# CMFormatDescription A media format descriptor that describes the samples in a sample buffer. ## Discussion `CMFormatDescriptions` are immutable Core Foundation objects that describe media data of various types, including audio, video, and muxed media data. There are two types of API: media-type-agnostic APIs (supported by all CMFormatDescriptions) and media-type-specific APIs. The media-type-agnostic APIs are prefixed with `CMFormatDescription`, and the media-type-specific APIs are prefixed with `CMAudioFormatDescription`, `CMVideoFormatDescription`, and so on. ## Topics ### Creating Format Descriptions [`func CMFormatDescriptionCreate(allocator: CFAllocator?, mediaType: CMMediaType, mediaSubType: FourCharCode, extensions: CFDictionary?, formatDescriptionOut: UnsafeMutablePointer) -> OSStatus`](/documentation/CoreMedia/CMFormatDescriptionCreate(allocator:mediaType:mediaSubType:extensions:formatDescriptionOut:)) Creates a format description for general use. ### Comparing Format Descriptions [`func CMFormatDescriptionEqual(CMFormatDescription?, otherFormatDescription: CMFormatDescription?) -> Bool`](/documentation/CoreMedia/CMFormatDescriptionEqual(_:otherFormatDescription:)) Returns a Boolean value that indicates whether two format descriptions are equal. [`func CMFormatDescriptionEqualIgnoringExtensionKeys(CMFormatDescription?, otherFormatDescription: CMFormatDescription?, extensionKeysToIgnore: CFTypeRef?, sampleDescriptionExtensionAtomKeysToIgnore: CFTypeRef?) -> Bool`](/documentation/CoreMedia/CMFormatDescriptionEqualIgnoringExtensionKeys(_:otherFormatDescription:extensionKeysToIgnore:sampleDescriptionExtensionAtomKeysToIgnore:)) Returns a Boolean value that indicates whether two format descriptions are equal, ignoring differences in the extension keys you specify. ### Inspecting Format Descriptions [`func CMFormatDescriptionGetMediaType(CMFormatDescription) -> CMMediaType`](/documentation/CoreMedia/CMFormatDescriptionGetMediaType(_:)) Returns the media type of a format description. [`func CMFormatDescriptionGetMediaSubType(CMFormatDescription) -> FourCharCode`](/documentation/CoreMedia/CMFormatDescriptionGetMediaSubType(_:)) Returns the media subtype of a format description. [`func CMFormatDescriptionGetExtension(CMFormatDescription, extensionKey: CFString) -> CFPropertyList?`](/documentation/CoreMedia/CMFormatDescriptionGetExtension(_:extensionKey:)) Returns an extension from the format description by using an extension key. [`func CMFormatDescriptionGetExtensions(CMFormatDescription) -> CFDictionary?`](/documentation/CoreMedia/CMFormatDescriptionGetExtensions(_:)) Returns all of the extensions for a format description. [`func CMFormatDescriptionGetTypeID() -> CFTypeID`](/documentation/CoreMedia/CMFormatDescriptionGetTypeID()) Returns the Core Foundation type identifier that identifies format description objects. ### Working with Audio Descriptions [`struct CMSoundDescriptionFlavor`](/documentation/CoreMedia/CMSoundDescriptionFlavor) Types that represent sound format descriptions. [`func CMAudioFormatDescriptionCreateSummary(allocator: CFAllocator?, formatDescriptionArray: CFArray, flags: UInt32, formatDescriptionOut: UnsafeMutablePointer) -> OSStatus`](/documentation/CoreMedia/CMAudioFormatDescriptionCreateSummary(allocator:formatDescriptionArray:flags:formatDescriptionOut:)) Creates a summary audio format description from an array of descriptions. [`func CMAudioFormatDescriptionCreate(allocator: CFAllocator?, asbd: UnsafePointer, layoutSize: Int, layout: UnsafePointer?, magicCookieSize: Int, magicCookie: UnsafeRawPointer?, extensions: CFDictionary?, formatDescriptionOut: UnsafeMutablePointer) -> OSStatus`](/documentation/CoreMedia/CMAudioFormatDescriptionCreate(allocator:asbd:layoutSize:layout:magicCookieSize:magicCookie:extensions:formatDescriptionOut:)) Creates a format description for an audio media stream. [`func CMAudioFormatDescriptionEqual(CMAudioFormatDescription, otherFormatDescription: CMAudioFormatDescription, equalityMask: CMAudioFormatDescriptionMask, equalityMaskOut: UnsafeMutablePointer?) -> Bool`](/documentation/CoreMedia/CMAudioFormatDescriptionEqual(_:otherFormatDescription:equalityMask:equalityMaskOut:)) Returns a Boolean value that indicates whether the two audio format descriptions are equal. [`func CMAudioFormatDescriptionGetChannelLayout(CMAudioFormatDescription, sizeOut: UnsafeMutablePointer?) -> UnsafePointer?`](/documentation/CoreMedia/CMAudioFormatDescriptionGetChannelLayout(_:sizeOut:)) Returns a read-only pointer to, and the size of, the audio channel layout inside an audio format description. [`func CMAudioFormatDescriptionGetFormatList(CMAudioFormatDescription, sizeOut: UnsafeMutablePointer?) -> UnsafePointer?`](/documentation/CoreMedia/CMAudioFormatDescriptionGetFormatList(_:sizeOut:)) Returns a read-only pointer to, and size of, the array of audio format list item structures in an audio format description. [`func CMAudioFormatDescriptionGetMagicCookie(CMAudioFormatDescription, sizeOut: UnsafeMutablePointer?) -> UnsafeRawPointer?`](/documentation/CoreMedia/CMAudioFormatDescriptionGetMagicCookie(_:sizeOut:)) Returns a read-only pointer to, and size of, the magic cookie in an audio format description. [`func CMAudioFormatDescriptionGetMostCompatibleFormat(CMAudioFormatDescription) -> UnsafePointer?`](/documentation/CoreMedia/CMAudioFormatDescriptionGetMostCompatibleFormat(_:)) Returns a read-only pointer to the appropriate audio format list item in an audio format description. [`func CMAudioFormatDescriptionGetRichestDecodableFormat(CMAudioFormatDescription) -> UnsafePointer?`](/documentation/CoreMedia/CMAudioFormatDescriptionGetRichestDecodableFormat(_:)) Returns a read-only pointer to the appropriate audio format list item in an audio format description. [`func CMAudioFormatDescriptionGetStreamBasicDescription(CMAudioFormatDescription) -> UnsafePointer?`](/documentation/CoreMedia/CMAudioFormatDescriptionGetStreamBasicDescription(_:)) Returns a read-only pointer to the audio stream description in an audio format description. [`func CMDoesBigEndianSoundDescriptionRequireLegacyCBRSampleTableLayout(CMBlockBuffer, flavor: CMSoundDescriptionFlavor?) -> Bool`](/documentation/CoreMedia/CMDoesBigEndianSoundDescriptionRequireLegacyCBRSampleTableLayout(_:flavor:)) Returns a Boolean value that indicates whether the sample tables need to use the legacy constant bit-rate encoding layout. [`func CMSwapBigEndianSoundDescriptionToHost(UnsafeMutablePointer, Int) -> OSStatus`](/documentation/CoreMedia/CMSwapBigEndianSoundDescriptionToHost(_:_:)) Converts a sound description data structure from big-endian to host-endian, in place. [`func CMSwapHostEndianSoundDescriptionToBig(UnsafeMutablePointer, Int) -> OSStatus`](/documentation/CoreMedia/CMSwapHostEndianSoundDescriptionToBig(_:_:)) Converts a sound description data structure from host-endian to big-endian, in place. [`func CMAudioFormatDescriptionCreateFromBigEndianSoundDescriptionData(allocator: CFAllocator?, bigEndianSoundDescriptionData: UnsafePointer, size: Int, flavor: CMSoundDescriptionFlavor?, formatDescriptionOut: UnsafeMutablePointer) -> OSStatus`](/documentation/CoreMedia/CMAudioFormatDescriptionCreateFromBigEndianSoundDescriptionData(allocator:bigEndianSoundDescriptionData:size:flavor:formatDescriptionOut:)) Creates an audio format description from a big-endian sound description data structure. [`func CMAudioFormatDescriptionCreateFromBigEndianSoundDescriptionBlockBuffer(allocator: CFAllocator?, bigEndianSoundDescriptionBlockBuffer: CMBlockBuffer, flavor: CMSoundDescriptionFlavor?, formatDescriptionOut: UnsafeMutablePointer) -> OSStatus`](/documentation/CoreMedia/CMAudioFormatDescriptionCreateFromBigEndianSoundDescriptionBlockBuffer(allocator:bigEndianSoundDescriptionBlockBuffer:flavor:formatDescriptionOut:)) Creates an audio format description from a big-endian sound description data structure in a buffer. [`func CMAudioFormatDescriptionCopyAsBigEndianSoundDescriptionBlockBuffer(allocator: CFAllocator?, audioFormatDescription: CMAudioFormatDescription, flavor: CMSoundDescriptionFlavor?, blockBufferOut: UnsafeMutablePointer) -> OSStatus`](/documentation/CoreMedia/CMAudioFormatDescriptionCopyAsBigEndianSoundDescriptionBlockBuffer(allocator:audioFormatDescription:flavor:blockBufferOut:)) Copies the contents of an audio format description to a buffer in big-endian byte ordering. ### Working with Video Descriptions [`struct CMImageDescriptionFlavor`](/documentation/CoreMedia/CMImageDescriptionFlavor) Types that represent image format descriptions. [`func CMVideoFormatDescriptionCreate(allocator: CFAllocator?, codecType: CMVideoCodecType, width: Int32, height: Int32, extensions: CFDictionary?, formatDescriptionOut: UnsafeMutablePointer) -> OSStatus`](/documentation/CoreMedia/CMVideoFormatDescriptionCreate(allocator:codecType:width:height:extensions:formatDescriptionOut:)) Creates a format description for a video media stream. [`func CMVideoFormatDescriptionCreateForImageBuffer(allocator: CFAllocator?, imageBuffer: CVImageBuffer, formatDescriptionOut: UnsafeMutablePointer) -> OSStatus`](/documentation/CoreMedia/CMVideoFormatDescriptionCreateForImageBuffer(allocator:imageBuffer:formatDescriptionOut:)) Creates a format description for a video media stream by using an image buffer. [`func CMVideoFormatDescriptionGetCleanAperture(CMVideoFormatDescription, originIsAtTopLeft: Bool) -> CGRect`](/documentation/CoreMedia/CMVideoFormatDescriptionGetCleanAperture(_:originIsAtTopLeft:)) Returns a rectangle that defines the portion of the encoded pixel dimensions that represent the image data that’s valid for displaying. [`func CMVideoFormatDescriptionGetDimensions(CMVideoFormatDescription) -> CMVideoDimensions`](/documentation/CoreMedia/CMVideoFormatDescriptionGetDimensions(_:)) Returns the video dimensions, in encoded pixels. [`func CMVideoFormatDescriptionGetExtensionKeysCommonWithImageBuffers() -> CFArray`](/documentation/CoreMedia/CMVideoFormatDescriptionGetExtensionKeysCommonWithImageBuffers()) Returns an array of keys that you use for video format description extensions, image buffer attachments, and attributes. [`func CMVideoFormatDescriptionGetPresentationDimensions(CMVideoFormatDescription, usePixelAspectRatio: Bool, useCleanAperture: Bool) -> CGSize`](/documentation/CoreMedia/CMVideoFormatDescriptionGetPresentationDimensions(_:usePixelAspectRatio:useCleanAperture:)) Returns the dimensions after taking the pixel aspect ratio and clean aperture into account. [`func CMVideoFormatDescriptionMatchesImageBuffer(CMVideoFormatDescription, imageBuffer: CVImageBuffer) -> Bool`](/documentation/CoreMedia/CMVideoFormatDescriptionMatchesImageBuffer(_:imageBuffer:)) Returns a Boolean value that indicates whether a format description matches an image buffer. [`func CMVideoFormatDescriptionCreateFromH264ParameterSets(allocator: CFAllocator?, parameterSetCount: Int, parameterSetPointers: UnsafePointer>, parameterSetSizes: UnsafePointer, nalUnitHeaderLength: Int32, formatDescriptionOut: UnsafeMutablePointer) -> OSStatus`](/documentation/CoreMedia/CMVideoFormatDescriptionCreateFromH264ParameterSets(allocator:parameterSetCount:parameterSetPointers:parameterSetSizes:nalUnitHeaderLength:formatDescriptionOut:)) Creates a format description for a video media stream that the parameter set describes. [`func CMVideoFormatDescriptionCreateFromHEVCParameterSets(allocator: CFAllocator?, parameterSetCount: Int, parameterSetPointers: UnsafePointer>, parameterSetSizes: UnsafePointer, nalUnitHeaderLength: Int32, extensions: CFDictionary?, formatDescriptionOut: UnsafeMutablePointer) -> OSStatus`](/documentation/CoreMedia/CMVideoFormatDescriptionCreateFromHEVCParameterSets(allocator:parameterSetCount:parameterSetPointers:parameterSetSizes:nalUnitHeaderLength:extensions:formatDescriptionOut:)) Creates a format description for a video media stream using HEVC (H.265) parameter set NAL units. [`func CMVideoFormatDescriptionGetH264ParameterSetAtIndex(CMFormatDescription, parameterSetIndex: Int, parameterSetPointerOut: UnsafeMutablePointer?>?, parameterSetSizeOut: UnsafeMutablePointer?, parameterSetCountOut: UnsafeMutablePointer?, nalUnitHeaderLengthOut: UnsafeMutablePointer?) -> OSStatus`](/documentation/CoreMedia/CMVideoFormatDescriptionGetH264ParameterSetAtIndex(_:parameterSetIndex:parameterSetPointerOut:parameterSetSizeOut:parameterSetCountOut:nalUnitHeaderLengthOut:)) Returns a parameter set that an H.264 format description contains. [`extern OSStatus CMVideoFormatDescriptionCopyTagCollectionArray(CMVideoFormatDescriptionRef formatDescription, CFArrayRef*tagCollectionsOut);`](/documentation/CoreMedia/CMVideoFormatDescriptionCopyTagCollectionArray) Copies the multi-image encoding properties as an array of CMTagCollections. [`func CMVideoFormatDescriptionCopyAsBigEndianImageDescriptionBlockBuffer(allocator: CFAllocator?, videoFormatDescription: CMVideoFormatDescription, stringEncoding: CFStringEncoding, flavor: CMImageDescriptionFlavor?, blockBufferOut: UnsafeMutablePointer) -> OSStatus`](/documentation/CoreMedia/CMVideoFormatDescriptionCopyAsBigEndianImageDescriptionBlockBuffer(allocator:videoFormatDescription:stringEncoding:flavor:blockBufferOut:)) Copies the contents of a video format description to a buffer in big-endian byte ordering. [`func CMVideoFormatDescriptionCreateFromBigEndianImageDescriptionBlockBuffer(allocator: CFAllocator?, bigEndianImageDescriptionBlockBuffer: CMBlockBuffer, stringEncoding: CFStringEncoding, flavor: CMImageDescriptionFlavor?, formatDescriptionOut: UnsafeMutablePointer) -> OSStatus`](/documentation/CoreMedia/CMVideoFormatDescriptionCreateFromBigEndianImageDescriptionBlockBuffer(allocator:bigEndianImageDescriptionBlockBuffer:stringEncoding:flavor:formatDescriptionOut:)) Creates a video format description from a big-endian image description inside a buffer. [`func CMVideoFormatDescriptionCreateFromBigEndianImageDescriptionData(allocator: CFAllocator?, bigEndianImageDescriptionData: UnsafePointer, size: Int, stringEncoding: CFStringEncoding, flavor: CMImageDescriptionFlavor?, formatDescriptionOut: UnsafeMutablePointer) -> OSStatus`](/documentation/CoreMedia/CMVideoFormatDescriptionCreateFromBigEndianImageDescriptionData(allocator:bigEndianImageDescriptionData:size:stringEncoding:flavor:formatDescriptionOut:)) Creates a video format description from a big-endian image description structure. [`func CMSwapBigEndianImageDescriptionToHost(UnsafeMutablePointer, Int) -> OSStatus`](/documentation/CoreMedia/CMSwapBigEndianImageDescriptionToHost(_:_:)) Converts an image description data structure from big-endian to host-endian, in place. [`func CMSwapHostEndianImageDescriptionToBig(UnsafeMutablePointer, Int) -> OSStatus`](/documentation/CoreMedia/CMSwapHostEndianImageDescriptionToBig(_:_:)) Converts an image description data structure from host-endian to big-endian, in place. ### Working with Muxed Descriptions [`func CMMuxedFormatDescriptionCreate(allocator: CFAllocator?, muxType: CMMuxedStreamType, extensions: CFDictionary?, formatDescriptionOut: UnsafeMutablePointer) -> OSStatus`](/documentation/CoreMedia/CMMuxedFormatDescriptionCreate(allocator:muxType:extensions:formatDescriptionOut:)) Creates a format description for a muxed media stream. ### Working with Metadata Descriptions [`struct CMMetadataDescriptionFlavor`](/documentation/CoreMedia/CMMetadataDescriptionFlavor) Types that represent metadata format descriptions. [`func CMMetadataFormatDescriptionCreateWithKeys(allocator: CFAllocator?, metadataType: CMMetadataFormatType, keys: CFArray?, formatDescriptionOut: UnsafeMutablePointer) -> OSStatus`](/documentation/CoreMedia/CMMetadataFormatDescriptionCreateWithKeys(allocator:metadataType:keys:formatDescriptionOut:)) Creates a metadata format description with the metadata keys you specify. [`func CMMetadataFormatDescriptionGetKeyWithLocalID(CMMetadataFormatDescription, localKeyID: OSType) -> CFDictionary?`](/documentation/CoreMedia/CMMetadataFormatDescriptionGetKeyWithLocalID(_:localKeyID:)) Returns the key for the local identifier. [`func CMMetadataFormatDescriptionCopyAsBigEndianMetadataDescriptionBlockBuffer(allocator: CFAllocator?, metadataFormatDescription: CMMetadataFormatDescription, flavor: CMMetadataDescriptionFlavor?, blockBufferOut: UnsafeMutablePointer) -> OSStatus`](/documentation/CoreMedia/CMMetadataFormatDescriptionCopyAsBigEndianMetadataDescriptionBlockBuffer(allocator:metadataFormatDescription:flavor:blockBufferOut:)) Copies the contents of a metadata format description to a buffer in big-endian byte order. [`func CMMetadataFormatDescriptionCreateByMergingMetadataFormatDescriptions(allocator: CFAllocator?, sourceDescription: CMMetadataFormatDescription, otherSourceDescription: CMMetadataFormatDescription, formatDescriptionOut: UnsafeMutablePointer) -> OSStatus`](/documentation/CoreMedia/CMMetadataFormatDescriptionCreateByMergingMetadataFormatDescriptions(allocator:sourceDescription:otherSourceDescription:formatDescriptionOut:)) Creates a metadata format description object by merging with another description. [`func CMMetadataFormatDescriptionCreateFromBigEndianMetadataDescriptionBlockBuffer(allocator: CFAllocator?, bigEndianMetadataDescriptionBlockBuffer: CMBlockBuffer, flavor: CMMetadataDescriptionFlavor?, formatDescriptionOut: UnsafeMutablePointer) -> OSStatus`](/documentation/CoreMedia/CMMetadataFormatDescriptionCreateFromBigEndianMetadataDescriptionBlockBuffer(allocator:bigEndianMetadataDescriptionBlockBuffer:flavor:formatDescriptionOut:)) Creates a metadata format description from a big-endian metadata description structure inside a buffer. [`func CMMetadataFormatDescriptionCreateFromBigEndianMetadataDescriptionData(allocator: CFAllocator?, bigEndianMetadataDescriptionData: UnsafePointer, size: Int, flavor: CMMetadataDescriptionFlavor?, formatDescriptionOut: UnsafeMutablePointer) -> OSStatus`](/documentation/CoreMedia/CMMetadataFormatDescriptionCreateFromBigEndianMetadataDescriptionData(allocator:bigEndianMetadataDescriptionData:size:flavor:formatDescriptionOut:)) Creates a metadata format description from a big-endian metadata description structure. [`func CMMetadataFormatDescriptionCreateWithMetadataFormatDescriptionAndMetadataSpecifications(allocator: CFAllocator?, sourceDescription: CMMetadataFormatDescription, metadataSpecifications: CFArray, formatDescriptionOut: UnsafeMutablePointer) -> OSStatus`](/documentation/CoreMedia/CMMetadataFormatDescriptionCreateWithMetadataFormatDescriptionAndMetadataSpecifications(allocator:sourceDescription:metadataSpecifications:formatDescriptionOut:)) Creates a metadata format description by extending an existing description with the values you specify. [`func CMMetadataFormatDescriptionCreateWithMetadataSpecifications(allocator: CFAllocator?, metadataType: CMMetadataFormatType, metadataSpecifications: CFArray, formatDescriptionOut: UnsafeMutablePointer) -> OSStatus`](/documentation/CoreMedia/CMMetadataFormatDescriptionCreateWithMetadataSpecifications(allocator:metadataType:metadataSpecifications:formatDescriptionOut:)) Creates a metadata format description with the specifications you specify. [`func CMSwapBigEndianMetadataDescriptionToHost(UnsafeMutablePointer, Int) -> OSStatus`](/documentation/CoreMedia/CMSwapBigEndianMetadataDescriptionToHost(_:_:)) Converts a metadata description data structure from big-endian to host-endian, in place. [`func CMSwapHostEndianMetadataDescriptionToBig(UnsafeMutablePointer, Int) -> OSStatus`](/documentation/CoreMedia/CMSwapHostEndianMetadataDescriptionToBig(_:_:)) Converts a metadata description data structure from host-endian to big-endian, in place. [`func CMMetadataFormatDescriptionGetIdentifiers(CMMetadataFormatDescription) -> CFArray?`](/documentation/CoreMedia/CMMetadataFormatDescriptionGetIdentifiers(_:)) Returns an array of metadata identifiers from a metadata format description. ### Working with Text Descriptions [`struct CMTextDescriptionFlavor`](/documentation/CoreMedia/CMTextDescriptionFlavor) Types that represent text format descriptions. [`func CMTextFormatDescriptionGetDefaultStyle(CMFormatDescription, localFontIDOut: UnsafeMutablePointer?, boldOut: UnsafeMutablePointer?, italicOut: UnsafeMutablePointer?, underlineOut: UnsafeMutablePointer?, fontSizeOut: UnsafeMutablePointer?, colorComponentsOut: UnsafeMutablePointer?) -> OSStatus`](/documentation/CoreMedia/CMTextFormatDescriptionGetDefaultStyle(_:localFontIDOut:boldOut:italicOut:underlineOut:fontSizeOut:colorComponentsOut:)) Returns the default text style. [`func CMTextFormatDescriptionGetDefaultTextBox(CMFormatDescription, originIsAtTopLeft: Bool, heightOfTextTrack: CGFloat, defaultTextBoxOut: UnsafeMutablePointer) -> OSStatus`](/documentation/CoreMedia/CMTextFormatDescriptionGetDefaultTextBox(_:originIsAtTopLeft:heightOfTextTrack:defaultTextBoxOut:)) Returns the default text box. [`func CMTextFormatDescriptionGetDisplayFlags(CMFormatDescription, displayFlagsOut: UnsafeMutablePointer) -> OSStatus`](/documentation/CoreMedia/CMTextFormatDescriptionGetDisplayFlags(_:displayFlagsOut:)) Returns the display flags. [`func CMTextFormatDescriptionGetFontName(CMFormatDescription, localFontID: UInt16, fontNameOut: AutoreleasingUnsafeMutablePointer) -> OSStatus`](/documentation/CoreMedia/CMTextFormatDescriptionGetFontName(_:localFontID:fontNameOut:)) Returns a font name for a local font identifier. [`func CMTextFormatDescriptionGetJustification(CMFormatDescription, horizontalOut: UnsafeMutablePointer?, verticalOut: UnsafeMutablePointer?) -> OSStatus`](/documentation/CoreMedia/CMTextFormatDescriptionGetJustification(_:horizontalOut:verticalOut:)) Returns the horizontal and vertical justification. [`func CMTextFormatDescriptionCopyAsBigEndianTextDescriptionBlockBuffer(allocator: CFAllocator?, textFormatDescription: CMTextFormatDescription, flavor: CMTextDescriptionFlavor?, blockBufferOut: UnsafeMutablePointer) -> OSStatus`](/documentation/CoreMedia/CMTextFormatDescriptionCopyAsBigEndianTextDescriptionBlockBuffer(allocator:textFormatDescription:flavor:blockBufferOut:)) Copies the contents of a text format description to a buffer in big-endian byte order. [`func CMTextFormatDescriptionCreateFromBigEndianTextDescriptionBlockBuffer(allocator: CFAllocator?, bigEndianTextDescriptionBlockBuffer: CMBlockBuffer, flavor: CMTextDescriptionFlavor?, mediaType: CMMediaType, formatDescriptionOut: UnsafeMutablePointer) -> OSStatus`](/documentation/CoreMedia/CMTextFormatDescriptionCreateFromBigEndianTextDescriptionBlockBuffer(allocator:bigEndianTextDescriptionBlockBuffer:flavor:mediaType:formatDescriptionOut:)) Creates a text format description from a big-endian text description structure inside a buffer. [`func CMTextFormatDescriptionCreateFromBigEndianTextDescriptionData(allocator: CFAllocator?, bigEndianTextDescriptionData: UnsafePointer, size: Int, flavor: CMTextDescriptionFlavor?, mediaType: CMMediaType, formatDescriptionOut: UnsafeMutablePointer) -> OSStatus`](/documentation/CoreMedia/CMTextFormatDescriptionCreateFromBigEndianTextDescriptionData(allocator:bigEndianTextDescriptionData:size:flavor:mediaType:formatDescriptionOut:)) Creates a text format description from a big-endian text description structure. [`func CMSwapBigEndianTextDescriptionToHost(UnsafeMutablePointer, Int) -> OSStatus`](/documentation/CoreMedia/CMSwapBigEndianTextDescriptionToHost(_:_:)) Converts a text description structure from big-endian to host-endian, in place. [`func CMSwapHostEndianTextDescriptionToBig(UnsafeMutablePointer, Int) -> OSStatus`](/documentation/CoreMedia/CMSwapHostEndianTextDescriptionToBig(_:_:)) Converts a text description structure from host-endian to big-endian, in place. ### Working with Time Code Descriptions [`struct CMTimeCodeDescriptionFlavor`](/documentation/CoreMedia/CMTimeCodeDescriptionFlavor) Types that represent time code format descriptions. [`func CMTimeCodeFormatDescriptionCreate(allocator: CFAllocator?, timeCodeFormatType: CMTimeCodeFormatType, frameDuration: CMTime, frameQuanta: UInt32, flags: UInt32, extensions: CFDictionary?, formatDescriptionOut: UnsafeMutablePointer) -> OSStatus`](/documentation/CoreMedia/CMTimeCodeFormatDescriptionCreate(allocator:timeCodeFormatType:frameDuration:frameQuanta:flags:extensions:formatDescriptionOut:)) Creates a format description for time code media. [`func CMTimeCodeFormatDescriptionGetFrameDuration(CMTimeCodeFormatDescription) -> CMTime`](/documentation/CoreMedia/CMTimeCodeFormatDescriptionGetFrameDuration(_:)) Returns the duration of each frame. [`func CMTimeCodeFormatDescriptionGetFrameQuanta(CMTimeCodeFormatDescription) -> UInt32`](/documentation/CoreMedia/CMTimeCodeFormatDescriptionGetFrameQuanta(_:)) Returns the frames per second for a time code, or frames per tick in counter mode. [`func CMTimeCodeFormatDescriptionGetTimeCodeFlags(CMTimeCodeFormatDescription) -> UInt32`](/documentation/CoreMedia/CMTimeCodeFormatDescriptionGetTimeCodeFlags(_:)) Returns time code flags. [`func CMTimeCodeFormatDescriptionCopyAsBigEndianTimeCodeDescriptionBlockBuffer(allocator: CFAllocator?, timeCodeFormatDescription: CMTimeCodeFormatDescription, flavor: CMTimeCodeDescriptionFlavor?, blockBufferOut: UnsafeMutablePointer) -> OSStatus`](/documentation/CoreMedia/CMTimeCodeFormatDescriptionCopyAsBigEndianTimeCodeDescriptionBlockBuffer(allocator:timeCodeFormatDescription:flavor:blockBufferOut:)) Copies the contents of a time code format description to a buffer in big-endian byte order. [`func CMTimeCodeFormatDescriptionCreateFromBigEndianTimeCodeDescriptionBlockBuffer(allocator: CFAllocator?, bigEndianTimeCodeDescriptionBlockBuffer: CMBlockBuffer, flavor: CMTimeCodeDescriptionFlavor?, formatDescriptionOut: UnsafeMutablePointer) -> OSStatus`](/documentation/CoreMedia/CMTimeCodeFormatDescriptionCreateFromBigEndianTimeCodeDescriptionBlockBuffer(allocator:bigEndianTimeCodeDescriptionBlockBuffer:flavor:formatDescriptionOut:)) Creates a time code format description from a big-endian time code description data structure in a buffer. [`func CMTimeCodeFormatDescriptionCreateFromBigEndianTimeCodeDescriptionData(allocator: CFAllocator?, bigEndianTimeCodeDescriptionData: UnsafePointer, size: Int, flavor: CMTimeCodeDescriptionFlavor?, formatDescriptionOut: UnsafeMutablePointer) -> OSStatus`](/documentation/CoreMedia/CMTimeCodeFormatDescriptionCreateFromBigEndianTimeCodeDescriptionData(allocator:bigEndianTimeCodeDescriptionData:size:flavor:formatDescriptionOut:)) Creates a time code format description from a big-endian time code description structure. [`func CMSwapBigEndianTimeCodeDescriptionToHost(UnsafeMutablePointer, Int) -> OSStatus`](/documentation/CoreMedia/CMSwapBigEndianTimeCodeDescriptionToHost(_:_:)) Converts a time code description data structure from big-endian to host-endian, in place. [`func CMSwapHostEndianTimeCodeDescriptionToBig(UnsafeMutablePointer, Int) -> OSStatus`](/documentation/CoreMedia/CMSwapHostEndianTimeCodeDescriptionToBig(_:_:)) Converts a time code description data structure from host-endian to big-endian, in place. ### Working with Closed Captioning Descriptions [`struct CMClosedCaptionDescriptionFlavor`](/documentation/CoreMedia/CMClosedCaptionDescriptionFlavor) Types that represent closed caption format descriptions. [`func CMClosedCaptionFormatDescriptionCopyAsBigEndianClosedCaptionDescriptionBlockBuffer(allocator: CFAllocator?, closedCaptionFormatDescription: CMClosedCaptionFormatDescription, flavor: CMClosedCaptionDescriptionFlavor?, blockBufferOut: UnsafeMutablePointer) -> OSStatus`](/documentation/CoreMedia/CMClosedCaptionFormatDescriptionCopyAsBigEndianClosedCaptionDescriptionBlockBuffer(allocator:closedCaptionFormatDescription:flavor:blockBufferOut:)) Copies the contents of a closed caption format description to a buffer in big-endian byte order. [`func CMClosedCaptionFormatDescriptionCreateFromBigEndianClosedCaptionDescriptionBlockBuffer(allocator: CFAllocator?, bigEndianClosedCaptionDescriptionBlockBuffer: CMBlockBuffer, flavor: CMClosedCaptionDescriptionFlavor?, formatDescriptionOut: UnsafeMutablePointer) -> OSStatus`](/documentation/CoreMedia/CMClosedCaptionFormatDescriptionCreateFromBigEndianClosedCaptionDescriptionBlockBuffer(allocator:bigEndianClosedCaptionDescriptionBlockBuffer:flavor:formatDescriptionOut:)) Creates a closed caption format description from a big-endian closed caption description structure in a buffer. [`func CMClosedCaptionFormatDescriptionCreateFromBigEndianClosedCaptionDescriptionData(allocator: CFAllocator?, bigEndianClosedCaptionDescriptionData: UnsafePointer, size: Int, flavor: CMClosedCaptionDescriptionFlavor?, formatDescriptionOut: UnsafeMutablePointer) -> OSStatus`](/documentation/CoreMedia/CMClosedCaptionFormatDescriptionCreateFromBigEndianClosedCaptionDescriptionData(allocator:bigEndianClosedCaptionDescriptionData:size:flavor:formatDescriptionOut:)) Creates a closed caption format description from a big-endian closed caption description structure. [`func CMSwapHostEndianClosedCaptionDescriptionToBig(UnsafeMutablePointer, Int) -> OSStatus`](/documentation/CoreMedia/CMSwapHostEndianClosedCaptionDescriptionToBig(_:_:)) Converts a closed caption description structure from host-endian to big-endian, in place. [`func CMSwapBigEndianClosedCaptionDescriptionToHost(UnsafeMutablePointer, Int) -> OSStatus`](/documentation/CoreMedia/CMSwapBigEndianClosedCaptionDescriptionToHost(_:_:)) Converts a closed caption description structure from big-endian to host-endian, in place. ### Format Description Types [`class CMFormatDescription`](/documentation/CoreMedia/CMFormatDescription) An object that describes a media format descriptor. [`typealias CMAudioFormatDescription`](/documentation/CoreMedia/CMAudioFormatDescription) A type you use to interact with audio format descriptions. [`typealias CMClosedCaptionFormatDescription`](/documentation/CoreMedia/CMClosedCaptionFormatDescription) A type you use to interact with closed caption format descriptions. [`typealias CMMetadataFormatDescription`](/documentation/CoreMedia/CMMetadataFormatDescription) A type you use to interact with metadata format descriptions. [`typealias CMMuxedFormatDescription`](/documentation/CoreMedia/CMMuxedFormatDescription) A type you use to interact with muxed format descriptions. [`typealias CMTextFormatDescription`](/documentation/CoreMedia/CMTextFormatDescription) A type you use to interact with text format descriptions. [`typealias CMTimeCodeFormatDescription`](/documentation/CoreMedia/CMTimeCodeFormatDescription) A type you use to interact with time code format descriptions. [`typealias CMVideoFormatDescription`](/documentation/CoreMedia/CMVideoFormatDescription) A type you use to interact with video format descriptions. ### Format Description Extension Keys [`let kCMFormatDescriptionExtension_ContentColorVolume: CFString`](/documentation/CoreMedia/kCMFormatDescriptionExtension_ContentColorVolume) [`let kCMFormatDescriptionExtension_HasAdditionalViews: CFString`](/documentation/CoreMedia/kCMFormatDescriptionExtension_HasAdditionalViews) [`let kCMFormatDescriptionExtension_HasLeftStereoEyeView: CFString`](/documentation/CoreMedia/kCMFormatDescriptionExtension_HasLeftStereoEyeView) [`let kCMFormatDescriptionExtension_HasRightStereoEyeView: CFString`](/documentation/CoreMedia/kCMFormatDescriptionExtension_HasRightStereoEyeView) [`let kCMFormatDescriptionExtension_HeroEye: CFString`](/documentation/CoreMedia/kCMFormatDescriptionExtension_HeroEye) [`let kCMFormatDescriptionExtension_HorizontalDisparityAdjustment: CFString`](/documentation/CoreMedia/kCMFormatDescriptionExtension_HorizontalDisparityAdjustment) [`let kCMFormatDescriptionExtension_LogTransferFunction: CFString`](/documentation/CoreMedia/kCMFormatDescriptionExtension_LogTransferFunction) [`let kCMFormatDescriptionExtension_StereoCameraBaseline: CFString`](/documentation/CoreMedia/kCMFormatDescriptionExtension_StereoCameraBaseline) [`let kCMFormatDescriptionHeroEye_Left: CFString`](/documentation/CoreMedia/kCMFormatDescriptionHeroEye_Left) [`let kCMFormatDescriptionHeroEye_Right: CFString`](/documentation/CoreMedia/kCMFormatDescriptionHeroEye_Right) ### Format Types [`typealias CMClosedCaptionFormatType`](/documentation/CoreMedia/CMClosedCaptionFormatType) A closed caption format type. [`typealias CMMetadataFormatType`](/documentation/CoreMedia/CMMetadataFormatType) A metadata format type. [Metadata Format Types](/documentation/CoreMedia/metadata-format-types) Constants that represent media format types. [`typealias CMSubtitleFormatType`](/documentation/CoreMedia/CMSubtitleFormatType) A type that represents a text subtitle format. [Subtitle Format Types](/documentation/CoreMedia/subtitle-format-types) Constants that represent subtitle format types. [`typealias CMTimeCodeFormatType`](/documentation/CoreMedia/CMTimeCodeFormatType) A time code format type. [Time Code Formats](/documentation/CoreMedia/time-code-formats) Constants that represent time code format types. [`typealias CMTextFormatType`](/documentation/CoreMedia/CMTextFormatType) A text format type. [`typealias CMPixelFormatType`](/documentation/CoreMedia/CMPixelFormatType) A pixel format type. [Tagged Buffer Group Format Types](/documentation/CoreMedia/tagged-buffergroup-format-types) ### Data Types [`struct CMVideoDimensions`](/documentation/CoreMedia/CMVideoDimensions) A structure that represents video dimensions. [`typealias CMAudioFormatDescriptionMask`](/documentation/CoreMedia/CMAudioFormatDescriptionMask) A type for mask bits that represent parts of an audio format description. [`typealias CMMediaType`](/documentation/CoreMedia/CMMediaType) Constants that represent media types. [`typealias CMAudioCodecType`](/documentation/CoreMedia/CMAudioCodecType) An audio codec type. [`typealias CMVideoCodecType`](/documentation/CoreMedia/CMVideoCodecType) A video codec type. [`typealias CMTextDisplayFlags`](/documentation/CoreMedia/CMTextDisplayFlags) An integer value that describes the display mode flags for text media. [`typealias CMTextJustificationValue`](/documentation/CoreMedia/CMTextJustificationValue) An integer value that describes the justification modes for text media. [Media Type Constants](/documentation/CoreMedia/media-type-constants) Constants that represent media types. [Muxed Stream Types](/documentation/CoreMedia/muxed-stream-types) Constants that represent muxed stream types. [Audio Codec Types](/documentation/CoreMedia/audio-codec-types) Constants that represent audio codec types. ### Constants [Audio Format Description Mask Codes](/documentation/CoreMedia/audio-format-desc-codes) Mask codes that identify audio formats. [Chroma Location Extension Constants](/documentation/CoreMedia/chroma-location-extension-constants) Constants that identify chroma location extensions. [Clean Aperture Extension Constants](/documentation/CoreMedia/clean-aperture-extension-constants) Constants that identify clean aperture extensions. [Closed Caption Format Type Constants](/documentation/CoreMedia/closed-caption-formats) Types that identify closed caption formats. [Color Primary Extension Constants](/documentation/CoreMedia/color-primary-extension-constants) Constants that identify color primary extensions. [Field Detail Extension Constants](/documentation/CoreMedia/field-detail-extension-constants) Constants that identify field detail extensions. [Format Description Bridge Error Codes](/documentation/CoreMedia/format-description-bridge-errors) Bridge errors the system returns from format description calls. [Format Description Constants](/documentation/CoreMedia/format-description-constants) Constants that identify format descriptions. [Format Description Error Codes](/documentation/CoreMedia/format-description-errors) Errors the system returns from format description calls. [HEVC Temporal Level Info Constants](/documentation/CoreMedia/hevc-temporal-level-info-constants) Constants that identify HEVC temporal level information. [Metadata Format Description Constants](/documentation/CoreMedia/metadata-format-description-constants) Constants that identify metadata format descriptions. [MPEG-2-conformant Formats](/documentation/CoreMedia/mpeg-2-conformant-formats) Constants that identify MPEG-2 formats. [Pixel Aspect Ratio Extension Constants](/documentation/CoreMedia/pixel-aspect-ratio-extension-constants) Constants that identify pixel aspect ratio extensions. [Text Display Flags](/documentation/CoreMedia/text-display-flags) Flags that identify text display methods. [Text Format Constants](/documentation/CoreMedia/text-format-constants) Types that identify text formats. [Text Format Description Constants](/documentation/CoreMedia/text-format-description-constants) Constants that identify text format descriptions. [Text Justification Constants](/documentation/CoreMedia/text-justification-constants) Types that identify text justifications. [Time Code Flags](/documentation/CoreMedia/time-code-flags) Flags that identify time codes. [Time Code Format Description Constants](/documentation/CoreMedia/time-code-format-description-constants) Constants that identify time code format descriptions. [Transfer Function Extension Constants](/documentation/CoreMedia/transfer-function-extension-constants) Constants that identify transfer function extensions. [Video Codec Constants](/documentation/CoreMedia/video-codec-constants) Types that identify video codecs. [Video Pixel Formats](/documentation/CoreMedia/video-pixel-formats) Constants that identify video pixel formats. [Video Profile Constants](/documentation/CoreMedia/video-profile-constants) Constants that identify video profiles. [YCbCrMatrix Extension Constants](/documentation/CoreMedia/ycbcrmatrix-extension-constants) Constants that identify YCbCrMatrix extensions. --- Copyright © 2026 Apple Inc. All rights reserved. | [Terms of Use](https://www.apple.com/legal/internet-services/terms/site.html) | [Privacy Policy](https://www.apple.com/privacy/privacy-policy)