There are four main methods of making video and audio content accessible for as many people as possible. These methods benefit all users, whether or not they have a disability. For example, captions or a transcript are necessary for a deaf student to understand the content, but also offer an alternative for a student on a bus during her commute to school, where the background noise is too loud to be able to hear the audio.
- Captions: Text synchronized with the media, for people who cannot hear the audio. There are two common types of captions:
- Closed Captions: Captions that can be turned on or off by the user and can often be customized to the user's preference for things like font size, font and background color, and more.
- Open Captions: Captions that are burned in as part of the file and cannot be turned off or customized by the user.
- Captions are required for prerecorded and live multimedia and should also be provided for live audio-only content.
- Transcripts: The full text of the spoken words and important visual cues in the media file.
- Transcripts are required for prerecorded audio-only content, like a podcast. They should also be provided for multimedia content and should describe the important visual aspects of video-only content.
- Audio descriptions: A narrator explaining important visual information occurring in the video for the benefit of people who cannot see what's happening. This is usually placed in natural pauses in the spoken content, but extended audio descriptions require the video itself to be paused in order to make enough room for a detailed description.
- Audio descriptions are required for prerecorded multimedia content and prerecorded video-only content.
- Sign language interpretation: Video of an interpreter, synchronized with the media file (or in the same video frame), for the benefit of people who know sign language.
There are additional aspects to multimedia files that are important to consider when creating and sharing a file with students as part of course content.
- High quality audio and video: People who are hard of hearing or who have visual impairments might find content more difficult to understand if it comes from low quality equipment or has prominent background noises.
- Preventing seizures: Flashing visual effects in videos can cause seizures in some people, especially when three or more flashes occur per second. It is recommended to not use any flashing visual effects.
- Accessible media player: The media player itself has to be keyboard-accessible and needs to communicate the names, roles, and values of the controls and the states of the controls to assistive technology.
- Preventing auto-play audio interference with screen readers: Media players that auto-play can interfere with screen reader users' ability to hear what their screen reader is saying, and could render the entire page's content impossible to use if it lacks the ability to pause or stop it.
Sources and Further Reading
- Accessibility Techniques for Audio and Video (external link) from Deque University
- What Does Accessibility Mean for Multimedia? (PDF)
- Inclusive teaching: audio describing your own presentations (external link)