DAVID SHORT /
04.01.2005
Originally featured on BroadcastEngineering.com
Is 2005 the year of interactive TV?


Commonly used applications, such as the EPG, sometimes are stored in the STB flash memory to improve reliability and response times. Image courtesy NDS.


The TV industry in the USA looks like it is planning big things for interactive TV (iTV) over the next year. This follows several false starts during trials in the dot.com boom, which basically involved putting Internet content on TV with some modification — viewers were not impressed! In the USA and Europe, the industry is now maturing and finding ways to work with the audio-visual content rather than in spite of it.

In this article, we will discuss the following categories of interactive content:

  • “Always on” magazine services

    These are not associated with any particular TV program. These services typically carry sports, weather and news. The EPG can be regarded as an always on application, albeit a rather special one.

  • Games

    We could include this in the “always on” category, but we have split it out to emphasize the importance of revenue from games. Viewers will pay $1 per game, so this can be a significant revenue generator.

  • tCommerce or TV commerce

    Although it is an always-on service, this deserves a special mention, as it requires end-to-end encryption to ensure secure transactions. It has not proved a popular category of iTV, so far.

  • Enhanced TV

    This is where an application is available to viewers watching a certain channel at a certain time. These are usually produced to correspond with the program, e.g. multi-screen, multi-camera, voting and quizzes. Voting can be a significant revenue generator.



PVR/DVR and VOD should also be regarded as “interactive” as they give the viewer control over the content, but we will focus on the categories mentioned above. They all have a common requirement for a middle-ware in the STB.

New developments

In the USA, DVR and VOD have been the most successful interactive offerings to date. HD also has been a significant new feature for many consumers. This is in contrast to Europe, where games, always on and enhanced TV have been deployed first, while DVR, HD and VOD are still in trial or early-adopter phases.

Much of the new momentum for iTV is coming from the deployment of NDS MediaHighway middleware on DirecTV. It is expected that News Corp. will leverage the iTV experience from the BSkyB platform and other Sky platforms, where they have found that iTV services reduce churn and make the service more compelling.

Generic architecture

The cable companies are working to deploy several solutions to compete with DirecTV, mainly based on the Open Cable Applications Platform (OCAP) standard.



Figure 1. In the traditional model of an STB, the middleware layer is left out. Click here to see an enlarged diagram.



The traditional model of an STB leaves out the middleware layer. (See Figure 1.) The STB vendor often provides applications such as EPGs and more recently DVRs that work in the native coding language of the STB. The problem with this is that the applications are not portable or flexible. This is not so bad for EPGs and DVRs, which don't need changing often, but it does not work for more general interactive applications. To address these issues, the concept of middleware was introduced to abstract the application programming interface (API) from the underlying hardware. (See Figure 2.) To support a wide range of interactive applications, the middleware must support an API that is:

  • Relatively easy to work with (so, quite high level). Although many applications are coded directly, there are authoring and content management tools to support all the middleware standards.

  • Consistency across the STB manufacturers and models. In practice, the main difference exposed to the application is the processor speed of the STB.



Figure 2. Middleware was introduced to abstract the application programming interface from the underlying hardware. Click here to see an enlarged diagram.

Applications are usually downloaded via the broadcast stream in MPEG packets. This gives a natural ability to associate an application with a channel. The application packet stream is treated as an extra element of the relevant MPEG program. Some middle-wares, such as MHP and OCAP, also can accept applications loaded via the return path.

All middlewares aimed at the cable and satellite markets can support interaction via the return path, e.g. shopping transactions and voting. This can be either via a dial-up modem or a cable modem. While a cable modem return path is generally superior, dial-up has an important advantage: By using premium rate numbers, STB applications easily can collect small sums of revenue to pay for things such as voting or pay-per-play games.

Sometimes commonly used applications, such as the EPG, are stored in the STB flash memory to improve reliability and response times.

Some implementations of interactive STBs use EPGs that are coded in the native STB language and run alongside the middleware. This is usually done where a middleware-based EPG would give inadequate performance, usually on low-end STBs.

The main middleware platforms deployed and planned in the USA are:

Middleware standards and products

  • OpenTV, which is deployed on Echostar.

  • MediaHighway, which is planned to launch on DirectTV mid-year.

  • OnRamp and OCAP, which are planned for several cable companies.

  • MSTV Foundation Edition, planned for Comcast.



Games are one example of interactive content. Viewers will pay $1 per game, so this can be a significant revenue generator. Image courtesy Free-Thinking.


The only “open” standard in this list is OnRamp/OCAP. OCAP is part of the CableLabs OpenCable standard for interoperable STBs. It is largely based on the Digital Video Broadcast (DVB) Multimedia Home Platform (MHP) specification, which is, in turn, based on Java. These standards provide a Java Virtual Machine (JVM) cut down to run on an STB, with classes added to support TV-specific functions, e.g. channel changing.

MHP and OCAP require relatively powerful STBs to run. To allow support for the current installed base, vendors and operators have been working together to define the “On-Ramp to OCAP,” a subset of the OCAP interface, which is small enough to implement on “legacy” STBs, e.g. Scientific-Atlanta and Motorola 2000 series. Liberate 5.0 (based on Liberate Compact) is an example of an OnRamp compliant middleware.

Microsoft's MSTV latest offering is Foundation Edition, and this is designed to run the whole range of cable STBs for legacy boxes upwards. It supports applications written in Micro-soft's C# language. It also has a version to support IPTV, which several telcos are using for their VOD over DSL deployments.

A large subscriber population is important to stimulate application development. The satellite operators are both using proprietary standards, which have no other significant user bases in the USA. However, the size and relative homogeneity of their STB populations makes this tenable as developers and content providers will make the effort to port their applications onto these platforms. OpenTV and Media-Highway have been widely deployed for a long time and so have mature development communities with the tools to support them.

Critical mass

Cable operators are mainly standardizing OnRamp/OCAP to create a large target population of interactive boxes to attract high-quality development houses and content providers.




David Short is a technical architect working on the design of new DTV systems. He also is a member of BroadcastProjects.com, an alliance of independent consultants. For more information, visit www.broadcastprojects.com.



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