WCAG 2.0 provides very specific and helpful guidelines for presenting audio and video media. The first consideration is what to do with information that's presented in only one format.

Audio-Only Content

Naturally, audio-only content is not accessible by the hearing impaired. Here's what WCAG 2.0 standard 1.2.1 says about the accessibility of audio-only content:

"Prerecorded Audio-only: An alternative for time-based media is provided that presents equivalent information for prerecorded audio-only content."

Whatever information is provided via audio needs to be provided in an alternative format. What does that allow for? Let's look at the two most common audio only scenarios and how they would be made accessible.

Example 1: A professor records a podcast of himself lecturing on a topic for a few minutes.

Alternative: In this case, there's no information being conveyed other than what is spoken by one person. A simple text transcript, posted as a document or web page, would be sufficient.

Example 2: A recorded radio interview between a talk show host and an interviewee is posted in an online course.

Alternative: In this case, a simple text transcript also works, but with one additional consideration: Because there's more than one speaker, each speaker needs to be identified, similar to the way a play script would appear. Also, especially if it's pertinent to the meaning of the interview, non-textual cues (laughing, stuttering, etc.) ideally should be identified.

Here is an example transcript of an Associated Press interview with Donald Trump.

Video-Only Content

Video-only content could be an animation, a demonstration, or a background video with superimposed text. When video only content is used, the same principles as images and audio-only content apply as well. WCAG 2.0 standard 1.2.1 says:

"Prerecorded Video-only: Either an alternative for time-based media or an audio track is provided that presents equivalent information for prerecorded video-only content."

An example of pre-recorded video with no audio information or user interaction is a silent movie. The purpose of the transcript is to provide an equivalent to what is presented visually. For prerecorded video content, authors have the option to provide an audio track. The purpose of the audio alternative is to be an equivalent to the video. This makes it possible for users with and without vision impairment to review content simultaneously. The approach can also make it easier for those with cognitive, language and learning disabilities to understand the content because it would provide parallel presentation (source: Understanding WCAG 2.0).

Note: A text equivalent is not required for audio that is provided as an equivalent for video with no audio information. For example, it is not required to caption video description that is provided as an alternative to a silent movie.

Example 1: A silent training film demonstrates the proper procedure to use a piece of equipment.

Alternative: In this case, it would be appropriate to have a detailed audio description of the actions taking place on the video screen.

Example 2: A video is used that plays music and images in the background and conveys images by presenting text on the screen.

Alternative: This video could be made accessible by either providing a transcript or an audio narration. If the music and video are simply decorative, no description is necessary.

Key Takeaway: Information should never be presented as audio-only or video-only without an alternative.