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The QTPlgDataDescriptor class and its derived classes provide a convenient way to store parameters appropriate to some operation and bring them around the world. Moreover, this hierarchy of classes constitute the QTPlugin interface to the various structure defined by QuickTime API

The QTPlgDataDescriptor class defines properties and methods inherited from any class derived from it.

Since version 6.7 of the plugin this class can be used in Console Applications






The class has not constructor at all (you can always use the Realbasic common constructor syntax, of course, but you will obtain an usless object). Its destructor, will be implicitly invoked every time one of its derived classes will be destroyed.
Anyway, once a new instance of a class derived from QTPlgDataDescriptor is returned, it is good practice to check the class property to be sure that the new object can be used. As a rule of thumb, a class derived from QTPlgDataDescriptor is valid if it has obtained access to the appropriate sample description structure to be used (that is the value of the property is not 0)

returns a handle to the sample description structure in use; the format of this structure depends on the type of the QTPlgDataDescriptor’s derived class; for example, a class instance will refer to an Image Description structure, a class instance to a Sound Description structure and so on. useful for toolbox programmers (use with care: you could invalidate the handle causing unpredictable results (probably an application crash))
specifies the total size, in bytes, of the sample description structure encapsulated within the class instance
indicates which of the media’s data references contains the sample data for this sample description
this property is set only if the data descriptor class instance has been created by a object
specifies the version of the sample description in use
a four character string that specifies the format of the sample description
usually the same value like the property; sometimes, is used to specify the type of compressor–decompressor component required to deal with sample data