The media types in Macromedia Director MX 2004

The media types in Macromedia Director MX 2004 provide access to the functionality of the various media types, such as RealMedia, DVD, Animated GIF, and so on, that are added to movies as cast members.
Literally, media types are not actually objects, but rather cast members that are of a specific type of media. When a media type is added to a movie as a cast member, it not only inherits the functionality of the core Member object, it also extends the Member object by providing additional functionality that is available only to the specified media type. For example, a RealMedia cast member has access to the Member object’s methods and properties, but it also has additional methods and properties that are specific to RealMedia. All other media types also exhibit this behavior.