The intent of this Success Criterion is to enable people who are deaf or hard of hearing to watch synchronized media presentations. Captions provide the part of the content available via the audio track. Captions not only include dialogue, but identify who is speaking and include non-speech information conveyed through sound, including meaningful sound effects.
It is acknowledged that at the present time there may be difficulty in creating captions for time-sensitive material and this may result in the author being faced with the choice of delaying the information until captions are available, or publishing time-sensitive content that is inaccessible to the deaf, at least for the interval until captions are available. Over time, the tools for captioning as well as building the captioning into the delivery process can shorten or eliminate such delays.
Captions are not needed when the synchronized media is, itself, an alternate presentation of information that is also presented via text on the Web page. For example, if information on a page is accompanied by a synchronized media presentation that presents no more information than is already presented in text, but is easier for people with cognitive, language, or learning disabilities to understand, then it would not need to be captioned since the information is already presented on the page in text or in text alternatives (e.g., for images).
See also 1.2.1: Captions (Live).
A captioned tutorial
A video clip shows how to tie a knot. The captions read,
"(music)
Using rope to tie knots was an important skill
for the likes of sailors, soldiers and woodsmen.."
From Sample Transcript Formatting by Whit Anderson.
An orchestra provides captions for videos of performances. In addition to capturing dialog and lyrics verbatim, captions identify non-vocal music by title, movement, composer, and any information that will help the user comprehend the nature of the audio. For instance captions read,
"[Orchestral Suite No. 3.2 in D major, BWV 1068, Air]
[Johann Sebastian Bach, Composer]
♪ Calm melody with a slow tempo ♪"
Style guides for captions may differ among different languages.
Providing closed captions using any of the technology-specific techniques below