---
title: inputToOutputCallback
framework: audiotoolbox
role: symbol
role_heading: Instance Property
path: audiotoolbox/auinputsamplesinoutputcallbackstruct/inputtooutputcallback
---

# inputToOutputCallback

The callback function that provides input-to-output sample mapping for an audio unit.

## Declaration

```swift
var inputToOutputCallback: AUInputSamplesInOutputCallback
```