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Legacy Document

Important: The information in this document is obsolete and should not be used for new development.

Audio Units

This chapter describes the functions, structures, and constants used throughout the Audio Unit framework. The section “Reference” describes the constants, data types, and functions that are relevant to audio unit development.

In this section:

Overview
Reference

Overview

In Core Audio, audio units serve a number of purposes. Audio units are used to generate, process, receive, or otherwise manipulate streams of audio. They are building blocks that may be used singly or connected together to form an audio signal graph, or AUGraph.

The Audio Unit Framework

The audio unit framework provides a set of services that developers can take advantage of in their own applications by using audio units. The framework also provides services for those who want to develop their own audio units.

Audio units are defined as processing units. Their input can come from a variety of sources (for example, encoded data, other audio units, or none); their output is generally a buffer of audio data.

Apple ships a set of AudioUnit components, as well as defining the interface for the AudioUnit component.

In Java, these services are available in the com.apple.audio.units package.

In the Macintosh system architecture, audio units are simply components, and like all components are identified based on their four-character code type, subType and ID field. The Component Manager provides a set of APIs for querying the available components on the system. You can use the FindNextComponent() call to find out what audio units are installed on the system. Instances are created by means of the OpenAComponent() call and released by the CloseComponent() call.

For more information on the Component Manager, consult More Macintosh Toolbox.

The Audio Unit API

The audio unit API presents the basic audio unit interface, as well as the constants that define the audio unit type, and the generic sub-types of an audio unit.

The specific ID of an audio unit represents the specific functionality of the audio unit itself. For example, the DLSMusicDevice is an audio unit that is able to use both Downloadable Sounds (DLS) and SoundFont 2 (SF2) files as sample data for sample-based synthesis. Its type is ‘aumu’–– an audio unit music device. Its sub-type is ‘dls ’ –– a DLS music device (note the space at the end).

For more specific information about components, refer to Inside Macintosh: More Macintosh Toolbox, Chapter 6, Component Manager.

Audio Unit State

The basic audio unit states are closed, open, and initialized, which correspond to these calls:

OpenAComponent()
CloseAComponent()
AudioUnitInitialize()
AudioUnitUninitalize()

No significant resource allocations are expected to occur when the audio unit component is first opened with OpenAComponent(). AudioUnitInitialize() is called after optional configuration has occured. This is where the audio unit allocates and is prepared to render.

AudioUnitReset() may be called on any initialized audio unit. The AudioUnitReset() call clears any buffers, resets filter memory, and stops any playing notes (for example, in a MusicDevice software synthesizer). It places the audio unit back to its initialized state.

Audio Unit Sources and Destinations

Audio units have sources and destinations. An audio unit can be just a source unit, such as software synthesizers, which are presented as a type of audio unit defined as a MusicDevice.

An audio unit can also be just a destination that is attached to a hardware output device.

Some audio units contain both input and output audio data. DSP processors, such as reverbs, filters, and mixers are examples, as are format converters, such as 16-bit integer to floating-point converters, interleavers-deinterleavers, and sample rate converters.

Audio Unit Properties

Properties represent a general and extensible mechanism for passing information to and from audio units. Information is communicated via a void* data parameter and a data byte-size parameter. The type of information is identified by an AudioUnitPropertyID.

Information is addressed to a particular section of an audio unit with AudioUnitScope and AudioUnitElement. AudioUnitScope includes the following constants:

kAudioUnitScope_Global
kAudioUnitScope_Input
kAudioUnitScope_Output
kAudioUnitScope_Group

AudioUnitElement is a zero-based index of a particular input, output, or group and is typically ignored for global scope. AudioUnitPropertyIDs are defined in Constants.

Audio Unit Parameters

Parameters are values that can change over time, and are generally time-sensitive and can be scheduled. Parameters could include such things as volume or panning of a particular output on the mixer audio unit, for instance.

I/O Management

Audio unit I/O Management relies on a “pull” I/O model, which specifies through its properties the number and format of its inputs and outputs. Each input/output is a set of audio buffers corresponding to audio channels.

Data can be supplied to an audio unit through one of two mechanisms:

Connecting an audio unit output to another audio unit that will provide input using kAudioUnitProperty_MakeConnection. Audio data is automatically routed to the input with no required user intervention.
Registering a client callback using kAudioUnitProperty_SetInputCallback where the client can provide audio source data to an audio unit through the supplied callback.

The AUGraph API provides a higher-level connection service, freeing the client from calling the audio unit directly.

The “Pull” I/O Model

As mentioned, audio units use a “pull” I/O model, with each unit specifying through its properties the number and format of its inputs and ouputs. Each output is in itself a set of audio buffers corresponding to audio channels. Connections between units are also managed via properties. Data is requested from an audio unit through its AudioUnitRender function being called by one of its destinations, or the AURenderCallback being called.

Key points about AudioUnitRender() arguments:

The AudioTimeStamp specifies the start time of the buffer to be rendered, synchronizing the hosttime of the machine with the sample time of the audio to lock it with other realtime events such as MIDI.
The AudioBufferList argument passes in and receives back a set of buffers of audio data. The client may pass in a list or let the AudioUnit provide it.

A client can request notifications of the rendering activity of an audio unit by installing a callback using kAudioUnitProperty_RenderNotification. The client’s callback will then be called by the audio unit, both before and after any call to the unit’s render slice function.

The ioActionFlags parameter provides the unit with instructions on how to handle the buffer supplied:

kAudioUnitRenderAction_Accumulate –– The unit should sum its output into the given buffer, rather than replace it. This action is only valid for formats that support easy stream mixing like linear PCM. In addition, a buffer will always be supplied.

kAudioUnitRenderAction_UseProvidedBuffer –– This flag indicates that the rendered audio must be placed in the buffer pointed the ioData argument. In this case, ioData must point to a valid piece of allocated memory. If this flag is not set, the mData member of ioData may possibly be changed upon return, pointing to a different buffer (owned by the audio unit ).

If the ioData member is NULL, then rendering may set ioData to a buffer list owned by the audio unit. In any case, on return, ioData points to the rendered audio data.

The inTimeStamp parameter gives the audio unit information about what the time is for the start of the rendered audio output.

The inOutputBusNumber parameter requests that audio be rendered for a particular audio output of the audio unit. Rendering is performed separately for each of its outputs. The audio unit is expected to cache its rendered audio for each output in the case that it is called more than once for the same output (inOutputBusNumber is the same) at the same time (inTimeStamp is the same). This solves the “fanout” problem.

Additional Information

Additional information and documentation is available with the Core Audio SDK, available from the Audio Developer webpage:

http://developer.apple.com/audio

Reference

This reference section describes the structures, constants, parameters, properties, and typedefs provided in the Audio Unit framework. Many of these are universal among all audio units, while some are specific to Apple-provided units.

Constants

Component Types and Subtypes

The following audio units are provided by Apple. The four-character codes identify each of these units with the Component Manager, allowing for you to find and use them.

kAudioUnitType_Output = FOUR_CHAR_CODE('auou'): The component type for all output units.
kAudioUnitSubType_HALOutput = FOUR_CHAR_CODE('ahal'): The component subtype for an output unit that uses a HAL output.
kAudioUnitSubType_DefaultOutput = FOUR_CHAR_CODE('def '): The component subtype for an output unit that uses the default output, as selected by the user.
kAudioUnitSubType_SystemOutput = FOUR_CHAR_CODE('sys '): The component subtype for an output unit that uses the system output.
kAudioUnitSubType_GenericOutput = FOUR_CHAR_CODE('genr'): The component subtype for a generic output unit.
kAudioUnitType_MusicDevice = FOUR_CHAR_CODE('aumu'): The component type for a music device unit.
kAudioUnitSubType_DLSSynth = FOUR_CHAR_CODE('dls '): The component subtype for the DLS synth music device unit
kAudioUnitType_MusicEffect = FOUR_CHAR_CODE('aumf'): The component type for a music effect unit.
kAudioUnitType_FormatConverter = FOUR_CHAR_CODE('aufc'): The component type for a format converter unit.
kAudioUnitSubType_AUConverter = FOUR_CHAR_CODE('conv'): The component subtype for an AUConverter format converter unit.
kAudioUnitSubType_Varispeed = FOUR_CHAR_CODE('vari'): The component subtype for a Varispeed effect unit.
kAudioUnitSubType_Delay = FOUR_CHAR_CODE('dely'): The component subtype for a delay effect unit.
kAudioUnitSubType_LowPassFilter = FOUR_CHAR_CODE('lpas'): The component subtype for a low-pass filter effect unit.
kAudioUnitSubType_HighPassFilter = FOUR_CHAR_CODE('hpas'): The component subtype for a high-pass filter effect unit.
kAudioUnitSubType_BandPassFilter = FOUR_CHAR_CODE('bpas'): The component subtype for a band-pass filter effect unit.
kAudioUnitSubType_HighShelfFilter = FOUR_CHAR_CODE('hshf'): The component subtype for a high-shelf filter effect unit.
kAudioUnitSubType_LowShelfFilter = FOUR_CHAR_CODE('lshf'): The component subtype for a low-shelf filter effect unit.
kAudioUnitSubType_ParametricEQ = FOUR_CHAR_CODE('pmeq'): The component subtype for a parametric equalizer effect unit.
kAudioUnitSubType_GraphicEQ = FOUR_CHAR_CODE('greq'): The component subtype for a graphic equalizer effect unit.
kAudioUnitSubType_PeakLimiter = FOUR_CHAR_CODE('lmtr'): The component subtype for a peak limiter effect unit.
kAudioUnitSubType_DynamicsProcessor = FOUR_CHAR_CODE('dcmp'): The component subtype for a dynamics processor effect unit.
kAudioUnitSubType_MultiBandCompressor = FOUR_CHAR_CODE('mcmp'): The component subtype for multi-band compressor effect unit.
kAudioUnitSubType_MatrixReverb = FOUR_CHAR_CODE('mrev'): The component subtype for a matrix reverb effect unit.
kAudioUnitType_Mixer = FOUR_CHAR_CODE('aumx'): The component type for a mixer unit.
kAudioUnitSubType_StereoMixer = FOUR_CHAR_CODE('smxr'): The component subtype for a stereo mixer unit.
kAudioUnitSubType_3DMixer = FOUR_CHAR_CODE('3dmx'): The component subtype for a three-dimensional mixer unit.
kAudioUnitSubType_MatrixMixer = FOUR_CHAR_CODE('mxmx'): The component subtype for a matrix mixer unit.
kAudioUnitType_Panner = FOUR_CHAR_CODE('aupn'): The component type for a panner unit.
kAudioUnitType_OfflineEffect = FOUR_CHAR_CODE('auol'): The component type fpr an offline effect unit.
kAudioUnitManufacturer_Apple = FOUR_CHAR_CODE('appl'): The component manufacturer type for all units provided by Apple.

Render Action Flags

These flags provide you with information on the status of a render within an audio unit.

kAudioUnitRenderAction_PreRender = (1 << 2): The audio unit is prepared to render.

kAudioUnitRenderAction_PostRender = (1 << 3): The audio unit is finished with the current render.

kAudioUnitRenderAction_OutputIsSilence = (1 << 4): The current output of the render is silence.

kAudioOfflineUnitRenderAction_Preflight = (1 << 5): The audio unit has not yet rendered.

AudioOfflineUnitRenderAction_Render = (1 << 6): The audio unit is prepared to render.

kAudioOfflineUnitRenderAction_Complete = (1 << 7): The audio unit has been used to render.

Errors

These errors may arrise when rendering audio with an audio unit.

kAudioUnitErr_InvalidProperty           = -10879

kAudioUnitErr_InvalidParameter          = -10878

kAudioUnitErr_InvalidElement            = -10877

kAudioUnitErr_NoConnection              = -10876

kAudioUnitErr_FailedInitialization      = -10875

kAudioUnitErr_TooManyFramesToProcess    = -10874

kAudioUnitErr_IllegalInstrument         = -10873

kAudioUnitErr_InstrumentTypeNotFound    = -10872

kAudioUnitErr_InvalidFile               = -10871

kAudioUnitErr_UnknownFileType           = -10870

kAudioUnitErr_FileNotSpecified          = -10869

kAudioUnitErr_FormatNotSupported        = -10868

kAudioUnitErr_Uninitialized             = -10867

kAudioUnitErr_InvalidScope              = -10866

kAudioUnitErr_PropertyNotWritable       = -10865

kAudioUnitErr_InvalidPropertyValue      = -10851

kAudioUnitErr_PropertyNotInUse          = -10850

kAudioUnitErr_Initialized               = -10849

kAudioUnitErr_InvalidOfflineRender      = -10848

kAudioUnitErr_Unauthorized              = -10847 kAudioUnitErr_CannotDoInCurrentContext  = -10863

Parameter Event Types

These values specify what type of parameter event is occuring.

kParameterEvent_Immediate   = 1

kParameterEvent_Ramped      = 2

Component Call Selectors

These selectors determine the state of an audio unit.

kAudioUnitInitializeSelect              = 0x0001,

kAudioUnitUninitializeSelect            = 0x0002,

kAudioUnitGetPropertyInfoSelect         = 0x0003,

kAudioUnitGetPropertySelect             = 0x0004,

kAudioUnitSetPropertySelect             = 0x0005,

kAudioUnitAddPropertyListenerSelect     = 0x000A,

kAudioUnitRemovePropertyListenerSelect  = 0x000B,

kAudioUnitAddRenderNotifySelect         = 0x000F,

kAudioUnitRemoveRenderNotifySelect      = 0x0010,

kAudioUnitGetParameterSelect            = 0x0006,

kAudioUnitSetParameterSelect            = 0x0007,

kAudioUnitScheduleParametersSelect      = 0x0011,

kAudioUnitRenderSelect                  = 0x000E,

kAudioUnitResetSelect                   = 0x0009

Audio Unit Properties

These properties can be queried of any audio unit instance.

kAudioUnitProperty_ClassInfo                    = 0

kAudioUnitProperty_MakeConnection               = 1

kAudioUnitProperty_SampleRate                   = 2

kAudioUnitProperty_ParameterList                = 3

kAudioUnitProperty_ParameterInfo                = 4

kAudioUnitProperty_FastDispatch                 = 5

kAudioUnitProperty_CPULoad                      = 6

kAudioUnitProperty_StreamFormat                 = 8

kAudioUnitProperty_SRCAlgorithm                 = 9

kAudioUnitProperty_ReverbRoomType               = 10

kAudioUnitProperty_BusCount                     = 11

kAudioUnitProperty_ElementCount                 = kAudioUnitProperty_BusCount,

kAudioUnitProperty_Latency                      = 12

kAudioUnitProperty_SupportedNumChannels         = 13

kAudioUnitProperty_MaximumFramesPerSlice        = 14

kAudioUnitProperty_SetExternalBuffer            = 15

kAudioUnitProperty_ParameterValueStrings        = 16

kAudioUnitProperty_MIDIControlMapping           = 17

kAudioUnitProperty_GetUIComponentList           = 18

kAudioUnitProperty_AudioChannelLayout           = 19

kAudioUnitProperty_TailTime                     = 20

kAudioUnitProperty_BypassEffect                 = 21

kAudioUnitProperty_LastRenderError              = 22

kAudioUnitProperty_SetRenderCallback            = 23

kAudioUnitProperty_FactoryPresets               = 24

kAudioUnitProperty_ContextName                  = 25

kAudioUnitProperty_RenderQuality                = 26

kAudioUnitProperty_HostCallbacks                = 27

kAudioUnitProperty_CurrentPreset                = 28

kAudioUnitProperty_InPlaceProcessing            = 29

kAudioUnitProperty_ElementName                  = 30

kAudioUnitProperty_CocoaUI                      = 31

kAudioUnitProperty_SupportedChannelLayoutTags   = 32

kAudioUnitProperty_ParameterValueName           = 33

kAudioUnitProperty_ParameterIDName              = 34

kAudioUnitProperty_ParameterClumpName           = 35

kAudioUnitProperty_PresentPreset                = 36

ProperkAudioUnitProperty_UsesInternalReverb     = 1005

Music Device Properties

These properties can be queried of any music device audio unit instance.

kMusicDeviceProperty_InstrumentCount            = 1000

kMusicDeviceProperty_InstrumentName             = 1001

kMusicDeviceProperty_GroupOutputBus             = 1002

kMusicDeviceProperty_SoundBankFSSpec            = 1003

kMusicDeviceProperty_InstrumentNumber           = 1004

kMusicDeviceProperty_UsesInternalReverb         = kAudioUnitProperty_UsesInternalReverb

kMusicDeviceProperty_MIDIXMLNames               = 1006

kMusicDeviceProperty_BankName                   = 1007

kMusicDeviceProperty_SoundBankData              = 1008

kMusicDeviceProperty_PartGroup                  = 1010

kMusicDeviceProperty_StreamFromDisk             = 1010

Output Unit Properties

These properties can be queried of any output audio unit instance.

kAudioOutputUnitProperty_CurrentDevice          = 2000

kAudioOutputUnitProperty_IsRunning              = 2001

kAudioOutputUnitProperty_ChannelMap             = 2002

kAudioOutputUnitProperty_EnableIO               = 2003

kAudioOutputUnitProperty_StartTime              = 2004

kAudioOutputUnitProperty_SetInputCallback       = 2005

kAudioOutputUnitProperty_HasIO                  = 2006

Various Audio Unit Properties

These properties can be queried of specific audio unit instances.

kAudioUnitProperty_SpatializationAlgorithm      = 3000

kAudioUnitProperty_SpeakerConfiguration         = 3001

kAudioUnitProperty_DopplerShift                 = 3002

kAudioUnitProperty_3DMixerRenderingFlags        = 3003

kAudioUnitProperty_3DMixerDistanceAtten         = 3004

kAudioUnitProperty_MatrixLevels                 = 3006

kAudioUnitProperty_MeteringMode                 = 3007

kAudioUnitProperty_PannerMode                   = 3008

kAudioUnitProperty_MatrixDimensions             = 3009

Offline Unit Properties

These properties can be queried of offline audio unit instances.

kAudioOfflineUnitProperty_InputSize             = 3020

kAudioOfflineUnitProperty_OutputSize            = 3021

kAudioUnitOfflineProperty_StartOffset           = 3022

kAudioUnitOfflineProperty_PreflightRequirements = 3023

kAudioUnitOfflineProperty_PreflightName         = 3024

Reverb Room-Type Properties

These properties can be queried of reverb audio unit instances.

kReverbRoomType_SmallRoom   = 0

kReverbRoomType_MediumRoom  = 1

kReverbRoomType_LargeRoom   = 2

kReverbRoomType_MediumHall  = 3

kReverbRoomType_LargeHall   = 4

kReverbRoomType_Plate       = 5

Spatialization Properties

These properties can be queried of panning audio unit instances.

kSpatializationAlgorithm_EqualPowerPanning      = 0

kSpatializationAlgorithm_SphericalHead          = 1

kSpatializationAlgorithm_HRTF                   = 2

kSpatializationAlgorithm_SoundField             = 3

kSpatializationAlgorithm_VectorBasedPanning     = 4

kSpatializationAlgorithm_StereoPassThrough      = 5

3D Mixer Properties

These properties can be queried of 3D Mixer audio unit instances.

k3DMixerRenderingFlags_InterAuralDelay          = (1L << 0)

k3DMixerRenderingFlags_DopplerShift             = (1L << 1)

k3DMixerRenderingFlags_DistanceAttenuation      = (1L << 2)

k3DMixerRenderingFlags_DistanceFilter           = (1L << 3)

k3DMixerRenderingFlags_DistanceDiffusion        = (1L << 4)

Render Quality Properties

These properties can be queried of any audio unit instance.

kRenderQuality_Max      = 0x7F

kRenderQuality_High     = 0x60

kRenderQuality_Medium   = 0x40

kRenderQuality_Low      = 0x20

kRenderQuality_Min      = 0

Panner Mode Properties

These properties can be queried of panning audio unit instances.

kPannerMode_Normal      = 0

kPannerMode_FaderMode   = 1

Offline Unit Preflight Properties

These properties can be queried of offline audio unit instances.

kOfflinePreflight_NotRequired   = 0

kOfflinePreflight_Optional      = 1

kOfflinePreflight_Required      = 2

Scope Properties

These properties can be queried of any audio unit instance.

kAudioUnitScope_Global  = 0

kAudioUnitScope_Input   = 1

kAudioUnitScope_Output  = 2

kAudioUnitScope_Group   = 3

kAudioUnitScope_Part    = 4

Preset Constants

These presets are used with AUPreset.

#define kAUPresetVersionKey         "version"

#define kAUPresetTypeKey            "type"

#define kAUPresetSubtypeKey         "subtype"

#define kAUPresetManufacturerKey    "manufacturer"

#define kAUPresetDataKey            "data"

#define kAUPresetNameKey            "name"

#define kAUPresetRenderQualityKey   "render-quality"

#define kAUPresetCPULoadKey         "cpu-load"

#define kAUPresetVSTDataKey         "vstdata"

#define kAUPresetElementNameKey     "element-name"

#define kAUPresetPartKey            "part"

Parameter Unit Constants

These presets are used with a parameter unit audio unit.

kAudioUnitParameterUnit_Generic             = 0

kAudioUnitParameterUnit_Indexed             = 1

kAudioUnitParameterUnit_Boolean             = 2

kAudioUnitParameterUnit_Percent             = 3

kAudioUnitParameterUnit_Seconds             = 4

kAudioUnitParameterUnit_SampleFrames        = 5

kAudioUnitParameterUnit_Phase               = 6

kAudioUnitParameterUnit_Rate                = 7

kAudioUnitParameterUnit_Hertz               = 8

kAudioUnitParameterUnit_Cents               = 9

kAudioUnitParameterUnit_RelativeSemiTones   = 10

kAudioUnitParameterUnit_MIDINoteNumber      = 11

kAudioUnitParameterUnit_MIDIController      = 12

kAudioUnitParameterUnit_Decibels            = 13

kAudioUnitParameterUnit_LinearGain          = 14

kAudioUnitParameterUnit_Degrees             = 15

kAudioUnitParameterUnit_EqualPowerCrossfade = 16

kAudioUnitParameterUnit_MixerFaderCurve1    = 17

kAudioUnitParameterUnit_Pan                 = 18

kAudioUnitParameterUnit_Meters              = 19

kAudioUnitParameterUnit_AbsoluteCents       = 20

kAudioUnitParameterUnit_Octaves             = 21

kAudioUnitParameterUnit_BPM                 = 22

kAudioUnitParameterUnit_Beats               = 23

kAudioUnitParameterUnit_Milliseconds        = 24

kAudioUnitParameterUnit_Ratio               = 25

Parameter Flags

These flags are used with an audio unit’s parameters.

kAudioUnitParameterFlag_CFNameRelease       = (1L << 4)

kAudioUnitParameterFlag_HasClump            = (1L << 20)

kAudioUnitParameterFlag_HasName             = (1L << 21)

kAudioUnitParameterFlag_DisplayLogarithmic  = (1L << 22)

kAudioUnitParameterFlag_IsHighResolution    = (1L << 23)

kAudioUnitParameterFlag_NonRealTime         = (1L << 24)

kAudioUnitParameterFlag_CanRamp             = (1L << 25)

kAudioUnitParameterFlag_ExpertMode          = (1L << 26)

kAudioUnitParameterFlag_HasCFNameString     = (1L << 27)

kAudioUnitParameterFlag_IsGlobalMeta        = (1L << 28)

kAudioUnitParameterFlag_IsElementMeta       = (1L << 29)

kAudioUnitParameterFlag_IsReadable          = (1L << 30)

kAudioUnitParameterFlag_IsWritable          = (1L << 31)

MIDI Controller Parameters

These parameters are used with MIDI Controller audio units.

kAUGroupParameterID_Volume                  = 7

kAUGroupParameterID_Sustain                 = 64

kAUGroupParameterID_AllNotesOff             = 123

kAUGroupParameterID_ModWheel                = 1

kAUGroupParameterID_PitchBend               = 0xE0

kAUGroupParameterID_AllSoundOff             = 120

kAUGroupParameterID_ResetAllControllers     = 121

kAUGroupParameterID_Pan                     = 10

kAUGroupParameterID_Foot                    = 4

kAUGroupParameterID_ChannelPressure         = 0xD0

kAUGroupParameterID_KeyPressure             = 0xA0

kAUGroupParameterID_Expression              = 11

kAUGroupParameterID_DataEntry               = 6

kAUGroupParameterID_Volume_LSB              = kAUGroupParameterID_Volume + 32

kAUGroupParameterID_ModWheel_LSB            = kAUGroupParameterID_ModWheel + 32

kAUGroupParameterID_Pan_LSB                 = kAUGroupParameterID_Pan + 32

kAUGroupParameterID_Foot_LSB                = kAUGroupParameterID_Foot + 32

kAUGroupParameterID_Expression_LSB          = kAUGroupParameterID_Expression + 32

kAUGroupParameterID_DataEntry_LSB           = kAUGroupParameterID_DataEntry + 32

kAUGroupParameterID_KeyPressure_FirstKey    = 256

kAUGroupParameterID_KeyPressure_LastKey     = 383

Bandpass Filter Unit Parameters

These parameters are used with the Bandpass Filter Unit.

kBandpassParam_CenterFrequency  = 0

kBandpassParam_Bandwidth        = 1

AUHipass Unit Parameters

These parameters are used with the AUHipass Unit.

kHighShelfParam_CutOffFrequency = 0

kHighShelfParam_Resonance       = 1

AULowpass Unit Parameters

These parameters are used with the AULowpass Unit.

kHighShelfParam_CutOffFrequency = 0

kHighShelfParam_Resonance       = 1

AUHighShelfFilter Unit Parameters

These parameters are used with the AUHighSelfFilter Unit.

kHipassParam_CutoffFrequency    = 0

kHipassParam_Gain               = 1

AULowShelfFilter Unit Parameters

These parameters are used with the AULowSelfFilter Unit.

kHipassParam_CutoffFrequency    = 0

kHipassParam_Gain               = 1

AUParametricEQ Unit Parameters

These parameters are used with the AUParametricEQ Unit.

kParametricEQParam_CenterFreq   = 0

kParametricEQParam_Q            = 1

kParametricEQParam_Gain         = 2

AUMatrixReverb Unit Parameters

These parameters are used with the AUMatrixReverb Unit.

kReverbParam_DryWetMix      = 0

kReverbParam_SmallLargeMix  = 1

kReverbParam_SmallSize      = 2

kReverbParam_LargeSize      = 3

kReverbParam_PreDelay       = 4

kReverbParam_LargeDelay     = 5

kReverbParam_SmallDensity   = 6

kReverbParam_LargeDensity   = 7

kReverbParam_LargeDelayRange= 8

kReverbParam_SmallBrightness= 9

kReverbParam_LargeBrightness= 10

kReverbParam_SmallDelayRange= 11

kReverbParam_ModulationRate = 12

kReverbParam_ModulationDepth= 13

Delay Unit Parameters

These parameters are used with the Delay Unit.

kDelayParam_WetDryMix   = 0

kDelayParam_DelayTime   = 1

kDelayParam_Feedback    = 2

kDelayParam_LopassCutoff= 3

AUPeakLimiter Unit Parameters

These parameters are used with the AUPeakLimiter Unit.

kLimiterParam_AttackTime = 0

kLimiterParam_DecayTime = 1

kLimiterParam_PreGain   = 2

AUDynamicsProcessor Unit Parameters

These parameters are used with the AUDynamicsProcessor Unit.

kDynamicsProcessorParam_Threshold           = 0

kDynamicsProcessorParam_HeadRoom            = 1

kDynamicsProcessorParam_ExpansionRatio      = 2

kDynamicsProcessorParam_ExpansionThreshold  = 3

kDynamicsProcessorParam_AttackTime          = 4

kDynamicsProcessorParam_ReleaseTime         = 5

kDynamicsProcessorParam_MasterGain          = 6

kDynamicsProcessorParam_CompressionAmount   = 1000

AUMultibandCompressor Unit Parameters

These parameters are used with the AUMultibandCompressor Unit.

kMultibandCompressorParam_Pregain           = 0

kMultibandCompressorParam_Postgain          = 1

kMultibandCompressorParam_Crossover1        = 2

kMultibandCompressorParam_Crossover2        = 3

kMultibandCompressorParam_Crossover3        = 4

kMultibandCompressorParam_Threshold1        = 5

kMultibandCompressorParam_Threshold2        = 6

kMultibandCompressorParam_Threshold3        = 7

kMultibandCompressorParam_Threshold4        = 8

kMultibandCompressorParam_Headroom1         = 9

kMultibandCompressorParam_Headroom2         = 10

kMultibandCompressorParam_Headroom3         = 11

kMultibandCompressorParam_Headroom4         = 12

kMultibandCompressorParam_AttackTime        = 13

kMultibandCompressorParam_ReleaseTime       = 14

kMultibandCompressorParam_EQ1               = 15

kMultibandCompressorParam_EQ2               = 16

kMultibandCompressorParam_EQ3               = 17

kMultibandCompressorParam_EQ4               = 18

kMultibandCompressorParam_CompressionAmount1 = 1000

kMultibandCompressorParam_CompressionAmount2 = 2000kMultibandCompressorParam_CompressionAmount3 = 3000

kMultibandCompressorParam_CompressionAmount4 = 4000

AUVarispeed Unit Parameters

These parameters are used with the AUVarispeed Unit.

kVarispeedParam_PlaybackRate    = 0

kVarispeedParam_PlaybackCents   = 1

3DMixer Unit Parameters

These parameters are used with the 3DMixer Unit.

k3DMixerParam_Azimuth           = 0

k3DMixerParam_Elevation         = 1

k3DMixerParam_Distance          = 2

k3DMixerParam_Gain              = 3

k3DMixerParam_PlaybackRate      = 4

k3DMixerParam_PreAveragePower   = 1000

k3DMixerParam_PrePeakHoldLevel  = 2000

k3DMixerParam_PostAveragePower  = 3000

k3DMixerParam_PostPeakHoldLevel = 4000

StereoMixer Unit Parameters

These parameters are used with the StereoMixer Unit.

kStereoMixerParam_Volume            = 0

kStereoMixerParam_Pan               = 1

kStereoMixerParam_PreAveragePower   = 1000

kStereoMixerParam_PrePeakHoldLevel  = 2000

kStereoMixerParam_PostAveragePower  = 3000

kStereoMixerParam_PostPeakHoldLevel = 4000

MatrixMixer Parameters

These parameters are used with the MatrixMixer Unit.

kMatrixMixerParam_Volume                    = 0

kMatrixMixerParam_Enable                    = 1

kMatrixMixerParam_PreAveragePower           = 1000

kMatrixMixerParam_PrePeakHoldLevel          = 2000

kMatrixMixerParam_PostAveragePower          = 3000

kMatrixMixerParam_PostPeakHoldLevel         = 4000

kMatrixMixerParam_PreAveragePowerLinear     = 5000

kMatrixMixerParam_PrePeakHoldLevelLinear    = 6000

kMatrixMixerParam_PostAveragePowerLinear    = 7000

kMatrixMixerParam_PostPeakHoldLevelLinear   = 8000

Output Unit Parameters

These parameters are used with Output Units.

kHALOutputParam_Volume = 14

DLSMusicDevice Parameters

These parameters are used with the DLSMusicDevice Unit.

kMusicDeviceParam_Tuning        = 0

kMusicDeviceParam_Volume        = 1

kMusicDeviceParam_ReverbVolume  = 2

Types

These basic types are common within the context of audio units.

typedef UInt32 AudioUnit

typedef UInt32 AudioUnitPropertyID

typedef UInt32 AudioUnitParameterID

typedef UInt32 AudioUnitScope

typedef UInt32 AudioUnitElement

typedef UInt32 AUParameterEventType

typedef UInt32 AudioUnitParameterUnit

Structures

These structures are used throughout the Audio Unit framework when working with properties and parameters.

AudioUnitParameter

Used by the Audio Unit Utilities to specify a parameter to be modified.

struct AudioUnitParameter {
   AudioUnit             mAudioUnit;
   AudioUnitParameterID  mParameterID;
   AudioUnitScope        mScope;
   AudioUnitElement      mElement;
};

Fields

mAudioUnit: The audio unit to be modified.
mParameterID: The parameter to be modified.
mScope: The scope in which the unit is being used.
mElement: The argument to be used with the parameter.

AudioUnitProperty

Used by the Audio Unit Utilities to specify a property to be modified.

struct AudioUnitProperty {
   AudioUnit             mAudioUnit;
   AudioUnitPropertyID   mPropertyID;
   AudioUnitScope        mScope;
   AudioUnitElement      mElement;
};

Fields

mAudioUnit: The audio unit to be modified.
mPropertyID: The parameter to be modified.
mScope: The scope in which the unit is being used.
mElement: The argument to be used with the property.

AudioUnitParameterEvent

Used to schedule a change in parameters during a render.

struct AudioUnitParameterEvent {
   AudioUnitScope          scope;
   AudioUnitElement        element;
   AudioUnitParameterID    parameter;
   AUParameterEventType    eventType;
   
   union {
      struct {
         SInt32          startBufferOffset;
         UInt32          durationInFrames;
         Float32         startValue;
         Float32         endValue;
      } ramp;
      struct {
         UInt32          bufferOffset;
         Float32         value;
      } immediate;
   } eventValues;
   
};

Fields

scope: The scope of the event.
element: Additional information about the scope of this event.
parameter: The parameter which is to be modified by the event.
eventType: A constant value; see Parameter Event Types.
eventValues: A union of the ramp and immediate event values.
ramp: The values if this event is a ramp event.
immediate: The values if this event is an immediate event.
durationInFrames: The length of the event, in frames.
startBufferOffset: The starting point of the event, after the beginning of the render.
startValue: The beginning value for the parameter.
endValue: The audio unit to be modifiedThe ending value of the parameter.
bufferOffset: Where in the current buffer the event should occur.
value: The value the parameter should be changed to.

AudioUnitConnection

Connects audio units together.

struct AudioUnitConnection {
   AudioUnit   sourceAudioUnit;
   UInt32      sourceOutputNumber;
   UInt32      destInputNumber;
}

Fields

sourceAudioUnit: The audio unit where data is coming from.
sourceOutputNumber: The output bus on the source audio unit.
destInputNumber: The destination bus on the recieving audio unit.

AURenderCallbackStruct

Encapsulates render callback information.

struct AURenderCallbackStruct {
   AURenderCallback    inputProc;
void *              inputProcRefCon; }

Fields

inputProc: The callback function.
inoutProcRefCon: Any arguments that should be passed to the callback.

AudioUnitExternalBuffer

Encapsulates information about an external buffer.

struct AudioUnitExternalBuffer {
   Byte*   buffer;
   UInt32  size;
}

Fields

buffer: A pointer to a buffer of audio data.
size: The size of the external buffer.

AUChannelInfo

Encapsulates channel information used in a connection.

struct AUChannelInfo {
   SInt16  inChannels;
   SInt16  outChannels;
}

Fields

inChannels: The number of channels on input.
outChannels: The number of channels on output.

AUPreset

Encapsulates channel information used in a connection.

struct AUPreset {
   SInt32      presetNumber;
   CFStringRef presetName;
}

Fields

presetNumber: An arbitrary value for a preset.
presetName: The name for a preset.

HostCallbackInfo

Encapsulates callbacks to a host for information.

struct HostCallbackInfo {
   void*                               hostUserData;
   HostCallback_GetBeatAndTempo        beatAndTempoProc;
   HostCallback_GetMusicalTimeLocation musicalTimeLocationProc;
}

Fields

hostUserData: Additional informaiton needed by the callbacks.
beatAndTempoProc: A callback that determines beat and tempo.
musicTimeLocationProc: A callback that determines the musical time, as numerator and denominator.

AudioUnitCocoaViewInfo

Encapsulates the information needed for a Cocoa view.

struct AudioUnitCocoaViewInfo {
   CFURLRef    mCocoaAUViewBundleLocation;
   CFStringRef mCocoaAUViewClass[1];
}

Fields

mCocoaAUViewBundleLocation: The location of the user interface bundle.
mCocoaAUViewClass: The names of the classes that implement the required protocol for an AUView.

AudioUnitParameterValueName

Encapsulates the information needed when determining a parameter value’s name.

struct AudioUnitParameterValueName {
   AudioUnitParameterID    inParamID;
   Float32*                inValue;
   CFStringRef             outName;
}

Fields

inParamID: The parameter in question.
inValue: The value being queried upon.
outName: The name corresponding to the value.

AudioUnitParameterNameInfo

Encapsulates the information needed when determining a parameter value’s name.

struct AudioUnitParameterNameInfo {
   UInt32          inID;
   SInt32          inDesiredLength;
   CFStringRef     outName;
}

Fields

inID: The parameter in question.
inDesiredLangth: The desired length of the string.
outName: The name corresponding to the parameter.

AudioUnitParameterInfo

Encapsulates an audio units parameter information.

struct AudioUnitParameterInfo {
   char                    name[56];
   UInt32                  clumpID;
   CFStringRef             cfNameString;
   AudioUnitParameterUnit  unit;
   Float32                 minValue;
   Float32                 maxValue;
   Float32                 defaultValue;
   UInt32                  flags;
}

Fields

name: The name of the parameter.
clumpID: The grouping to which the parameter belongs.
cfNameString: The name of this parameter as a CFString.
unit: The parameter unit for this parameter.
minValue: The smallest value for the parameter.
maxValue: The largest value for the parameter.
defaultValue: The default value for this parameter.
flags: Any flags that the parameter has attached to it.

AudioUnitMIDIControlMapping

Encapsulates MIDI and corresponding audio unit information.

struct AudioUnitMIDIControlMapping {
   UInt16                  midiNRPN;
   UInt8                   midiControl;
   UInt8                   scope;
   AudioUnitElement        element;
   AudioUnitParameterID    parameter;
}

Fields

midiNRPN: The MIDI note information.
midiControl: The MIDI control information.
scope: The scope of the mapping.
element: Additional scope information.
parameter: The parameter to which the MIDI data is to be applied.

AudioOutputUnitStartAtTimeParam

Encapsulates the information needed when a parameter is to take effect at a certain time.

struct AudioOutputUnitStartAtTimeParams {
   AudioTimeStamp  mTimestamp;
   UInt32          mFlags;
}

Fields

mTimestamp: The start time for the parameter.
mFlags: The flags for this parameter event.

Functions

These functions provide the bulk of the functionality of the Audio Unit framework, and are needed when using or developing an audio unit.

AudioUnitInitialize

Initializes an audio unit instance.

ComponentResult AudioUnitInitialize(
AudioUnit           ci
)

Parameters

ci: The audio unit to be initialized.

Availability

Available in Mac OS X v10.0 and later.

Declared In

AUComponent.h

AudioUnitUninitialize

Uninitializes an audio unit instance.

ComponentResult AudioUnitUninitialize(
AudioUnit ci
)

Parameters

ci: The audio unit to be uninitialized.

Availability

Available in Mac OS X v10.0 and later.

Declared In

AUComponent.h

AudioUnitRender

Performs the action on a buffer of audio data.

ComponentResult AudioUnitRender(
   AudioUnit                     ci,
   AudioUnitRenderActionFlags*   ioActionFlags,
   const AudioTimeStamp*         inTimeStamp,
   UInt32                        inOutputBusNumber,
   UInt32                        inNumberFrames,
   AudioBufferList*              ioData
)

Parameters

ci: The audio unit to be changed.
ioActionFlags: Flags that provide information on the render; see “Render Action Flags.”
inTimeStamp: The time the render is begun.
inOutputBusNumber: The bus on which the output will be placed.
inNumberFrames: The number of frames to be rendered.
ioData: The audio data, before and after the render.

Availability

Available in Mac OS X v10.2 and later.

Declared In

AUComponent.h

AudioUnitReset

Resets an audio unit.

ComponentResult AudioUnitReset(
   AudioUnit          ci,
   AudioUnitScope     inScope,
   AudioUnitElement   inElement
)

Parameters

ci: The audio unit to be reset.
inScope: The scope in which the unit is to be reset.
inElement: Additional information about the scope of the audio unit.

Availability

Available in Mac OS X v10.0 and later.

Declared In

AUComponent.h

AudioUnitGetPropertyInfo

Returns the size of the data that will be returned when calling AudioUnitGetProperty for the specified property.

ComponentResult AudioUnitGetPropertyInfo(
   AudioUnit             ci,
   AudioUnitPropertyID   inID,
   AudioUnitScope        inScope,
   AudioUnitElement      inElement,
   UInt32*               outDataSize,
   Boolean*              outWritable
)

Parameters

ci: The audio unit on which the property is to be queried.
inID: The property to be queried upon.
inScope: The scope in which the property is applicable.
inElement: Further specifies the scope of the property.
outDataSize: The size, in bytes, of the property.
outWritable: A boolean showing if the property is writable.

Availability

Available in Mac OS X v10.0 and later.

Declared In

AUComponent.h

AudioUnitGetProperty

Returns the size of the data for a specified property.

ComponentResult AudioUnitGetProperty(
   AudioUnit             ci,
   AudioUnitPropertyID   inID,
   AudioUnitScope        inScope,
   AudioUnitElement      inElement,
   void*                 outData,
   UInt32*               ioDataSize
)

Parameters

ci: The audio unit on which the property is to be queried.
inID: The property to be queried upon.
inScope: The scope in which the property is applicable.
inElement: Further specifies the scope of the property.
outData: A pointer to the data corresponding to the property.
ioDataSize: The expected data size and the actual data size returned.

Availability

Available in Mac OS X v10.0 and later.

Declared In

AUComponent.h

AudioUnitSetProperty

Sets a property’s value to the supplied value.

ComponentResult AudioUnitSetProperty(
   AudioUnit             ci,
   AudioUnitPropertyID   inID,
   AudioUnitScope        inScope,
   AudioUnitElement      inElement,
   const void*           inData,
   UInt32                inDataSize
)

Parameters

ci: The audio unit on which the property is to be applied.
inID: The property to be modified.
inScope: The scope in which the property is applicable.
inElement: Further specifies the scope of the property.
inData: A pointer to the data to be applied to the property.
inDataSize: The size of the data being passed in.

Availability

Available in Mac OS X v10.0 and later.

Declared In

AUComponent.h

AudioUnitAddPropertyListener

Monitors an audio unit’s property for changes and issues a callback notification upon the change.

ComponentResult AudioUnitAddPropertyListener(
   AudioUnit                         ci,
   AudioUnitPropertyID               inID,
   AudioUnitPropertyListenerProc     inProc,
   void*                             inProcRefCon
)

Parameters

ci: The audio unit to be monitored.
inID: The property to be monitored.
inProc: The callback to be made when a property is changed.
inProcRefCon: Additional parameters to be passed to the callback.

Availability

Available in Mac OS X v10.0 and later.

Declared In

AUComponent.h

AudioUnitRemovePropertyListener

Removes the specified listener from a property.

ComponentResult AudioUnitRemovePropertyListener(
   AudioUnit                         ci,
   AudioUnitPropertyID               inID,
   AudioUnitPropertyListenerProc     inProc
)

Parameters

ci: The audio unit being monitored.
inID: The property being monitored.
inProc: The callback to be removed.

Availability

Available in Mac OS X v10.0 and later.
Deprecated in Mac OS X v10.5.
Not available to 64-bit applications.

Declared In

AUComponent.h

AudioUnitAddRenderNotify

Specifies a callback to be used before and after an audio unit render occurs.

ComponentResult AudioUnitAddRenderNotify(
   AudioUnit         ci,
   AURenderCallback  inProc,
   void*             inProcRefCon
)

Parameters

ci: The audio unit to bemonitored.
inProc: The callback to be issued.
inProcRefCon: Additional parameters to be passed to the callback.

Availability

Available in Mac OS X v10.2 and later.

Declared In

AUComponent.h

AudioUnitRemoveRenderNotify

Removes a callback from an audio unit.

ComponentResult AudioUnitRemoveRenderNotify(
   AudioUnit          ci,
   AURenderCallback   inProc,
   void *             inProcRefCon
)

Parameters

ci: The audio unit being monitored.
inProc: The callback being issued.
inProcRefCon: Additional parameters to be passed to the callback.

Availability

Available in Mac OS X v10.2 and later.

Declared In

AUComponent.h

AudioUnitGetParameter

Returns the current value for a parameter.

ComponentResult AudioUnitGetParameter(
   AudioUnit             ci,
   AudioUnitParameterID  inID,
   AudioUnitScope        inScope,
   AudioUnitElement      inElement,
   Float32*              outValue
)

Parameters

ci: The audio unit being queried.
inID: The parameter being queried.
inScope: The scope in which the parameter works.
inElement: Additional information about the scope of the parameter.
outValue: The current value of the parameter.

Availability

Available in Mac OS X v10.0 and later.

Declared In

AUComponent.h

AudioUnitSetParameter

Returns the current value for a parameter.

ComponentResult AudioUnitSetParameter(
   AudioUnit             ci,
   AudioUnitParameterID  inID,
   AudioUnitScope        inScope,
   AudioUnitElement      inElement,
   Float32               inValue,
   UInt32                inBufferOffsetInFrames
)

Parameters

ci: The audio unit to be changed.
inID: The parameter to be changed.
inScope: The scope in which the parameter works.
inElement: Additional information about the scope of the parameter.
inValue: The new value for the parameter.
inBufferOffsetInFrames: When in the next render the parameter should be changed.

Availability

Available in Mac OS X v10.0 and later.

Declared In

AUComponent.h

AudioUnitScheduleParameters

Adds events that change certain parameters.

ComponentResult AudioUnitScheduleParameters(
   AudioUnit                         ci,
   const AudioUnitParameterEvent*    inParameterEvent,
   UInt32                            inNumParamEvents )

Parameters

ci: The audio unit to be changed.
inParameterEvent: An event or events to be placed.
inNumParamEvents: The number of events being added.

Availability

Available in Mac OS X v10.2 and later.

Declared In

AUComponent.h

Callbacks

These callbacks are provided by you and are used throughout the Audio Unit framework.

AURenderCallback

A callback set by kAudioUnitProperty_SetRenderCallback for performing an audio unit’s render.

typedef CALLBACK_API_C( OSStatus , AURenderCallback )(void *inRefCon, AudioUnitRenderActionFlags *ioActionFlags, const AudioTimeStamp *inTimeStamp, UInt32 inBusNumber, UInt32 inNumberFrames, AudioBufferList *ioData)

OSStatus AURenderCallback(
void *      inRefCon;
AudioUnitRenderActionFlags      * ioActionFlags;
const AudioTimeStamp    *   inTimeStamp;
UInt32       inBusNumber;
UInt32       inNumberFrames;
AudioBufferList*       ioData
)

Parameters

inRefCon: Parameters passed to the callback.
ioActionFlags: Flags for rendering options.
inTimeStamp: The time that the callback is invoked.
inBusNumber: The bun on which data will be supplied.
inNumberFrames: The number of frames to be rendered.
ioData: The audio data to be rendered upon.

Availability

Available in Mac OS X v10.2 and later.

Declared In

AUComponent.h

AudioUnitPropertyListenerProc

A callback set by kAudioUnitProperty_SetRenderCallback for performing an audio unit’s render.

typedef CALLBACK_API_C( void , AudioUnitPropertyListenerProc )(void *inRefCon, AudioUnit ci, AudioUnitPropertyID inID, AudioUnitScope inScope, AudioUnitElement inElement);

void AudioUnitPropertyListenerProc(
void *    inRefCon,
AudioUnit     ci,
AudioUnitPropertyID     inID,
AudioUnitScope     inScope,
AudioUnitElement     inElement
)

Parameters

inRefCon: Parameters passed to the callback.
ci: The audio unit whose property was modified.
inID: The property that was changed.
inScope: The scope of the unit and the property that was changed.
inElement: The value that the property was changed to.

Availability

Available in Mac OS X v10.0 and later.

Declared In

AUComponent.h

AudioUnitGetParameterProc

A callback for returning developer specified parameter values.

typedef CALLBACK_API_C( ComponentResult , AudioUnitGetParameterProc )(void *inComponentStorage, AudioUnitParameterID inID, AudioUnitScope inScope, AudioUnitElement inElement, Float32 *outValue);

ComponentResult AudioUnitGetParameterProc(
void*                  inComponentStorage, 
AudioUnitParameterID                  inID, 
AudioUnitScope                  inScope, 
AudioUnitElement                  inElement, 
Float32*                  outValue
)

Parameters

inComponentStore: A pointer to the audio unit.
inID: The parameter being queried.
inScope: The scope of the parameter.
inElement: Additional information about the scope of the parameter.
outValue: The value returned for the parameter.

Availability

Available in Mac OS X v10.0 and later.

Declared In

AUComponent.h

AudioUnitSetParameterProc

A callback for setting developer specified parameter values.

typedef CALLBACK_API_C( ComponentResult , AudioUnitSetParameterProc )(void *inComponentStorage, AudioUnitParameterID inID, AudioUnitScope inScope, AudioUnitElement inElement, Float32 inValue, UInt32 inBufferOffsetInFrames);

ComponentResult AudioUnitSetParameterProc(
void*                  inComponentStorage
AudioUnitParameterID                  inID
AudioUnitScope                  inScope
AudioUnitElement                  inElement
Float32                  inValue
UInt32                  inBufferOffsetInFrames
)

Parameters

inComponentStore: A pointer to the audio unit.
inID: The parameter to be set.
inScope: The scope of the parameter.
inElement: Additional information about the scope of the parameter.
inValue: The value for the parameter to be set.
inBufferOffsetInFrames: The place in the buffer where the parameter change is to happen.

Availability

Available in Mac OS X v10.0 and later.

Declared In

AUComponent.h

AudioUnitRenderProc

A callback for setting developer specified parameter values.

typedef CALLBACK_API_C( ComponentResult , AudioUnitRenderProc )(void *inComponentStorage, AudioUnitRenderActionFlags *ioActionFlags, const AudioTimeStamp *inTimeStamp, UInt32 inOutputBusNumber, UInt32 inNumberFrames, AudioBufferList *ioData);

ComponentResult AudioUnitRenderProc(
void *      inComponentStorage,
AudioUnitRenderActionFlags*       ioActionFlags,
const AudioTimeStamp    *   inTimeStamp,
UInt32       inOutputBusNumber,
UInt32       inNumberFrames,
AudioBufferList*       ioData
)

Parameters

inComponentStorage: A pointer to the audio unit.
ioActionFlags: Flags that provide information on the render; see “Render Action Flags.”
inTimeStamp: The time the render is begun.
inOutputBusNumber: The bus on which the output will be placed.
inNumberFrames: The number of frames to be rendered.
ioData: The audio data, before and after the render.

Availability

Available in Mac OS X v10.2 and later.

Declared In

AUComponent.h

HostCallback_GetBeatAndTempo

A callback for setting developer specified parameter values.

typedef OSStatus (*HostCallback_GetBeatAndTempo) (void * inHostUserData, Float64 *outCurrentBeat, Float64    * outCurrentTempo);

OSStatus HostCallback_GetBeatAndTempo (
void    inHostUserData,
Float64 *   outCurrentBeat,
Float64 *    outCurrentTempo
)

Parameters

inHostUserData: Any arguments needed by the callback.
outCurrentBeat: The beat of the buffered data.
outCurrentTempo: The tempo of the buffered data.

Availability

Available in Mac OS X v10.2 and later.

Declared In

AudioUnitProperties.h

HostCallback_GetBeatAndTempo

A callback for setting developer specified parameter values.

typedef OSStatus (*HostCallback_GetMusicalTimeLocation) (void *inHostUserData, UInt32 *outDeltaSampleOffsetToNextBeat, Float32 *outTimeSig_Numerator, UInt32 *outTimeSig_Denominator, Float64 *outCurrentMeasureDownBeat);

OSStatus HostCallback_GetMusicalTimeLocation(
void*    inHostUserData,
UInt32*    outDeltaSampleOffsetToNextBeat,
Float32*    outTimeSig_Numerator,
UInt32*    outTimeSig_Denominator,
Float64*    outCurrentMeasureDownBeat
)

Parameters

inHostUserData: Any arguments needed by the callback.
outDeltaDampleOffsetToNextBeat: The average time between beats.
outTimeSig_Numerator: The numerator of the time signature.
outTimeSig_Denominator: The denominator of the time signature.
outCurrentMeasureDownBeat: The beats in the current measure.

Availability

Available in Mac OS X v10.2 and later.

Declared In

AudioUnitProperties.h

HostCallback_GetBeatAndTempo

A callback for setting developer specified parameter values.

typedef OSStatus (*HostCallback_GetMusicalTimeLocation) (void *inHostUserData, UInt32 *outDeltaSampleOffsetToNextBeat, Float32 *outTimeSig_Numerator, UInt32 *outTimeSig_Denominator, Float64 *outCurrentMeasureDownBeat);

OSStatus HostCallback_GetMusicalTimeLocation(
void*    inHostUserData,
UInt32*    outDeltaSampleOffsetToNextBeat,
Float32*    outTimeSig_Numerator,
UInt32*    outTimeSig_Denominator,
Float64*    outCurrentMeasureDownBeat
)

Parameters

inHostUserData: Any arguments needed by the callback.
outDeltaDampleOffsetToNextBeat: The average time between beats.
outTimeSig_Numerator: The numerator of the time signature.
outTimeSig_Denominator: The denominator of the time signature.
outCurrentMeasureDownBeat: The beats in the current measure.

Availability

Available in Mac OS X v10.2 and later.

Declared In

AudioUnitProperties.h

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