The default value of this property is NULL, which means that the master clock is automatically chosen. When non-NULL, this property overrides the automatic choice of master clock for item timebases. This is most useful when you are synchronizing video-only movies with audio played by another source.
Cancels any pending preroll requests and invokes the corresponding completion handlers if present.
This documentation contains preliminary information about an API or technology in development. This information is subject to change, and software implemented according to this documentation should be tested with final operating system software.