Video element visual-only content has audio track alternative

Rule Type:atomic
Rule Id: d7ba54
Last modified: Mar 21, 2022
Accessibility Requirements Mapping:
- G166: Providing audio that describes the important video content and describing it as such
  - Learn More about technique G166
  - Not required to conformance to any W3C accessibility recommendation.
  - Outcome mapping:
    Any failed outcomes: technique is not satisfied.
    All passed outcomes: technique needs further testing.
    An inapplicable outcome: technique needs further testing.
Used in rules:
- Video element visual-only content has accessible alternative
Input Aspects:

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.

Assumptions

A mechanism is available to start the video and that the video element is not simply used to display the poster.
The language of each test target can be correctly determined (either programmatically or by analyzing the content), and sufficiently understood.

Accessibility Support

There are no major accessibility support issues known for this rule.

Background

Bibliography

Test Cases

Passed

Passed Example 1

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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

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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

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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

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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

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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

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.

Content is defined in WCAG.

For more details, see examples of visible.

Useful Links

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

Acknowledgments

Authors

Brian Bors

Funding

WAI-Tools

Assets

Table of Contents

Glossary
Useful Links
Implementations
Acknowledgments