1.5 For multimedia, ensure that timing of alternative descriptions is synchronised with the presentation
Contents
WAI checkpoint 1.4
Full WAI text: "For any time-based multimedia presentation (e.g., a movie or animation), synchronize equivalent alternatives (e.g., captions or auditory descriptions of the visual track) with the presentation."
Movies and animations are examples of time-based presentations, where content constantly changes from moment to moment. Captions or auditory descriptions are examples of equivalent alternatives. They are non-visual descriptions that communicate the content of the visual or auditory part of a presentation. Alternative equivalents should be inserted in appropriate gaps or silences in auditory or textual content or they should be positioned so they do not interfere with the visual content of a presentation.
Rationale
Users who can't see the visual content of a multimedia presentation require an auditory description because they can't get close enough to the display monitor, have poor eyesight or they could be blind.
Users who can't hear the audio track require a text description. They may be working in a quiet environment, like a library, with the sound turned down or they might be in a noisy environment where the sound is obscured by noise. They could have poor hearing or could be deaf.
Movies, videos and animations often include audio content. This could be a voice over or important sound effects. They may also include important text content, like the name and job title of a person in an interview or dialogue subtitles in a translated film. The alternative equivalents - be they captions or auditory descriptions - should not -blot out' or interfere with this important content.
Directions and Techniques
There are no specific techniques recommended for this guideline.
How you could check for this:
View the presentation with captions activated
Open the presentation in a media player which supports captions and enable the caption feature to see if captions are present and whether or not they interfere with important visual content, such as on screen text, subtitles, graphs, etc.
Listen to the audio description of the presentation without looking at the screen
When you do this, listen to see if the auditory description interferes with the audio content of the presentation. Looking away from the screen, or turning it off will mean that you have to interpret the presentation without the aid of the visual information.
Guidelines for Web Accessibility - Priority 1- 1.1 Provide a text equivalent for every non-text element
- 1.2 Ensure that information does not rely on colour perception
- 1.3 Avoid causing the screen to flicker
- 1.4 Provide an auditory description of the visual information in multimedia presentations
- 1.5 For multimedia, ensure that timing of alternative descriptions is synchronised with the presentation
- 1.6 Use the clearest and simplest language appropriate
- 1.7 Identify language changes in text
- 1.8 Ensure that equivalents for dynamic content are updated when the dynamic content changes
- 1.9 For data tables, identify row and column headers
- 1.10 For complex data tables, use mark-up to associate data cells and header cells
- 1.11 Add titles to frames
- 1.12 Ensure that documents can be read without style sheets
- 1.13 Provide text links to emulate server-side image maps
- 1.14 Use client-side image maps rather than server-side image maps where possible
- 1.15 Ensure that scripts and applets that provide the only source of important functionality are directly accessible or compatib
- 1.16 Ensure that pages are usable without support for scripts, applets, or other programmatic objects
- 1.17 If you cannot make a page accessible, provide an equivalent accessible page
