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Proposed Video element auditory content has captions

Description

This rule checks that captions are available for audio information in non-streaming video elements.

Applicability

This rule applies to every non-streaming video element that is visible where the video contains audio that is not only silence.

Expectation

For each test target, audio information that is not conveyed visually in the video, is available through captions.

Note: Captions can be either embedded in the video file itself or can be made available trough a separate track.

Assumptions

This rule assumes that the video element is used to play a video (for example, not only used to display an image), and that there is a mechanism to start the video.

Accessibility Support

There are no accessibility support issues known.

Background

Bibliography

Accessibility Requirements Mapping

Secondary Requirements

This rule is related to the following accessibility requirements, but was not designed to test this requirements directly. These secondary requirements can either be stricter than the rule requires, or may be satisfied in ways not tested by the rule:

Input Aspects

The following aspects are required in using this rule.

Test Cases

Passed

Passed Example 1

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A video element that has open captions for all of the audio content.

<video src="/test-assets/perspective-video/perspective-video-with-captions.mp4" controls></video>

Passed Example 2

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A video element with an associated track element that contains captions for all of the audio content.

<video src="/test-assets/perspective-video/perspective-video.mp4" controls>
	<track src="/test-assets/perspective-video/perspective-caption.vtt" kind="captions" />
</video>

Failed

Failed Example 1

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A video element without any form of captions.

<video src="/test-assets/perspective-video/perspective-video.mp4" controls></video>

Failed Example 2

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A video element with an associated track element that contains incorrect captions. Specifically, the captions flip the role of the mouse and computer by saying, “Not being able to use your mouse because your computer doesn’t work is frustrating.”

<video src="/test-assets/perspective-video/perspective-video.mp4" controls>
	<track src="/test-assets/perspective-video/perspective-incorrect-caption.vtt" kind="captions" />
</video>

Failed Example 3

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A video element with text on the same page that describes the audio in the video.

<p>
	The video below shows a man working on a keyboard. A voiceover is heard saying the following text: Web accessibility
	perspectives. Keyboard compatibility. 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.
</p>
<video src="/test-assets/perspective-video/perspective-video.mp4" controls></video>

Failed Example 4

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A video element with an explicitly associated text on the same page that describes the audio in the video.

<p id="text">
	The video below shows a man working on a keyboard. A voiceover is heard saying the following text: Web accessibility
	perspectives. Keyboard compatibility. 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.
</p>
<video src="/test-assets/perspective-video/perspective-video.mp4" controls ariadescribedby="text"></video>

Inapplicable

Inapplicable Example 1

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A video element without audio.

<video src="/test-assets/perspective-video/perspective-video-silent.mp4" controls></video>

Inapplicable Example 2

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A video element that is not visible.

<video src="/test-assets/perspective-video/perspective-video.mp4" controls style="display: none;"></video>

Glossary

Audio output

This test aspect includes all auditory data output from the web page into an audio channel.

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:

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.

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 Alfa (semi-automated) Report
Trusted Tester 5.1 Test methodology Partial Trusted Tester Report
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This is an unpublished draft preview that might include content that is not yet approved. The published website is at w3.org/WAI/.