Non-streaming media element
A non-streaming media element is an HTML Media Element for which the duration property is not 0.
Video element visual content has strict accessible alternative
Description
This rule checks that video elements with audio have audio description.
Applicability
This rule applies to every non-streaming video element that is visible, where the video contains audio.
Expectation
For each test target, the outcome of at least one of the following rules is passed:
VideoElement Visual Content Has Audio DescriptionVideoElement Content Is Media Alternative For Text
Assumptions
- This rule assumes that a mechanism is available to start the video and that the video element is not simply used to display the poster.
- This rule assumes that the language of each test target can be correctly determined (either programmatically or by analyzing the content), and sufficiently understood.
Accessibility Support
The HTML video element can also have a track element that provides an audio description. This should provide assistive technologies with a timed text description of visual information in a video. However, there is no native support in any major browser for this technique. Technique H96: Using the track element to provide audio descriptions can not be relied upon to conform to 1.2.5: Audio Description (Prerecorded).
Background
Bibliography
- Understanding Success Criterion 1.2.5: Audio Description (Prerecorded)
- G78: Providing a second, user-selectable, audio track that includes audio descriptions
- G173: Providing a version of a movie with audio descriptions
- G8: Providing a movie with extended audio descriptions
Test Cases
Passed
Passed Example 1
Open in a new tabA video element with a voiceover that describes the visual information.
<html lang="en">
<video controls>
<source src="/test-assets/rabbit-video/video-with-voiceover.mp4" type="video/mp4" />
<source src="/test-assets/rabbit-video/video-with-voiceover.webm" type="video/webm" />
</video>
</html>Passed Example 2
Open in a new tabA video element that describes some of the text on the same page. The text on the page labels the video as an alternative.
<html lang="en">
<p>
Not being able to use your computer because your mouse doesn't work, is frustrating. Many people use only the
keyboard to navigate websites. Either through preference or circumstance. This is solved by keyboard compatibility.
Keyboard compatibility is described in WCAG. See the video below to watch the same information again in video form.
</p>
<video src="/test-assets/perspective-video/perspective-video.mp4" controls></video>
</html>Failed
Failed Example 1
Open in a new tabA video element with an incorrect audio description.
<html lang="en">
<video controls>
<source src="/test-assets/rabbit-video/video-with-incorrect-voiceover.mp4" type="video/mp4" />
<source src="/test-assets/rabbit-video/video-with-incorrect-voiceover.webm" type="video/webm" />
</video>
</html>Failed Example 2
Open in a new tabA video element with a link to a text transcript.
<html lang="en">
<video controls>
<source src="/test-assets/rabbit-video/video.mp4" type="video/mp4" />
<source src="/test-assets/rabbit-video/video.webm" type="video/webm" />
</video>
<a href="/test-assets/rabbit-video/transcript.html">Transcript</a>
</html>Failed Example 3
Open in a new tabA video element with a description track element. The description track is not supported.
<html lang="en">
<video controls>
<source src="/test-assets/rabbit-video/video.mp4" type="video/mp4" />
<source src="/test-assets/rabbit-video/video.webm" type="video/webm" />
<track kind="descriptions" src="/test-assets/rabbit-video/descriptions.vtt" />
</video>
</html>Inapplicable
Inapplicable Example 1
Open in a new tabA video element without audio.
<html lang="en">
<video controls>
<source src="/test-assets/rabbit-video/silent.mp4" type="video/mp4" />
<source src="/test-assets/rabbit-video/silent.webm" type="video/webm" />
</video>
</html>Inapplicable Example 2
Open in a new tabA video element that is not visible.
<html lang="en">
<video controls style="display: none;">
<source src="/test-assets/rabbit-video/video.mp4" type="video/mp4" />
<source src="/test-assets/rabbit-video/video.webm" type="video/webm" />
</video>
</html>Glossary
Outcome
An outcome is a conclusion that comes from evaluating an ACT Rule on a test subject or one of its constituent test target. An outcome can be one of the three following types:
- Inapplicable: No part of the test subject matches the applicability
- Passed: A test target meets all expectations
- Failed: A test target does not meet all expectations
Note: A rule has one passed or failed outcome for every test target. When there are no test targets the rule has one inapplicable outcome. This means that each test subject will have one or more outcomes.
Note: Implementations using the EARL10-Schema can express the outcome with the outcome property. In addition to passed, failed and inapplicable, EARL 1.0 also defined an incomplete outcome. While this cannot be the outcome of an ACT Rule when applied in its entirety, it often happens that rules are only partially evaluated. For example, when applicability was automated, but the expectations have to be evaluated manually. Such "interim" results can be expressed with the incomplete outcome.
Visible
Content perceivable through sight.
Content is considered visible if making it fully transparent would result in a difference in the pixels rendered for any part of the document that is currently within the viewport or can be brought into the viewport via scrolling.
For more details, see examples of visible.
Useful Links
- Github issues related to this rule
- Changelog
- Propose a change to the rule
- Test case file for use in the WCAG-EM Report Tool
Implementations
This section is not part of the official rule. It is populated dynamically and not accounted for in the change history or the last modified date. This section will not be included in the rule when it is published on the W3C website.
| Tool | Consistency | Complete | Report |
|---|---|---|---|
| QualWeb | consistent | Yes | View Report |