Video types are used by the engine to optimize storage of the original files. Video types can also be used by viewers to assign type information to a file or a group. Video types can help viewers generate a default player interface without calling a specific format function.
1. (@song [http://youtube.com…] (d video mp4)) ⇒ video stream
2. (@song (d videowebm) (f video new-player)) ⇒ video alternative file type
3. (v disney-videos (d video mov) (@vid1 [filespec])…) ⇒ set type for video library