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Since QuickTime 7, a new architecture has been introduced in order to read and write metainformation in a QuickTime movie. This architecture defines a new metainformation storage format called the QuickTime metadata format. In this type of storage, metadata is accessed via . There is one metadata reference per , , or . A single metadata reference can pick out one or more metadata containers, which are distinguished from one another by their .

A metadata container holds one or more metadata items. Each metadata item is accessed by a . A given metadata item has a number of attributes, including its and its key. The key is analogous to the , insofar as it is a label for the sort of data contained in the metadata item. The of the key for a specific metadata item depends on the of that item.

The QTPlgMetaDataKey class lets you deal with such a metadata keys

This class requires QuickTime 7 or later.







The QTPlgMetaDataKey class constructors are called when you create a new instance of the class, while the ˜QTPlgMetaDataKey class destructor, is called automatically when the class is no more in use. Also, you can invoke the class destructor by setting the instance of the class to nil.
Once a new class instance is returned, it is good practice to check the class property to be sure that the new object can be used. A QTPlgMetaDataKey object is valid if it is fully identified (that is it has a valid and )

The class provides you with the following initializer methods:
()
This is the default constructor. The new class instance will be initialized to an unspecified metadata key; it is up to you set any of the required class properties before using the class instance
(keyFormat as )
This constructor initialize a metadata key object of type specified in the keyFormat parameter; to find about the acceptable formats take a look at the section below
(other as QTPlgMetaDataKey)
This is the copy constructor. The properties of the object to be copied will be used to initialize the new class instance properties

indicates the size, in bytes, of the metadata key
specifies the format of the metadata key. Acceptable values are those defined in the section below. Once you have specified a valid metadata key format, you can inspect the and class properties to find about the type of value you can use
specifies if the metadata key is an
specifies if the meta datakey is a string
specifies the value of the metadata key. Setting this property is effective only for keys that accept this type of value
specifies the value of the metadata key. Setting this property is effective only for keys that accept this type of value


this key format indicates a special type of key that can be used to access metadata items in any kind of storage container, regardless of its native format. This key type is specified in the format
the metadata key is a string in a reverse–DNS form, such as "com.apple.quicktime.copyright" and "com.apple.quicktime.author"
the metadata key is a that indicates the user data type (see also the class)
the metadata key is a string in a reverse–DNS form, such as "com.apple.quicktime.copyright" and "com.apple.quicktime.author"
the metadata key is a that indicates the user data type (see also the class)