video element visual-only content has transcript


Description

Non-streaming video elements without audio must have all visual information available in a transcript.

Applicability

The 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 in a text transcript that is available either on the page or through a link. The text transcript needs to be visible and included in the accessibility tree.

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

Test Cases

Passed

Passed Example 1

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This video element, which has no audio, has a text transcript available on the same page.

<html lang="en">
<video controls>
  <source src="/test-assets/rabbit-video/silent.mp4" type="video/mp4"></source>
  <source src="/test-assets/rabbit-video/silent.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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This video element, which has no audio, has a transcript which does not convey information included in the video-only content. The transcript is available through a link on the same page.

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

Failed

Failed Example 1

Open in a new tab

This video element, which has no audio, has an incorrect text transcript available on the same page.

<html lang="en">
<video controls>
  <source src="/test-assets/rabbit-video/silent.mp4" type="video/mp4"></source>
  <source src="/test-assets/rabbit-video/silent.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

Open in a new tab

This video element, which has no audio, has a incorrect text transcript available through a link on the same page.

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

Failed Example 3

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This video element, which has no audio, has a text transcript available on the same page, but the transcript is not visible.

<html lang="en">
<video controls>
  <source src="/test-assets/rabbit-video/silent.mp4" type="video/mp4"></source>
  <source src="/test-assets/rabbit-video/silent.webm" type="video/webm"></source>
</video>
<p style="text-indent: -9999px;">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>

Failed Example 4

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This video element, which has no audio, has a text transcript available on the same page, but the transcript is not included in the accessibility tree.

<html lang="en">
<video controls>
  <source src="/test-assets/rabbit-video/silent.mp4" type="video/mp4"></source>
  <source src="/test-assets/rabbit-video/silent.webm" type="video/webm"></source>
</video>
<p aria-hidden="true">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>

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

Glossary

Included in the accessibility tree

Elements included in the accessibility tree of platform specific accessibility APIs. Elements in the accessibility tree are exposed to assistive technologies, allowing users to interact with the elements in a way that meet 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.

Note: Users of assistive technologies might still be able to interact with elements that are not included in the accessibility tree. An example of this is a focusable element with an aria-hidden attribute with a value of true. Such an element could still be interacted using sequential keyboard navigation regardless of the assistive technologies used, even though the element would not be included in the accessibility tree.

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.

No Implementations

Implementation reports are not provided for this rule.

Acknowledgments

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