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

Some Useful Examples and ScenariosCreating Movies with Modifier TrackskTrackModifierReference, &referenceIndex);QTInsertChild(inputMap, kParentAtomIsContainer,kTrackModifierInput, referenceIndex, 0, 0, nil, &inputAtom);The QTInsertChild function returns the offset of the new modifier input atom in the inputAtom parameter.You now need to add the name and type of the source track to the modifier input atom. Again, calling theQTInsertChild function does this, as shown in the following code snippet:inputType = VideoMediaType;QTInsertChild(inputMap, inputAtom,kTrackModifierType, 1, 0, sizeof(inputType), &inputType,nil);aType = 'srcA';QTInsertChild(inputMap, inputAtom, kEffectDataSourceType, 1, 0,sizeof(aType), &aType, nil);This process is repeated for each source for the effect.Creating Movies with Modifier TracksQuickTime 2.1 added additional functionality for media handlers. By way of modifier tracks, a media handlercan send its data to another media handler rather than presenting its media directly. See “Modifier Tracks” (page247) for a complete discussion of this feature.To create a movie with modifier tracks, first you create a movie with all the desired tracks, then you create themodifier track. To link the modifier track to the track that it modifies, you use the AddTrackReference functionas shown in Listing 6-12 (page 343).Listing 6-12Linking a modifier track to the track it modifieslong addedIndex;AddTrackReference(aVideoTrack, aModifierTrack,kTrackModifierReference, &addedIndex);2012-08-14 | © 2004, 2012 Apple Inc. All Rights Reserved.343