MHEG-5

Not to be confused with MPEG, a video encoding technology by the Moving Picture Experts Group.

MHEG-5, or ISO/IEC 13522-5, is part of a set of international standards relating to the presentation of multimedia information, standardised by the Multimedia and Hypermedia Experts Group (MHEG). It is most commonly used as a language to describe interactive television services.

Characteristics

MHEG-5 is an object-based declarative programming language which can be used to describe a presentation of text, images and video. An MHEG-5 application consists of a number of Scenes which the user of the application can move between. Each Scene lists the items of text and graphics to be presented and can contain blocks of procedural code which are executed in response to one of a predefined set of events such as keys being pressed, timers firing or content being successfully loaded into memory. These blocks of code consist of elementary actions which can perform operations such as changing the text displayed by a text object, or starting a video clip playing.

MHEG-5 specifies a hierarchy of classes that are available to the application author. Unlike in object oriented languages, it is not possible for new classes to be defined. The standard defines two representations of MHEG applications, one of which is textual and the other is represented in ASN.1. Applications are normally written in the textual notation and then encoded into ASN.1 for interpretation by the MHEG engine.

MHEG-5 is suited to programming interactive kiosks and interactive television services.

Profiles

The MHEG-5 language itself is just that, a language. To be useful in any particular context, the language needs to be profiled.

In the UK and in New Zealand, MHEG-5 is used to provide interactive services for digital television. The full specification of how MHEG-5 is used in the context of the UK Freeview platform is the UK Profile of MHEG-5. The same profile, with minor additions, is used in New Zealand. MHEG is also used on Freesat, as opposed to the proprietary OpenTV platform used on Sky.

In Hong Kong, TVB has also selected MHEG-5 middleware for interactive services available on its digital broadcasting channels.

Ireland has selected MHEG-5 (UK Profile, v1.06) middleware for interactive services as a recommended feature of its Minimum Receiver Requirements for DTT in Ireland.

A broadcast profile of the language has also been standardized by ETSI forming ETSI standard ES 202 184.

Class hierarchy

File:Mheg5.classes.png
Note: You can download the PDF version of above image from http://user.chol.com/~mheg5/down/class.pdf.

See also

• Multimedia Home Platform (MHP), an alternative technology used for interactive television services in some European countries.
• OpenTV, a proprietary system used for interactive television on Sky in the UK.
• MediaHighway, a proprietary middleware for interactive television owned by NDS.

External links

• Media Receive MHEG-5 Application (archive)
• Strategy & Technology Ltd
• MHEG Official site
• Pixsan Digital Software
• Cabot Communications
• IMPALA (International MHEG Promotion Alliance)
• Hello World in MHEG-5
• ASN.1 encoder/decoder + source code
• Open Source MHEG-5 engine for Linux
• Open Source MHEG-5 engine for Windows
• General Information
• OpenCaster free GPL licensed software for transport stream broadcasting