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Proposed Audio and visuals of video element have transcript

Description

This rule checks that non-streaming video elements have all audio and visual information available in a transcript.

Applicability

This rule applies to every non-streaming video element that is visible.

Expectation

The visual information of each test target is available through a text transcript that is visible, included in the accessibility tree, and is either on the page or linked.

Note: A “text transcript” in the context of this rule is defined in WCAG 2 as an alternative for time based media.

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 major accessibility support issues known for this rule.

Background

Bibliography

Accessibility Requirements Mapping

Input Aspects

The following aspects are required in using this rule.

Test Cases

Passed

Passed Example 1

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A video element with a text transcript on the same page.

<html lang="en">`
<video controls>
  <source src="/test-assets/rabbit-video/video.mp4" type="video/mp4"></source>
  <source src="/test-assets/rabbit-video/video.webm" type="video/webm"></source>
</video>
<p>The above video shows a giant fat rabbit climbing out of a hole in the ground.
He stretches, yaws, and then starts walking.
Then he stops to scratch his bottom.</p>
</html>

Passed Example 2

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A video element with a link to a text transcript on a different page.

<html lang="en">`
<video controls>
  <source src="/test-assets/rabbit-video/video.mp4" type="video/mp4"></source>
  <source src="/test-assets/rabbit-video/video.webm" type="video/webm"></source>
</video>
<a href="/test-assets/rabbit-video/transcript.html">Transcript</a>
</html>

Failed

Failed Example 1

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A video element with an incorrect text transcript on the same page.

<html lang="en">`
<video controls>
  <source src="/test-assets/rabbit-video/video.mp4" type="video/mp4"></source>
  <source src="/test-assets/rabbit-video/video.webm" type="video/webm"></source>
</video>
<p>The above video shows a giant fat dog climbing out of a hole in the ground.
He stretches, yaws, and then starts walking.
Then he stops to scratch his bottom.</p>
</html>

Failed Example 2

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A video element with a link to an incorrect text transcript on a different page.

<html lang="en">`
<video controls>
  <source src="/test-assets/rabbit-video/video.mp4" type="video/mp4"></source>
  <source src="/test-assets/rabbit-video/video.webm" type="video/webm"></source>
</video>
<a href="/test-assets/rabbit-video/incorrect-transcript.html">Transcript</a>
</html>

Inapplicable

Inapplicable Example 1

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A 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>
  <source src="/test-assets/rabbit-video/video.webm" type="video/webm"></source>
</video>
<a href="/test-assets/rabbit-video/transcript.html">Transcript</a>
</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.

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
QualWeb 3.0.0 Automated tool Partial QualWeb 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/.