Captioning is the process of converting the audio content of a television broadcast, webcast, film, video, CD-ROM, DVD, live event, or other productions into text and displaying the text on a screen, monitor, or other visual display system. Captions not only display words as the textual equivalent of spoken dialogue or narration, but they also include speaker identification, sound effects, and music description. It is important that the captions are (1) synchronized and appear at approximately the same time as the audio is delivered; (2) equivalent and equal in content to that of the audio, including speaker identification and sound effects; and (3) accessible and readily available to those who need or want them. Captions must have sufficient size and contrast to ensure readability, and be timely, accurate, complete, and efficient. When displayed, captions must be in the same line of sight as any corresponding visual information, such as a video, speaker, field of play, activity, or exhibition.
Captioning makes audio and audiovisual material accessible and provides a critical link to communication, information, education, news, and entertainment for more than 36 million Americans who are deaf or hard of hearing. For individuals with limited English proficiency and for English-language learners, English-language captions improve comprehension and fluency. Captions can also help to improve the literacy skills of children and adults alike.
When captions are visible only when selected and activated, such as when they are visible on a television screen, they are called “closed captions.” When captions cannot be selected or activated, such as when they are permanently embedded in the audiovisual material, they are called “open captions.” Captions may also be presented selectively to individuals with specialized caption display equipment.
Captions are commonly produced in advance for pre-recorded material. When captions are provided for live presentations, they are called “real-time” captions. Communication Access Realtime Translation (CART) is a form of captioning that can be provided on-site or remotely, usually for live presentations such as meetings, classes, or conferences.