# AudioDeviceStartAtTime(_:_:_:_:) ``` func AudioDeviceStartAtTime(_ inDevice: AudioObjectID, _ inProcID: AudioDeviceIOProcID?, _ ioRequestedStartTime: UnsafeMutablePointer, _ inFlags: UInt32) -> OSStatus ``` ## Parameters `inDevice` The AudioDevice to start the IOProc on. `inProcID` The AudioDeviceIOProcID to start. Note that this can be NULL, which starts the hardware regardless of whether or not there are any IOProcs registered. `ioRequestedStartTime` A pointer to an AudioTimeStamp that, on entry, is the requested time to start the IOProc. On exit, it will be the actual time the IOProc will start. `inFlags` A UInt32 containing flags that modify how this function behaves. ## Return Value An OSStatus indicating success or failure. kAudioHardwareUnsupportedOperationError will be returned if the AudioDevice does not support starting at a specific time and inProc and ioRequestedStartTime are not NULL. ## Discussion \abstract Starts IO for the given AudioDeviceIOProcID and aligns the IO cycle of the AudioDevice with the given time. --- 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)