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

Media Data Atom TypesMovie Mediain the movie media sample or by using a wired action. If this atom is not present, the embedded moviedefaults to not slaved.kMovieMediaSlaveAudioA Boolean that indicates whether or not the audio properties of the embedded movie should be slavedto those of the parent movie. When audio is slaved, all audio properties of the containing track areduplicated in the embedded movie. These properties include sound volume, balance, bass and treble,and level metering. If this atom is not present, the embedded movie defaults to not slaved audio.kMovieMediaSlaveGraphicsModeA Boolean that indicates how the graphics mode of the containing track is applied to the embeddedmovie. If the graphics mode is not slaved, then the entire embedded movie is imaged using its owngraphics modes. The result of the drawing of the embedded movie is composited onto the containingmovie using the graphics mode of the containing track. If the graphics mode is slaved, then the graphicsmode of each track in the embedded movie is ignored and instead the graphics mode of the containingtrack is used. In this case, the tracks of the embedded movie composite their drawing directly into theparent movie’s contents. If this atom is not present, the graphics mode defaults to not slaved. Graphicsmode slaving is useful for compositing semi-transparent media––for example, a PNG with an alphachannel––on top of other media.kMovieMediaSlaveTrackDurationA Boolean that indicates how the Movie Media Handler should react when the duration of the embeddedmovie is different than the duration of the movie media sample that it is contained by. When the moviemedia sample is created, the duration of the embedded movie may not yet be known. Therefore, theduration of the media sample may not be correct. In this case, the Movie Media Handler can do one oftwo things. If this atom is not present or it contains a value of false, the Movie Media Handler will respectthe duration of media sample that contains the embedded movie. If the embedded movie has a longerduration than the movie media sample, the embedded movie will be truncated to the duration of thecontaining movie media sample. If the embedded movie is shorter, there will be a gap after it is finishedplaying. If this atom contains a value of true, the duration of the movie media sample will be adjustedto match the actual duration of the embedded movie. Because it is not possible to change an existingmedia sample, this will cause a new media sample to be added to the movie and the track’s edit list tobe updated to reference the new sample instead of the original sample.2012-08-14 | © 2004, 2012 Apple Inc. All Rights Reserved.311