Video Accessibility Key Terms to know

Audio descriptions are added to a video by a voice-over narrator in order to describe important visual details that cannot be understood from the main soundtrack alone. The goal with audio description is to make the visual information in media accessible to people who are blind, but others may benefit from the explicit explanations as well.

CART (Communications Access Real-Time Translation) is usually provided for live events, such as conference presentations, classroom lectures, or webinars. Typically a stenographer types the captions in real time and the text appears on a separate screen near the speaker.

Closed captions are a text alternative for the audio portion of a video program. They are usually shown at the bottom of the screen (in the lower third) as light text on a dark background, but most video players now allow them to be customized. Closed captions are added to the video as a separate track that can be shown or hidden as needed for maximum flexibility. Closed captions include not just the dialogue, but also speaker identification and a textual representation of any sound effects and other audio that is important for understanding the video content (a police siren, an alarm clock going off, etc.).

Open captions are similar to closed captions in function, but they are always in view and cannot be turned off. The person editing the video chooses how the captions are displayed, and they are “burned” into the video file. As a result, the viewer does not have the option of adjusting the text size and other properties.

Subtitles are intended for translating the content of a video from a foreign language.

Subtitles for the deaf and hard of hearing (SDH) combine the information of both captions and subtitles. Like captions, SDH can include non-dialogue audio and speaker identification, but like subtitles they can also be translated into other languages. SDH also support digital connections used in newer DVD and Blu-ray players, such as HDMI, while captions do not.

The above information is from the National Center on Accessible Educational Materials  (https://aem.cast.org/use/teaching-accessible-video) licensed under a Creative Commons Attribution-ShareAlike 4.0 International License.