Glossary · Accessibility term
Audio description
Audio description is narration added to a video's soundtrack that describes the visual detail the soundtrack alone does not carry. Actions, characters, scene changes, text on screen. In its standard form it goes into the pauses that already exist in the dialogue, which is why a video with wall-to-wall talking is harder to describe than a quiet one. It turns up at all three WCAG levels rather than only one, and every one of the three is about prerecorded video with a soundtrack. At Level A you can choose between a full text alternative and description. At Level AA the choice disappears and the description itself is required. At Level AAA you owe an extended version, where the video pauses to make room when the natural gaps are too short.
In practice
It is needed when the picture carries information the sound does not, and the standard says as much in reverse. Where the visual information is already in the audio, no description is necessary. A talking head usually needs none. A product demo where somebody says you just click here needs it badly, because here is nothing by ear. Slides are the case teams miss, since text burned into a slide is visual information the presenter rarely reads out loud.
The cheapest version is a scripting decision and it costs nothing at all. Write the description into what the presenter says. Instead of you just click here, have them say click the blue Save button at the top right. W3C names this integrated description as a first-class route, and for the kind of video most businesses make it removes the second audio track, the studio time and the budget line in one go. It is a route for a video you have not made yet, though. Add description to something already shot and you are back to writing it, recording it and fitting it into the gaps, or shipping it as a separate track.
Two production questions this settles. An audio description track does not itself need captioning, because it is describing something already presented visually. And there is a named failure for having usable pauses in the dialogue and not putting the description into them, which is the difference between we could not and we did not.
Why it matters
Captions and description serve different people, and a team that stops at captions has done half the job. Captions carry the sound to somebody who cannot hear it. Description carries the picture to somebody who cannot see it. Skip the second and your video is a soundtrack with holes in it, and the holes are usually where the instructions were. The gap widens on exactly the videos that matter most commercially, because a demo, a walkthrough or a how-to is mostly somebody pointing at things.
The test, and what it misses
Play the video and do not look at it. If you lose the thread, you need description. That test has a blind spot of its own, though, and it is the thing the standard names first. Text burned into the picture gets read by a sighted viewer without them noticing they read it, so it never shows up as something missing from the audio.
Where this shows up on the site
Related terms
- CaptionsCaptions are a synchronized text version of everything you would hear in a video, covering speech and the non-speech sound that matters as well.
- TranscriptA transcript is the text version of audio or video, and two different things go by that one word.
- Low visionLow vision is sight loss that ordinary glasses cannot correct, and it covers far more ground than a single blurred-vision picture suggests.
- Screen readerA screen reader is software that reads the screen out loud, or sends it to a braille display, for people who cannot see it.
Knowing the word is the easy part.
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