Emerging High-Definition television digital broadcasting technology is providing a basis for an interesting partnership between rivals for your leisure time: TV broadcasters and Web sites. The HDTV effort stems from a US Federal Communications Commission mandate. Last November, the FCC ordered broadcasters in major markets to start broadcasting several hours of high-definition digital television signals each evening. By 2006, all broadcasters must convert completely to digital signals. The cost of implementing the technology is high and offers little payback; relatively few consumers are expected to buy the typically $4000-plus (around £2,500) HDTV sets you need to see high-resolution programming. But you might be willing to buy a £200 receiver to get high-quality, high-speed datacasts via that same HDTV spectrum on your PC. Broadcasters hope so. The deals they're cutting could widen the horizons of your browser. For example, startup Geocast plans to deliver aggregate Web pages and digital programs to local TV broadcasters. The broadcasters will then send a datacast, at speeds averaging more than 5Mbps, to £200 desktop receivers built by Thomson Multimedia. The speed is more than five times that of most cable modem services. A joint venture called WaveXpress is preparing a rival service. Its backers are Sarnoff, Wave Systems, and The Fantastic Corporation. Initially, these ventures are aimed at PC users, but future plans call for TV-based set-top receivers. In many ways, datacast is the next generation of the "push" technology that was much heralded but not widely adopted. Pointcast, the pioneer, recently pulled the plug on its long-floundering push-media service. While datacasting has found some success here in the UK, US-based experiments such as Intel's Intercast have languished. Yet, a number of companies are eating different pieces of the DTV datacasting pie. For example, Microtune makes DTV tuner chips for low-cost receivers, and SkyStream offers a media router that combines and transmits IP data with digital broadcasts. However, Geocast's approach appears among the most comprehensive and developed. Last year, the company signed with two TV broadcasting syndicates - Belo and Hearst-Argyle Television - claiming access to more than 30 million US viewers in prime markets. The broadcasters in turn invested in Geocast, as have Thomson Multimedia, Electronic Arts (which hopes to datacast games) and Liberty Media, which will provide much of the content. Granite Broadcasting recently signed up for field trials. How can Geocast (or anyone else) succeed where the push programs failed? "Bandwidth," answers Gerry Kaufhold, principal analyst with multimedia and digital TV services at Cahners In-Stat Group. "With digital terrestrial broadcast, you have three orders of magnitude more bandwidth." PointCast pushed its data at dial-up speeds, and early datacasting used very low bandwidth side channels. But Geocast's service averages more than 5Mbps, and because data accumulates around the clock, you never have to wait for a download. "Because we are downloading massive amounts of data, we can provide 30-fps video clips at full screen, and there's no such thing as an hourglass," says Brian Klosterman, Geocast's vice president of marketing. Not only is the download faster, the material is sufficiently varied to mimic the Web experience better than PointCast could. "We plan on having such a wide breadth of data, chances are we're going to have what people are looking for," Klosterman says. Initial emphasis is on video programming not generally available on the Web. As with early push technology, you'll be able to complete a user profile that will help filter the material of greatest interest. The Thomson receiver will come with a multi-gigabyte hard drive, but it won't take long to fill; and older data will be deleted automatically. To surf the Web at large, or to complete ecommerce transactions, send email, and chat, you'll still have to connect through an existing modem and an Internet service provider. But installation is much easier than with other broadband solutions, Klosterman says. "You'll be able to walk into a consumer electronics store and buy a Geocast box for no more than £180, bring it home, plug it into the Universal Serial Bus port of your PC [Pentium II or higher], run the auto-install, and you're rolling," Klosterman says. "The service is free; the revenue model is driven by ads and ecommerce." The biggest immediate obstacle to Geocast and its competitors stems from a standards war over the Advanced Television Systems Committee's recommended 8-VSB modulation standard. Sinclair Broadcasting recommends scrapping 8-VSB due to the poor performance of early models, and instead adopt the European COFDM standard. Most American vendors are sticking with 8-VSB, insisting technical problems will be solved. Some skeptics claim the technology may require roof antennas instead of smaller antennas mounted on desktop receivers. Unless the next round of 8-VSB equipment performs better, the entire DTV market could slow down to a crawl. Easy installation and no-monthly-payment offers could lure consumers. They may be particularly attractive in many urban areas that will not get cable or digital subscriber line broadband for some time, Kaufhold notes. "If they hit the market right they could become the Yahoo for rich media," Kaufhold says. Klosterman expects Geocast will drive adoption of cable-modem and DSL broadband, rather than compete with it. As Geocast customers become accustomed to working in such a fast, media-rich environment, they won't want to switch to a slow 56Kbps connection to surf the Web, he says. Yet, given its past attempts, push technology still has much to prove, even at 5Mbps. Web-surfing is essentially aggressive and exploratory - people seek out specific information to accomplish particular tasks. Geocast may find a better home on a TV set-top, where the experience is more passive and we're accustomed to selecting from a smorgasbord of passing media. Or maybe this time there's just enough bandwidth to pull off the illusion.