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

Media Data Atom TypesTween MediaNote As a time-based media playback format, QuickTime may drop frames when necessary tomaintain its schedule. As a consequence, frames of a SWF file may be dropped during playback. Ifthis is not satisfactory for your application, you can set the playback mode of the movie to Play AllFrames, which will emulate the playback mode of ShockWave. QuickTime’s SWF file importer setsthe Play All Frames mode automatically when adding a SWF file to an empty movie.QuickTime support for Flash 3.0 also includes the DoFSCommand mechanism. This allows JavaScript routineswith a specific function prototype to be invoked with parameters passed from the Flash track. Refer toMacromedia’s Flash 3 documentation for more details on how to author a .SWF 3.0 file with a Flash FSCommand.Tween MediaNote Tween media is deprecated in the QuickTime file format. The information that follows isintended to document existing content containing tween media and should not be used for newdevelopment.Tween media is used to store pairs of values to be interpolated between in QuickTime movies. These interpolatedvalues modify the playback of other media types by using track references and track input maps. For example,a tween media could generate gradually changing volume levels to cause a sound track to fade out. It has amedia type of 'twen'.Every tween operation is based on a collection of one or more values from which a range of output values canbe algorithmically derived. Each tween is assigned a time duration, and an output value can be generated forany time value within the duration. In the simplest kind of tween operation, a pair of values is provided asinput and values between the two values are generated as output.A tween track is a special track in a movie that is used exclusively as a modifier track. The data it contains,known as tween data, is used to generate values that modify the playback of other tracks, usually by interpolatingvalues. The tween media handler sends these values to other media handlers; it never presents data.Tween Sample DescriptionThe tween sample description uses the standard sample description header, as described in “Sample TableAtoms” (page 96).The data format field in the sample description is always set to 'twen'. The tween media handler adds noadditional fields to the sample description.2012-08-14 | © 2004, 2012 Apple Inc. All Rights Reserved.235