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Enhanced DTV evolves at ATSC

An industry effort to standardize the digital broadcasting of enhanced-television content is making slow but steady progress, according to the Advanced Television Systems Committee.

Work has been under way on the proposed DASE (DTV Application Software Environment) standard for more than two years. DASE would govern a layer of software in digital TV receivers that would allow broadcasters to transmit ancillary data and have it displayed in a consistent way. Applications could include offering statistics along with a football game or adding exit-poll data to live election coverage.

Such applications are already being offered by broadcast networks today in a "two-box" mode through a combination of Internet content shown on PCs and traditional television programming (see story, page 40). But DASE would enable such functionality on one digital TV screen as part of a "lean-back" interactive TV experience.

The standard is distinct from the ATSC data-broadcasting standard ratified in July. That standard, known as S13, defines protocols for how broadcasters insert data into their 19.4 Mb/s digital streams. The standard is agnostic as to content and applies equally to sending nonprogramming-related data to PCs, as proposed by Geocast and iBlast, as to broadcasting enhanced content to digital television sets.

"DASE determines the kind of content that you can transmit and the middleware in the receivers," explains ATSC Executive Director Mark Richer. "We want it to be defined just enough so the content can be received and processed properly. Manufacturers can still choose the hardware and the operating system they want."

The technology-specialists group that is developing DASE (known within the ATSC as T3/S17) has been holding frequent meetings and is "progressing along very well," says Richer. He expects that the standard, which currently comprises about six separate documents, will be balloted at the technical-group level by the end of the year. If it passes that step, DASE will be presented to the general ATSC membership in early 2001 for a six-week balloting process. The key parts of the standard could be formalized by NAB 2001, says Richer. Other sources say that time frame is overly optimistic and predict the standard won't near completion until summer 2001.

The latest DASE development adds support for applications based on the HTML programming language (and the related XHTML and XML languages) as well as for those using the more complex Java programming language. Such HTML-based applications, known within DASE as "declarative applications" compared with Java-based "procedural applications," should make it easier for broadcasters to create interactive content.

"The DASE technical committee wanted to use the technology created for the Internet by WC3 [the World Wide Web Consortium] as a means of creating interactive television content," says Dr. Glenn Adams, Gemstar-TV Guide International's systems architect for digital television and the primary author of the declarative-applications component in DASE. "Typical graphics designers are not Java coders, but they know how to create content with their tools and then output them to XHTML. If a creative enhancement is based on Java, then you need a staff of programmers. With Java-based programming, you can do a lot more with the box, but it has a higher cost. So we needed both types of content, Java and Web-like, and an environment to support that."

Whereas Java is good for complex applications like creating an electronic-program guide, putting a small logo bug on the screen or displaying player statistics is "real easy to do with HTML," says Mike Dolan, a consultant for DirecTV and an active DASE participant. "There's a class of problems where it's really obvious which one you would choose."

The inclusion of declarative applications in DASE should make it easier for PBS to repurpose its extensive Web content for DTV, says PBS Chief Technology Officer John Tollefson. "The basic dilemma we find ourselves in is attempting to support a standard that will allow the use of existing content authored in HTML, while still allowing future applications that are much richer."

But don't expect enhanced applications to reach DTV sets anytime soon. Even if DASE is ratified this spring, a DASE-enabled DTV set wouldn't hit store shelves until 2002 at the earliest, says Ed Milbourn, manager of advanced television planning for Thomson Consumer Electronics. "Before it's commercialized, we have to make sure it works as advertised."

In the meantime, Thomson will wait to see how the DASE standard evolves before it "puts a whole bunch of code" which may not be used into a digital TV set.

"Anticipating something like that can cost a lot of money," says Milbourn.