---
title: AURenderObserver
framework: audiotoolbox
role: symbol
role_heading: Type Alias
path: audiotoolbox/aurenderobserver
---

# AURenderObserver

A block called when an audio unit renders audio.

## Declaration

```swift
typealias AURenderObserver = (AudioUnitRenderActionFlags, UnsafePointer<AudioTimeStamp>, AUAudioFrameCount, Int) -> Void
```

## Discussion

Discussion This block is called by the base class’s AURenderBlock block before and after each render cycle. The observer can distinguish between before and after using the unitRenderAction_PreRender and unitRenderAction_PostRender  action flag values. The block takes the following parameters:

## See Also

### Audio Unit Types

- [ScheduledAudioFileRegion](audiotoolbox/scheduledaudiofileregion.md)
- [ScheduledAudioSlice](audiotoolbox/scheduledaudioslice.md)
- [ScheduledAudioFileRegionCompletionProc](audiotoolbox/scheduledaudiofileregioncompletionproc.md)
- [ScheduledAudioSliceCompletionProc](audiotoolbox/scheduledaudioslicecompletionproc.md)
- [MIDIChannelNumber](audiotoolbox/midichannelnumber.md)
- [AUAudioObjectID](audiotoolbox/auaudioobjectid.md)
- [AUMIDICIProfileChangedBlock](audiotoolbox/aumidiciprofilechangedblock.md)
- [AUAudioChannelCount](audiotoolbox/auaudiochannelcount.md)
- [AUAudioFrameCount](audiotoolbox/auaudioframecount.md)
- [AUAudioUnitStatus](audiotoolbox/auaudiounitstatus.md)
- [AUEventListenerProc](audiotoolbox/aueventlistenerproc.md)
- [AUEventListenerRef](audiotoolbox/aueventlistenerref.md)
- [AUEventSampleTime](audiotoolbox/aueventsampletime.md)
- [AUImplementorValueObserver](audiotoolbox/auimplementorvalueobserver.md)
- [AUImplementorValueProvider](audiotoolbox/auimplementorvalueprovider.md)