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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 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 HDTV sets you need to see high-resolution programming. But you might be willing to buy a $300 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 5 mbps, to $300 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.

Push Done Right?

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 in Great Britain, U.S. 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 U.S. 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 5 mbps, and because data accumulates around the clock, you never have to wait for a download.