# AudioQueueInputCallback Called by the system when a recording audio queue has finished filling an audio queue buffer. ``` typealias AudioQueueInputCallback = (UnsafeMutableRawPointer?, AudioQueueRef, AudioQueueBufferRef, UnsafePointer, UInt32, UnsafePointer?) -> Void ``` ## Parameters `inUserData` The custom data you’ve specified in the `inUserData` parameter of the [`AudioQueueNewInput(_:_:_:_:_:_:_:)`](/documentation/AudioToolbox/AudioQueueNewInput(_:_:_:_:_:_:_:)) function. Typically, this includes format and state information for the audio queue. `inAQ` The recording audio queue that invoked the callback. `inBuffer` An audio queue buffer, newly filled by the recording audio queue, containing the new audio data your callback needs to write. `inStartTime` The sample time for the start of the audio queue buffer. This parameter is not used in basic recording. `inNumberPacketDescriptions` The number of packets of audio data sent to the callback in the `inBuffer` parameter. When recording in a constant bit rate (CBR) format, the audio queue sets this parameter to `NULL`. `inPacketDescs` For compressed formats that require packet descriptions, the set of packet descriptions produced by the encoder for audio data in the `inBuffer` parameter. When recording in a CBR format, the audio queue sets this parameter to `NULL`. ## Discussion If you name your callback function `MyAudioQueueInputCallback`, you would declare it like this: ### Discussion You specify a recording audio queue callback when calling the [`AudioQueueNewInput(_:_:_:_:_:_:_:)`](/documentation/AudioToolbox/AudioQueueNewInput(_:_:_:_:_:_:_:)) function. The callback is invoked each time its recording audio queue has filled an audio queue buffer with fresh audio data. Typically, your callback writes the data to a file or other buffer, and then reenqueues the audio queue buffer to receive more data. --- 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)