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A top the agenda at IBC2001, interactive television (iTV) is not only a hot topic, but also a growing reality in Europe and Japan. It is datacasting taken to the next level. iTV is, in effect, IP for the family screen. Here is a summary of IBC papers at the session “Viewer Power — Interactive Services.”

Sophisticated interactive services would not be possible without digital technology. This is particularly true for terrestrial network broadcasters. Two key technologies are Multimedia Hypertext Experts Group Language (MHEG-5) and Digital Storage Media-Command and Control (DSM-CC). These provided the foundation for a regional iTV system rolled out by the UK's Independent Television Network (ITV). The ITV digital multiplex is especially complex because there are 14 regional centers, each providing regional content, and there are additional sub-regions inside some of these.

David Cutts of Strategy & Technology (S&T) and Rhys Gambling of ITV described how the pilot task was done in their paper, “Rolling out the Interactive Network.” S&T was appointed as the main systems integrator and core application provider using a detailed list of functional requirements organized by ITV teams. Two targets were set for the pilot project: Keep costs low, and design a system flexible enough to enable both high and low engagement by the regional broadcasters.

Above all, the system had to conform to DVB DTT standards, including MHEG-5, Profile 1.05 and the DVB DSM-CC Object Carousel. The latter is based on the core ISO-MPEG specification and has since been included in the DVB MHP (multimedia home platform) specification. The Object Carousel allows the transmission of data files in a directory file-system so that applications running on a client receiver can acquire and use individual files from the carousel. Objects can be cached with different priority levels and delivered with varying repetition rates.

Because the ITV network carries national feeds and regional segments such as news and weather, a key objective of the pilot project is to provide means to add applications that are directly related to individual programs. The authors explained that these may be added on a national or regional basis and must be validated for conformance to technical and design specifications.

“The complete architecture is most readily described in three parts,” they stated. “First, the basic object carousel and transport stream creation and transmission system; secondly, the core application; and thirdly, the means of introducing new applications and exporting data to third-party systems.”

The data provision for the core service includes all the processing required to acquire data from external sources and to enable staff and journalists to input new material. (See Figure 1.)

The acquired data then is processed into the format required for transmission. These items are delivered to a central server by the data providers on an irregular basis. The delivery is via FTP over specific ISDN connections. The incoming data from all sources is monitored by an automatic process that builds the content for transmission when it is received. The hourly build and distribution of the carousels for all the regions then takes place quickly. This can be overridden with more rapid update, if required.

The authors emphasized the need to test all applications on a representative farm of digital terrestrial receivers. “One of the major features of the system is the test configuration, which now features the ability to run MPEG-2 streams into a software multiplexer and subsequently output via ASI to an RF modulator,” they explained. “This means that all applications commissioned for ITV are tested in as near a live environment as possible prior to real transmission as the test system is able to provide three test loops of MPEG video and audio along with the four data services to emulate the real services.”

Interactive data service delivery

DVB-Data (ETSI/EN 301 192) provides the technical framework for the delivery of data over DVB networks, and DSM-CC (Data Storage Module-Command and Control) provides the mechanism for insertion of data services into the transport stream, according to Allan Arthurs and Andrew Collins of Sony Broadcast & Professional Europe in their IBC paper, “Delivery of Interactive Data Services by Multiple Networked Content Providers.”

As in the ITV paper, DSM-CC Object Carousel is the foundation technology. The authors point out that DSM-CC is an open standard widely deployed in consumer receivers, including digital set-top boxes and integrated digital TVs.

They add that DVB-Service Information (SI) specifies the mandatory and optional descriptions required for digital broadcast services. These standards are vital to the interface between broadcasters and multiple content providers.

“The very nature of the digital platform and the ability to leverage multiple revenue streams from an ever-increasing number of content providers lies at the very heart of most business propositions,” the authors add.

A simple data service can be deployed using only a DSM-CC object carousel server. However, the task of managing multiple dynamic services from several different content providers, some of whom may be independent organizations operating from outside of the host broadcast environment, presents a rather more substantial challenge. In addition, broadcasters have to make optimal use of their bandwidth.

Attention then must focus on reliability. This requirement brings to bare server configurations incorporating RAID (Redundant Array of Independent Disks) storage holding multiple object carousels. (See Figure 2.)

Having worked with ONdigital (now ITV Digital) in the UK and Finland's pubcaster YLE, Sony Europe developed a workflow concept of a Data Service Stream (DSS) that serves to coordinate the relationship between the content provider and the broadcaster. At the server, the broadcaster creates a DSS on behalf of one or more content providers. The content provider, in turn, populates the allocated DSS with content to be broadcast in accordance with an agreed schedule.

The broadcaster establishes an account on the server and creates one or more DSSs allocated to each content provider. Each DSS will represent an allocation of bandwidth for a particular period to be populated by the specified content provider and will be configured with the appropriate DVB multiplex parameters.

Once assigned a DSS, a registered content provider is able to access the server and publish content to be broadcast. The content provider is responsible for the scheduling of data services within the allocated DSS and the associated carousel configuration.

The multimedia dilemma

While the DVB-MHP initiative was hailed as a breakthrough in solving multimedia, interactive service delivery, legacy issues remain. This legacy of deployed technologies will exist for delivery platforms that are either unable or unwilling to migrate to MHP. It is a situation faced by the BBC, where technologies as diverse at MHEG-5, Open TV and Liberate have entered the digital TV arena.

A paper from BBC Research and Development, “Delivering Interactive DTV Services to Multiple Target Platforms,” addressed this dilemma. The authors, Dr. Richard Bradbury, Dr. Richard Cartwright and Toby Steele, pointed out that the BBC has launched interactive services on all three major DTV platforms in the UK: terrestrial, satellite and cable. The problem is that the three platforms have independent network operators that have chosen different middleware platforms for commercial and technical reasons.

“If a broadcaster wishes to launch a new interactive service, it is currently necessary to write bespoke application code separately for each target middleware layer: MHEG-5 for DTT, OpenTV for satellite and Liberate DTV Navigator for cable. Three separate programming teams are required, and coordinating their efforts involves complex project management,” the authors warned. While MHEG-5 is an ISO/IEC standard, the other two are proprietary systems.

The three platforms differ in font, image, palette and remote control characteristics. (See Figure 3.)

The problem with deployed platforms is to find a flexible balance between head-end and receiver processing, tuned to provide high-quality services for each target platform.

BBC R&D has defined an initial data model. A prototype implementation of a publication engine that supports the description syntax has been developed. Using Java programming language, the publication engine manages the dependencies that are established between content and templates. The main objective is a data model that supports the separation of production roles. And the publication engine supports the development of the data model. With these tools, it may be possible to support interactive services across the three platforms, which will become more and more important for public broadcasters.

TV production on a PC

The ultimate in iTV may be reached when viewers in effect produce their own programs on their PCs. An IBC paper from NHK Science and Technical Research Laboratories in Japan described a TV program-making language (TVML) for making complete TV programs on a PC.

It is a text-based language to describe a TV program. A script written in TVML is interpreted by a TVML player running on a PC to generate a TV program in real time, using real-time computer graphics, synthesized voice and other multimedia functions. (See Figure 4 on page 12.)

The authors, Maskai Hayashi, Mamoru Douke, Kyoko Ariyasu and Narichika Hamaguchi, state that TVML can describe an entire television program. Based on a description method used in the real program script from which television programs are actually produced, the language is designed so that even those with little experience can use it easily. The TVML player that reproduces a program script is a kind of software program installed in a PC. It comes will all the functions necessary to produce an information-oriented program.

The researchers now are applying TVML for automatic production of talk shows from an interview Web page, television with hyper-dials and iTV by TVML. They pointed out that TVML's language specification itself does not have a function that supports interactive applications. But if the player is used for such an application, it comes with a function called “external control mode.”

The player performs a complete interpreter operation, meaning that the moment a line of script is read, its syntactic structure is analyzed and instantly executed and so on with each line. While the TVML player is turned on, it instantly executes a script that has been sent asynchronously from an external application and then waits for the next one.

For example, an interactive quiz program could be programmed with the player in external control mode. In the program, a CG figure encourages the user to ask questions. The user clicks a selection on the screen, and the story continues in response to this The user's selection changes the course of the story.

The authors conclude, “In Japan, NHK local stations and cable television operators are using TVML to produce on-air programs.”