---
title: AudioQueueInputCallback
framework: audiotoolbox
role: symbol
role_heading: Type Alias
path: audiotoolbox/audioqueueinputcallback
---

# AudioQueueInputCallback

Called by the system when a recording audio queue has finished filling an audio queue buffer.

## Declaration

```swift
typealias AudioQueueInputCallback = (UnsafeMutableRawPointer?, AudioQueueRef, AudioQueueBufferRef, UnsafePointer<AudioTimeStamp>, UInt32, UnsafePointer<AudioStreamPacketDescription>?) -> Void
```

## Parameters

- `inUserData`: The custom data you’ve specified in the inUserData parameter of the doc://com.apple.audiotoolbox/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

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(_:_:_:_:_:_:_:) 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.

## See Also

### Callbacks

- [AudioQueueOutputCallback](audiotoolbox/audioqueueoutputcallback.md)
- [AudioQueuePropertyListenerProc](audiotoolbox/audioqueuepropertylistenerproc.md)