Video only element 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 visible where the video doesn't contain audio.

Expectation

The visual information of each test target is available through 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.

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

Test Cases

Passed

Passed Example 1

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

<video controls data-rule-target>
  <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>

Passed Example 2

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

<video controls data-rule-target>
  <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</p>

Failed

Failed Example 1

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

<video controls data-rule-target>
  <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>

Failed Example 2

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

<video controls data-rule-target>
  <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</p>

Failed Example 3

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

<video controls data-rule-target>
  <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>

Failed Example 4

A silent video element with a text transcript on the same page that is not included in the accessibility tree.

<video controls data-rule-target>
  <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>

Inapplicable

Inapplicable Example 1

A silent video element that is not visible on the page.

<video controls style="display: none;" data-rule-target>
  <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</p>

Inapplicable Example 2

A video element with audio.

<video controls data-rule-target>
  <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</p>

Glossary

Included in the accessibility tree

key: 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 (work in progress) and the SVG accessibility API mappings (work in progress).

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 with using sequential keyboard navigation regardless of the assistive technologies used, even though the element would not be included in the accessibility tree.

Outcome

key: outcome

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: Implementers 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

key: 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.


Changelog

Aug 21, 2019fix: update links to WCAG21 resources (#776)
Aug 21, 2019Editorial changes (#725)
Jul 17, 2019fix: test if definition for all referenced glossary terms exist (#634)
Jul 2, 2019Composite rules: Fix broken links in expectations (#627)
May 18, 2019chore: Validating rules frontmatter on CI (#551)
May 9, 2019Chore: Adapt site to ACT Rules CR format (#547)
May 7, 2019Template update - video only element has transcript (#540)
Apr 29, 2019chore: rename files and update associations (#489)
Apr 16, 2019chore: add unique id to all rules (#478)
Apr 15, 2019chore: WCAG ACT RULES CG Website Update (#437)
Jan 9, 20191.2.1 audio only and video only (#276)

Useful Links



Acknowledgements