Returns the specified extension of a CMFormatDescription.


func CMFormatDescriptionGetExtension(_ desc: CMFormatDescription, extensionKey: CFString) -> CFPropertyList?



CMFormatDescription being interrogated.


Key of extension to be returned. Cannot be NULL.

Return Value

The specified extension of the CMFormatDescription. May be NULL.


If the named extension does not exist, NULL is returned. The extension is always a valid property list object. This means that it will be either a CFNumber, CFString, CFBoolean, CFArray, CFDictionary, CFDate, or CFData. If it is a CFDictionary, the keys will all be CFStrings. The returned extension is not retained by this call, so it is only valid as long as the CMFormatDescription is valid. Clients are required to retain it if they need to keep it longer.

See Also

Common Functions

func CMFormatDescriptionCreate(allocator: CFAllocator?, mediaType: CMMediaType, mediaSubType: FourCharCode, extensions: CFDictionary?, formatDescriptionOut: UnsafeMutablePointer<CMFormatDescription?>) -> OSStatus

Creates a generic CMFormatDescription object. You should not call this method for the media types that has specific create functions such as audio, video, text, muxed, metaData and timeCode.

func CMFormatDescriptionEqualIgnoringExtensionKeys(CMFormatDescription?, otherFormatDescription: CMFormatDescription?, extensionKeysToIgnore: CFTypeRef?, sampleDescriptionExtensionAtomKeysToIgnore: CFTypeRef?) -> Bool

Compares two CMFormatDescription objects for equality, ignoring differences in the specified lists of format description extension keys and sample description extension keys.

func CMFormatDescriptionGetExtensions(CMFormatDescription) -> CFDictionary?

Returns an immutable dictionary containing all the extensions of a CMFormatDescription.

func CMFormatDescriptionGetMediaSubType(CMFormatDescription) -> FourCharCode

Returns the media subtype of a CMFormatDescription.

func CMFormatDescriptionGetMediaType(CMFormatDescription) -> CMMediaType

Returns the media type of a CMFormatDescription.

func CMFormatDescriptionGetTypeID() -> CFTypeID

Returns the CFTypeID of CMFormatDescription objects.