Technical Q&A QTMTB51

ConvertMovieToFile unexpected results

Q: When I call the ConvertMovieToFile function to convert a movie to a specified file and type, I get unexpected results unless I've first displayed and played the movie. I'm not using a movie controller, just the movie toolbox. If I display and play the movie first, ConvertMovieToFile correctly saves the movie with no problems. However, if I don't display and play the movie first, I get just a white movie of the right size and length along with the sound track. In neither case do I get an error from ConvertMovieToFile. What's going on?

A: The white frames you are seeing in the video track are a result of the movie not being active. Use the SetMovieActive function described in Inside Macintosh:QuickTime pages 2-145 to activate the movie before calling ConvertMovieToFile (if not already active). You can determine whether a movie is active by calling the GetMovieActive function, which is described on pages 2-146 of Inside Macintosh:QuickTime.

Finally, don't forget to set a valid port for the movie. Use the SetMovieGWorld function (Inside Macintosh:QuickTime, pages 2-159) to set the graphics world for displaying a movie.

[Jun 14 1999]