Indicates whether a movie file can be opened asynchronously if possible (NSNumberYES) or not (NSNumberNO).

Opening a movie file and initializing a QTMovie object for that file may require a considerable amount of time, perhaps to convert the data in the file from one format to another. By setting this attribute to an NSNumber wrapping the value YES, you grant QTMovie permission to return a non-nil QTMovie identifier to your application immediately and then to continue processing the file data internally. If a movie is opened asynchronously, you must monitor the movie load state and ensure that it has reached the appropriate threshold before attempting to perform certain operations on the movie. For instance, you cannot export or copy a QTMovie object until its load state has reached QTMovieLoadStateComplete.

Available in Mac OS X v10.4 and later.