Hey everyone 
In the lecture “What Are Good Ways to Make Audio and Video Content Accessible?” in the new full-stack curriculum, the instructor says:
Other ways to make your video and audio content accessible include adding a sign language overlay for videos for deaf people and those hard of hearing […]
This confused me. I don’t know much about accessibility (hence my question), so I certainly don’t mean to be presumptive, impose my preferences, or anything of the sort, but I genuinely don’t understand how deaf / hard of hearing people would be better served with a sign language overlay instead of captions.
Wouldn’t captions provide the same service that a sign language overlay would (allowing people to understand what they cannot hear) while also being less distracting or intrusive?
Please help me understand. Thank you!