A11ying with Sanna - Web Content Accessibility Guidelines a guide to the accessibility requirements
1 Perceivable

1.2.7 Extended Audio Description (Prerecorded)

Conformance level: AAA
Criterion released in WCAG version: 2.0

Official description of the success criterion

Where pauses in foreground audio are insufficient to allow audio descriptions to convey the sense of the video, extended audio description is provided for all prerecorded video content in synchronized media.

What to do?

Provide extended audio descriptions for all prerecorded video content where pauses in the original audio are insufficient.

Why is it important?

Allows detailed visual information to be conveyed to users who are blind or have low vision.

More about this criterion elsewhere