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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 metadata item reference. A given metadata item has a number of attributes, including its and its . 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 QTPlgMetaDataItem class lets you deal with such a metadata items reference

This class requires QuickTime 7 or later.







The QTPlgMetaDataItem class constructors are called when you create a new instance of the class, while the ˜QTPlgMetaDataItem 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 QTPlgMetaDataItem object is valid if it has a valid

The class provides you with the following initializer methods:
()
This is the default constructor. The new class instance will be initialized with the kStorageQuickTime
(other as QTPlgMetaDataItem)
This is the copy constructor. The properties of the object to be copied will be used to initialize the new class instance properties

indicates if the metadata item has been picked out from a metadata container or has been created from scratch
specifies the metadata container this metadata item belongs to
specifies the label for the data associated to the metadata item. The of the key influence the value reported by the property (i.e. if the key has a format of value kFormatUserData the value of the property will be )
specifies the data that has to be associated to the metadata item
specifies the locale identifier based on the naming convention defined by the International Components for Unicode (ICU). The identifier consists of two pieces of ordered information: a language code and a region code. The language code is based on the ISO 639–1 standard, which defines two–character codes, such as "en" and "fr", for the world’s most commonly used languages. If a two–letter code is not available, then ISO 639–2 three–letter identifiers are accepted as well, for example "haw" for Hawaiian. The region code is defined by ISO 3166–1. The region code is in all caps and appended, after an underscore, after the language code, for example "en_US", "en_GB", and "fr_FR"