1. Perceivable
1.2 Time-Based Media (Level A)
Contents
Guideline 1.2 Time-Based Media
Provide alternatives for time-based media.
Definition
Time-Based Media: Time-based media includes various forms of media like video, audio, slides, computer simulations, or any other media that has duration as a property and is presented over time.
Why do I need to include alternatives for “time-based media” (multimedia)?
If a website includes a multimedia presentation like a movie or video, some people will be unable to perceive (or will have difficulty perceiving) the visuals and/or the audio. By providing alternatives, web content authors improve accessibility for a wide range of individuals with and without disabilities:
- Individuals who have trouble understanding the visual track include people with visual impairments, certain cognitive disabilities, language disabilities, and learning disabilities. Text alternatives make the multimedia presentation accessible to these people.
- Individuals who have trouble understanding the audio track include people who are hard of hearing or deaf or who have certain cognitive, language, or learning disabilities. Text alternatives and captioning are the two most common ways to enhance accessibility for people who have trouble processing the audio portion of a multimedia presentation.
- People who are deaf and blind may have trouble (or be unable to) understand the visual track, the audio track, or both. A special type of text alternative, the alternative for time-based media, can make multimedia accessible to people who are deaf and blind.
- Second-language learners benefit from text alternatives, especially those who understand a second language better when they read it rather than listen to it.
- Some people are visual learners — they are “wired” to understand best by looking rather than by hearing or doing. Others are auditory learners — they learn best by listening rather than seeing or doing. Text alternatives help them all get the most from a multimedia presentation.
- Text alternatives and captions are convenient. For example, a captioned video can be understood in a noisy environment (like a bar) or in a quiet environment (like a bedroom where one person is sleeping while the other is watching a movie).
- Text alternatives make multimedia searchable. When search engines “crawl” websites to index their content, they cannot “read” movies and videos. Search engines only understand text (though image recognition technology is currently emerging).
Level A Success Criteria for Time-Based Media
Success Criterion 1.2.1 Audio-Only and Video-Only (Prerecorded)
Level A
For prerecorded audio-only and prerecorded video-only media, the following are true, except when the audio or video is a media alternative for text and is clearly labelled as such:
- Prerecorded Audio-only: An alternative for time-based media is provided that presents equivalent information for prerecorded audio-only content.
- Prerecorded Video-only: Either