To allow multimedia (synchronized audio/video) content to reach the broadest audience possible, captions, a text transcript, and audio description should be provided. This will benefit users who are deaf, blind, deafblind, and those with cognitive disabilities. Including captions and/or a text transcript may also positively impact search engine optimization (SEO).
For deaf viewers, captions provide on-screen text of the dialogue and other important audio information (such as a doorbell ringing, or a lion roaring) necessary to understand the content. By definition, captions must be synchronized – there should be no delay between what is audibly heard and the associated text.
The intention of a transcript is to provide all visual and audible information needed to understand the content of a multimedia presentation in plain text. Transcripts are arguably the most accessible means of conveying the content and information in audio/visual presentations, as text is the most perceivable medium by assistive technology and humans alike. A good text transcript should identify the current speaker, note any auditory elements or sound effects that are important to understanding the content, note any visual elements that are important to understanding the content, and be accurate, comprehensive, unedited, and uncensored.
Audio descriptions are narration added to the soundtrack of a presentation to describe important visual details that cannot be understood from the main soundtrack alone. Important visual information about characters, actions, scene changes, on-screen text, and other content should be conveyed through these added narrations. Audio descriptions are critical for providing a means for blind and low-vision users to comprehend the multimedia presentation.