Wireless HDMI - Why you would need one and how to choose one



Wireless HDMI

Wireless connectivity is rapidly taking over from wired, or at least as fast as manufacturers can come out with the necessary devices. While this is relatively simple for some devices, systems which transmit large volumes of data, such as HDMI, are much harder to design and produce.

Early Wireless HDMI systems left much to be desired, as they didn’t provide excellent connectivity, which ultimately caused the image quality to suffer. In most cases, they couldn’t handle the full data bandwidth necessary for 1080p, but were only able to provide interconnectivity for 720p. While still considered HDTV, 720p never really took hold, as HDTV manufacturers quickly moved to bring out units that provided a full 1080p image.

Newer Wireless HDMI units can and do provide connectivity for 1080p, and do so with excellent image quality. Extremely complex images, such as a screen full of small text, may not come through perfectly clearly. Likewise, the SMPTE color bars which are used as a widely recognized standard may show some ghosting between adjacent colors. Nevertheless, the amount of image quality loss in these highly controlled tests is not enough to indicate that there would be a discernible difference between a wired or wireless connection for normal movie viewing.

Advantages and Disadvantages of Wireless HDMI

The major reason for using Wireless HDMI over normal wired in connections is for convenience. If a Blue Ray player is parked next to a HDTV, there’s really no reason to use a Wireless connection. The normal copper wire connection will provide better connectivity, with excellent image quality, at a much lower cost. However, not all installations are this simple. In cases where a video is being projected from a ceiling-mounted projector, using a cable may be inconvenient or even impossible. In those cases, Wireless HDMI is a superior choice.

The biggest disadvantage of Wireless HDMI is the low power of the units, to avoid causing signal crossover to other types of wireless equipment. This creates the potential for signal problems with the Wireless HDMI connection, especially if there is an opportunity for anything to interrupt the signal. Manufacturers highly recommend mounting the sending and receiving units with a clear line of sight and provide very clear guidelines for the maximum distance they can be used.

Walls, bodies and large pieces of furniture all have the potential of blocking the signal, or at least reducing it to unacceptable levels. This would cause the image to suffer severely. This problem is drastically increased if the walls or furniture have any metal structure in them. A metal stud framed wall could totally block off the signal form the Wireless HDMI transmitter to the receiver.

Selecting a Wireless HDMI System

When looking at a Wireless HDMI system, the specs are everything. There are three major things to look at: resolution, distance, and HDCP compliancy.

Most current Wireless HDMI extensions will work for up to 1080p resolution; but don’t assume that the one you’re looking at will. If the unit doesn’t say that it will work for 1080p, it may not. There are still some units available on the market, especially units that ship from China, which will not meet this requirement.

The second thing to look at is the range of the unit. Most Wireless HDMI extension adapters are only good for 30 feet. However, there are a few that are designed to work at up to 100 feet. These use a stronger signal to allow for that distance. However, that stronger signal has a higher probability of causing interference with other wireless equipment as well. So, don’t buy more than you need. If you only have to cover 20 feet of range, don’t buy a unit that’s designed for 100 feet.

Another aspect of range is the ability to transmit through walls. A stronger signal will have a higher probability to transmit through walls, without problem. Even so, they probably won’t be able to transmit through steel studded walls. Those may as well be solid steel. They are excellent at blocking radio waves.

Finally, some Wireless HDMI extenders are HDCP (high-bandwidth digital content protection) compliant. This system, developed by Intel, is designed to prevent copying of digital audio and video content as it travels across wireless connections. While you may not care about this for your home movies, this is an important consideration for preventing corporate espionage. Devices that use this technology do a digital handshake before transmitting data, to verify that the receiver is authorized to receive the material. Once the handshake is successfully completed, the information is encrypted and transmitted.


Rich Murphy