Inside Macintosh: QuickTime
The PlayMoviePreview function (described on PlayMoviePreview ) plays a movie's preview. You provide a pointer to a movie callout function in the callOutProc parameter.
The Movie Toolbox calls your movie callout function repeatedly while the movie preview is playing. You can use this function to stop the preview. If you do not want to assign a function, set the callOutProc parameter to nil .
Your movie callout function should present the following interface:
pascal Boolean MyCallOutProc (long refcon);
Your movie callout function returns a Boolean value. The Movie Toolbox examines this value before continuing. If your function sets this value to false , the Movie Toolbox stops the preview and returns to your application.
If you call the GetMovieActiveSegment function (described on GetMovieActiveSegment ) from within your movie callout function, the Movie Toolbox will have changed the active movie segment to be the preview segment of the movie. The Movie Toolbox restores the active segment when the preview is done playing.