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# AVMediaCharacteristic

A structure that defines media data characteristics.

```
struct AVMediaCharacteristic
```

## Discussion

QuickTime Movie and MPEG-4 video files may contain tracks that provide tagged media characteristics to indicate a purpose, trait, or feature of the track’s media. For example, an audio track that mixes original program content with additional narrative descriptions of visual action may have the media characteristic `public.accessibility.describes-video` to distinguish it from other audio tracks stored in the same file that don’t contain additional narrative.

You inspect the tagged media characteristics of a track as shown below:

```objc
NSArray *userDataItems = [myAVAssetTrack metadataForFormat:AVMetadataFormatQuickTimeUserData];
NSArray *trackTaggedMediaCharacteristics = [AVMetadataItem metadataItemsFromArray: userDataItems
        withKey: AVMetadataQuickTimeUserDataKeyTaggedCharacteristic
        keySpace: AVMetadataKeySpaceQuickTimeUserData];
for (AVMetadataItem *metadataItem in trackTaggedMediaCharacteristics) {
     NSString *thisTrackMediaCharacteristic = [metadataItem stringValue];
}
```

You write tagged media characteristics to files of type [`mov`](/documentation/AVFoundation/AVFileType/mov) and [`m4v`](/documentation/AVFoundation/AVFileType/m4v) by using an instance of [`AVAssetWriter`](/documentation/AVFoundation/AVAssetWriter). You indicate tagged characteristics for a track by setting metadata on its associated asset writer input as shown below:

```objc
AVMutableMetadataItem *myTaggedMediaCharacteristic = [[AVMutableMetadataItem alloc] init];
[myTaggedMediaCharacteristic setKey:AVMetadataQuickTimeUserDataKeyTaggedCharacteristic];
[myTaggedMediaCharacteristic setKeySpace:AVMetadataKeySpaceQuickTimeUserData];
[myTaggedMediaCharacteristic setValue:aMeaningfulCharacteristicAsNSString];
[myMutableArrayOfMetadata addObject:myTaggedMediaCharacteristic];
[myAssetWriterInput setMetadata:myMutableArrayOfMetadata];
```

## Topics

### Visual

[`visual`](/documentation/AVFoundation/AVMediaCharacteristic/visual)

A media characteristic that indicates that a track or media selection option includes visual content.

[`containsAlphaChannel`](/documentation/AVFoundation/AVMediaCharacteristic/containsAlphaChannel)

A media characteristic that indicates that a track contains an alpha channel.

[`containsHDRVideo`](/documentation/AVFoundation/AVMediaCharacteristic/containsHDRVideo)

A media characteristic that indicates that a track contains HDR video.

[`frameBased`](/documentation/AVFoundation/AVMediaCharacteristic/frameBased)

A media characteristic that indicates that a track or media selection option includes frame-based content.

[`usesWideGamutColorSpace`](/documentation/AVFoundation/AVMediaCharacteristic/usesWideGamutColorSpace)

A media characteristic that indicates that a track uses a wide-gamut color space.

[`containsStereoMultiviewVideo`](/documentation/AVFoundation/AVMediaCharacteristic/containsStereoMultiviewVideo)

A media characteristic that indicates that a track contains stereoscopic video captured in a multiview compression format.

[`carriesVideoStereoMetadata`](/documentation/AVFoundation/AVMediaCharacteristic/carriesVideoStereoMetadata)

A media characteristic that indicates that the stereoscopic video track carries additional information related to the stereoscopic video.

[`indicatesHorizontalFieldOfView`](/documentation/AVFoundation/AVMediaCharacteristic/indicatesHorizontalFieldOfView)

A media characteristic that indicates the video track carries information related to the horizontal field of view.

[`indicatesNonRectilinearProjection`](/documentation/AVFoundation/AVMediaCharacteristic/indicatesNonRectilinearProjection)

A media characteristic that indicates the video track carries information related to how it should be projected for display.

### Audible

[`audible`](/documentation/AVFoundation/AVMediaCharacteristic/audible)

A media characteristic that indicates that a track or media selection option includes audible content.

[`dubbedTranslation`](/documentation/AVFoundation/AVMediaCharacteristic/dubbedTranslation)

A media characteristic that indicates that a track or media selection option contains audio language or dialect translation of the original content.

[`voiceOverTranslation`](/documentation/AVFoundation/AVMediaCharacteristic/voiceOverTranslation)

A media characteristic that indicates that a track or media selection option contains a language translation and verbal interpretation of spoken dialog.

[`enhancesSpeechIntelligibility`](/documentation/AVFoundation/AVMediaCharacteristic/enhancesSpeechIntelligibility)

A media characteristic that indicates a track or media selection option includes audio processed to enhance the intelligibility of speech.

[`describesMusicAndSoundForAccessibility`](/documentation/AVFoundation/AVMediaCharacteristic/describesMusicAndSoundForAccessibility)

A media characteristic that indicates that a track or media selection option includes legible content in the language of its specified locale.

[`tactileMinimal`](/documentation/AVFoundation/AVMediaCharacteristic/tactileMinimal)

A media characteristic that indicates that a track or media selection option includes haptic content.

### Legible

[`legible`](/documentation/AVFoundation/AVMediaCharacteristic/legible)

A media characteristic that indicates that a track or media selection option includes legible content.

[`easyToRead`](/documentation/AVFoundation/AVMediaCharacteristic/easyToRead)

A media characteristic that indicates a track or media selection option provides legible content that’s edited for easy reading.

[`describesVideoForAccessibility`](/documentation/AVFoundation/AVMediaCharacteristic/describesVideoForAccessibility)

A media characteristic that indicates the media includes audible content that describes the visual portion of the presentation.

[`containsOnlyForcedSubtitles`](/documentation/AVFoundation/AVMediaCharacteristic/containsOnlyForcedSubtitles)

A media characteristic that indicates that a track or media selection option presents only forced subtitles.

[`languageTranslation`](/documentation/AVFoundation/AVMediaCharacteristic/languageTranslation)

A media characteristic that indicates that a track or media selection option contains a language or dialect translation of the original content.

[`transcribesSpokenDialogForAccessibility`](/documentation/AVFoundation/AVMediaCharacteristic/transcribesSpokenDialogForAccessibility)

A media characteristic that indicates that a media selection option includes legible content that transcribes spoken dialog.

### Content

[`isOriginalContent`](/documentation/AVFoundation/AVMediaCharacteristic/isOriginalContent)

A media characteristic that indicates that a track or media selection option contains original content.

[`isMainProgramContent`](/documentation/AVFoundation/AVMediaCharacteristic/isMainProgramContent)

A media characteristic that indicates a track or media selection option includes content its author indicates is essential to the asset’s presentation.

[`isAuxiliaryContent`](/documentation/AVFoundation/AVMediaCharacteristic/isAuxiliaryContent)

A media characteristic that indicates a track or media selection option includes content its author indicates is auxiliary to the asset’s presentation.

[`machineGenerated`](/documentation/AVFoundation/AVMediaCharacteristic/machineGenerated)

A media characteristic that indicates that a track was generated in an automated fashion by a machine.

### Initializers

[`init(_:)`](/documentation/AVFoundation/AVMediaCharacteristic/init(_:))

Creates a media characteristic.

[`init(rawValue:)`](/documentation/AVFoundation/AVMediaCharacteristic/init(rawValue:))

Creates a media characteristic with a string value.


---

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