---
title: Audio Unit v2 (C) API
framework: audiotoolbox
role: collectionGroup
role_heading: API Collection
path: audiotoolbox/audio-unit-v2-c-api
---

# Audio Unit v2 (C) API

Configure an Audio Unit and prepare it to render audio.

## Topics

### Initializing the Audio Unit

- [AudioUnitInitialize(_:)](audiotoolbox/audiounitinitialize(_:).md)
- [AudioUnitUninitialize(_:)](audiotoolbox/audiounituninitialize(_:).md)
- [AudioUnitProcess(_:_:_:_:_:)](audiotoolbox/audiounitprocess(_:_:_:_:_:).md)
- [AudioUnitProcessMultiple(_:_:_:_:_:_:_:_:)](audiotoolbox/audiounitprocessmultiple(_:_:_:_:_:_:_:_:).md)
- [AudioUnitReset(_:_:_:)](audiotoolbox/audiounitreset(_:_:_:).md)
- [AudioUnit](audiotoolbox/audiounit.md)

### Starting and Stopping Output

- [AudioOutputUnitStart(_:)](audiotoolbox/audiooutputunitstart(_:).md)
- [AudioOutputUnitStop(_:)](audiotoolbox/audiooutputunitstop(_:).md)
- [AudioOutputUnitStartProc](audiotoolbox/audiooutputunitstartproc.md)
- [AudioOutputUnitStopProc](audiotoolbox/audiooutputunitstopproc.md)

### Rendering the Audio

- [AudioUnitRender(_:_:_:_:_:_:)](audiotoolbox/audiounitrender(_:_:_:_:_:_:).md)
- [AudioUnitAddRenderNotify(_:_:_:)](audiotoolbox/audiounitaddrendernotify(_:_:_:).md)
- [AudioUnitRemoveRenderNotify(_:_:_:)](audiotoolbox/audiounitremoverendernotify(_:_:_:).md)
- [AURenderCallback](audiotoolbox/aurendercallback.md)
- [AudioUnitRenderActionFlags](audiotoolbox/audiounitrenderactionflags.md)

### Configuring Audio Unit Properties

- [AudioUnitGetProperty(_:_:_:_:_:_:)](audiotoolbox/audiounitgetproperty(_:_:_:_:_:_:).md)
- [AudioUnitSetProperty(_:_:_:_:_:_:)](audiotoolbox/audiounitsetproperty(_:_:_:_:_:_:).md)
- [AudioUnitGetPropertyInfo(_:_:_:_:_:_:)](audiotoolbox/audiounitgetpropertyinfo(_:_:_:_:_:_:).md)
- [AudioUnitAddPropertyListener(_:_:_:_:)](audiotoolbox/audiounitaddpropertylistener(_:_:_:_:).md)
- [AudioUnitRemovePropertyListenerWithUserData(_:_:_:_:)](audiotoolbox/audiounitremovepropertylistenerwithuserdata(_:_:_:_:).md)

### Responding to Events

- [AUEventListenerCreateWithDispatchQueue(_:_:_:_:_:)](audiotoolbox/aueventlistenercreatewithdispatchqueue(_:_:_:_:_:).md)
- [AUEventListenerCreate(_:_:_:_:_:_:_:)](audiotoolbox/aueventlistenercreate(_:_:_:_:_:_:_:).md)
- [AUListenerDispose(_:)](audiotoolbox/aulistenerdispose(_:).md)
- [AUEventListenerNotify(_:_:_:)](audiotoolbox/aueventlistenernotify(_:_:_:).md)
- [AUEventListenerAddEventType(_:_:_:)](audiotoolbox/aueventlisteneraddeventtype(_:_:_:).md)
- [AUEventListenerRemoveEventType(_:_:_:)](audiotoolbox/aueventlistenerremoveeventtype(_:_:_:).md)
- [AUListenerAddParameter(_:_:_:)](audiotoolbox/aulisteneraddparameter(_:_:_:).md)
- [AUListenerRemoveParameter(_:_:_:)](audiotoolbox/aulistenerremoveparameter(_:_:_:).md)
- [AUEventListenerBlock](audiotoolbox/aueventlistenerblock.md)

### Getting and Setting Parameters

- [AudioUnitGetParameter(_:_:_:_:_:)](audiotoolbox/audiounitgetparameter(_:_:_:_:_:).md)
- [AudioUnitScheduleParameters(_:_:_:)](audiotoolbox/audiounitscheduleparameters(_:_:_:).md)
- [AudioUnitSetParameter(_:_:_:_:_:_:)](audiotoolbox/audiounitsetparameter(_:_:_:_:_:_:).md)

### Monitoring Parameter Changes

- [AUListenerCreateWithDispatchQueue(_:_:_:_:)](audiotoolbox/aulistenercreatewithdispatchqueue(_:_:_:_:).md)
- [AUListenerCreate(_:_:_:_:_:_:)](audiotoolbox/aulistenercreate(_:_:_:_:_:_:).md)
- [AUParameterListenerNotify(_:_:_:)](audiotoolbox/auparameterlistenernotify(_:_:_:).md)
- [AUParameterFormatValue(_:_:_:_:)](audiotoolbox/auparameterformatvalue(_:_:_:_:).md)
- [AUParameterSet(_:_:_:_:_:)](audiotoolbox/auparameterset(_:_:_:_:_:).md)
- [AUParameterValueFromLinear(_:_:)](audiotoolbox/auparametervaluefromlinear(_:_:).md)
- [AUParameterValueToLinear(_:_:)](audiotoolbox/auparametervaluetolinear(_:_:).md)
- [AUParameterListenerBlock](audiotoolbox/auparameterlistenerblock.md)
- [AUParameterListenerProc](audiotoolbox/auparameterlistenerproc.md)
- [AUParameterListenerRef](audiotoolbox/auparameterlistenerref.md)
- [AUImplementorDisplayNameWithLengthCallback](audiotoolbox/auimplementordisplaynamewithlengthcallback.md)
- [AUImplementorStringFromValueCallback](audiotoolbox/auimplementorstringfromvaluecallback.md)
- [AUImplementorValueFromStringCallback](audiotoolbox/auimplementorvaluefromstringcallback.md)

### 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)
- [AUMIDIOutputCallback](audiotoolbox/aumidioutputcallback.md)

### Getting the Configuration Information

- [kAudioUnitConfigurationInfo_BusCountWritable](audiotoolbox/kaudiounitconfigurationinfo_buscountwritable.md)
- [kAudioUnitConfigurationInfo_ChannelConfigurations](audiotoolbox/kaudiounitconfigurationinfo_channelconfigurations.md)
- [kAudioUnitConfigurationInfo_HasCustomView](audiotoolbox/kaudiounitconfigurationinfo_hascustomview.md)
- [kAudioUnitConfigurationInfo_IconURL](audiotoolbox/kaudiounitconfigurationinfo_iconurl.md)
- [kAudioUnitConfigurationInfo_InitialInputs](audiotoolbox/kaudiounitconfigurationinfo_initialinputs.md)
- [kAudioUnitConfigurationInfo_InitialOutputs](audiotoolbox/kaudiounitconfigurationinfo_initialoutputs.md)
- [kAudioUnitConfigurationInfo_SupportedChannelLayoutTags](audiotoolbox/kaudiounitconfigurationinfo_supportedchannellayouttags.md)

### Configuring the Audio Unit UI

- [AudioUnitCocoaViewInfo](audiotoolbox/audiounitcocoaviewinfo.md)
- [GetAudioUnitParameterDisplayType(_:)](audiotoolbox/getaudiounitparameterdisplaytype(_:).md)
- [SetAudioUnitParameterDisplayType(_:_:)](audiotoolbox/setaudiounitparameterdisplaytype(_:_:).md)

### 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)
- [AUInputHandler](audiotoolbox/auinputhandler.md)
- [AUNodeConnection](audiotoolbox/aunodeconnection.md)
- [AUParameterAddress](audiotoolbox/auparameteraddress.md)
- [AUParameterAutomationObserver](audiotoolbox/auparameterautomationobserver.md)
- [AUParameterObserver](audiotoolbox/auparameterobserver.md)
- [AUParameterObserverToken](audiotoolbox/auparameterobservertoken.md)
- [AUParameterRecordingObserver](audiotoolbox/auparameterrecordingobserver.md)
- [AURenderBlock](audiotoolbox/aurenderblock.md)
- [AURenderObserver](audiotoolbox/aurenderobserver.md)
- [AURenderPullInputBlock](audiotoolbox/aurenderpullinputblock.md)
- [AUScheduleParameterBlock](audiotoolbox/auscheduleparameterblock.md)
- [AUValue](audiotoolbox/auvalue.md)
- [AudioUnitAddPropertyListenerProc](audiotoolbox/audiounitaddpropertylistenerproc.md)
- [AudioUnitAddRenderNotifyProc](audiotoolbox/audiounitaddrendernotifyproc.md)
- [AudioUnitComplexRenderProc](audiotoolbox/audiounitcomplexrenderproc.md)
- [AudioUnitElement](audiotoolbox/audiounitelement.md)
- [AudioUnitGetParameterProc](audiotoolbox/audiounitgetparameterproc.md)
- [AudioUnitGetPropertyInfoProc](audiotoolbox/audiounitgetpropertyinfoproc.md)
- [AudioUnitGetPropertyProc](audiotoolbox/audiounitgetpropertyproc.md)
- [AudioUnitInitializeProc](audiotoolbox/audiounitinitializeproc.md)
- [AudioUnitParameterID](audiotoolbox/audiounitparameterid.md)
- [AudioUnitParameterNameInfo](audiotoolbox/audiounitparameternameinfo.md)
- [AudioUnitParameterIDName](audiotoolbox/audiounitparameteridname.md)
- [AudioUnitParameterValue](audiotoolbox/audiounitparametervalue.md)
- [AudioUnitProcessMultipleProc](audiotoolbox/audiounitprocessmultipleproc.md)
- [AudioUnitProcessProc](audiotoolbox/audiounitprocessproc.md)
- [AudioUnitPropertyID](audiotoolbox/audiounitpropertyid.md)
- [AudioUnitPropertyListenerProc](audiotoolbox/audiounitpropertylistenerproc.md)
- [AudioUnitRemoteControlEventListener](audiotoolbox/audiounitremotecontroleventlistener.md)
- [AudioUnitRemovePropertyListenerProc](audiotoolbox/audiounitremovepropertylistenerproc.md)
- [AudioUnitRemovePropertyListenerWithUserDataProc](audiotoolbox/audiounitremovepropertylistenerwithuserdataproc.md)
- [AudioUnitRemoveRenderNotifyProc](audiotoolbox/audiounitremoverendernotifyproc.md)
- [AudioUnitRenderProc](audiotoolbox/audiounitrenderproc.md)
- [AudioUnitResetProc](audiotoolbox/audiounitresetproc.md)
- [AudioUnitScheduleParametersProc](audiotoolbox/audiounitscheduleparametersproc.md)
- [AudioUnitScope](audiotoolbox/audiounitscope.md)
- [AudioUnitSetParameterProc](audiotoolbox/audiounitsetparameterproc.md)
- [AudioUnitSetPropertyProc](audiotoolbox/audiounitsetpropertyproc.md)
- [AudioUnitUninitializeProc](audiotoolbox/audiounituninitializeproc.md)

### Enumerations

- [Audio Unit Types](audiotoolbox/1584142-audio_unit_types.md)
- [Inter-App Audio Unit Types](audiotoolbox/1619501-inter-app-audio-unit-types.md)
- [Audio Unit Manufacturer Identifier](audiotoolbox/1584143-audio_unit_manufacturer_identifi.md)
- [Audio Unit Output Subtypes](audiotoolbox/1584148-audio-unit-output-subtypes.md)
- [I/O Audio Unit Subtypes](audiotoolbox/1619485-i-o-audio-unit-subtypes.md)
- [Converter Audio Unit Subtypes](audiotoolbox/1584145-converter_audio_unit_subtypes.md)
- [Reserved Audio Unit Clump Identifier](audiotoolbox/1533986-reserved_audio_unit_clump_identi.md)
- [Offline Audio Unit Properties](audiotoolbox/1534054-offline_audio_unit_properties.md)
- [MIDI Audio Unit Parameters](audiotoolbox/1389613-midi_audio_unit_parameters.md)
- [General Audio Unit Function Selectors](audiotoolbox/1584140-general_audio_unit_function_sele.md)
- [Generator Audio Unit Subtypes](audiotoolbox/1619493-generator_audio_unit_subtypes.md)
- [Input/Output Audio Unit Subtypes](audiotoolbox/1584139-input_output_audio_unit_subtypes.md)
- [Audio Unit Panner Subtypes](audiotoolbox/1584151-audio-unit-panner-subtypes.md)
- [Audio Unit Player Subtypes](audiotoolbox/1584155-audio-unit-player-subtypes.md)
- [Audio Unit Pitch Subtypes](audiotoolbox/1584152-audio-unit-pitch-subtypes.md)
- [AudioUnitEventType](audiotoolbox/audiouniteventtype.md)
- [AudioUnitParameterOptions](audiotoolbox/audiounitparameteroptions.md)
- [AudioUnitParameterUnit](audiotoolbox/audiounitparameterunit.md)
- [AudioUnitRemoteControlEvent](audiotoolbox/audiounitremotecontrolevent.md)
- [Audio Unit Sample Rate Converter Complexity](audiotoolbox/1534173-audio_unit_sample_rate_converter.md)
- [Audio Unit Scopes](audiotoolbox/1534214-audio_unit_scopes.md)
- [Audio Unit SRC Algorithms](audiotoolbox/1533994-audio-unit-src-algorithms.md)
- [Audio Unit Full Name Parameter](audiotoolbox/1534055-audio-unit-full-name-parameter.md)
- [Audio Unit Parameter Flags](audiotoolbox/1534035-audio-unit-parameter-flags.md)
- [Audio Unit Filter Parameters](audiotoolbox/1390052-audio-unit-filter-parameters.md)
- [Audio Unit Generic Properties](audiotoolbox/1533969-audio-unit-generic-properties.md)
- [Audio Unit Parameter Flags](audiotoolbox/1534166-audio-unit-parameter-flags.md)
- [Audio Unit Scheduled Sound Player Properties](audiotoolbox/1534024-audio-unit-scheduled-sound-playe.md)
- [Audio Unit Offline Preflight Flags](audiotoolbox/1534010-audio-unit-offline-preflight-fla.md)
- [Audio Unit Migration Properties](audiotoolbox/1534149-audio-unit-migration-properties.md)
- [Audio Unit File Player Properties](audiotoolbox/1534079-audio-unit-file-player-propertie.md)
- [Audio Unit Parameter Listener](audiotoolbox/1509425-audio-unit-parameter-listener.md)
- [Audio Unit Errors](audiotoolbox/1584138-audio-unit-errors.md)
- [AUAudioUnitBusType](audiotoolbox/auaudiounitbustype.md)
- [AUEventSampleTime](audiotoolbox/1387633-aueventsampletime.md)
- [AUHostTransportStateFlags](audiotoolbox/auhosttransportstateflags.md)
- [AUParameterAutomationEventType](audiotoolbox/auparameterautomationeventtype.md)
- [AUParameterEventType](audiotoolbox/auparametereventtype.md)
- [AURenderEventType](audiotoolbox/aurendereventtype.md)
- [AUScheduledAudioSliceFlags](audiotoolbox/auscheduledaudiosliceflags.md)
- [AUParameterMIDIMappingFlags](audiotoolbox/auparametermidimappingflags.md)

## See Also

### Audio Units

- [Generating spatial audio from a multichannel audio stream](audiotoolbox/generating-spatial-audio-from-a-multichannel-audio-stream.md)
- [Audio Unit v3 Plug-Ins](audiotoolbox/audio-unit-v3-plug-ins.md)
- [Audio Components](audiotoolbox/audio-components.md)
- [Audio Unit Properties](audiotoolbox/audio-unit-properties.md)
- [Audio Unit Voice I/O](audiotoolbox/audio-unit-voice-i-o.md)