Accessible names
In addition to visible captions, each image must be briefly described for blind users. This should be a very short description, not a repetition of the entire caption.
In addition to visible captions, each video thumbnail must be briefly described. This should be a very short description, usually just the video title. Since screen readers don't automatically announce that a file is a video, this must be included in the description. Add "- video player" to your video descriptions (e.g., "New digital strategy - video player").