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Background - accessible television



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3. Background - accessible television

3.1 Moving to digital television - challenges and opportunities


Some accessibility issues are the same for both analogue and digital television e.g. accessing printed instructions and user manuals, recognising buttons on the remote control and reading on-screen text. These issues have an impact on both the systems.
However, the increased functionality and complexity of digital television introduces some new barriers. These may be due to differences in hardware, user interface or programme content.
Increased functionality and the massively expanded number of television channels available through digital make it more difficult to locate a particular channel or programme. With old analogue systems offering as few as four or five channels, finding out what was on and changing to the channel of choice was relatively straightforward. However, with hundreds of channels, it becomes necessary to remember many channel numbers or use some sort of navigation system, usually presented as an on-screen electronic programme guide (EPG).
The increased functionality of digital television brings more choices, but the need to memorise controls or sequences of actions presents a usability problem, particularly for blind people. Increased functionality also allows more information to be given to the user – programme information, setup menus, programme guides, parental controls, etc. This information is provided using text and graphics displayed on the screen which can be difficult or impossible to read for people who are blind or partially sighted. These problems can be solved by allowing users to change the size and colour of on-screen text and by providing text to speech output for blind users.
Although the increased capability of digital television introduces new accessibility problems, it also solves some problems.
Notably, it allows for the inclusion of user-selectable audio description with all television programmes, something which is not possible with most analogue systems.

3. 2 Audio description


Audio description is a verbal description of the visual scene in a television programme, spoken by a narrator during the pauses between dialogue. It is provided as an aid to understanding and enjoyment particularly, but not exclusively, for blind and partially sighted people.
It is delivered as an auxiliary sound channel and control signals that can be selected to override the normal programme sound when the audio description track or DVS® is detected. To avoid incompatibility and clipping, audio description signals need to be recorded with the same line up as the main audio channels [-18 db for the stereo or mono in the UK]. These criteria are often referred to as ancillary audio standards in technical specifications.
Audio description delivery requires broadcasters to produce and broadcast the description soundtrack and receiver manufacturers to enable support for description in their products. A way to achieve this is to provide a framework for delivery of access services such as audio description. This framework involves governments adopting and mandating legislative measures to ensure audio description is delivered.
In view of the need for description on television, in 1996 the UK introduced the Broadcasting Act which made it mandatory for digital terrestrial programme services to provide description on at least 10% of their programming. The Communications Act (2003) extended this mandate to include cable and satellite services as well, so broadcasters and service providers were left with no choice but to provide description as an additional track that could be selected.
In contrast to the model above, in 2008 Canada launched the world's first open description channel, The Accessible Channel, a 24 hour national, English-language, described video, closed-captioned, basic HD digital television [HDTV] specialty service.
In October 2010, the 21st Century Communications and Video Accessibility Act was turned into a law in the US. The legislation gives individuals with vision or hearing loss improved access to television programming, smart phones, the internet, menus on DVD players, programme guides on cable television and more.

Many other countries such as Germany, France, Spain and South Korea have also had audio description on their television programs for some time now.


For a list of the current status of audio description in various countries and the framework they have adopted to deliver the description track, please see Appendix 2.

3.2.1 Delivery of audio description on television


Availability of audio description on television is quite varied across the world.
The technology required to deliver and render the basic description track is rather simple, being an additional component of the common audio-processing solutions. Audio-visual equipment that supports multiple audio channels are ideal for delivery of description, and most products dealing with broadcast television content are capable of providing adequate support for audio description.

Audio description has been available on television since the 1990s. However, with the arrival of DTV, the technology used to deliver audio description has undergone constant evolution and it continues to progress with the advancements in technology.




3.2.1.1 Analogue television - secondary audio programming Track


Secondary audio programming (SAP) is a supplementary audio channel for analogue television that can be broadcast or transmitted by any transmission system including cable, satellite and IPTV. It was often used for an alternate language, or for the DVS® offered in the U.S before the digital switchover. The description track was combined with the original sound track on the SAP channel of televised programming. Analogue television systems used in most countries have not had the capability to include user-selectable audio description in this way.

Digital television - broadcast mix and receiver mix


Today, the following mature accessibility services can be broadcast and received with regular DTV equipment:
3.2.1.2 Broadcast mix : An additional audio track consisting of the original audio and the narrator is pre-mixed at the broadcaster side and is transmitted in dual channel mode together with the original audio track in the audio elementary stream.
3.2.1.3 Receiver mix : As an alternative to broadcast mix, the mixing takes place inside the receiver. The audio description sound track is received along with the main audio soundtrack and the digital receiver mixes them together.
Receiver mix offers certain advantages for the user which can be incorporated into the system, including the ability to adjust the sound level of the description track, and routing the description to headphones so that only one person can hear it while others in the room hear the regular audio track.
Both of the above mixing methods provide what is, in effect, 'closed' audio description. This means that the audio description is separated from the main programme audio in a way that the individual viewer can choose whether to hear it or not. This contrasts with 'open' description which is mixed in with the main audio so that all viewers receive it without having a choice.
In the absence of the delivery platforms as mentioned above, 'open' description also exists i.e. The Accessible Channel [TAC] in Canada broadcasts open description on 100 per cent of its programming. The channel broadcasts programmes that have been quite successful in the past but this time around, they are broadcast with AD. About 75-80% of the programmes on the channel have never been aired with audio description before (TAC, 2010).


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