USA.gov has published a resource guide on multimedia online materials and accessibility:
Make Your Multimedia Section 508 Compliant and Accessible (WebContent.gov)
This is a thorough survey of the topic, with many links to examples, legal references, and further resources.
On a few points it seems to me to set a high standard for federal agencies.:
- Captioning must be provided for live video (such as live speeches);
- Audiodescription as well as captioning must be included where necessary;
- The accessibility rules apply to agencies posting material to public websites (Youtube etc.) “Many agencies have found that a practical approach to providing accessible content is to post videos and presentations
on these sites and also post the same content, in an accessible manner, on their own agency sites.”
These points have been “gray areas” in the past. For example, captioning of live video gets a lower priority rating in the Web Content Accessibility Guidelines 2.0. However, the USA.gov document stresses the affirmative need for access on all three of the above issues.