Editing MHEG-5 (section)

== Characteristics ==
MHEG-5 is a licence-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 (UK)|Freeview]] and [[Freesat]] in the UK, [[Freeview (New Zealand)|Freeview]] in New Zealand, [[Television Broadcasts Limited|TVB]] in Hong Kong, [[Freeview (Australia)|Freeview]] in Australia, [[Saorview]] in Ireland and has been specified in South Africa.

Recent{{when|date=November 2017}} 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 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 programming|procedural]] code which are executed in response to one of a predefined set of [[event driven programming|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 (computer science)|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 [[Abstract Syntax Notation One|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 kiosk]]s and [[interactive television]] services.