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Picture This: The New Format War?

Aug 1, 2008 12:00 PM, By Jeff Sauer

Competition over wireless HD technology.


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WHY WHDI?

Why would companies such as Sony, Sharp, and Samsung now come to support WHDI after months working toward the WirelessHD standard? First, each likely recognizes that establishing a working, interoperable, wireless HD technology will help sell their core display products of the future. If nothing else, they are hedging their bets with multiple efforts to create one. And of the competing wireless options, WHDI seems to be the furthest along and thus the quickest to implement into forthcoming products. Amimon is now offering WHDI technology on silicon integrated circuits for integration.

Amimon has demonstrated that WHDI has enough channel bandwidth (1.5Gbps) to send uncompressed 1080i HD video — as well as XGA for data — wirelessly, and it will soon support 1080p at 3Gbps. It does so over the same potentially crowded 5GHz frequency as 802.11a, but Amimon claims that the technology is able to find other frequencies if necessary to ensure delivery of the data stream.

However, although the transmission frequency is important, Amimon's secret sauce is in how it prioritizes video information to accommodate the inevitable wireless network congestion or less-than-ideal transmission conditions one is likely to face in the real world. Amimon insists that such prioritizing is not a form of video compression, but rather a hierarchy of data that amounts to an on-the-fly method of reacting to the uncertainly of wireless bandwidth.

Amimon remains tight-lipped about its specific prioritization methods, but other examples of prioritization are as old as recorded video, and many have been used at the highest levels of video production. For example, because our eyes are more aware of luminance variations than chromanance subtleties, chroma sub-sampling — or taking one color sample for every two (or more) luminance samples — typically goes unnoticed. The longtime professional videotape standard, Betacam SP, used 3:1:1 sub-sampling with only one sample of red and blue for each of the three luminance samples. The MPEG-1 digital video format and the DV tape format both use a 4:1:1 color sub-sampling, while high-quality MPEG-2 in the standard profile uses 4:2:2.

Although it's not literally the same, WHDI similarly places greater importance on core aspects of an image and sends those data bits first, with others following. If those later image elements are delayed by network congestion and are not received in time, WHDI is still able to display the picture — and usually still without any visible degradation.

Thus, while Amimon has focused on the 5GHz frequency for transmission, the company's core solution could ultimately remain viable even if the industry moves toward a different transmission method or alternative transmission frequencies. For example, WirelessHD focuses on the unlicensed 60GHz frequency band to achieve data rate of several gigabits per second. However, where the 5GHz frequency allows wireless transmission through walls to roughly 100ft. through a building or house, 60GHz has a much shorter, in-room range.

Given that difference, it's possible that WirelessHD and WHDI might even coexist in the future — with Amimon's secret-sauce prioritization at the center of both. Indeed, regardless of the theoretical bandwidth of any wireless frequency range, there will always be the probability of network congestion. And for wireless HD video to successfully reach the consumer market, there has to be a foolproof way to accommodate non-ideal situations. It's even possible that Amimon's technology could ultimately be married to other competitive solutions such as UWB or 802.11n.

For the most part, each of the competing technologies focuses on a different way to send video and each promotes its own as the better way to send video. Amimon's solution, on the other hand, begins with making the video better to send. And with major display manufacturers joining the effort, wireless HD video may yet be the next big thing coming to a display near you.



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