Image is everything
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It’s unlikely there will ever be a Golden Globe or Academy Award category for “Best Cinematography in a Movie Developed for Mobile Phones.” But that doesn’t mean service quality—and, ultimately, image quality—are unimportant. The convenience of having TV entertainment in a mobile phone handset is perhaps the most obvious selling point of mobile TV. But quality can’t be taken for granted, or the service won’t be worth the price users must pay—and the cost for entertainment companies to develop content for it.
There’s a lot the mobile industry is still trying to figure out about how the future of mobile video and TV will play out. Will the video content be original or repurposed from traditional TV? Will it be long-form or all short subjects? Will it continue to be downloaded ala a unicast model, or will the new broadcast networks take over from here? There are no single answers so far to any of these questions, but no one is debating whether or not quality will be important, regardless of the originality of the content, its length, or on what type of network it is delivered.
Mobile TV quality begins with bandwidth, and in the case of new third-party broadcast networks dedicated to mobile video, a strong signal is a big part of a successful mobile video game plan. But no network is perfect, with even the best-planned transport systems vulnerable to constrained bandwidth or spots of signal interference or weakness.
Network operators can only do so much, but there are some things that can be done behind the scenes to improve the chances that consumers are likely to see high-quality mobile TV images on a consistent basis. Those efforts start with the image itself—how it is converted, formatted and compressed for delivery. From there, compression encoding schemes and technologies like forward error correction (FEC) can also play a role in delivering higher-quality images to mobile devices, while reducing the amount of bandwidth or signal strength required to do so.
U.K. firm Snell & Wilcox is one of the companies working in the area of image pre-processing and conversion. The company has won technical Emmy awards for its content mastering in HDTV and cable TV environments; now it is applying its technology to mobile TV. It uses a software-based automated conversion system that remasters content and repurposes it from traditional TV resolution (typically 1920x1080 pixels) to something more appropriate for small mobile handset screens (around 176x144 in many cases). In doing so, Snell & Wilcox has to analyze each individual image to determine its area of interest—the section around which the conversion process should tighten to keep the most interesting aspect of the image on the small mobile TV screen.
“We’re not trying to create the ‘Lawrence of Arabia’ sort of experience on a mobile handset,” said Joe Zaller, vice president of strategic marketing at Snell & Wilcox. “What we are doing is making the pictures look as good as they can possibly look on a mobile handset. The variables in mobile TV are that you want compression that is as low as possible and frame rates that are as high as possible. Fifteen frames per second is the 3G standard.”
Image processing isn’t a very network-centric part of making mobile TV a quality service. But without it, content wouldn’t accurately fit onto mobile phone screens, leaving users to wonder why anyone would want to watch TV that way. It’s a complex task; in addition to reformatting images to make sure the most significant part is on screen, the content needs to fit form factors of hundreds of device models.
Making the image quality proportionately correct to the mobile device also helps the carriers delivering that content to manage bandwidth and other resources more efficiently because clips can be compressed more efficiently. “When you are dealing with better higher-quality images, you can upload more clips with fewer people, thus producing video content at a lower cost,” Zaller said. “There’s a bandwidth savings for the operator in that you can send content to more people on the same bandwidth. The final benefit is that the consumer is getting a good picture—good enough that they will pay for it.”
FEC is another technology that, though applied in transport, contributes to higher-quality images and improved bandwidth efficiency. FEC works by taking a group of packets ready for transmission across a network and adding repair packets to the load, which analyze and restore any packets that become disassembled or lost during transport, said Mike Luby, co-founder and chief technology officer at FEC specialist Digital Fountain.
Though FEC actually adds more packets to the bandwidth load—anywhere from 10% to 20% more on top of the actual content transmission—the technology eliminates the need to resend packets that often would otherwise occur. “By adding redundant packets, you actually make the transmission more efficient,” Luby said. The result is an image worth watching.
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