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
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
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)