Audio description is the addition of a separate audio track which provides description of the video’s visual content. The audio description is timed to fit in between existing audio tracks. Unfortunately, the technology for adding audio description tracks is behind that for captioning.
MAGpie is a free tool from the National Center for Accessible Media (NCAM) that can be used to add audio description and captions to a variety of video formats. Here’s an example of audio description from NCAM:
If you will be using a video in multiple classes over several semesters, it is worth spending the time to incorporate audio description. Any visual content should be available to students who are blind or low vision.