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Interactive TV: Set-Top Box Operating Systems

  • July 28, 1999
  • By Jeff Rule
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The desktop Operating System (OS) wars are over. Microsoft is the undisputed champion despite talk of Linux, which is frankly destroying other UNIX OS's faster than Windows. Microsoft is upward of 95% of the installed base. The real challenge for Microsoft is new non-computer devices connected to the web running non-Intel CPUs. A few weeks ago, I wrote about the set-top box and how TV was growing an analog channel changer into a full-blown computer. This time I'll be focusing on the OS's that will run on set-top boxes, and the battles shaping up for control of this new environment. Remember, computers are stalling out at about 50% market penetration, who is going to own the rest of the eyeballs?

WebTV is slowly being reworked into a Windows CE based interactive TV platform.

Microsoft WebTV

Microsoft has not been sitting still during this gathering battle. With their purchase of WebTV, they grabbed the most prominent name in the emerging convergence space of TV and the Web. WebTV is slowly being reworked into a Windows CE based interactive TV platform. Recently, at the NCTA cable show in Chicago, Microsoft showed WebTV running on Windows CE on prototype boxes from the two leading set-top box developers, Scientific Atlanta and General Instruments. WebTV is also running on boxes from EchoStar satellite TV with HDTV on a prototype from Panasonic.

Microsoft is extending the client server model of the web to Interactive TV. The backend will consist of Windows 2000 Server, Backoffice, and their new Broadcast Server which is part of NetShow Theater Server. The client end consists of WebTV running on Windows CE and WebTV for Windows built into Windows 98. WebTV for Windows lies latent in Windows 98 until a TV tuber card is installed. Once installed, Windows 98 users can get all the benefits of having a WebTV box; and developers can create for a large group of TV viewers and computer users in the same development environment. Microsoft's forethought on issues like this does not bode well for creators of other operating systems.

Microsoft has not stopped there, they have invested $5 billion in AT&T to ensure that at least 7.5 million cable set-tops would use Microsoft's Windows CE software. In addition to the current installed base of WebTV boxes, 1 million by years end, and several other deals, this places Microsoft's installed base at close to 10 million. Once again, while the industry sleeps, Microsoft has taken a clear lead.


Old timers may remember Kaleida, an IBM-Apple joint venture, which began with big hopes and ended with a whimper. Never let it be said that nothing good emerged from this union. From the dying embers of Kaleida came PowerTV. PowerTV's main installed based is on Scientific Atlanta's Explorer 2000 set-top box, the specs for which were discussed in my last article. They have also recently signed deals with Excite@Home to provide local news information on cable systems.

PowerTV is also working with a number of software companies to provide the all important development tools.

PowerTV is a true operating system. It has a very small memory footprint running in 1MB of RAM, 128K of Flash RAM and 200K of DRAM. This makes it quite capable of running on today's set-top boxes unlike Windows CE which requires much greater system resources. PowerTV is also working with a number of software companies to provide the all important development tools. They are currently working with Argonaut, Oracle, Scala, Sybase, Thomson-Sun Interactive and Wink to create tools for developing Interactive TV. They also have developed the Bali authoring system for creating applications.

PowerTV provides many services such as E-mail, E-commerce and web browsing. I'm always disappointed in the functionality of web browsers for Interactive TV. The PowerTV browser downloads to the set-top box from the network and then runs in available memory. Given these limitations, it supports HTML 3.2 with some extensions from Internet Explorer, Netscape and WebTV's TVML. It also supports Javascript 1.2 and Java. However, it does not support any plug-ins, such as Shockwave, Real, or Quicktime. I guess as computer users we've become spoiled at the richness available through multimedia datatypes. Until the set- top boxes catch up, I'd rather watch broadband web content with streaming video than Interactive TV.


OpenTV is not really an operating system. It is an application environment that runs on top of other real time OS's and acts as an application layer. Think of Windows 3.1 running on top of DOS if you want an analogy. Also, despite the fact that Sun is a major backer, OpenTV is not Java based and despite the word "open" in their title, the OpenTV system is very proprietary, though it does somewhat resemble Java.

OpenTV's main deployments are in Europe. They currently have an installed base of around three million homes including Australia, Europe and the US.

This hardware and OS independence makes OpenTV portable and allows it to run in many different cable TV environments.

OpenTV runs on top of other operating systems such as pSOS, VxWorks and OS-9. It uses bit code that passes through an abstraction layer and communicates with the underlying OS. This way, the bit code is passed to the OS which controls all device drivers. This hardware and OS independence makes OpenTV portable and allows it to run in many different cable TV environments. However, though I don't have direct evidence of this in OpenTV's case, writing applications that run smoothly across all these different OS's is nearly impossible and minor compatibility problems often develop.

OpenTV, like PowerTV, also comes with a downloadable web browser. This browser is even more limited than PowerTV and supports only HTML 3.2 with no Javascript, Java forms, or Cascading Style Sheets. The lack of forms makes e-commerce difficult and this must be accomplished through a complicated non-web compatible work around.


The Interactive TV set-top box market for Operating Systems is very fragmented. Microsoft, working from its position of strength outside the market, thrives in such an environment by bringing order to chaos. What the cable industry lacks, expertise in client-server applications, operating system development, and web development, are the things at which Microsoft excels. Microsoft does not have the cable knowledge, but are curing this by throwing around money and partnering with industry leaders such as AT&T. If the cable market does not stop bickering, the set-top box OS market will soon resemble the desktop OS market.

About the author:

Jeff Rule is a principal at RuleWeb Development specializing in Interactive TV, Broadband Web Development, DHTML, SMIL, and Java-based multimedia. His first book, Dynamic HTML: The HTML Developer's Guidewas published in January 1999 by Addison Wesley Longman.

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