Derived Media Handler Components

Overview

This chapter discusses derived media handler components. Derived media handler components allow the Movie Toolbox to play the data in a media. These components isolate the Movie Toolbox from the details of how or where a particular media is stored. This not only frees the Movie Toolbox from reading and writing media data, but also makes QuickTime extensible to new data formats.

These components are referred to as derived components because they rely on the services of a common base media handler component, which is supplied by Apple. The base media handler component handles most of the duties that must be performed by all media handlers. Your derived media handler component extends the services provided by the base media handler.

This chapter addresses developers of derived media handler components. You should never need to use the facilities of a derived media handler directly--only the Movie Toolbox calls derived media handler components. The functions described in this chapter define the functional interface that your component must support.

As components, derived media handlers rely on the facilities of the Component Manager. To use any component, your application must also use the Component Manager. If you are not familiar with this manager, see the chapter "Component Manager" in Inside Macintosh: More Macintosh Toolbox. In addition, you should be familiar with the Movie Toolbox in general and the concept of media structures in particular. See the chapter "Movie Toolbox" in Inside Macintosh: QuickTime for more information.

Throughout this chapter, the terms media handler and handler refer to media handler components. Apple's sound and video handlers are not derived media handlers, so you cannot override them using the functions described in this chapter. Apple's text media handler, on the other hand, is built on the base media handler.