# Format Description Constants Constants that identify format descriptions. ## Topics ### Description Constants [`let kCMFormatDescriptionAlphaChannelMode_PremultipliedAlpha: CFString`](/documentation/CoreMedia/kCMFormatDescriptionAlphaChannelMode_PremultipliedAlpha) [`let kCMFormatDescriptionAlphaChannelMode_StraightAlpha: CFString`](/documentation/CoreMedia/kCMFormatDescriptionAlphaChannelMode_StraightAlpha) [`let kCMFormatDescriptionTransferFunction_ITU_R_2100_HLG: CFString`](/documentation/CoreMedia/kCMFormatDescriptionTransferFunction_ITU_R_2100_HLG) [`let kCMFormatDescriptionTransferFunction_Linear: CFString`](/documentation/CoreMedia/kCMFormatDescriptionTransferFunction_Linear) [`let kCMFormatDescriptionTransferFunction_SMPTE_ST_2084_PQ: CFString`](/documentation/CoreMedia/kCMFormatDescriptionTransferFunction_SMPTE_ST_2084_PQ) [`let kCMFormatDescriptionTransferFunction_sRGB: CFString`](/documentation/CoreMedia/kCMFormatDescriptionTransferFunction_sRGB) ### Description Extension Keys [`let kCMFormatDescriptionExtensionKey_MetadataKeyTable: CFString`](/documentation/CoreMedia/kCMFormatDescriptionExtensionKey_MetadataKeyTable) ### Description Extension Constants [`let kCMFormatDescriptionExtension_AlphaChannelMode: CFString`](/documentation/CoreMedia/kCMFormatDescriptionExtension_AlphaChannelMode) [`let kCMFormatDescriptionExtension_AlternativeTransferCharacteristics: CFString`](/documentation/CoreMedia/kCMFormatDescriptionExtension_AlternativeTransferCharacteristics) [`let kCMFormatDescriptionExtension_AmbientViewingEnvironment: CFString`](/documentation/CoreMedia/kCMFormatDescriptionExtension_AmbientViewingEnvironment) [`let kCMFormatDescriptionExtension_AuxiliaryTypeInfo: CFString`](/documentation/CoreMedia/kCMFormatDescriptionExtension_AuxiliaryTypeInfo) [`let kCMFormatDescriptionExtension_BitsPerComponent: CFString`](/documentation/CoreMedia/kCMFormatDescriptionExtension_BitsPerComponent) [`let kCMFormatDescriptionExtension_BytesPerRow: CFString`](/documentation/CoreMedia/kCMFormatDescriptionExtension_BytesPerRow) [`let kCMFormatDescriptionExtension_ChromaLocationBottomField: CFString`](/documentation/CoreMedia/kCMFormatDescriptionExtension_ChromaLocationBottomField-swift.var) [`let kCMFormatDescriptionExtension_ChromaLocationTopField: CFString`](/documentation/CoreMedia/kCMFormatDescriptionExtension_ChromaLocationTopField-swift.var) [`let kCMFormatDescriptionExtension_CleanAperture: CFString`](/documentation/CoreMedia/kCMFormatDescriptionExtension_CleanAperture-swift.var) [`let kCMFormatDescriptionExtension_ColorPrimaries: CFString`](/documentation/CoreMedia/kCMFormatDescriptionExtension_ColorPrimaries-swift.var) [`let kCMFormatDescriptionExtension_ContainsAlphaChannel: CFString`](/documentation/CoreMedia/kCMFormatDescriptionExtension_ContainsAlphaChannel) [`let kCMFormatDescriptionExtension_ContentLightLevelInfo: CFString`](/documentation/CoreMedia/kCMFormatDescriptionExtension_ContentLightLevelInfo) [`let kCMFormatDescriptionExtension_Depth: CFString`](/documentation/CoreMedia/kCMFormatDescriptionExtension_Depth) [`let kCMFormatDescriptionExtension_FieldCount: CFString`](/documentation/CoreMedia/kCMFormatDescriptionExtension_FieldCount-swift.var) [`let kCMFormatDescriptionExtension_FieldDetail: CFString`](/documentation/CoreMedia/kCMFormatDescriptionExtension_FieldDetail-swift.var) [`let kCMFormatDescriptionExtension_FormatName: CFString`](/documentation/CoreMedia/kCMFormatDescriptionExtension_FormatName) [`let kCMFormatDescriptionExtension_FullRangeVideo: CFString`](/documentation/CoreMedia/kCMFormatDescriptionExtension_FullRangeVideo) [`let kCMFormatDescriptionExtension_GammaLevel: CFString`](/documentation/CoreMedia/kCMFormatDescriptionExtension_GammaLevel-swift.var) [`let kCMFormatDescriptionExtension_HorizontalFieldOfView: CFString`](/documentation/CoreMedia/kCMFormatDescriptionExtension_HorizontalFieldOfView) [`let kCMFormatDescriptionExtension_ICCProfile: CFString`](/documentation/CoreMedia/kCMFormatDescriptionExtension_ICCProfile) [`let kCMFormatDescriptionExtension_MasteringDisplayColorVolume: CFString`](/documentation/CoreMedia/kCMFormatDescriptionExtension_MasteringDisplayColorVolume) [`let kCMFormatDescriptionExtension_OriginalCompressionSettings: CFString`](/documentation/CoreMedia/kCMFormatDescriptionExtension_OriginalCompressionSettings) [`let kCMFormatDescriptionExtension_PixelAspectRatio: CFString`](/documentation/CoreMedia/kCMFormatDescriptionExtension_PixelAspectRatio-swift.var) [`let kCMFormatDescriptionExtension_ProtectedContentOriginalFormat: CFString`](/documentation/CoreMedia/kCMFormatDescriptionExtension_ProtectedContentOriginalFormat) [`let kCMFormatDescriptionExtension_SampleDescriptionExtensionAtoms: CFString`](/documentation/CoreMedia/kCMFormatDescriptionExtension_SampleDescriptionExtensionAtoms) [`let kCMFormatDescriptionExtension_TransferFunction: CFString`](/documentation/CoreMedia/kCMFormatDescriptionExtension_TransferFunction-swift.var) [`let kCMFormatDescriptionExtension_VerbatimISOSampleEntry: CFString`](/documentation/CoreMedia/kCMFormatDescriptionExtension_VerbatimISOSampleEntry) [`let kCMFormatDescriptionExtension_VerbatimImageDescription: CFString`](/documentation/CoreMedia/kCMFormatDescriptionExtension_VerbatimImageDescription-swift.var) [`let kCMFormatDescriptionExtension_VerbatimSampleDescription: CFString`](/documentation/CoreMedia/kCMFormatDescriptionExtension_VerbatimSampleDescription) [`let kCMFormatDescriptionExtension_YCbCrMatrix: CFString`](/documentation/CoreMedia/kCMFormatDescriptionExtension_YCbCrMatrix-swift.var) --- Copyright © 2026 Apple Inc. 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