Digital and interactive television is emerging as a real advancement in electronic media, but its success requires that diverse technologies from multiple vendors work together seamlessly. The consumer has no tolerance for high-tech problems plaguing his or her television set or set-top box.
The good news is that the interactive TV industry has taken steps to ensure that its products really work by defining a number of open standards. These standards are designed to foster interoperability between technologies supplied by different vendors.
The bad news is that not all vendors agree on which standards are important and supported.
The standardization effort has progressed on several levels, from basic digital video encoding technology to interfaces for conditional access (encryption), and transmission technologies to higher-level standards that enable advanced interactive services.
Still, some of these efforts work against each other. In the United States, the Advanced Television Systems Committee (ATSC) and the OpenCable consortium have been the major proponents of standards. In Europe, South America and parts of Asia, the Digital Video Broadcasting (DVB) consortium has had the most influence. DVB-based deployments are also commonly used in satellite broadcasts in North America.
With interactive TV about to boom, it’s time to take a good, hard look at standards and to make some industry decisions, a practice that will facilitate interactive TV’s acceptance.
Digital video encoding
MPEG-2 digital video encoding technology is the foundation of digital video broadcasts. It is used by virtually all digital video services deployed today and supports both standard and high-definition display. Terrestrial broadcast standards, on the other hand, are being hotly debated between the ATSC and DVB.
ATSC and DVB have competing transmission schemes with different broadcast characteristics. This disagreement is illustrated by the home page of the DVB consortium at www.dvb.org, featuring an article bashing the National Association of Broadcasters in the United States for “flawed tests” that allegedly unfairly characterized the DVB broadcast standard.
Conditional access
Conditional access and similar protocols for cable transmission differ between OpenCable and DVB. However, this divergence will not negatively impact consumers because cable service is regional in nature and each cable network operator will install a complete working system.
In practice, standardization at this level is more advanced in Europe and other DVB-based locations than in North America. In the United States and Canada, the domination of Scientific-Atlanta and Motorola in cable set-top box deployments has reduced the reliance on standards in favor of proprietary solutions, at least for now. Both companies are committed to standards-based solutions and are active in the OpenCable effort.
Advanced interactive services
The standards discussed above enable digital television reception with higher quality than the familiar analog television in common use today. Still, advanced interactive television services add a new dimension to the television experience. Interactive television is dynamic and allows the viewer to participate. These new interactive services require standardization to ensure interoperability of broadcast content and to promote the wide adoption of new features.
One of the major driving forces behind interactive television is the convergence of Internet technologies with television. As a result, many of the standards that have been proposed in this area are derivative of Internet protocols, such as HTML, JavaScript and Macromedia Flash. The OpenCable consortium has recently released the Open Cable Application Platform (OCAP), which has a core presentation engine based on an HTML browser with extensions for interactive television. OCAP and a similar specification from the DVB consortium called the Multimedia Home Platform (DVB-MHP) provide a common framework for developing interactive television applications.
The Advanced Television Enhancement Forum (ATVEF) has produced a standard set of HTML extensions that has been adopted by OpenCable as well as some of the key software providers such as Microsoft and Liberate. A few content providers are broadcasting ATVEF content today. WebTV users may be familiar with interactive “Jeopardy!” which allows viewers to play along with the popular game show. In addition, informational networks such as The Weather Channel telecast ATVEF content that enables the television viewer to “go interactive” and access detailed weather maps and local forecasts.
The ATVEF standard goes beyond enhancing the presentation of interactive programs. It also provides standards for broadcasting data and synchronizing broadcast data with the video feed. These features are important because the power of interactive television lies in the combined delivery of video with enhanced content.
While ATVEF is a powerful tool for creating and deploying interactive television, it provides for only a limited computer-programming model. In an effort to provide a richer environment for developing interactive content, Sun Microsystems and others have defined the Java TV application programming interface (API). Some of the features of Java TV overlap with ATVEF features-and to an extent the standards are competitive.
Nevertheless, it is possible to build an advanced set-top box that supports both Java and ATVEF. Java TV adds the rich programming paradigms of Java but also requires that a Java virtual machine (VM) be running on the target set-top box. The requirement for a Java VM can increase the overall memory requirement for the set-top, potentially increasing the basic cost of the box.
From local to global
The cable and broadcast industries are taking the initiative to use standards to deliver higher-quality and more innovative television to their viewers. The standardization efforts in digital and interactive TV are well under way, but tend to be somewhat localized and fractured. This localization is understandable, since standardization bodies are geographical. Some of the key standards, such as MPEG, have garnered wide acceptance and form the basis for deployments of digital video around the world. Other standards have been regionally adopted and provide for interoperability within their purview. Additional ones are being defined to allow for more advanced interactive services, many of which provide overlapping features and are vying for acceptance.

A standards-based approach is critical to interactive television adoption, as interactive television developers require a common platform to avoid having to re-create their offerings for each individual system. The resulting situation would quickly prove too labor-intensive and costly, while segmenting viewer markets by the technology brand deployed. Interactive TV standards will allow software developers and content providers to make interactive TV successful.