Open Cable Set-Top Brewing
Electronic Engineering Times
February 25, 1998
Open Cable Set-Top Brewing
Junko Yoshida
Will there ever be a day when consumers go out to retail outlets like Circuit City to choose their brand-new set-top cable boxes from an array of brands, designer colors, shapes, sizes and luxury options? This seems an optimistic outlook today, but it roughly characterizes the ultimate goal of the OpenCable initiative, according to Don Dulchinos, OpenCable project leader at CableLabs Inc. "We want to see that start happening in 1999, " he said.
The OpenCable initiative, led by CableLabs, a Louisville, Colo.-based R &D consortium for U.S. cable operators, is seeking to define by mid-1998 specifications for an open set-top that handles digital data and audio/video.
For the U.S. cable-TV industry, accustomed to proprietary solutions, the movement toward openness is revolutionary, if not unthinkable. Some people in the electronics industry question how quickly the cable industry could actually transform its traditionally closed operations to an open, retail- based business model.
After all, this is the same U.S. cable industry that, abuzz with an emerging 500-channel, digital interactive cable-TV nirvana only four years ago, gravely miscalculated the complexity of its underlying technology and business models. Cable providers eventually delivered very little of what they had promised. Indeed, as far as most U.S. cable subscribers are concerned, there's no such thing as 500 channels. And there are no digital audio/video signals, let alone interactivity on a TV. At least not yet.
Many cable operators claim, however, that they haven't stood still. They've gone through major overhauls in new cable head-end infrastructure development and in the way they view open standards.
The biggest change lies in the fact that the cable industry is focusing design of its next-generation advanced set-tops around the Internet.
The catalyst in this new direction has been the industry's own efforts to offer high-speed access to the Internet through cable modems. The push toward data-friendly standards-already seen in cable modems with the Data Over Cable System Interface Spec (DOCSIS), also led by CableLabs-is migrating to the back-end infrastructure of cable networks. Cable operators today make no secret of their strong interest in parlaying their investment in an infrastructure for cable modems based on the Internet Protocol by using it for interactive digital set-tops as well.
In short, the Internet has already gotten cable operators to start building their head-end equipment and end-to-end services based on the TCP/IP protocol stack. With that new standards-based infrastructure in place, the Internet has also renewed the cable industry's interest in interactive services and digital set-tops. But this time around, cable operators and set-top vendors are committed to open, interoperable standards instead of proprietary solutions, and to set-top designs capable of taking advantage of content already available on the Internet. The "Internet has been a great equalizer, " said David Limp, vice president of consumer marketing at Network Computer Inc. (Redwood Shores, Calif.)
Robert Van Orden, a director at Scientific-Atlanta Inc. (Norcross, Ga.), said at the Western Cable Show in December, "Three barriers that hampered the development of digital set-tops have finally started to crash through. " The cost of a set-top box is coming down, agreement on standards is falling into place, and content-whether already available on the Web or newly created in HTML and JavaScript-is finally emerging to generate service revenue, he explained.
If this is true, then what are the basic building blocks for OpenCable specifications, and what share of the specifications already has been agreed upon by the cable industry?
CableLabs executives note that major elements of an interoperable digital cable systems specification for North America are already in place. Such agreed-upon technologies include audio/video decoding standards, demodulation schemes and an encryption standard.
The OpenCable system will conform to MPEG-2 Main Profile @ Main Level parameters; the transport multiplex specification will also be MPEG-2. The audio element will be the Dolby Digital AC-3. Downstream digital modulation will be based on 64 and 256 Quadrature Amplitude Modulation (QAM). That would allow a cable channel that today carries one analog video channel to carry 27 Mbits/second of information in digital, or enough for multiple video programs, by using 64 QAM. When using 256 QAM, the standard 6-MHz cable channel could carry 40 Mbits/s.
Through a so-called harmony platform agreement between General Instrument Corp. and Scientific-Atlanta, cable operators and cable technology suppliers have specified the General Instrument DigiCipher implementation of the DES encryption standard as the core encryption system. They've also agreed that multiple conditional access and control data streams such as DigiCipher and PowerKEY will be supported.
Further, the cable industry has agreed on two crucial elements of an open cable set-top. It "will have to be operating-system-independent and microprocessor-independent, " said Richard Green, president and chief executive of CableLabs. The OpenCable specifications are intended to foster competition among vendors for key elements of digital cable networks while ensuring the interoperability of devices connected to cable networks. The goal is to establish competitive pricing for set-tops and to introduce digital cable-ready TV sets and set-tops in retail distribution, he explained.
While hardware blocks in a set-top box are relatively easy to identify and implement, harder to define and select are the software components- application programming interfaces (APIs)-required in the advanced set- top.
Obviously, the design of the cable industry's advanced set-top will require the smooth melding of dozens of hardware and software components. These components must be able to communicate with each other through APIs. Among the APIs classified as key so far by the OpenCable initiative are operating system- network APIs, OS-application APIs, OS-hardware APIs, client-server APIs, application-file APIs, client-content APIs, content-access APIs and browser-resident engine APIs.
Some APIs are obviously less important than others for cable operators to control. However, members of the OpenCable initiative say they are fully aware that control of practically all the key APIs is "paramount, " since some APIs can grow to take control of others, and even one closed API in an otherwise open box could make the entire box a closed environment. While some APIs are already well-defined by de-facto industry standards, a majority of middleware for advanced set-tops has multiple competing APIs, or in some cases, no industry APIs at all. "Making a clearly defined set of APIs is one task the OpenCable initiative must finish, " Green said.
A good example of this challenge is the OS and application APIs. These APIs control the heart of the set-top box. Native applications, written specifically for the advanced set-top requiring maximum performance and hardware interaction, will be built upon OS services and libraries, provided through the APIs. In set-tops with any important native applications, these APIs will be crucial. If cable operators do not control these APIs, it would be virtually impossible for them to switch operating systems; these APIs also can be leveraged to control the majority of the other APIs on the set-tops.
The most contentious API battle is likely to rage in the area of remote execution environments and virtual machines. Today, the competing APIs are platform-independent Java and Windows-specific ActiveX. Such an API allows applications stored on the network to be downloaded, executed and discarded, while it also encapsulates the run-time environment, security model and object model. OpenCable members recognize this as an extremely important API that should be under the cable operators' control or be an open standard. They noted that those who control this API can dictate which virtual-machine applications and content can run on advanced set-tops, their performance and a host of other related technologies that this API can easily encapsulate.
The recent announcement by Tele-Communications Inc. (TCI) that it will license both Sun Microsystems Inc.'s Personal/Embedded Java and Microsoft Corp.'s Windows CE in the company's next-generation digital interactive cable set-tops has sent mixed signals to the rest of the cable industry. Some observers noted that it's a brilliant business move to pit Java against Windows CE, since the last thing the cable industry wants is to let either Sun or Microsoft control the destiny of cable APIs. It remains to be seen, however, just how much influence Windows CE may have over Personal Java in defining cable APIs, or vice versa. Asked to clarify the role Personal Java and/or Windows CE may play in the cable API definitions, CableLabs' Dulchinos declined to comment. "We can't talk about it, because we haven't written any of those APIs yet for the OpenCable specs, " he said.
In the latest announcement between TCI and Microsoft, the two companies made it clear that every set-top TCI purchases will contain Windows CE, but not every box may incorporate the Java Virtual Machine (JVM), due to the memory constraints of a set-top. In theory, no JVM in a set-top could mean no major play for Personal Java on the API front. Many experts in the cable industry agree, however, that the cable APIs will most likely require basic support for HTML and JavaScript. At issue, then, is how many mainstream cable applications in the future may need to be written in Java, rather than in JavaScript, by requiring full support for Personal Java's class libraries, thus needing a full JVM integration in a set-top. Curtis Sasaki, group manager of product marketing at JavaSoft, cautioned that "it's too early in the game to tell exactly what TCI wants to do. "
Industry observers pointed out that it would be repetitive if TCI put both Windows CE and Personal Java in the same box, especially when Windows CE supports a subset of Java. Windows CE alone eats up a lot of memory. Personal Java, separately, needs at least "2 Mbytes or less memory, " according to Sasaki. He pointed out that in a lower-end box, for example, there is a chance that cable operators may want to put a non-Windows CE RTOS combined with Personal Java.
It may not be an overstatement to say that the success of the OpenCable initiative is now almost entirely dependent on how the cable industry resolves the thorny issue of defining key cable APIs for the advanced set-top- box and application developers. Unfinished sets of APIs, whether designed for cable or terrestrial broadcast services, could wreak confusion among consumer- system design engineers. "I can't determine what interactive TV features my DTV is supposed to support unless I know whether such features will be written in Windows CE, Visual Basic or Java applet, " said Lance Gentry, director of DTV product planning and strategy at Philips Consumer Electronics.
Although not central to broadcast APIs currently discussed among cable operators, the connectivity of a cable set-top with other consumer- electronics devices within a home network is expected to become a significant issue. Sony Corp. has been working on the development of APIs for command and control of a variety of non-CPU and CPU-based consumer appliances. As advanced set-tops compliant with the OpenCable specs are expected to be sold in retail shops as early as 1999, it "will be very important to design a set- top that can not only talk to, but also command and control, the rest of the consumer systems at home, " said James Bonan, vice president of new business development at the Consumer Audio/ Video Products Group at Sony Electronics Inc. Bonan said Sony's recent 5 percent purchase of General Instrument reflects its vision to contribute that technology to the cable world.
Copyright (c) 1998 CMP Media Inc. |
