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[FXLA11Y] Media Overlays Section
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wareid authored Feb 9, 2024
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Expand Up @@ -479,10 +479,90 @@ <h5>Font face</h5>
</section>
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<section id="media-overlays">
<h3>Media overlays</h3>
<section id="media">
<h3>Media in fixed layout</h3>

<p>Media content such as audio, video, and interactive elements present both an opportunity and a challenge for fixed layout content. When media content is implemented with accessibility in mind, it can greatly improve the reading experience of a book. Done poorly, it can be a major barrier to access.</p>

<p>Media content can be incorporated into fixed layout EPUBs in a variety of ways. When working with media content in EPUB, it is important to consider WCAG [[wcag2]] criteria relating to media accessibility:</p>

<ul>
<li>1.1.1 Non-text Content (A)</li>
<li>1.2.1 Audio-only and Video-only (Prerecorded) (A)</li>
<li>1.2.2 Captions (Prerecorded) (A)</li>
<li>1.2.3 Audio Description or Media Alternative (Prerecorded) (A)</li>
<li>1.2.5 Audio Description (Prerecorded) (AA)</li>
<li>1.2.6 Sign Language (Prerecorded) (AA)</li>
<li>1.4.2 Audio Control (A)</li>
<li>2.2.2 Pause, Stop, Hide (A)</li>
<li>2.3.1 Three Flashes or Below Threshold (A)</li>
</ul>

<section id="media-overlays">
<h4>Media overlays</h4>

<p><a href="https://www.w3.org/TR/epub-33/#sec-media-overlays">Media overlays</a> allow EPUB creators to create an enhanced textual reading experience by synchronizing text and pre-recorded audio content. Media overlays in EPUB (reflowable or fixed layout) are not equivalent to audiobooks. Media overlays are also not a replacement or substitute for features like screen reader support or text to speech. Currently, media overlays in EPUB only support synchronizing audio media with textual content.</p>

<p>To maximize the effectiveness of synchronized text-audio playback for people with different reading needs, EPUB creators are strongly encouraged to meet the success criteria defined in WCAG [[wcag2]].</p>

<p>The provision of synchronized text-audio playback helps address various user needs. It not only enables a seamless visual and auditory reading experience from beginning to end of an EPUB publication, but is useful to users who require audio playback (e.g., who cannot see the text or have difficulties reading visually) or who benefit from reading with text highlighting (e.g., readers with dyslexia).</p>

<p>Unlike purely linear listening experiences, EPUB with synchronized text-audio playback preserves the user's ability to navigate around the publication, such as via the table of contents, and also introduces audio-centric reading features like phrase navigation, and ways to control which parts of the content are read aloud.</p>

<p>In order to offer users greater control over content presentation, EPUB creators need to add structure and semantics so that the reading system has the necessary context to enable this type of user experience. With greater context, a reading system can provide the ability to skip past secondary content that interferes with the primary narrative and escape users from deeply nested structures like tables.</p>

<p>Adding structure and semantics to synchronized text-audio playback broadly falls under the objective of the Info and Relationships success criterion [[wcag2]]. Without structured and semantically meaningful playback sequences, the effect is to deprive users of rich navigation of the content.</p>

<p>EPUB Accessibility 1.1 [[epub-a11y-11]] recommends the following objectives for content with <a href="https://www.w3.org/TR/epub-a11y-11/#sec-sync-text-audio">synchronized text-audio playback</a>:</p>

<ul>
<li>Ebook creators must ensure synchronized text-audio playback matches logical reading order.</li>
<li>Users must be able to automatically skip over content, and all skippable structures should be identified.</li>
<li>Users must be able to automatically escape from structured content. Ebook creators must encode structural semantics of elements such as lists, sidebars and figures so reading systems can facilitate escaping, skimming, or locating desired information.</li>
<li>Ebook creators must ensure auditory playback for epub navigation. This gives reading systems the ability to use auditory labels for links.</li>
</ul>
</section>

<section id="all-time-based-media">
<h4>Time-based media</h4>

<p>TBD</p>
<p>Accessible alternatives must be provided for all prerecorded audio and video content in an EPUB, with the exception of audio synchronized to the text through a method like media overlays.</p>

<p>The following success criteria apply to media content inserted into the publication outside of media overlays:</p>

<ul>
<li>1.2.1 Audio-only and Video-only (Prerecorded) (A)</li>
<li>1.2.2 Captions (Prerecorded) (A)</li>
<li>1.2.3 Audio Description or Media Alternative (Prerecorded) (A)</li>
<li>1.2.5 Audio Description (Prerecorded) (AA)</li>
</ul>

<p>For media that is audio-only, it is recommended that the EPUB creator provide an accompanying text-based alternative. Depending on the purpose and type of content, this alternative can be something like a transcript, a description, or a captioned video. For example, if the audio content is a music track that accompanies the book content, the alternative might either be the name of the song, a description of the song, or the lyrics. For content like an audio recording of a conversation or speaker, it is recommended to use a transcript that identifies the speakers and what is being said.</p>

<p>For media that is video-only, it is recommended to provide an audio description of the content, as well as a text-based version of that description. This description should include everything happening in the video, including descriptions of the setting, expressions, and any text that may appear on the screen that is required for understanding the content. The audio description should be its own track within the video player.</p>

<p>For media that has both audio and video, all of the recommendations for audio-only and video-only apply.</p>

<p>In EPUB 3.3 [[epub-33]], resources referenced in the [[html]] <code>track</code> element (e.g., captions, audio descriptions, and subtitles) are considered <a href="https://www.w3.org/TR/epub-33/#sec-exempt-resources">Exempt Resources</a>, which means file formats may not have guaranteed EPUB reading system support, but also do not require a fallback. It is important to test your EPUB file if it contains any of these exempt resources, to ensure compatibility.</p>
</section>

<section id="animations">
<h4>Animations</h4>

<p>If an EPUB creator is considering including animations and motion-based content, they should consider the following success criteria:</p>

<ul>
<li>2.2.2 Pause, Stop, Hide (A)</li>
<li>2.3.1 Three Flashes or Below Threshold (A)</li>
</ul>

<p>Animations, auto-updating content, or content in motion (e.g., blinking, scrolling) can distract users, cause discomfort, or even trigger conditions like migraine. When these features are included, it is important for EPUB creators to provide a mechanism that allows the user to stop or hide the animations. EPUB creators should also be conscious that any animations or motion do not contain anything that flashes more than three times in a one second period.</p>

<p class="note">
While this document focuses on WCAG recommendations up to level AA, there is a AAA Success Criteria for animations that EPUB creators should consider when designing their book content. <a href="https://www.w3.org/WAI/WCAG22/Understanding/animation-from-interactions.html">2.3.3 Animation from Interactions</a> recommends that if an interation triggers a motion animation, it should be possible for the user to disable it, unless the motion is essential to the functionality or information being conveyed.
</p>

</section>
</section>

<section id="tables">
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