# Audio Queue Property IDs ## Topics ### Constants [`var kAudioQueueDeviceProperty_NumberChannels: AudioQueuePropertyID`](/documentation/AudioToolbox/kAudioQueueDeviceProperty_NumberChannels) Value is a read-only `UInt32` value representing the number of channels in the audio hardware device associated with an audio queue. [`var kAudioQueueDeviceProperty_SampleRate: AudioQueuePropertyID`](/documentation/AudioToolbox/kAudioQueueDeviceProperty_SampleRate) Value is a read-only `Float64` value representing the sampling rate of the audio hardware device associated with an audio queue. [`var kAudioQueueProperty_ChannelLayout: AudioQueuePropertyID`](/documentation/AudioToolbox/kAudioQueueProperty_ChannelLayout) Describes an audio queue channel layout. [`var kAudioQueueProperty_ConverterError: AudioQueuePropertyID`](/documentation/AudioToolbox/kAudioQueueProperty_ConverterError) Value is a read-only `UInt32` value that indicates the most recent error (if any) encountered by the audio queue’s internal encoding/decoding process. [`var kAudioQueueProperty_CurrentDevice: AudioQueuePropertyID`](/documentation/AudioToolbox/kAudioQueueProperty_CurrentDevice) The unique identifier (UID) of the audio hardware device. [`var kAudioQueueProperty_CurrentLevelMeter: AudioQueuePropertyID`](/documentation/AudioToolbox/kAudioQueueProperty_CurrentLevelMeter) A read-only array of level meter status structures. [`var kAudioQueueProperty_CurrentLevelMeterDB: AudioQueuePropertyID`](/documentation/AudioToolbox/kAudioQueueProperty_CurrentLevelMeterDB) Value is a read-only array of [`AudioQueueLevelMeterState`](/documentation/AudioToolbox/AudioQueueLevelMeterState) structures, one array element per audio channel. The member values in the structure are in decibels. [`var kAudioQueueProperty_DecodeBufferSizeFrames: AudioQueuePropertyID`](/documentation/AudioToolbox/kAudioQueueProperty_DecodeBufferSizeFrames) Value is a read/write `UInt32` value that is the size of the buffer into which a playback (output) audio queue decodes buffers. A larger buffer provides more reliability and better long-term performance at the expense of memory and decreased responsiveness in some situations. [`var kAudioQueueProperty_EnableLevelMetering: AudioQueuePropertyID`](/documentation/AudioToolbox/kAudioQueueProperty_EnableLevelMetering) Value is a read/write `UInt32` value that indicates whether audio level metering is enabled for an audio queue. `0` = metering off, `1` = metering on. [`var kAudioQueueProperty_EnableTimePitch: AudioQueuePropertyID`](/documentation/AudioToolbox/kAudioQueueProperty_EnableTimePitch) [`var kAudioQueueProperty_IsRunning: AudioQueuePropertyID`](/documentation/AudioToolbox/kAudioQueueProperty_IsRunning) Value is a read-only `UInt32` value indicating whether or not the audio queue is running. A nonzero value means running; `0` means stopped. A notification is sent when the associated audio queue starts or stops, which may occur sometime after the [`AudioQueueStart(_:_:)`](/documentation/AudioToolbox/AudioQueueStart(_:_:)) or [`AudioQueueStop(_:_:)`](/documentation/AudioToolbox/AudioQueueStop(_:_:)) function is called. [`var kAudioQueueProperty_MagicCookie: AudioQueuePropertyID`](/documentation/AudioToolbox/kAudioQueueProperty_MagicCookie) Value is a read/write void pointer to a block of memory, which you set up, containing an audio format magic cookie. If the audio format you are playing or recording to requires a magic cookie, you must set a value for this property before enqueuing any buffers. [`var kAudioQueueProperty_MaximumOutputPacketSize: AudioQueuePropertyID`](/documentation/AudioToolbox/kAudioQueueProperty_MaximumOutputPacketSize) Value is a read-only`UInt32` value that is the size, in bytes, of the largest single packet of data in the output format. Primarily useful when encoding VBR compressed data. [`var kAudioQueueProperty_StreamDescription: AudioQueuePropertyID`](/documentation/AudioToolbox/kAudioQueueProperty_StreamDescription) An audio queue’s data format. [`var kAudioQueueProperty_TimePitchAlgorithm: AudioQueuePropertyID`](/documentation/AudioToolbox/kAudioQueueProperty_TimePitchAlgorithm) [`var kAudioQueueProperty_TimePitchBypass: AudioQueuePropertyID`](/documentation/AudioToolbox/kAudioQueueProperty_TimePitchBypass) --- 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)