A lot of this Level AAA mandate is a bit redundant if you provided a text description. This mandate is much more in-depth and requires that all audible and visual cues be described in sync with the media. Since a lot of this is already covered, we'll go into a bit more technical detail on how to embed something like this on your site (assuming you're using a platform such as YouTube or Vimeo) and embedding the video on your site.
Let's take the following embed code for a video concerning an invasion of Golden Retriever puppies...
The above video will have the following embed code:
For a screen reader to pick up the link to the extended audio description, you could simply use <noembed> to insert the URL of the text page.
Lastly, if the video describes any 'calls to action' or URLs, those must also be listed in the description.