Streams of Thought: Signs, Signs, Everywhere a Sign
Digital signage is an industry that has evolved in parallel to streaming, with a variety of technical offerings that offer clues about how streaming might address its next challenge.
The Five Man Electrical Band’s 1971 hit "Signs" has a line that sums up what most people think of when they hear about digital signage: "Do this, don’t do that, can’t you read the signs?" Digital signage is thought of as flat panels hung in airport gates, hotel lobbies, or other places where text must be constantly updated. In reality, digital signage is an industry that has evolved in parallel to streaming, with a variety of technical offerings that offer clues about how streaming might address its next challenge: moving beyond HD delivery.
One reason for digital signage’s limited exposure in the streaming industry is the large number of names it has had over the years, from the intracampus business TV systems I designed early in my career to the continuing search for interactive advertisements and signage found in kiosks. Digital signage itself began as a way to provide a thinner, sleeker business TV experience, eventually morphing into the ability to send a discrete signal to each monitor rather than the same signal to every one. In an emergency situation, some companies have even designed a "big red button" that can be pressed to simultaneously send a still image to all locations.
Digital signage doesn’t need to display staid reference information, such as facility or room schedules, nor static advertising content. Discrete delivery to each monitor paved the way for targeted advertisements being sent to single monitors or groups of monitors, which then led to systems designs that incorporated store-and-forward content delivery, meaning that content needed to be sent ahead to a caching device, at the digital sign itself or at a central location that a group of monitors could access. This move toward discrete advertising meant that pieces of content—Flash files, still images, previously encoded video content—were delivered more like a traditional content delivery network (CDN). In fact, CDNs such as AT&T have responded with digital signage offerings.
Some companies have pushed digital signage toward closed-circuit video, using streaming appliances as part of the mix. Take, for instance, Hollister’s digital signage. The company sells clothing marketed toward those involved in outdoor activities, with an emphasis on surfing. Hollister opted to stream video of a prime surfing location to its stores so that customers are constantly reminded of the company’s credibility. Hollister has two cameras aimed at the surf from the Huntington Beach Pier in California. The camera output is fed via T-1 lines to a North Carolina satellite uplink facility, then broadcast via satellite IP delivery to stores across the U.S.
Microspace Communications, the satellite uplink provider that Hollister uses, is an interesting microcosm of digital signage’s parallel growth. Microspace is located in Raleigh, N.C., and is tightly tied to WRAL, one of the first HD television stations. It also shares an investor with Inlet Technologies, although to date, Microspace’s customers have chosen broadcast MPEG-2 encoders instead of streaming ones. Still, the seeds of parallel growth and eventual convergence are present in the Raleigh area.
So what’s the biggest challenge facing digital signage today? Because a majority of content delivered is still intracampus, coupled with the fact that digital signage is often installed by audio-visual systems integrators who are used to the high-quality of computer graphics signals beyond HD resolutions, the industry has made multiple attempts to deliver computer graphics to all signs. Yet the majority of these attempts are rooted in the analog delivery world, where VGA signals are passed via coaxial, fiber, and, more recently, Cat5 or Cat6 twisted pair.
To deliver the same signal to two monitors requires either a distribution amplifier or, if the option is required to send the same video signal at one point and a separate video signal at another point, a 2x2 video matrix. Extrapolate this up to 128 monitors, the current maximum video matrix on the market today, and you’ll encounter both a significant number of headaches and a price tag that’s well beyond that of even the best HD streaming encoders on the market.
Since lossless delivery is key to the traditional audio-visual installation, a few attempts have been made to push computer graphics signals via the use of a modified digital cinema spec, using JPEG-2000 as a series of stitched-together stills. This approach requires 150Mbps for a single delivery, making the move beyond more than five to six discrete streams impractical on a Gig-E network, with even that requiring that no other traffic be present.
So can we take some of the things we’ve learned about delivering HD content to the web and help grow the digital signage market? I think so, and I look forward to hearing ideas on how to optimize computer graphics delivery.