DVB Update: Interactive Systems in DVB

All receivers for DVB transmissions include microcomputers to manage the digital processes required, but to save costs, early receivers for DVB transmissions had small amounts of processor power and memory.

Companies such as Canal+ and OpenTV, however, soon began to exploit the computation power of the receivers to add the functionality that started the industry of interactive TV. Receivers could run interactive applications, that is, small programs that enabled the display of information and graphics to the user, and the management of user interaction with the receiver and any return channel.

This was also much analyzed and specified in the international DAVIC standards creating group that was focused on the subject, primarily to serve up video-on-demand, but also to address enhanced and interactive TV requirements.

DAVIC made three key selections in this area that have been followed by other bodies since. First, working with the MPEG committees, it created the DSM-CC standards, which include specifications for carousels called the Data Carousel and the Object Carousel. DAVIC also worked with MHEG to create MHEG-5, an interactive display language specifically for TV, and chose to enhance this by providing it with access to a Java Virtual Machine, in a specification that would evolve to be called MHEG-6.

The introduction of MHP

In the market, the first digital TV operators showed that having an interactive component could produce new services and revenues. It was clear that there would be advantages to the market as a whole if the DVB Group (the DVB) could create a standard for the deployment of interactive services and the software environment of receivers for DVB. The concept of the Multimedia Home Platform (MHP) arose from this discussion, and this is now the basis of the DVB approach to interactivity. In parallel with the DVB’s discussions, the UK DTT (digital terrestrial television) market — firmly based on open standards — adopted the MHEG-5 and DSM-CC technology based on the DAVIC discussions, and added specifications for some enhanced functions as well as font and graphics, in order to provide a complete system. Many of these detailed elements were later adopted by the DVB in the MHP specification.

The MHP specification, formed after the DVB’s crucial commercial requirements process, has three key profiles: the Enhanced TV profile, the Interactive TV profile and the Internet access profile. These are intended to be able to support a horizontal market model, where deployment is not dependent on a particular system operator to ensure system interoperability.

The key specifications are based on a core set of technologies used in the MHP system. These are Java with extensions developed by DAVIC and the DVB for TV use, the DSM-CC Object Carousel for transmission of applications, and HTTP over IP in the return channel. The Interactive and Internet Access profiles also can include a version of HTML.

Current specifications

The MHP specification contains the Java programming language and many of the standard facilities that Java brings with it, including security, internationalization and screen management techniques. Thus, it can adapt to the many varying requirements that will emerge as interactive TV develops. The requirement for the growing play-along interactivity market is already supported, as is the security needed for the growing gambling market, and there are many facilities for building EPG services and classic news and information services, as well as T-commerce applications. Because Java is able to support sophisticated file handling and is network-friendly, support of home networking and PVR applications is likely to be readily available with the simple evolution of the MHP.

The specifications DVB 1.0 for the enhanced profile and DVB 1.1 for the interactive profile were first published in 2001, and a version of 1.0 — namely 1.0.2, which includes many adjustments arising from implementation and testing work — has been issued as a recent upgrade.

Delivering interactivity

The DVB determined, as part of the effort to make the standard truly interoperable, that a condition of use of the MHP brand on receivers would be conformance with a substantial set of tests designed to ensure that the market could work properly with a range of independently supplied receivers. The production of these tests is continuing during 2002, with a goal to have properly tested and conformant receivers on the market this fall.

In the transmission part of the system, S&T software for creating Object Carousels is included in the test harness for MHP testing and in developer and broadcast systems. Other companies, including Sony Broadcast, offer broadcast systems. Companies such as Digisoft, Snap2 and SofiaDigital have started to write interactive applications, some of which are already being used in Finland.

Other areas of activity include Australia, where the DTT broadcasters have selected to use MHP, and Korea, where the satellite broadcaster KDB also has selected MHP.

Meanwhile, the horizontal market concept, with manufacturers providing a range of equipment for the market unconstrained by an operator’s budget or requirements, is being tried out in the UK. Here, the DTT unit market of more than a million will shortly see the roll-out of new free-to-air digital services that include MHEG-5 interactive content. It also will see low-cost consumer equipment in the region of (US) $142 to $213, which will be readily available later in 2002 without subscription or rental cost to the user. These developments will start to show the real power of the horizontal market model targeted by MHP. At the same time, work is continuing in the UK to examine how the established and low-cost open market using MHEG-5 can co-exist with an MHP environment.

In the USA, Cablelabs works on behalf of the U.S. cable operators to select and test the best-of-breed technology for future deployment in U.S. cable, and it has selected MHP as the basis of its OCAP specification for Open Cable. Although this will require significant engineering along the way, it is the start of a project that should lead to real implementation.

David Cutts is the director of Strategy & Technology (S&T) Ltd.