Video-only as a media alternative for text


Description

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

Applicability

The rule applies to every non-streaming video element that is visible, where the video doesn't 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 labelled as an video alternative for text on the page.

Expectation 3

The label (from expectation 2) is visible and included in the accessibility tree

Note: The term label does not refer to the label element.

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 video element without audio. The text on the page labels the video as an alternative.

<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>

Failed

Failed Example 1

A video element that describes some of the text on the same page. The video contains more information than the text does.

<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>

Failed Example 2

A video element that describes some of the text on the same page. The text is not visible on the page.

<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>

Failed Example 3

A video element that describes some of the text on the same page. The text on the page does not label the video as an alternative.

<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>

Failed Example 4

A video element that describes some of the text on the same page. The text on the page labels the video as an alternative but the label is not visible on the page.

<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>

Inapplicable

Inapplicable Example 1

A video element with audio.

<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>

Inapplicable Example 2

A video element that describes some of the text on the same page. The text on the page labels the video as an alternative but the video is not visible on the page.

<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>

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 13, 2019fix: update test assets being referred for media rules (f51b46,… (#731)
Jul 19, 2019chore: run prettier (#688)
Jul 17, 2019fix: test if definition for all referenced glossary terms exist (#634)
May 9, 2019Chore: Adapt site to ACT Rules CR format (#547)
May 7, 2019Template update - Video-only as a media alternative for text (#541)
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)
Feb 1, 2019tweak language of media as alternative for text rules (#357)
Jan 22, 2019rule: SC 1.2.3 & 1.2.5 Video alternatives (#204)
Jan 9, 20191.2.1 audio only and video only (#276)
Nov 12, 2018chore: remove selector `data-rule-target` (#347)
Oct 29, 2018chore: change references to included in accessibility tree (#322)
Oct 12, 2018"Included in accessibility tree" instead of "exposed to assistive technologies" (#269)
Oct 9, 2018Fix: testcase generation (#296)
Aug 30, 2018Chore: Update test cases format and descriptions (#230)
Aug 9, 2018chore: rules table & yml front matter (#209)
Aug 8, 2018SC1.2.1-Audio-captions (#159)

Useful Links



Acknowledgements