Explanation

Code 20 is used to indicate that a publication provides readers the ability to play back pre-recorded audio that is synchronized with the text content.

This value should only be set if the audio substantively covers the content of the publication, including image descriptions.

For EPUB 3, the inclusion of media overlays to synchronize text and audio content is sufficient to meet this requirement.

Examples

Example 1 — Prerecorded audio synchronized with the text 
<ProductFormFeature>
   <ProductFormFeatureType>09</ProductFormFeatureType>
   <ProductFormFeatureValue>20</ProductFormFeatureValue>
</ProductFormFeature>

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