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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 value 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 QTPlgMetaDataValue class lets you deal with values of a metadata item

This class requires QuickTime 7 or later.







The QTPlgMetaDataValue class constructors are called when you create a new instance of the class, while the ˜QTPlgMetaDataValue 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 QTPlgMetaDataValue 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 kDataTypeBinary
(other as QTPlgMetaDataValue)
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 stored data
specifies the format of the metadata item value. Acceptable values are those defined in the section below. Once established the type of data in use, you can get or set the data associated to the object by using the appropriate property. Note that changing the format of the metadata item value will cause the deletion of any data previously stored
specifies if the data associated to the metadata item represent a block of untyped data
specifies if the data associated to the metadata item represent a string
specifies if the data associated to the metadata item represent a number. You can find about the type of stored number by inspecting the value of the property
specifies if the data associated to the metadata item represent an image
if the property is set to true, sets or gets the metadata item value with a block of untyped data otherwise is nil
if the property is set to true, sets or gets the metadata item value with a string otherwise is an empty string. Note that you can set this property with an UTF16 encoded string
if the property is set to true, sets or gets the metadata item value with a number otherwise is an empty string. You specify the type of number you want to store by setting the property with the appropriate
if the property is set to true, sets or gets the metadata item value with a picture otherwise is nil


the type of the stored data is unknown
the stored data represent an untyped block of data
the stored data represent a sequence of characters
the stored data represent an UInt8
the stored data represent an UInt16
the stored data represent an UInt32
the stored data represent a short
the stored data represent a long
the stored data represent a single
the stored data represent a double
the stored data represent an image