Type Method

identifierForKey:keySpace:

Provides the metadata identifier that’s equivalent to a key and key space.

Declaration

+ (AVMetadataIdentifier)identifierForKey:(id)key keySpace:(AVMetadataKeySpace)keySpace;

Parameters

key

The metadata key.

keySpace

The metadata key space.

Return Value

A metadata identifier equivalent to key and keySpace, or nil if no identifier can be constructed

Discussion

Metadata keys that are not instances of NSString, NSNumber, or NSData cannot be converted to metadata identifiers; they also cannot be written to media resources via AVAssetExportSession or AVAssetWriter. Metadata item keySpaces must be a string of one to four printable ASCII characters.

For custom identifiers, the keySpace AVMetadataKeySpaceQuickTimeMetadata is recommended. This keySpace defines its key values to be expressed as reverse-DNS strings, which allows third parties to define their own keys in a well established way that avoids collisions.

See Also

Accessing Metadata Values

value

The value of the metadata item.

time

The timestamp of the metadata item.

duration

The duration of the metadata item.

locale

The locale of the metadata item.

dataValue

The raw bytes of the value for the metadata item.

extraAttributes

The additional attributes supplied by the metadata item.

AVMetadataExtraAttributeKey

A value that defines extra attribute keys.

dataType

The data type of the metadata item's value.

extendedLanguageTag

The IETF BCP 47 (RFC 4646) language identifier of the metadata item.

startDate

The start date of the timed metadata.

AVMetadataKeySpace

A value that defines a metadata key space.

identifier

The identifier of the metadata item.

+ keyForIdentifier:

Returns the metadata key associated with the identifier.

+ keySpaceForIdentifier:

Returns the metadata key space associated with the identifier.

AVMetadataIdentifier

A value that defines the metadata identifiers for different file formats.