QuickTime 4 Reference

Identifying Containers With Data References

A container is the system element that contains the movie data and can be any element that can contain data. For example, a container may be an in-memory data structure, a local disk file, or a file on a networked multimedia server. As is the case throughout QuickTime, all data handlers identify their movie-data containers with data references. Data references identify the location of the container and its type.

Different container types may require different types of references. For example, files are identified using aliases, while memory-based movies are identified by handles. The data reference data type is flexible enough to accommodate all these cases. The data handler component must specify the type of reference it requires and verify that the references supplied by client applications are valid. Data handler components use the component subtype value to specify the reference type they support.

Whenever an application opens a container, the Movie Toolbox determines the most appropriate data handler component to use in order to access that container. The Movie Toolbox makes this determination by querying the various data handlers installed on the user's computer. If your application uses the Movie Toolbox, this selection process is transparent to your program. If you develop your own data handler, your component must support the selection functions. See "Data Handler Components Reference" , for more information).