YouDescribe is a free accessibility tool to add audio description to YouTube videos. It allows anyone, anywhere to contribute description of an existing video and let a viewer who is visually impaired check it out right away. The best part is that it does so without modifying or redistributing the existing YouTube video. It's not a separate version, but rather it's the same version with description added while you watch.
How does YouDescribe work?
Those who are interested are invited to register on the site for free and step-by-step guidelines are provided on the site.
Video Demonstration of Recording Descriptions with YouDescribe
In the video below, Dr. Yue-Ting Siu shows how to add audio descriptions to a YouTube video with YouDescribe.