Video description (aka audio description) is a technology of applying additional soundtracks into the video (TV show or movie) in which spoken explanations and descriptions of visual elements are inserted into a television or video program without interfering with the sounds and dialogue that are a regular part of the program.
Video description technology is intended for people who are blind or have visual impairments. This technique is available on a limited basis on certain broadcast and cable television channels, on Public Broadcasting Service (PBS) television shows, and on DVDs.
The additional soundtrack contains all the audio of the original soundtrack and supplemented with additional audio that complements a performance, not interfering with it. Additional audio contains narration that conveys the settings, costumes, body language, scene changes, visual jokes, costumes or other content in a visual presentation or performance. Concise, objective descriptions are inserted between portions of dialogue or song that allow the listener to understand important visual elements.