MHEG-5, or ISO/IEC 13522-5, is part of a set of international standards relating to the presentation of multimedia information, standardized by the Multimedia and Hypermedia Experts Group (MHEG). It is most commonly used as a language to describe interactive television services.
MHEG-5 is a license-free and public standard for interactive TV middleware that is used both to send and receive interactive TV signals. It allows a wide range of TV-centric interactive services to be deployed. It is used by Freeview and Freesat in the UK, Freeview in New Zealand, TVB in Hong Kong, Freeview in Australia, Saorview in Ireland and has been specified in South Africa.
Recent work by the DTG in the UK has led to the development of the MHEG-5 Interaction Channel (MHEG-IC), which enables an extension of broadcast interactive services to be delivered via an IP connection. The principles behind the MHEG-IC are to provide a seamless viewer experience of broadcast delivered content augmented with content delivered over IP as an extension of the channel or network. Broadcasters have full editorial control of the user experience. The MHEG-IC gives access to streamed on-demand video content in addition to traditional text and graphics as well as the ability to support secure transactions.
MHEG-5 is an object-based declarative programming language that 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 that 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.