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Interactive Digital Television

There is much confusion over what interactive TV means. At its lowest level this may simply mean accessing information through basic analogue teletext or digital text services, and many are not clear about the difference between enhanced ‘one way’ and true ‘two way’ interactive ‘return path’ based alternatives. So far there is no real ‘two-way’ communication from digital terrestrial set top boxes – current ‘interactive’ services are merely allowing the viewer to find the way to information through large numbers of pages continuously broadcast on a ‘carousel’ of thousands of pages.

There have been technical trials of real two-way DTT services, DVB RCT (Return Channel Terrestrial) with a mini-transmitter in the home sending signals back to the main TV transmitter via the receiving aerial, but there are many complexities involved, and any such systems are many years away from being practical. Similarly, it is possible to send signals from a home dish back to the satellite, but this has so far been restricted to business data systems.

Interactivity that requires that a viewer will be able to send messages from the TV set to communicate with their relatives, friends and colleagues, ask for shopping, repairs, medical services, appointments, on-line banking or any other daily life activities requires proper two-way communication. This is fine for cable, which has two-way communication built in, and for satellite, with the return channel by telephone line that is extremely common, even ‘compulsory’ on services such as SKY (the set top box generally makes a phone call when interactivity is required), but DTT will need a telephone or broadband connection from the set top box before it can provide true interactivity. This facility is not currently available on most set top boxes, and even if the boxes can be equipped with telephone facilities there will also be a need for a ‘back-office’ infrastructure to cope with the interactive messages.

Photograph of a remote control showing the "red button"There can be problems when no distinction is made between Freeview DTT and the other platforms that have return channel capabilities. Digital TV users are told to ‘go interactive, press the red button’ and ‘vote by pressing the red button’, but this only works on systems with a return path capability, so is restricted to those viewing on cable or satellite, which can be frustrating for the Freeview user, whose red button cannot provide the service indicated.

Problems can occur even with the ‘one way’ services, with one example being during the BBC’s Wimbledon Tennis when viewers are given the option to view any of 6 different recorded screens, which is fine for cable and satellite viewers, whereas Freeview viewers, due to bandwidth constraints, can only see two screens. As an example, BBC commissioning guidelines for such services take account of the fact that interactive features should work on each of the three major digital platforms, but acknowledge that because the platforms have widely divergent capacities and capabilities the available formats for each platform may differ. The BBC aims to deliver an identical service on all 3 platforms, and offers software applications to interactive programme producers to help to achieve this as best as possible.

The government has said that interactive digital television will be one of the key weapons in tackling social exclusion and improving the convenience of public services, since integrated DTVs or set-top boxes will be in every home, are relatively inexpensive and familiar, perhaps offering a short cut to the e-society for the population at large. Interactive digital television thus has the potential to be a prime means for widespread domestic use of the Internet and government e-services, appealing to people who might find the use of a computer difficult. Some believe that Interactive DTV will help to bridge ‘the digital divide’ between those who have computers and those who don’t.

TV remote controls may be simple to operate, but are certainly not ideal for sending anything other than the simplest of messages, so some form of keyboard may well be required for true interactivity. People with a wide range of disabilities, including those who are blind or partially sighted and those who are hard of hearing, can have problems in getting the best from the many facilities offered by a modern digital television receiver. A much greater number of elderly people, however, people who would in no way consider themselves as disabled, have physical mobility problems and arthritis which can make it difficult to operate TV equipment via remote controls with small, closely spaced buttons bearing legends that are difficult both to see and to understand.

‘Enhanced TV’ is probably a better term to refer to one-way applications such as teletext, EPG access etc., and it could be advantageous to restrict the term ‘interactive TV’ to two-way services reliant on some form of return path.

Usability of Interactive Digital TV

The page displays of interactive services are often based on HTML-like web screens, which assume the use of mouse and keyboard for interactivity. It cannot be assumed that TV audiences will be familiar with computer use, so page designers for interactive TV must realise that a TV is not a PC and therefore cannot be treated as such. Important factors are that standards TV screens usually have much lower screen resolution than computers and TVs have only limited means of control and input. The low resolution display can make it difficult to distinguish colours, shapes, graphical information or moving information, so to compensate for this, the legibility of features on the screen must be made as clear as possible. When blind or partially sighted people want to make use of interactive TV they may use magnifying devices such as monoculars, binoculars, hand held or stand magnifiers, and some people may sit very close to their screens.

Blind people prefer audio assistance to interact with such systems, but this is not generally available. There are only a few (very expensive) current set top boxes that provide speech output and audio prompts. They have been specifically designed to make digital Freeview services of television, radio and teletext accessible to blind and partially sighted people by generating high quality speech messages about key actions and program information from an electronic programme guide, these functions being controlled from either an integral keyboard or from the remote control.

For information on currently available set-top boxes with accessible features see the Devices page.



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