Proposed Test Rule: video element auditory content has captions

Description

This rule checks that captions are available for audio information in non-streaming video elements.

Applicability

This rule applies to every non-streaming video element that is visible where the video contains audio.

Expectation

For each test target, audio information that is not conveyed visually in the video, is available through captions.

Note: Captions can be either embedded in the video file itself or can be made available trough a separate track.

Assumptions

This rule assumes that the video element is used to play a video (for example, not only used to display an image), and that there is a mechanism to start the video.

Accessibility Support

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

Background

Bibliography

Accessibility Requirements Mapping

G87: Providing closed captions
- Learn more about technique G87
- Not required for 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
G93: Providing open (always visible) captions
- Learn more about technique G93
- Not required for 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
H95: Using the track element to provide captions
- Learn more about technique H95
- Not required for 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

The following aspects are required in using this rule.

DOM Tree
CSS Styling
Audio output (no link available)
Visual output (no link available)

Test Cases

Passed

Passed Example 1

A video element that has captions for all the audio baked into it.

<video src="/test-assets/perspective-video/perspective-video-with-captions.mp4" controls></video>

Passed Example 2

A video element with an associated track element that contain captions for all the audio.

<video src="/test-assets/perspective-video/perspective-video.mp4" controls>
	<track src="/test-assets/perspective-video/perspective-caption.vtt" kind="captions" />
</video>

Failed

Failed Example 1

A video element without any form of captions.

<video src="/test-assets/perspective-video/perspective-video.mp4" controls></video>

Failed Example 2

A video element with an associated track element that contain incorrect captions.

<video src="/test-assets/perspective-video/perspective-video.mp4" controls>
	<track src="/test-assets/perspective-video/perspective-incorrect-caption.vtt" kind="captions" />
</video>

Failed Example 3

A video element with a text on the same page that described the audio in the video.

<p>
	The video below shows a man working on a keyboard. A voiceover is heard saying the following text: Web accessibility
	perspectives. Keyboard compatibility. 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.
</p>
<video src="/test-assets/perspective-video/perspective-video.mp4" controls></video>

Failed Example 4

A video element with an explicitly associated text on the same page that described the audio in the video.

<p id="text">
	The video below shows a man working on a keyboard. A voiceover is heard saying the following text: Web accessibility
	perspectives. Keyboard compatibility. 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.
</p>
<video src="/test-assets/perspective-video/perspective-video.mp4" controls ariadescribedby="text"></video>

Inapplicable

Inapplicable Example 1

A video element without audio.

<video src="/test-assets/perspective-video/perspective-video-silent.mp4" controls></video>

Inapplicable Example 2

A video element that is not visible.

<video src="/test-assets/perspective-video/perspective-video.mp4" controls style="display: none;"></video>

Glossary

Audio output

This test aspect includes all auditory data output from the web page into an audio channel.

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:

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.

Implementations

There are currently no known implementations for this rule. If you would like to contribute an implementation, please read the ACT Implementations page for details.

Changelog

This is the first version of this ACT rule.