The Digital Set-Top-Box Decision and Your Interactive Business

Choosing the right set-top box (STB) for digital pay television is acomplex decision, which a broadcaster has to make carefully. It is evenmore important for a broadcaster planning to generate additionalrevenue by offering interactive TV services. This paper examines theimpact of interactive applications on the cost and the performance ofthe STB.

WHAT IS AN STB?

The set-top box is designed to receive the television signal, runthe interactive applications and pass them to the TV. Its hardware andsoftware depends on the nature of those signals and applications.

Each broadcaster follows a set of standards that help define whatthose signals look like. The most basic and commonly used is the MPEG-2compression standard that allows you to broadcast highly compresseddigital signals. The digital video broadcast (DVB) standards define thetransmission format and describe the video and audio signals.

The ways in which the interactive applications are delivered to theSTB are different between different middleware vendors. However, thereis a growing trend to use HTML and XML as the language to author anddisplay the interactive services. This enables the applications to bedeveloped by using the widely available Internet tools and to draw onthe large number of programmers with web development skills.

The set-top box is a specialised computer designed for television.Its basic hardware components are:

• Computing Subsystem:

  the part of the STB that handles basic computing functions. Thispart includes standard computer components like CPU, memory andmodems.

• TV Subsystem:

  the part of the STB that understands and processes TV signalsspecifically. It includes MPEG-2 processing capability and video/audiooutput to TV or video recorder.

• Conditional Access Subsystem:

  the part of the STB that permits or denies permission to viewprograms based on viewer entitlements. It includes the smart card anddescrambling hardware also.

The STB software is made up of several distinct layers:

• Hardware Drivers

  that interface between the software and the hardware. These areprovided by the STB vendors.

• Core Software

  that provides the software platform for the applications running onthe STB. This category includes the operating system, boot loader, TVCore, middleware, and conditional access.

• Applications

  that perform the functions that the viewers need, from theubiquitous EPG to the variety of interactive TV applications.

INTERACTIVE APPLICATIONS

In a digital video broadcasting network, the STB is the interfacebetween the network and the viewer. It is also the vehicle to run manyapplications, such as the electronic program guide and interactive andenhanced TV applications. As the popularity of interactive servicesgrows among viewers, so will the opportunity to generate revenue forthe broadcaster. The STB will need to have the capacity to support anincreasing number of interactive applications, each with uniquesoftware and hardware requirements.

In general, interactive TV applications can be summarized into thefollowing four categories:

One-way interactive applications: One-way interactiveapplications may include services such as weather reports, trafficreports, news headlines, sports statistics, sports news, games, viewerquizzes, local events calendar and schedules, and financial news andinformation.

In one-way interactive applications: a broadcaster bundlesand transmits the information in the proper format and structure to theSTB using the high bandwidth digital channel, and the subscriber willaccess the information interactively using their remote control.

Two-way interactive applications: Two-way interactiveapplications have all the functionality of the one-way interactiveapplications. In addition, two-way interactive applications allowtwo-way communication between the viewers and broadcaster. The viewerscan send their response, feedback, and even transaction information toa broadcaster via the return path of the broadcast system.

Some typical two-way interactive applications are on-line betting,home banking, home shopping, share trading, and event ticketpurchasing.

One-way messaging applications: One-way messagingapplications establish an efficient way for a broadcaster to conveyinformation to the viewers. Such information can include emergencyalerts, program promotional messages and bulk mail messages from thebroadcaster. One-way messaging can be broadcasted to group users andalso can be unicast to selected viewers. Two-way messagingapplications: Two-way messaging applications require minimalinteraction with the viewer at home. The viewer is asked to respond toa simple message that appears on screen. The viewer’s responsecan be reported to the headend. Some typical two-way messagingapplications include polling, lotteries, quizzes, and interactiveadvertising.

In order to attract more viewers, the interactive applications needsome technical “killer characteristics” to make them moreengaging and entertaining. These technical capabilities are veryimportant considerations for planning the broadcast network and theset-top box. These are some of the most important “killercharacteristics,” that we feel will be the most important in thenext two to three years:

• High-quality video, audio and graphics, with more fonts that can bescalable. All these characteristics influence the interface and are keydifferentiators for the viewers interacting with the service.

• Ability to synchronize the interactive service with the programmingcontent. For example, with a television shopping service, if theinteractive service is synchronized with the live programming, viewerswill be able to see an item on display and push the button to instantlybuy that item. This will make the application dynamic and make it anintegrated part of the real-time programming offering.

• Live video window within the data and information services toprovide viewers a more dynamic service. For example, if a viewer iswatching a documentary, they could activate the interactive option andthen watch live programming in the scalable video window whilesimultaneously viewing on screen display of data or informationrelating directly to the content of the programming.

• Addressability. The capability of the application to address theindividual subscriber according to their demographic information. Thiswill give the broadcaster the ability to customize messages for anindividual viewer, and open up new opportunities for viewer feedback,direct mail messaging, and targeted interactive advertising.

• Return path capability. Previously broadcasting was a vehicle forone-to-many transmission. Now with developments in interactive TV, theviewer is able to provide feeedback, request information or buy goodsthrough their television. The return path is required for systems withthis advanced functionality.

All of these characteristics need support from the set-top box, sonow we will study the impact of these requirements on the STB.

THE IMPACT OF INTERACTIVE APPLICATIONS ON STB HARDWARE

As described in the previous section, there are many excitingservices that can be offered by interactive TV, and each of these posesdifferent requirements for the STB hardware.

A broadcaster normally introduces interactive services gradually andover a period of time, from the more simple to the more complex viewernavigation and operation. The STB is a consumer device that will beused in the home for a very long time, and the model of upgrading thehardware as seen in the PC market cannot be realistically implemented.A broadcaster has to ensure that the STB initially deployed in themarket can still perform satisfactorily in several years time whilerunning an increasing number of interactive applications.

The most affected part of the STB hardware is the computingsubsystem.

The CPU (central processing unit), the brain of any computer,is the main processor that runs the software in the STB, and it has tobe powerful enough to handle the applications. The experience of nothaving enough computational power in the PC world is now repeatingitself in the STB. The applications are getting increasinglycomplicated and the graphics are getting richer. The CPU performance isthe key to adding functionality to the box. The faster the CPU, theeasier it is to add functions like browsing and interactivity to thebox.

A few interactive services mentioned previously require multipleplanes of graphical capability. It is certain the applications in thefuture, for example games, will require increasing amounts ofcomputational and graphical power.

Apart from the CPU, the memory is another deciding factor tothe performance of the STB. There are many types of memory used in theSTB for storing software, character fonts, buffering video, and otheruses. Identical to the PC, more memory means more performance and addedfuture proofing for the STB.

A large amount of memory is used in STB's to hold the programs thathandle the digital services. Storage is also required for supportingcharacter-based languages such as, Chinese, Korean and Japanese. In thepast, read-only memory (ROM) was often used for this. Today, ROM isbeing replaced in almost all STB's by the more flexible flash memory.Its major advantage is the fact that most of it can be erased andreprogrammed with new software delivered through the broadcaststream.

Flash memory is suitable for the main software that resides and runsthe STB, rather than transient applications that change depending onwhich TV channel the viewer is currently watching and which interactiveservice is selected. Some of applications are best stored in the STB,such as the electronic program guide.

Another type of memory is dynamic random access memory, which isused in a STB for data storage and video/graphics decoding.

The CPU uses DRAM to execute its software as well as for informationneeded by the current application. For TV viewing, DRAM can hold a fewdays' worth of program guides. For interactive applications, it storesthe application itself that is downloaded from the stream, and the datarequired for running the application.

An interesting way to make the STB work faster is to store the mainsoftware on the flash, but to run it from a copy in RAM. It isimportant for the broadcaster to specify some extra DRAM space whilepossible, which can give better performance while running more complexinteractive applications. It also provides a possibility that thefuture additional applications may still run on this same STB.

The video DRAM is used in a STB for decoding and storing thevideo/graphics image that is being output to the television or videorecorder. The amount of video DRAM required depends almost totally onthe video resolution of the picture. There is an increasing trend thatthe DRAM and the video DRAM are shared in the STB.

The natures of the interactive applications require very richgraphical contents. The number of graphics planes supported determineshow the STB will be able to put text and/or graphic bitmap overlaysover the TV picture, and how many different layers can besupported.

THE IMPACT OF INTERACTIVE APPLICATIONS ON STB SOFTWARE

With the right hardware in place, the next most important decisionthat the broadcaster has to make is the choice of middleware. Themiddleware or virtual machine might be generically called “theapplication portability layer.” This layer provides a level ofabstraction from the hardware that gives application developers accessto all features and functions of the STB and of network data, butwithout being tied to the specific hardware application. This is whatmakes a STB able to run a variety of applications, including unknownones that will be written in the future.

The variety of different middleware approaches makes it particularlyhard to choose the right one. What issues should you consider when makethis decision?

• First and most important, you need to be sure it provides thefeature set that you need. You probably know which interactiveapplications you want now and have a good idea of which you will wantin the near future. Does this middleware support the features you willneed for these applications?

• How many different applications are available? Are the middlewareand its applications integrated with conditional access you want?

• Does it support the languages used in your market? Is it capable ofsupporting scalable fonts that will be required for interactiveapplications?

• Is it ready when you need it? One of the most important issues foryou is time to market for your service. You need a middleware that canprovide the right functionality at the right time.

Whatever the choice of middleware is, it is important to make surethat the middleware you select can support download of the middlewareat a later date. It will enable you to launch with one solution andmigrate over time to newer versions of that middleware, or even toother middleware products.

CONCLUSION

The latest STB technologies offer a broadcaster many choices toprovide exciting interactive services and to generate revenue. Theselection of STB technologies is one of the most important decisionsthe broadcaster has to make. The broadcaster has to make sure that theSTB they select will enable them to offer the latest applications totheir box population.

The investment in the STB will affect the business of thebroadcaster for years to come. To succeed, the broadcaster has to makesure the decision made will stand the test of time.