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The Described and Captioned Media Program (DCMP) holds the standards for described and captioned media. It is funded by the U.S. Department of Education and provides a variety of resources to serve students with sensory disabilities. The Described and Captioned Media Program Description Key provides examples of what to describe.
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Creating Accessible Videos with caption options and do-it-yourself audio description instructions by the University of Washington
What is math accessibility? By Design Science
Accessibility | Equations: MathML, Images, and LaTeX by Penn State
Video Accessibility Guidelines by Boise State Teaching & Learning Tools (LTS)
How do I manage video options in the New Rich Content Editor as an Instructor? by Canvas