video element visual-only content has transcript

Rule Type:
atomic
Rule ID:
ee13b5
Last Modified:
June 3, 2021
Accessibility Requirements Mapping:
G159: Providing an alternative for time-based media for video-only content
  • 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
Input Aspects:
DOM Tree
CSS Styling
Audio output
Visual output
Language

Description

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

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 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

Accessibility Support

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

Background

Test Cases

Passed

Passed Example 1

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

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

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

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

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

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

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

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

Focusable

Elements that can become the target of keyboard input as described in the HTML specification of focusable and can be focused.

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.

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.

Acknowledgements

This rule was written in the ACT Rules community group, with the support of the EU-funded WAI-Tools Project.

Authors

Changelog

This is the first version of this ACT rule.

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