How MHEG-5 Works and Applications

The MHEG-5 end-to-end system is simple and its client software can be implemented in a wide range of low-cost digital TV receivers. The client software consists of an MHEG-5 engine (or virtual machine) that interprets MHEG-5 applications and presents information delivered to it via a broadcast file system or via a ‘return channel’. MHEG-5 enables interaction between the user and the application through the remote control and in some implementations allows the application to exchange information with a remote server via an IP connection.

MHEG-5 programming language broadly comprises objects for presentation, links that respond to events and Resident Programs. Presentation objects include video, audio, lists, text and graphics. Events respond to input from the remote control, a timer, a stream event message in the broadcast or the result of a logical condition in the application. Resident Programs are native functions, defined in the Profile, that extend the basic MHEG-5 to provide specific tools to manipulate data, and can also be used for market specific profile extensions to enable MHEG-5 to work with conditional access systems, PVR control, Push VOD or an IP return channel.

The broadcast MHEG-5 profiles have a simple life-cycle, allowing only one application running at a time. One MHEG-5 application can launch others but on doing so the original is terminated. In a broadcast system, an auto-launch application may be started when a service is selected with which it is associated. The auto-launch can then start other applications and select to tune to other services. Information can be passed between applications by making use of persistent store in the receiver.

An application is normally loaded from the DSM-CC object carousel or optionally from the return channel or from a DVB-CI module. Data loaded from the carousel can be updated rapidly onscreen as the content of a data object changes. Information is presented either as “included” content, where the text or graphic is embedded in the application, or as “referenced” content, which is acquired from the carousel as required. A strategy of building applications with predominantly referenced content enables them to remain stable, with changing content and graphics and even detailed layout, over an extended period.

MHEG-5 can be used, for example, to build an EPG application that has data efficiently delivered in the DSM-CC object carousel and presented using MHEG-5. These systems allow the user to tune to a chosen channel from the EPG and this provides the platform operator with the opportunity to provide a consistent EPG rather than rely on receiver manufacturer’s implementations.

MHEG-5, when running, takes control over scaling and presentation of video and presentation of audio. This provides the means to tune to other services and to switch between running video streams in the same multiplex. This allows a broadcaster to show more than one view of an event – for example different matches at a tennis tournament, different players in a golf tournament or views of a soccer match. Control of video and audio selection is achieved using the MHEG-5 application associated with the service, not by the receiver navigator.

Applications

MHEG-5 applications can present and navigate around textual information such as news, weather, financial data and sports results. Navigation can be through ‘list and select’ processes and applications can also replicate the page number navigation of Teletext. Advertising within such applications can be graphically rich and related to individual pages of information.

MHEG-5 can also be used for basic (and extended) EPGs, interactive games, multi-screen/mosaic applications and the standard is currently being extended to cater for HD application support, interaction with an IP-based return channel, and Push VOD applications.