---
title: HostCallbackInfo
framework: audiotoolbox
role: symbol
role_heading: Structure
path: audiotoolbox/hostcallbackinfo
---

# HostCallbackInfo

The time- and transport-related callback functions for an audio unit.

## Declaration

```swift
struct HostCallbackInfo
```

## Topics

### Initializers

- [init()](audiotoolbox/hostcallbackinfo/init().md)
- [init(hostUserData:beatAndTempoProc:musicalTimeLocationProc:transportStateProc:transportStateProc2:)](audiotoolbox/hostcallbackinfo/init(hostuserdata:beatandtempoproc:musicaltimelocationproc:transportstateproc:transportstateproc2:).md)

### Instance Properties

- [beatAndTempoProc](audiotoolbox/hostcallbackinfo/beatandtempoproc.md)
- [hostUserData](audiotoolbox/hostcallbackinfo/hostuserdata.md)
- [musicalTimeLocationProc](audiotoolbox/hostcallbackinfo/musicaltimelocationproc.md)
- [transportStateProc](audiotoolbox/hostcallbackinfo/transportstateproc.md)
- [transportStateProc2](audiotoolbox/hostcallbackinfo/transportstateproc2.md)

## Relationships

### Conforms To

- [BitwiseCopyable](swift/bitwisecopyable.md)

## See Also

### General

- [Other Plug-In Formats](audiotoolbox/1534082-other-plug-in-formats.md)
- [RenderQuality](audiotoolbox/1534177-renderquality.md)
- [General Audio Unit Properties](audiotoolbox/general-audio-unit-properties.md)