Proposed Video element visual-only content has audio track alternative
Description
Non-streaming video elements without audio must have an audio alternative.
Applicability
This rule applies to any non-streaming video element that is visible where the video does not contain audio.
Expectation
The visual information of each test target is available through an audio track.
Background
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.
Accessibility Support
There are no accessibility support issues known.
Bibliography
- Understanding Success Criterion 1.2.1: Audio-only and Video-only (Prerecorded)
- G166: Providing audio that describes the important video content and describing it as such
Accessibility Requirements Mapping
G166: Providing audio that describes the important video content and describing it as such
- Learn more about technique G166
- Not required for conformance to any W3C accessibility recommendation.
- Outcome mapping:
- Any
failedoutcomes: technique is not satisfied - All
passedoutcomes: technique needs further testing - An
inapplicableoutcome: technique needs further testing
- Any
Input Aspects
The following aspects are required in using this rule.
- DOM Tree
- CSS Styling
- Audio output
- Visual output (no link available)
- Language
Test Cases
Passed
Passed Example 1
This video element, which has no audio, has a separate audio track that describes the visual information.
<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>
<audio controls>
<source src="/test-assets/rabbit-video/audio-description.mp3" type="audio/mpeg" />
</audio>
</html>
Failed
Failed Example 1
This video element, which has no audio, does not have an audio track describing the visual information.
<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>
Failed Example 2
This video element, which has no audio, has a separate audio track that incorrectly describes the visual information.
<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>
<audio controls>
<source src="/test-assets/rabbit-video/incorrect-audio-description.mp3" type="audio/mpeg" />
</audio>
</html>
Inapplicable
Inapplicable Example 1
This video element has audio.
<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>
</html>
Inapplicable Example 2
This video element is not visible.
<html lang="en">
<video controls style="display: none;">
<source src="/test-assets/rabbit-video/silent.mp4" type="video/mp4" />
<source src="/test-assets/rabbit-video/silent.webm" type="video/webm" />
</video>
</html>
Glossary
Non-streaming media element
A non-streaming media element is an HTML Media Element for which the duration property is not 0.
Outcome
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 five 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
- cantTell: Whether the rule is applicable, or not all expectations were met could not be fully determined by the tester.
- Untested: The tester has not attempted to evaluate the test subject.
Note: A rule has one passed or failed outcome for every test target. When a tester evaluates a test target it can also be reported as cantTell if the rule cannot be tested in its entirety. For example, when applicability was automated, but the expectations have to be evaluated manually.
When there are no test targets the rule has one inapplicable outcome. If the tester is unable to determine whether there are test targets there will be one cantTell outcome. And when no evaluation has occurred the test target has one untested outcome. This means that each test subject always has one or more outcomes.
Outcomes used in ACT Rules can be expressed using the outcome property of the [EARL10-Schema][].
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.
Rule Versions
This is the first version of this ACT rule.
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.
| Implementation | Type | Consistency | Report |
|---|---|---|---|
| Alfa (semi-automated) 0.80.0 | Semi-automated tool | Consistent |  |
| QualWeb 3.0.0 | Automated tool | Partial | |