How Do You Connect Your Display?


Are you using some out-of-date analog interface like VGA or DVI? Or, worse yet, composite, component or RGB with multiple coaxial cables? Or perhaps you are using an older digital interface like HDMI?
At Insight Media’s Projection Summit on June 11th, in Las Vegas just before InfoComm, there was a session on newer digital interfaces, both wired and wireless. There were four speakers presenting information on four different formats: Micha Risling, marketing committee chair, spoke for the HDBaseT Alliance; Leslie Chard, president, WHDI LLC spoke on WHDI; Quoqing Li, research scientist at Intel Labs spoke for the WiGig alliance; and Jeffery Gilbert, CTO, Silicon Image, spoke for the Wireless HD Consortium.
Not only were the four presentations good, there was also a lively debate during the panel discussion. While the debate may have not settled the question, “Which is the best interface?”, it certainly clarified the relative merits of the four new standards. “Which is the best interface?” is an unanswerable question anyway because it gets the immediate response from anyone knowledgeable about interfaces, including the four speakers, “For what application?”
Risling opened the session with a discussion of the HDBaseT standard, which uses CAT5e Ethernet cable to transmit video, two-way control signals and power, and has bandwidth left over for other 100BaseT Ethernet uses. The video is not limited to uncompressed HD; it can be 3D, 4K or High Frame Rate. He started with a list of challenges that all video connectivity interfaces must face:
  • Distance
  • Cost of installation
  • Cost of ownership
  • Convergence
  • Flexibility & Scalability
Since HDBaseT uses Cat5e wiring, this may already be installed and can be used.  If it isn’t installed already, a new ProAV project may require it so it may not represent an added cost. Distance for HDBaseT is up to 100 meters (328 feet) according to the specification, or perhaps more, according to Risling. Within that distance, intervening walls, floors, etc. are not an issue, nor is interference between multiple signals, unlike wireless solutions.


He gave a long list of supporters of HDBaseT, including Crestron and Extron. If you don’t have the support of these two companies, you are a nobody in the ProAV crowd atInfoComm. HDBaseT is not just an approach for the future: projectiondesign was demonstrating HDBaseT connectivity in their booth at InfoComm.
The standard supports up to 100 watts of power, which is only enough for microprojectors — not lamp-based projectors, so power will still need to be run to the projector location.
The other three interfaces are wireless interfaces and are targeted mostly at consumer markets, although they can be used for ProAV applications as well.  Chard discussed WHDI, an interface that uses the same 5GHz band that is used by Wi-Fi. WHDI transmits HD video with little latency. Since it shares the same band as Wi-Fi, it can be integrated with Wi-Fi for minimal additional cost, perhaps only $1 more than a Wi-Fi-only interface on a device.
According to Chard, there have been WHDI products available since 2008, which predates the specification itself. He said that in the 2012/2013 time frame, WHDI will be embedded in laptop and tablet computers and by 2014 it will be embedded in phone handsets. If you happen to have a WHDI-enabled display, this would certainly simplify the interfacing problem as you travel. WHDI-enabled pico, micro or ultra-portable projectors anybody?
WirelessHD and WiGig are competing standards and both are in the 60GHz band.  This band has just recently been allocated for unlicensed operation so there are relatively few products of any type or any format that actually use the band.  One characteristic of the band is its short range and minimal ability to penetrate barriers. This makes the 60GHz band suited for applications where you put your video source (e.g., handset) down near a display (e.g., projector or TV) and the two automatically connect and show the source content on the display with minimal human intervention.
Channels in the 60GHz band are much wider bandwidth than channels in the 5GHz band and can carry much more data. This enables other high data rate applications besides displays, such as wireless docking stations for laptops.  Plop your laptop down on your desk and suddenly you are connected to all the corporate resources, including wide-bandwidth Internet and multi-terabyte disk drives.


Unlike the 5GHz band, signals in the 60 GHz band are highly directional and the systems must use a steerable antenna. If you are thinking of some big satellite dish with a servo motor, think again. The antennas are small and electronically steerable in times of less than 1 mS. Gilbert says they are very small, typically requiring < 1 percent area of 5GHz antennas.
I don’t want to go into the differences between the two 60GHz standards for two main reasons:  1) this Display Daily is running out of room and 2) I’m not sure I fully understand the advantages and disadvantages of the two standards compared to each other. However, the speakers did note that WiGig is an open standard whereas Wireless HD requires royalty payments.
As mentioned before, there was a lively discussion after the formal presentations over the advantages of wired vs. 5GHz vs. 60GHZ. Two topics of particular interest were interference between multiple users of wireless displays and penetration through walls and other barriers. Of course, for these interference and penetration discussions, Risling was content and self satisfied:  Interference is simply not a problem for a wired connection.
The Projection Summit proceedings, including the presentations by these four speakers, are available from Insight Media. Click HERE for details.