Interactive television describes any number of efforts to allow viewers to interact with television content as they view. It is sometimes called interactive TV, iTV, idTV or ITV (not to be confused with the British Independent Television network). To be truly Interactive, the viewer must be able to alter the viewing experience (eg choose which angle to watch a football match), or return information to the broadcaster. This "return path" or "back channel" can be by telephone, mobile SMS (text messages), or cable. Cable viewers receive their programs via a cable, and in the integrated cable return path enabled platforms, they use the same cable as a return path. Satellite viewers (mostly) return information to the broadcaster via their regular telephone lines. They are charged for this service on their regular telephone bill.

Interactive TV is often described as "lean back" interaction, as users are typically relaxing in the living room environment with a remote control in one hand. This is in contrast to the personal computer-oriented "lean forward" experience of a keyboard, mouse and monitor.

Interactivity is supplied by the manipulation of the API of the particular software installed on a set-top box, referred to as 'middleware' due to its intermediary position in the operating environment. Software programs are broadcast to the set-top box in a 'carousel'.

On UK DTT (Freeview), in MHP systems and for OCAP, this is a DSM-CC Object Carousel.

The set-top box can then load and execute the application. In the UK this is typically done by a viewer pressing a 'trigger' button on their remote control (e.g. the red button, as in 'press red ').

Typically the distribution system is based on the MPEG-2 specification.

• Examples of commonly-found middlewares include:
  • OpenTV (ANSI C) - BSkyB
  • WapTV (WTVML ) - BSkyB (WapTV is an abstraction layer that sits on top of the OpenTV Middleware)
  • Mediahighway (MHEG-5, Pantalk) - UK terrestrial, Canal+
  • Liberate (HTML/JavaScript) - NTL, Telewest
  • ICTV (HTML/JavaScript) - NTL, VNL
  • MHEG-5 (used in UK DTT)
  • DVB-MHP (Java/HTML)
  • Alcatel Open Media Suite - Sasktel, BBTV, Kingston
  • Microsoft TV (XHTML)

Development of applications using these technologies is traditionally drawn out due to the limitations of the set-top box, the large amount of testing required and the lack of standardisation of deployed units. Almost all are proprietary and subject to heavy licensing restrictions.

Some interactive television projects are consumer electronics boxes which provide set-top interactivity, while other projects are supplied by the cable television companies (or multiple system operator, or MSO) as a system-wide solution. Some examples of interactive television include:

• MSO systems
  • Time Warner (US)
  • Comcast (US)
  • Cablevision (US)

• MSO trials or demos
  • Full Service Network from Time Warner (US)

• Consumer electronics solutions
  • TiVo
  • ReplayTV
  • UltimateTV
  • Microsoft Windows XP Media Center

See also

• Digital television
• Set-top box (STB)

External links

• The Enhanced Television Cookbook: PBS's (US Public Television) Interactive Television How to
• OpenTV Inc.
• Tracy Swedlow's InteractiveTV Today, otherwise known as [itvt], a weekly email newsletter covering all aspects of interactive television; offers news, features and interviews.
• BSkyB for WapTV
• MediaHighway
• MHEG ISO standard
• Liberate Inc.
• DVB-MHP standard
• Alcatel Open Media Suite
• Microsoft TV
• Jobs in UK Digital Television
• Interactive TV Authoring Software
• Understanding Interactive Television (UITV.INFO): Interactive TV Research Resources