# CMIOExtensionStreamProperties An object that describes the properties of an extension stream. ``` class CMIOExtensionStreamProperties ``` ## Topics ### Creating Stream Properties [`+ (instancetype) streamPropertiesWithDictionary:(NSDictionary *) propertiesDictionary;`](/documentation/CoreMediaIO/CMIOExtensionStreamProperties/streamPropertiesWithDictionary:) Returns a new properties object that provides the specified properties and default states. [`init(dictionary: [CMIOExtensionProperty : CMIOExtensionPropertyState])`](/documentation/CoreMediaIO/CMIOExtensionStreamProperties/init(dictionary:)) Creates a properties object that provides the specified properties and default states. ### Configuring Sink Properties [`var sinkBufferQueueSize: Int?`](/documentation/CoreMediaIO/CMIOExtensionStreamProperties/sinkBufferQueueSize-9b80c) The buffer queue size. [`var sinkBuffersRequiredForStartup: Int?`](/documentation/CoreMediaIO/CMIOExtensionStreamProperties/sinkBuffersRequiredForStartup-1bgyq) The number of buffers the stream requires for startup. [`var sinkBufferUnderrunCount: Int?`](/documentation/CoreMediaIO/CMIOExtensionStreamProperties/sinkBufferUnderrunCount-1qmbb) The buffer underrun count. [`var sinkEndOfData: Int?`](/documentation/CoreMediaIO/CMIOExtensionStreamProperties/sinkEndOfData-8fswu) A value that indicates whether the stream has reached its end. [`@property (atomic, strong, nullable) NSNumber * sinkBufferQueueSize;`](/documentation/CoreMediaIO/CMIOExtensionStreamProperties/sinkBufferQueueSize-4kpug) The buffer queue size. [`@property (atomic, strong, nullable) NSNumber * sinkBuffersRequiredForStartup;`](/documentation/CoreMediaIO/CMIOExtensionStreamProperties/sinkBuffersRequiredForStartup-4b5te) The number of buffers the stream requires for startup. [`@property (atomic, strong, nullable) NSNumber * sinkBufferUnderrunCount;`](/documentation/CoreMediaIO/CMIOExtensionStreamProperties/sinkBufferUnderrunCount-9sph5) The buffer underrun count. [`@property (atomic, strong, nullable) NSNumber * sinkEndOfData;`](/documentation/CoreMediaIO/CMIOExtensionStreamProperties/sinkEndOfData-30he9) A value that indicates whether the stream has reached its end. ### Configuring Source Properties [`var activeFormatIndex: Int?`](/documentation/CoreMediaIO/CMIOExtensionStreamProperties/activeFormatIndex-83u7z) The index of the active format. [`var frameDuration: CMTime?`](/documentation/CoreMediaIO/CMIOExtensionStreamProperties/frameDuration-4rnl9) The duration of the frame. [`var maxFrameDuration: CMTime?`](/documentation/CoreMediaIO/CMIOExtensionStreamProperties/maxFrameDuration-5qqg) The maximum duration of a frame. [`@property (atomic, strong, nullable) NSNumber * activeFormatIndex;`](/documentation/CoreMediaIO/CMIOExtensionStreamProperties/activeFormatIndex-8czm7) The index of the active format. [`@property (atomic, strong, nullable) NSDictionary * frameDuration;`](/documentation/CoreMediaIO/CMIOExtensionStreamProperties/frameDuration-lrfi) A dictionary representation of a frame duration. [`@property (atomic, strong, nullable) NSDictionary * maxFrameDuration;`](/documentation/CoreMediaIO/CMIOExtensionStreamProperties/maxFrameDuration-8fo5t) The maximum duration of a frame. ### Managing Property State [`var propertiesDictionary: [CMIOExtensionProperty : CMIOExtensionPropertyState]`](/documentation/CoreMediaIO/CMIOExtensionStreamProperties/propertiesDictionary) A dictionary representation of the property state. [`func setPropertyState(CMIOExtensionPropertyState?, forProperty: CMIOExtensionProperty)`](/documentation/CoreMediaIO/CMIOExtensionStreamProperties/setPropertyState(_:forProperty:)) Sets the state of the specified property. ## Relationships ### Conforms To [`CustomStringConvertible`](/documentation/Swift/CustomStringConvertible) [`Equatable`](/documentation/Swift/Equatable) [`CustomDebugStringConvertible`](/documentation/Swift/CustomDebugStringConvertible) [`NSObjectProtocol`](/documentation/ObjectiveC/NSObjectProtocol) [`Hashable`](/documentation/Swift/Hashable) [`CVarArg`](/documentation/Swift/CVarArg) ### Inherits From [`NSObject-swift.class`](/documentation/ObjectiveC/NSObject-swift.class) --- 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)