Quicktime File Format (2012-08-14).pdf

Some Useful Examples and ScenariosOptimizing QuickTime VR Movies for Web PlaybackThe important change that took place to allow this to happen was for QuickTime to place global movieinformation at the beginning of the file. Originally, this information was at the end of the file. After that, theframe data simply needs to be in order in the file. Similarly, QuickTime VR files also need to be laid out in acertain manner in order to get some sort of quick feedback when viewing on the web. Roughly speaking thisinvolves writing out all of the media samples in the file in a particular order. Apple now provides a movie exportcomponent that does this for you: the QTVR Flattener.The QTVR FlattenerThe QTVR Flattener is a movie export component that converts an existing QuickTime VR single node movieinto a new movie that is optimized for the Web. Not only does the flattener reorder the media samples, butfor panoramas it also creates a small preview of the panorama. When viewed on the Web, this preview appearsafter 5% to 10% of the movie data has been downloaded, allowing users to see a lower-resolution version ofthe panorama.Using the QTVR flattener from your application is quite easy. After you have created the QuickTime VR movie,you simply open the QTVR Flattener component and call the MovieExportToFile routine as shown in Listing6-17 (page 366).Listing 6-17Using the flattenerComponentDescription desc;Component flattener;ComponentInstance qtvrExport = nil;desc.componentType = MovieExportType;desc.componentSubType = MovieFileType;desc.componentManufacturer = QTVRFlattenerType;flattener = FindNextComponent(nil, &desc);if (flattener) qtvrExport = OpenComponent (flattener);if (qtvrExport)MovieExportToFile (qtvrExport, &myFileSpec, myQTVRMovie, nil, 0, 0);The code fragment shown in Listing 6-17 (page 366) creates a flattened movie file specified by the myFileSpecparameter. If your QuickTime VR movie is a panorama, the flattened movie file includes a quarter size, blurredJPEG, compressed preview of the panorama image.2012-08-14 | © 2004, 2012 Apple Inc. All Rights Reserved.366