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Proposed Video element visual-only content is media alternative for text

Description

This rule checks non-streaming silent video is a media alternative for text on the page.

Applicability

This rule applies to any non-streaming video element that is visible where the video does not contain audio.

Expectation 1

All the information contained in each target element is available as text (directly or via text alternatives) that is visible and included in the accessibility tree.

Expectation 2

Each target element is labeled as a video alternative for text on the page by content that is visible and included in the accessibility tree.

Assumptions

Accessibility Support

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

Background

The term label used in expectations 2 and 3 does not refer to the label element.

Bibliography

Accessibility Requirements Mapping

This rule is not required for conformance.

Input Aspects

The following aspects are required in using this rule.

Test Cases

Passed

Passed Example 1

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This video element, which has no audio, is a media alternative for the text in the page and it is labeled as such.

<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-with-captions-silent.mp4" controls></video>
</html>

Failed

Failed Example 1

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This video element, which has no audio, has more information than the text on the page.

<html lang="en">
	<p>
		Not being able to use your computer because your mouse doesn't work, is frustrating. 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-with-captions-silent.mp4" controls></video>
</html>

Failed Example 2

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This video element, which has no audio, is a media alternative for the text in the page and labeled as such, but the text is not visible.

<html lang="en">
	<p style="display: none;">
		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-with-captions-silent.mp4" controls></video>
</html>

Failed Example 3

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This video element, which has no audio, is a media alternative for the text in the page but not labeled as such.

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

Failed Example 4

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This video element, which has no audio, is a media alternative for the text in the page and labeled as such, but the label is not visible.

<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.
	</p>
	<p style="display: none;">
		See the video below to watch the same information again in video form.
	</p>
	<video src="/test-assets/perspective-video/perspective-video-with-captions-silent.mp4" controls></video>
</html>

Inapplicable

Inapplicable Example 1

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This video element has audio.

<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>

Inapplicable Example 2

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This video element is not visible.

<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-with-captions-silent.mp4"
		controls
		style="display: none;"
	></video>
</html>

Glossary

Focusable

An element is focusable if one or both of the following are true:

Exception: Elements that lose focus during a period of up to 1 second after gaining focus, without the user interacting with the page the element is on, are not considered focusable.

Notes:

Included in the accessibility tree

Elements included in the accessibility tree of platform specific accessibility APIs are exposed to assistive technologies. This allows users of assistive technology to access the elements in a way that meets the requirements of the individual user.

The general rules for when elements are included in the accessibility tree are defined in the core accessibility API mappings. For native markup languages, such as HTML and SVG, additional rules for when elements are included in the accessibility tree can be found in the HTML accessibility API mappings (working draft) and the SVG accessibility API mappings (working draft).

For more details, see examples of included in the accessibility tree.

Programmatically hidden elements are removed from the accessibility tree. However, some browsers will leave focusable elements with an aria-hidden attribute set to true in the accessibility tree. Because they are hidden, these elements are considered not included in the accessibility tree. This may cause confusion for users of assistive technologies because they may still be able to interact with these focusable elements using sequential keyboard navigation, even though the element should not be included in the accessibility tree.

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.

Programmatically Hidden

An HTML element is programmatically hidden if either it has a computed CSS property visibility whose value is not visible; or at least one of the following is true for any of its inclusive ancestors in the flat tree:

Note: Contrary to the other conditions, the visibility CSS property may be reverted by descendants.

Note: The HTML standard suggests setting the CSS display property to none for elements with the hidden attribute. While not required by HTML, all modern browsers follow this suggestion. Because of this the hidden attribute is not used in this definition. In browsers that use this suggestion, overriding the CSS display property can reveal elements with the hidden attribute.

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.

Implementations

There are currently no known implementations for this rule. If you would like to contribute an implementation, please read the ACT Implementations page for details.

Changelog

This is the first version of this ACT rule.

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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/.