to throw the cable away.
But if an HDMI cable is working correctly, your TV’s picture will look exactly the same no matter how much the cable costs. Paying more for a cable will have no effect on picture quality.
Now that you know this, you can see what you need to do as a consumer. When buying an HDMI cable, you can buy on price and get the cheapest one.
That being said, there is one two things you do need to be aware of when purchasing an HDMI cable. First, you have to get the right length. If the cable isn’t long enough, it won’t reach to the HDTV. Second, HDMI cables have version numbers. For example, version 1.3 of HDMI can carry twice as much data as prior versions. If you buy a high-end HDTV that needs a version 1.3 cable, you need to make sure that the cable you buy supports version 1.3. Otherwise you are not getting everything that the equipment has to offer. In that case buy the cheapest version 1.3 cable available, and it will work fine.