Inside Macintosh: QuickTime
The Movie Toolbox lets your application perform custom error notification. Your application must identify its custom error-notification function to the Movie Toolbox. Error-notification functions are particularly helpful when you are debugging your program.
The SetMoviesErrorProc function (described on SetMoviesErrorProc ) allows you to identify your application's error-notification function in the errProc parameter.
The entry point to your error-notification function should take the following form:
pascal void MyErrProc (OSErr theErr, long refcon);