# CMAudioClock A specialized reference clock that synchronizes with audio sources. ## Discussion An audio clock is a specialized [`CMClock`](/documentation/CoreMedia/CMClock) that you use to synchronize with audio sources. For details on clocks and synchronization, see [`CMClock`](/documentation/CoreMedia/CMClock). ## Topics ### Creating Audio Clocks [`CMAudioClockCreate(allocator:clockOut:)`](/documentation/CoreMedia/CMAudioClockCreate(allocator:clockOut:)) Creates a clock that advances at the same rate as audio output. [`CMAudioDeviceClockCreate(allocator:deviceUID:clockOut:)`](/documentation/CoreMedia/CMAudioDeviceClockCreate(allocator:deviceUID:clockOut:)) Creates a clock that tracks playback through a Core Audio device with the specified unique identifier. [`CMAudioDeviceClockCreateFromAudioDeviceID(allocator:deviceID:clockOut:)`](/documentation/CoreMedia/CMAudioDeviceClockCreateFromAudioDeviceID(allocator:deviceID:clockOut:)) Creates a clock that tracks playback through a Core Audio device with the specified identifier. ### Configuring Audio Clocks [`CMAudioDeviceClockGetAudioDevice(_:deviceUIDOut:deviceIDOut:trackingDefaultDeviceOut:)`](/documentation/CoreMedia/CMAudioDeviceClockGetAudioDevice(_:deviceUIDOut:deviceIDOut:trackingDefaultDeviceOut:)) Returns the Core Audio device the clock is tracking. [`CMAudioDeviceClockSetAudioDeviceUID(_:deviceUID:)`](/documentation/CoreMedia/CMAudioDeviceClockSetAudioDeviceUID(_:deviceUID:)) Changes the Core Audio device the clock is tracking by specifying a new device unique identifier. [`CMAudioDeviceClockSetAudioDeviceID(_:deviceID:)`](/documentation/CoreMedia/CMAudioDeviceClockSetAudioDeviceID(_:deviceID:)) Changes the Core Audio device the clock is tracking by specifying a new device identifier. --- 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)