---
title: AUMIDIOutputCallback
framework: audiotoolbox
role: symbol
role_heading: Type Alias
path: audiotoolbox/aumidioutputcallback
---

# AUMIDIOutputCallback

When called by a host application, gets MIDI data from an audio unit.

## Declaration

```swift
typealias AUMIDIOutputCallback = (UnsafeMutableRawPointer?, UnsafePointer<AudioTimeStamp>, UInt32, UnsafePointer<MIDIPacketList>) -> OSStatus
```

## Parameters

- `userData`: Custom data.
- `timeStamp`:
- `midiOutNum`:
- `pktlist`:

## Discussion

Discussion If you named your callback function MyAUMIDIOutputCallback, you would declare it like this:

## See Also

### Getting Information from the Host

- [HostCallback_GetBeatAndTempo](audiotoolbox/hostcallback_getbeatandtempo.md)
- [HostCallback_GetMusicalTimeLocation](audiotoolbox/hostcallback_getmusicaltimelocation.md)
- [HostCallback_GetTransportState](audiotoolbox/hostcallback_gettransportstate.md)
- [HostCallback_GetTransportState2](audiotoolbox/hostcallback_gettransportstate2.md)
- [AUInputSamplesInOutputCallback](audiotoolbox/auinputsamplesinoutputcallback.md)