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# Media Object Attribute Keys

Attribute keys for a media object. These constants are used to specify keys within a media object’s [`attributes`](/documentation/MediaLibrary/MLMediaObject/attributes) dictionary.

## Topics

### Constants

[`MLMediaObjectDurationKey`](/documentation/MediaLibrary/MLMediaObjectDurationKey)

Specifies the media object’s duration, in seconds. The value for this key is a number (<doc://com.apple.documentation/documentation/Foundation/NSNumber>).

[`MLMediaObjectArtistKey`](/documentation/MediaLibrary/MLMediaObjectArtistKey)

Specifies the media object’s artist. The value for this key is a string (<doc://com.apple.documentation/documentation/Foundation/NSString>).

[`MLMediaObjectAlbumKey`](/documentation/MediaLibrary/MLMediaObjectAlbumKey)

Specifies the media object’s album. The value for this key is a string (<doc://com.apple.documentation/documentation/Foundation/NSString>).

[`MLMediaObjectGenreKey`](/documentation/MediaLibrary/MLMediaObjectGenreKey)

Specifies the media object’s genre. The value for this key is a string (<doc://com.apple.documentation/documentation/Foundation/NSString>).

[`MLMediaObjectKindKey`](/documentation/MediaLibrary/MLMediaObjectKindKey)

Used by iTunes only. Specifies the media object’s file format (shown in the “Kind” column in iTunes). The value for this key is a string (<doc://com.apple.documentation/documentation/Foundation/NSString>).

[`MLMediaObjectTrackNumberKey`](/documentation/MediaLibrary/MLMediaObjectTrackNumberKey)

Specifies the media object’s track number. The value for this key is a number (<doc://com.apple.documentation/documentation/Foundation/NSNumber>).

[`MLMediaObjectBitRateKey`](/documentation/MediaLibrary/MLMediaObjectBitRateKey)

Specifies the media object’s bit rate, in kilobits per second. The value for this key is a number (<doc://com.apple.documentation/documentation/Foundation/NSNumber>).

[`MLMediaObjectSampleRateKey`](/documentation/MediaLibrary/MLMediaObjectSampleRateKey)

Specifies the media object’s sample rate, in samples per second (Hz). The value for this key is a number (<doc://com.apple.documentation/documentation/Foundation/NSNumber>).

[`MLMediaObjectChannelCountKey`](/documentation/MediaLibrary/MLMediaObjectChannelCountKey)

Specifies the media object’s channel count. The value for this key is a number (<doc://com.apple.documentation/documentation/Foundation/NSNumber>).

[`MLMediaObjectResolutionStringKey`](/documentation/MediaLibrary/MLMediaObjectResolutionStringKey)

Specifies the media object’s resolution. The value for this key is a string (<doc://com.apple.documentation/documentation/Foundation/NSString>) intended to be converted to a size (<doc://com.apple.documentation/documentation/Foundation/NSSize>) using the <doc://com.apple.documentation/documentation/Foundation/NSSizeFromString(_:)> method.

[`MLMediaObjectCommentsKey`](/documentation/MediaLibrary/MLMediaObjectCommentsKey)

Specifies the contents of the comments field associated with the media object. The value for this key is a string (<doc://com.apple.documentation/documentation/Foundation/NSString>).

[`MLMediaObjectKeywordsKey`](/documentation/MediaLibrary/MLMediaObjectKeywordsKey)

Specifies the keywords associated with the media object. The value for this key is an array (<doc://com.apple.documentation/documentation/Foundation/NSArray>) of strings (<doc://com.apple.documentation/documentation/Foundation/NSString>).

[`MLMediaObjectProtectedKey`](/documentation/MediaLibrary/MLMediaObjectProtectedKey)

Specifies whether the media object is protected by DRM (Digital Rights Management). The value for this key is a number (<doc://com.apple.documentation/documentation/Foundation/NSNumber>), 0 or 1, that represents a Boolean value.


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