QuickTime 3 Reference

Required Atoms of an Effects Description

There are several required atoms that an effect description must contain. The first is the kParameterWhatName atom that contains the name of the effect. This selects which of the available effects will be used.

The code snippet shown in Listing 6 adds a kParameterWhatName atom to the atom container effectDesc . The constant kCrossFadeTransitionType contains the name of the built-in cross fade effect. The cross fade effect is described in detail in "Cross Fade" .

Listing 6 Adding a kParameterWhatName atom with the value kCrossFadeTransitionType to the QTAtomContainer effectDesc



 
effectCode = kCrossFadeTransitionType;

QTInsertChild(effectDescription,

                kParentAtomIsContainer,

                kParameterWhatName,

                kParameterWhatID,

                0,

                sizeof(effectCode),

                &effectCode,

                nil);

In addition to the kParameterWhatName atom, the effect description must also contain zero or more kEffectSourceName atoms. Each of these atoms contains the name of one of the effect's sources. An input map is used to map these names to the actual tracks of the movie that are the sources. "Creating an Input Map" describes how to create the input map.