Joe Clark: Accessibility | Design | Writing

Understanding media-access terminology:
A glossary of terms

The techniques and technologies behind media access are hard to understand, obscure, and poorly documented. It’s hard, for example, to learn about audio description, or dubbing, or subtitling.

So here is a quickie introduction to the various techniques and technologies in use to make media of information accessible to people with disabilities and others. (This list is adapted from an entry, “Opening up accessibility,” at the NUblog, a Weblog on online content. You may also have seen a variation of this discussion in my article “Flash access: Unclear on the concept” over at A List Apart or my series on Macintosh accessibilty at Tidbits.)

Blindness and visual impairment

For audiovisual media like TV, video, and film, and for online multimedia, is used: Narration, read out loud by a human being (or, in the future, by voice synthesis), that succinctly explains visual details not apparent from the audio alone. Audio description takes a movie, for example, and talks you through it. A narrator tells you everything that's happening onscreen that you can't figure out just from the soundtrack.


  1. It is important to get the terminology right. Audio description is often misnamed:
    • “video description” (more than video can be described; the technique started in live theatre)
    • “Descriptive Video” (a service mark of WGBH’s Descriptive Video Service)
    • and various clueless abominations like “audio captioning”
    • The only generic term is “audio description.”
    • The French generic term is descriptions sonores (usually plural).
  2. There are next to no online resources; some dry background research is here. But see also Audio Description International.
  3. I have a set of pages available on DVDs and accessibility.

In traditional Web sites: Coding for meaning and structure (colgroup, strong, address). Also, textual equivalents (alt, longdesc; see NUblog discussion).

Further details on Web accessibility can be found at the Web AccessiBlog and in my book, Building Accessible Websites.

Deafness and hearing impairment

  1. Captioning: Rendering of speech and other audible information in the written language of the audio. (See Gary Robson’s FAQ.) Usually closed: Captions are encoded or invisible and must be decoded or made visible. Some captions are open and can’t be turned off.
  2. Sign language is still used to a certain extent in television broadcasting, particularly in the United Kingdom. (See the “guideline” document, available only in Microsoft Word format over here.)


  1. Subtitling, rendering a translation of dialogue and certain onscreen elements in visible words. Not the same as captioning. Despite their seeming similarity, captioning and subtitling have very little in common.
    1. Captions are intended for deaf and hard-of-hearing audiences. The assumed audience for subtitling is hearing people who do not understand the language of dialogue.
    2. Captions move to denote who is speaking; subtitles are almost always set at bottom centre.
    3. Captions can explicitly state the speaker’s name:
      1. Cigarette Smoking Man:
      2. [MARTIN]
      3. >> Announcer:
    4. Captions notate sound effects and other dramatically significant audio. Subtitles assume you can hear the phone ringing, the footsteps outside the door, or a thunderclap.
    5. Subtitles are usually open. Captions are usually closed (i.e., require a decoder, usually built into television sets, or a seat-mounted display, as in the WGBH Rear Window system).
    6. Captions are usually in the same language as the audio. Subtitles are usually a translation.
    7. Subtitles also translate onscreen type in another language, e.g., a sign tacked to a door, a computer monitor display, a newspaper headline, or opening credits.
    8. Subtitles never mention the source language. A film with dialogue in multiple languages will feature continuous subtitles that never indicate that the source language has changed. (Or only dialogue in one language will be subtitled – Cf. Life Is Beautiful, where only the Italian is subtitled, not the German.)
    9. Captions tend to render the language of dialogue, transliterate the dialogue, or state the language:
      2. OGENKI DESU KA?
    10. Captions ideally render all utterances. Subtitles do not bother to duplicate some verbal forms, e.g., proper names uttered in isolation (“Jacques!”), words repeated (“Help! Help! Help!”), song lyrics, phrases or utterances in the target language, or phrases the worldly hearing audience is expected to know (“Danke schön”).
    11. Captions render tone and manner of voice where necessary:
      1. whispering )
      3. [ Vincent, Narrating ]
    12. A subtitled program can be captioned (subtitles first, captions later). Captioned programs aren’t subtitled after captioning.
  2. Dubbing: Replacing vocal tracks with vocal tracks in another language. Dubbed programs can be and are captioned.

British terminology

As described in the comments on U.K. “guidelines” on “subtitling,” our dear British friends employ the worst possible terminology for captioning and subtitling. Captioning, as far as they are concerned, is subtitling, while subtitling is also subtitling. Clear as mud, huh?

National differences and history be damned. The British terminology is objectively inferior and confusing. Call captioning captioning. Call subtitling subtitling. Then everyone knows what we’re talking about.

Web access in particular

What are some of the technologies used for Web access? The techniques are somewhat obscure. I am writing a book on the topic and I maintain the Web AccessiBlog of links on Web accessibility.

There are few, if any, specialized hardware or software products used by deaf and hard-of-hearing net-surfers, in large part because the Web, as a visual medium, is rarely inaccessible to that group. Blind and visually-impaired netters, however, tend to use one or more of the following:

  1. Screen magnifiers: Software blows up the image on a standard or auxiliary monitor. May also change the onscreen colours or move text from left to right in an inset window.
  2. Screen readers: Software and hardware that reads Web pages out loud in a computer voice. On the net, most modern screen readers sit on top of standard Web browsers. You usually control a screen reader by keyboard, not mouse. Some links to screen-reader homepages are found in the Web AccessiBlog.
  3. Braille displays: Despite the common misconception, very few blind people read Braille, and it’s a somewhat inefficient way to handle text-dense Web pages. Braille displays can produce a single line of Braille or many lines. (These days the most famous user of a Braille display is Bruce Maguire, who launched a successful action against the Sydney Organizing Committee for the Olympic Games’ inaccessible Web site.)

Updated: 2003.02.09, 2008.11.06

Homepage: Joe Clark Homepage: Joe Clark Media access (captioning, Web accessibility, etc.) Graphic and industrial design Journalism, articles, book