World Blind Union Office 1929 Bayview Avenue Toronto, on m4G 3E

Different requirements for different visual needs

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1.1 Different requirements for different visual needs

The techniques adopted to promote accessibility will need to cater to the needs of blind and partially sighted people. Blind people or people with very limited remaining vision may benefit from a text-to-speech facility, whereas those with a degree of usable remaining vision may be able to take advantage of adaptable interface that allows them to enhance the colour contrast between text and background or even zoom into the characters on the screen.
The need for these different access features for blind and partially sighted people have been illustrated through a series of user profiles in Appendix 1.

1.2 Sections in the document

This document comprises of two main parts.
Part 1 gives the reader some background information on the need for user requirements for access to television and the work that has been done so far in the field.

  • Section 1 introduces and lays out the scope of the user requirements identified in this document

  • Section 2 briefly defines the terms that have been used throughout the report.

  • Section 3 is split into 6 segments.

  • First segment discusses the difference between analogue television and the relatively recently introduced digital television.

  • Second segment summarises the delivery mode for audio description on the two platforms - analogue and digital.

  • Third segment examines the characteristics of audible feedback and related benefits

  • Fourth segment looks at on-screen displays and relevant desirables

  • Fifth segment goes on to discuss accessible remote controls and the importance of introducing audible feedback or text to speech on digital television.

  • Sixth segment contains consumer equipment standards and how they affect the interoperability and product design.

Part 2 actually lists the WBU user requirements for access to television. This again split into 2 sections.

  • Section 1 looks at the current barriers to access television receiving equipment for blind and partially sighted people.

  • Section 2 lists user requirements to counter the barriers specified in the previous section. This section also investigates the user requirements for additional services such as audio description and subtitles.

2. Terms and definitions

Some of the definitions given below are tailored to the context of accessibility to television.

  • Accessibility: Accessibility can be defined as a degree to which a person with disability is able to perceive, understand, navigate and interact with a service or a product. In the context of this report, it specifically focuses on the ability of blind and partially sighted people to use different television platforms currently available.

  • Analogue television: Preceding digital television [DTV], all televisions encoded pictures as an analogue signal by varying signal voltage and radio frequencies. All systems preceding DTV can be considered analogue.

  • Audio description: Audio description is like a narrator telling a story. An additional commentary describes body language, expressions and movements, making the story clear through sound. It describes what might otherwise be missed by a blind or partially sighted person. Audio description is also known as video description in some countries. See also Descriptive Video Service (DVS).

  • Barrier: Any impediment, hindrance or obstacle that limits or prevents the decorous, convenient and safe access, use, enjoyment or interaction with the environment.

(AENOR, Report UNE 41500).

  • Captioning: Another term for subtitling used in many countries such as USA, Canada, and Australia. Even though the terms caption and subtitle have similar definitions, captions commonly refer to on-screen text specifically designed for hearing impaired viewers, while subtitles are straight transcriptions or translations of the dialogue. Captions are usually positioned below the person who is speaking and they include descriptions of sounds (such as gunshots or closing doors) and music. Closed captions are not visible until the viewer activates them. Open captions are always visible, such as subtitles on foreign language content. See also subtitling.

[Website:; Accessed on September 30 2010]

  • Descriptive Video Service®: Descriptive Video Service® (DVS) is the registered trademark WGBH created for its video description service; video description is another name for audio description and is widely used in North America. See also audio description.

  • Digital Television [DTV]: DTV is the transmission of audio and video by digital signals, in contrast to the analogue signals used by analogue television. It supports the transmission of many more channels and also access services such as audio description and subtitles. DTV is gradually replacing analogue television and several countries such as Germany, Spain, USA and the UK have switched, or are in the process of, carrying out nationwide digital switchovers.

  • Digital Terrestrial Television [DTT]: DTT uses the terrestrial aerial/antenna signal, instead of cable or satellite, to broadcast.

  • Digital Video Recorder [DVR]: Digital video recorder refers to set top boxes that have the capacity to record video in a digital format to a disk drive or other mass storage device.

  • Internet television: Internet television is a streaming service distributed via the internet. It allows the users to choose programmes that they want to watch from an archive of programmes or from a channel directory. Some internet television services that have gained popularity in the past few years are:

  • RTÉ Player in the Republic Of Ireland,

  • Hulu and Revision3 in the United States,

  • Nederland 24 in the Netherlands,

  • ABC iView and Australia Live TV in Australia,

  • SeeSaw, BBC iPlayer, 4oD, ITV Player and Demand Five in the UK

  • Internet Protocol Television [IPTV]: IPTV services can be grouped into 3 main categories:

  • Live television, with or without interactivity linked to the television programme in progress;

  • Time-shifted programming and catch-up television;

  • Video on demand (VoD): browse a catalogue of videos

  • Subtitling: Communication support service that translates the oral dialogue and sound effects in any audiovisual production to text and graphics displayed on the screen. See also captioning.

[Nationwide CERMI, 2006, Accessibility to Digital Television for People with Disabilities]

  • Subtitles for deaf and hard of hearing [SDH]: This term is often used to differentiate subtitles used to translate foreign language content from subtitles specially targeted at deaf and hard of hearing people.

[Nationwide CERMI, 2006, Accessibility to Digital Television for People with Disabilities]

  • Synthetic speech: Synthetic speech is artificial human speech, which is produced by a computer. There are a number of different software applications through which this process can be achieved.

  • Text to Speech [TTS]: Some speech synthesisers use pre-recorded human speech and fit words together to form sentences (this is most often used in applications with a limited vocabulary, such as a talking clock). Other synthesisers are more complex in that they fit together tiny portions of speech (sounds) to form words and sentences. Using this method, a synthesiser is able to produce an unlimited vocabulary, and can therefore read aloud any text input. This is known as text-to-speech synthesis.

  • Universal design: Design of products and environments to be usable by all people, to the greatest extent possible, without the need for adaptation or specialized design.

[The Center for Universal Design: Universal Design, North Carolina State University, 1995, cited in White Paper on Accessibility]

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