Proposed Video element visual content has audio description
Description
This rule checks that non-streaming video
elements have all visual information also contained in the audio.
Applicability
This rule applies to every non-streaming video
element that is visible where the video contains audio.
Expectation
The visual information of each test target is available through its audio, or through an audio description track.
Background
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 only a few implementations of video players (without third party technologies) that support audio description tracks at the time of writing.
Bibliography
- Understanding Success Criterion 1.2.3: Audio Description or Media Alternative (Prerecorded)
- G78: Providing a second, user-selectable, audio track that includes audio descriptions
- G173: Providing a version of a movie with audio descriptions
- G8: Providing a movie with extended audio descriptions
Accessibility Requirements Mapping
G8: Providing a movie with extended audio descriptions
- Learn more about technique G8
- 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
- Any
G78: Providing a second, user-selectable, audio track that includes audio descriptions
- Learn more about technique G78
- 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
- Any
G173: Providing a version of a movie with audio descriptions
- Learn more about technique G173
- 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
- Any
Input Aspects
The following aspects are required in using this rule.
- DOM Tree
- CSS Styling
- Audio output
- Visual output (no link available)
- Language
Test Cases
Passed
Passed Example 1
A video element with a voiceover that describes the visual information.
<html lang="en">
<video controls>
<source src="/test-assets/rabbit-video/video-with-voiceover.mp4" type="video/mp4" />
<source src="/test-assets/rabbit-video/video-with-voiceover.webm" type="video/webm" />
</video>
</html>
Passed Example 2
A video element with an audio description.
<html lang="en">
<link rel="stylesheet" href="https://ozplayer.global.ssl.fastly.net/3.3/ozplayer-core/ozplayer.min.css" />
<link rel="stylesheet" href="https://ozplayer.global.ssl.fastly.net/3.3/ozplayer-skin/highlights-blue.css" />
<link rel="stylesheet" href="https://ozplayer.global.ssl.fastly.net/3.3/transcript.css" />
<figure id="ozplayer-1-container" class="ozplayer-container">
<div data-controls="stack" class="ozplayer" id="ozplayer-1">
<video controls="controls" preload="none">
<source src="/test-assets/rabbit-video/video.mp4" type="video/mp4" />
</video>
<audio data-default="default" preload="none">
<source src="/test-assets/rabbit-video/audio-description.mp3" type="audio/mp3" />
</audio>
</div>
</figure>
<script src="https://ozplayer.global.ssl.fastly.net/3.3/ozplayer-core/mediaelement.min.js"></script>
<script src="https://ozplayer.global.ssl.fastly.net/3.3/ozplayer-core/ozplayer.free.js"></script>
<script src="https://ozplayer.global.ssl.fastly.net/3.3/ozplayer-lang/en.js"></script>
<script src="https://ozplayer.global.ssl.fastly.net/3.3/config.js"></script>
</html>
Failed
Failed Example 1
A video element without an audio description.
<html lang="en">
<video controls>
<source src="/test-assets/rabbit-video/video.mp4" type="video/mp4" />
<source src="/test-assets/rabbit-video/video.webm" type="video/webm" />
</video>
</html>
Failed Example 2
A video element with an incorrect audio description.
<html lang="en">
<video controls>
<source src="/test-assets/rabbit-video/video-with-incorrect-voiceover.mp4" type="video/mp4" />
<source src="/test-assets/rabbit-video/video-with-incorrect-voiceover.webm" type="video/webm" />
</video>
</html>
Failed Example 3
A video element with an incorrect audio description.
<html lang="en">
<link rel="stylesheet" href="https://ozplayer.global.ssl.fastly.net/3.3/ozplayer-core/ozplayer.min.css" />
<link rel="stylesheet" href="https://ozplayer.global.ssl.fastly.net/3.3/ozplayer-skin/highlights-blue.css" />
<link rel="stylesheet" href="https://ozplayer.global.ssl.fastly.net/3.3/transcript.css" />
<figure id="ozplayer-1-container" class="ozplayer-container">
<div data-controls="stack" class="ozplayer" id="ozplayer-1">
<video controls="controls" preload="none">
<source src="/test-assets/rabbit-video/video.mp4" type="video/mp4" />
</video>
<audio data-default="default" preload="none">
<source src="/test-assets/rabbit-video/incorrect-audio-description.mp3" type="audio/mp3" />
</audio>
</div>
</figure>
<script src="https://ozplayer.global.ssl.fastly.net/3.3/ozplayer-core/mediaelement.min.js"></script>
<script src="https://ozplayer.global.ssl.fastly.net/3.3/ozplayer-core/ozplayer.free.js"></script>
<script src="https://ozplayer.global.ssl.fastly.net/3.3/ozplayer-lang/en.js"></script>
<script src="https://ozplayer.global.ssl.fastly.net/3.3/config.js"></script>
</html>
Inapplicable
Inapplicable Example 1
A video element without audio.
<html lang="en">
<video controls>
<source src="/test-assets/rabbit-video/silent.mp4" type="video/mp4" />
<source src="/test-assets/rabbit-video/silent.webm" type="video/webm" />
</video>
</html>
Inapplicable Example 2
A video element that is not visible.
<html lang="en">
<video controls style="display: none;">
<source src="/test-assets/rabbit-video/video.mp4" type="video/mp4" />
<source src="/test-assets/rabbit-video/video.webm" type="video/webm" />
</video>
</html>
Glossary
Non-streaming media element
A non-streaming media element is an HTML Media Element for which the duration
property is not 0.
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 five 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
- cantTell: Whether the rule is applicable, or not all expectations were met could not be fully determined by the tester.
- Untested: The tester has not attempted to evaluate the test subject.
Note: A rule has one passed
or failed
outcome for every test target. When a tester evaluates a test target it can also be reported as cantTell
if the rule cannot be tested in its entirety. For example, when applicability was automated, but the expectations have to be evaluated manually.
When there are no test targets the rule has one inapplicable
outcome. If the tester is unable to determine whether there are test targets there will be one cantTell
outcome. And when no evaluation has occurred the test target has one untested outcome. This means that each test subject always has one or more outcomes.
Outcomes used in ACT Rules can be expressed using the outcome property of the [EARL10-Schema][].
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.
For more details, see examples of visible.
Rule Versions
This is the first version of this ACT rule.
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.