Audio Unit Parameters Reference

Framework
/System/Library/Frameworks/AudioUnit.framework
Declared in
AudioUnitParameters.h

Overview

An audio unit parameter is a key, defined by the audio unit it applies to, whose corresponding value specifies the setting for an adjustable attribute such as volume, pitch, or filter cutoff frequency. Parameters are typically varied by the user during audio processing, by way of a user interface that you provide. All parameter values are of the same data type: 32-bit floating point. The audio unit that defines a parameter also defines the meaning of the value, the default value, and the permissible range.

Constants

3D Mixer Unit Parameters

Parameters for the 3D Mixer unit.

enum {
   k3DMixerParam_Azimuth                 = 0,
   k3DMixerParam_Elevation               = 1,
   k3DMixerParam_Distance                = 2,
   k3DMixerParam_Gain                    = 3,
   k3DMixerParam_PlaybackRate            = 4,
   k3DMixerParam_Enable                  = 5,
   k3DMixerParam_MinGain                 = 6,
   k3DMixerParam_MaxGain                 = 7,
   k3DMixerParam_ReverbBlend             = 8,
   k3DMixerParam_GlobalReverbGain        = 9,
   k3DMixerParam_OcclusionAttenuation    = 10,
   k3DMixerParam_ObstructionAttenuation  = 11
};
Constants
k3DMixerParam_Azimuth

Specifies the horizontal azimuth of the sound source relative to the listener.

Used on the input scope. Range is from –180° through +180°, each of which indicate a source position that is directly behind the listener. –90° indicates extreme left; +90° indicates extreme right. Default is , which indicates straight ahead.

For the azimuth setting to be audible, the 3D Mixer unit’s k3DMixerParam_Distance parameter value must be set to a positive value.

Available in iOS 2.0 and later.

Declared in AudioUnitParameters.h.

k3DMixerParam_Elevation

Specifies the vertical elevation of the sound source relative to the listener.

Used on the input scope. Range is from –90° (straight down) through +90° (straight up). Default is , indicating a line parallel to the earth’s surface.

For the elevation setting to be audible, the 3D Mixer unit’s k3DMixerParam_Distance parameter value must be set to a positive value.

Available in iOS 2.0 and later.

Declared in AudioUnitParameters.h.

k3DMixerParam_Distance

Specifies the apparent distance of the sound source from the listener.

Used on the input scope. Range is from 0 through 10,000 meters. Default is 0 meters, which indicates that the sound source and the listener are positioned together at the same point.

For changes to the k3DMixerParam_Azimuth or k3DMixerParam_Elevation parameters to be audible, set this parameter to a positive value.

Available in iOS 2.0 and later.

Declared in AudioUnitParameters.h.

k3DMixerParam_Gain

Specifies audio gain.

Used on the input and output scopes. Range is from –120 dB (near silence) through 20 dB. Default is 0 dB, indicating unity gain.

Available in iOS 2.0 and later.

Declared in AudioUnitParameters.h.

k3DMixerParam_PlaybackRate

Specifies the playback rate relative to normal-speed playback.

Used on the input scope. Range is from 0.5 (half speed) through 2.0 (twice normal speed). Default value is 1.0, corresponding to normal-speed playback.

When you vary the playback rate away from 1.0, playback pitch changes accordingly. For example, using a playback rate of 2.0, sounds are higher in pitch by one octave.

Available in iOS 2.0 and later.

Declared in AudioUnitParameters.h.

k3DMixerParam_Enable

Enables or disables a mixer input.

Use 0 to disable, or mute, an input. Use 1 to enable, or unmute, an input. Inputs are enabled by default.

Available in iOS 4.0 and later.

Declared in AudioUnitParameters.h.

k3DMixerParam_MinGain

Specifies a lower constraint for range of the k3DMixerParam_Gain parameter.

Range is from 0.0 through 1.0. Default value is 0.0.

Available in iOS 4.0 and later.

Declared in AudioUnitParameters.h.

k3DMixerParam_MaxGain

Specifies an upper constraint for range of the k3DMixerParam_Gain parameter.

Range is from 0.0 through 1.0. Default value is 1.0.

Available in iOS 4.0 and later.

Declared in AudioUnitParameters.h.

k3DMixerParam_ReverbBlend

Specifies the dry/wet blend for a mixer input, using an equal-power percentage.

Range is from 0.0 through 100.0. Used on the input scope.

Available in iOS 5.0 and later.

Declared in AudioUnitParameters.h.

k3DMixerParam_GlobalReverbGain

Specifies the reverb gain, globally, for the mixer unit, in decibels.

Range is from –40.0 through +40.0. Used on the global scope.

Available in iOS 5.0 and later.

Declared in AudioUnitParameters.h.

k3DMixerParam_OcclusionAttenuation

Specifies the amount of 5 kHz low-pass filter attenuation for an input, in decibels, applied before the send to the mixer’s reverb effect.

Range is from –100.0 through 0.0. A value of 0 results in no attenuation. A value of –100 results in maximum muffling effect. See also k3DMixerParam_ObstructionAttenuation.

Use this parameter to simulate the listener and the sound source being in different rooms, or one being outside and the other inside. The simulation is that not only is line of sight blocked, but all acoustic reflections are blocked as well.

Available in iOS 5.0 and later.

Declared in AudioUnitParameters.h.

k3DMixerParam_ObstructionAttenuation

Specifies the amount of 5 kHz low-pass filter attenuation for an input, in decibels, applied after the send to the mixer’s reverb effect.

Range is from –100.0 through 0.0. A value of 0 results in no attenuation. A value of –100 results in maximum muffling effect. See also k3DMixerParam_OcclusionAttenuation.

Use this parameter to simulate an object that blocks the line of sight between the listener and the sound source, but does not block all acoustic reflections.

Available in iOS 5.0 and later.

Declared in AudioUnitParameters.h.

Multichannel Mixer Unit Parameters

Parameters for the Multichannel Mixer unit.

enum {
   kMultiChannelMixerParam_Volume            = 0,
   kMultiChannelMixerParam_Enable            = 1,
   kMultiChannelMixerParam_Pan               = 2,
   kMultiChannelMixerParam_PreAveragePower   = 1000,
   kMultiChannelMixerParam_PrePeakHoldLevel  = 2000,
   kMultiChannelMixerParam_PostAveragePower  = 3000,
   kMultiChannelMixerParam_PostPeakHoldLevel = 4000
};
Constants
kMultiChannelMixerParam_Volume

Sets the audio gain for a mixer input or the output.

Range is from 0 (for silence) through 1 (for unity gain).

Available in iOS 2.0 and later.

Declared in AudioUnitParameters.h.

kMultiChannelMixerParam_Enable

Enables or disables a mixer input.

Use 0 to disable, or mute, an input. Use 1 to enable, or unmute, an input.

Available in iOS 2.0 and later.

Declared in AudioUnitParameters.h.

kMultiChannelMixerParam_Pan

Sets the stereo panning position for a mixer input.

Range is from -1 (extreme left) through +1 (extreme right). Default value is 0, indicating center.

Available in iOS 4.0 and later.

Declared in AudioUnitParameters.h.

kMultiChannelMixerParam_PreAveragePower

Indicates the average “pre” power in decibels (dB). Read only.

Available in iOS 2.0 and later.

Declared in AudioUnitParameters.h.

kMultiChannelMixerParam_PrePeakHoldLevel

Indicates the “pre” peak hold level in decibels (dB). Read only.

Available in iOS 2.0 and later.

Declared in AudioUnitParameters.h.

kMultiChannelMixerParam_PostAveragePower

Indicates the average “post” power in decibels (dB). Read only.

Available in iOS 2.0 and later.

Declared in AudioUnitParameters.h.

kMultiChannelMixerParam_PostPeakHoldLevel

Indicates the “post” peak hold level in decibels (dB). Read only.

Available in iOS 2.0 and later.

Declared in AudioUnitParameters.h.

Bandpass Unit Parameters

Parameters for the Bandpass unit.

enum {
   kBandpassParam_CenterFrequency  = 0,
   kBandpassParam_Bandwidth        = 1
};
Constants
kBandpassParam_CenterFrequency

Range is from 20 Hz to less than the Nyquist frequency (half the sample rate). Default value is 5,000 Hz. Used on the Global scope.

Available in iOS 5.0 and later.

Declared in AudioUnitParameters.h.

kBandpassParam_Bandwidth

Range is from 100 through 12000 cents. Default value is 600 cents. Used on the Global scope.

Available in iOS 5.0 and later.

Declared in AudioUnitParameters.h.

Highpass Unit Parameters

Parameters for the Highpass unit.

enum {
   kHipassParam_CutoffFrequency  = 0,
   kHipassParam_Resonance        = 1
};
Constants
kHipassParam_CutoffFrequency

Range is from 10 Hz to less than the Nyquist frequency (half the sample rate). Default value is 6900 Hz. Used on the Global scope.

Available in iOS 5.0 and later.

Declared in AudioUnitParameters.h.

kHipassParam_Resonance

Range is from –20 through +40 dB. Default value is 0 dB. Used on the Global scope.

Available in iOS 5.0 and later.

Declared in AudioUnitParameters.h.

Lowpass Unit Parameters

Parameters for the Lowpass unit.

enum {
   kLowPassParam_CutoffFrequency  = 0,
   kLowPassParam_Resonance        = 1
};
Constants
kLowPassParam_CutoffFrequency

Range is from 10 Hz to less than the Nyquist frequency (half the sample rate). Default value is 6900 Hz. Used on the Global scope.

Available in iOS 5.0 and later.

Declared in AudioUnitParameters.h.

kLowPassParam_Resonance

Range is from –20 through +40 dB. Default value is 0 dB. Used on the Global scope.

Available in iOS 5.0 and later.

Declared in AudioUnitParameters.h.

High Shelf Filter Unit Parameters

Parameters for the High Shelf Filter unit.

enum {
   kHighShelfParam_CutOffFrequency  = 0,
   kHighShelfParam_Gain             = 1
};
Constants
kHighShelfParam_CutOffFrequency

Range is from 10000 Hz to less than the Nyquist frequency (half the sample rate). Default value is 10000 Hz. Used on the Global scope.

Available in iOS 5.0 and later.

Declared in AudioUnitParameters.h.

kHighShelfParam_Gain

Range is from –40 through +40 dB. Default value is 0 dB. Used on the Global scope.

Available in iOS 5.0 and later.

Declared in AudioUnitParameters.h.

Low Shelf Filter Unit Parameters

Parameters for the Low Shelf Filter unit.

enum {
   kAULowShelfParam_CutoffFrequency  = 0,
   kAULowShelfParam_Gain             = 1
};
Constants
kAULowShelfParam_CutoffFrequency

Range is from 10 through 200 Hz. Default value is 80 Hz. Used on the Global scope.

Available in iOS 5.0 and later.

Declared in AudioUnitParameters.h.

kAULowShelfParam_Gain

Range is from –40 through +40 dB. Default value is 0 dB. Used on the Global scope.

Available in iOS 5.0 and later.

Declared in AudioUnitParameters.h.

Parametric EQ Unit Parameters

Parameters for the Parametric EQ unit.

enum {
   kParametricEQParam_CenterFreq  = 0,
   kParametricEQParam_Q           = 1,
   kParametricEQParam_Gain        = 2
};
Constants
kParametricEQParam_CenterFreq

Range is from 20 Hz to less than the Nyquist frequency (half the sample rate). Default value is 2000 Hz. Used on the Global scope.

Available in iOS 5.0 and later.

Declared in AudioUnitParameters.h.

kParametricEQParam_Q

Range is from 0.1 through 20 (Q is an absolute value and has no unit). Default value is 1.0. Used on the Global scope.

Available in iOS 5.0 and later.

Declared in AudioUnitParameters.h.

kParametricEQParam_Gain

Range is from –20 through +20 dB. Default value is 0 dB. Used on the Global scope.

Available in iOS 5.0 and later.

Declared in AudioUnitParameters.h.

Multitype EQ (NBandEQ) Unit Parameters

Parameters for the Multitype EQ unit.

enum {
   kAUNBandEQParam_BypassBand  = 1000,
   kAUNBandEQParam_FilterType  = 2000,
   kAUNBandEQParam_Frequency   = 3000,
   kAUNBandEQParam_Gain        = 4000,
   kAUNBandEQParam_Bandwidth   = 5000
};
Constants
kAUNBandEQParam_BypassBand

Boolean value, with a value of 1 meaning bypass. Default value is 1. Used on the Global scope.

Available in iOS 5.0 and later.

Declared in AudioUnitParameters.h.

kAUNBandEQParam_FilterType

An indexed value using one of the values from “Mutitype EQ Unit Filter Types.” Default value is kAUNBandEQFilterType_Parametric. Used on the Global scope.

Available in iOS 5.0 and later.

Declared in AudioUnitParameters.h.

kAUNBandEQParam_Frequency

Range is from 20 Hz to less than the Nyquist frequency (half the sample rate). Default value is 1000 Hz. Used on the Global scope.

Available in iOS 5.0 and later.

Declared in AudioUnitParameters.h.

kAUNBandEQParam_Gain

Range is from –96 through +24 dB. Default value is 0 dB. Used on the Global scope.

Available in iOS 5.0 and later.

Declared in AudioUnitParameters.h.

kAUNBandEQParam_Bandwidth

Range is from 0.05 through 5.0 octaves. Default value is 0.5 octaves. Used on the Global scope.

Available in iOS 5.0 and later.

Declared in AudioUnitParameters.h.

Discussion

The Multitype EQ unit (of subtype kAudioUnitSubType_NBandEQ) provides an equalizer that can be configured as any one of the types described in “Mutitype EQ Unit Filter Types.”

Note that the parameter IDs listed correspond to band 0 (zero) of the unit. The parameter IDs for higher bands can be obtained by adding the zero-indexed band number to the corresponding band 0 parameter ID up to the number of bands minus one, where the number of bands is described by the AUNBandEQ property kAUNBandEQProperty_NumberOfBands. For example, the parameter ID corresponding to the filter type of band 4 would be kAUNBandEQParam_FilterType + 3.

Mutitype EQ Unit Filter Types

Values for the kAUNBandEQParam_FilterType parameter of the Multitype EQ (NBandEQ) unit.

enum {
   kAUNBandEQFilterType_Parametric                  = 0,
   kAUNBandEQFilterType_2ndOrderButterworthLowPass  = 1,
   kAUNBandEQFilterType_2ndOrderButterworthHighPass = 2,
   kAUNBandEQFilterType_ResonantLowPass             = 3,
   kAUNBandEQFilterType_ResonantHighPass            = 4,
   kAUNBandEQFilterType_BandPass                    = 5,
   kAUNBandEQFilterType_BandStop                    = 6,
   kAUNBandEQFilterType_LowShelf                    = 7,
   kAUNBandEQFilterType_HighShelf                   = 8,
   kAUNBandEQFilterType_ResonantLowShelf            = 9,
   kAUNBandEQFilterType_ResonantHighShelf           = 10,
   
   kNumAUNBandEQFilterTypes                         = 11
};
Constants
kAUNBandEQFilterType_Parametric

Parametric filter based on the Butterworth analog prototype.

Uses parameterization where the bandwidth is specified as the relationship of the upper band edge frequency to the lower band edge frequency in octaves, where the upper and lower band edge frequencies are the respective frequencies above and below the center frequency at which the gain is equal to half the peak gain.

Applicable parameters when using this filter type:

Available in iOS 5.0 and later.

Declared in AudioUnitParameters.h.

kAUNBandEQFilterType_2ndOrderButterworthLowPass

Simple Butterworth 2nd order low pass filter.

The only application parameter when using this filter type is kAUNBandEQParam_Frequency (–3 dB cutoff frequency).

Available in iOS 5.0 and later.

Declared in AudioUnitParameters.h.

kAUNBandEQFilterType_2ndOrderButterworthHighPass

Simple Butterworth 2nd order high pass filter.

The only application parameter when using this filter type is kAUNBandEQParam_Frequency (–3 dB cutoff frequency).

Available in iOS 5.0 and later.

Declared in AudioUnitParameters.h.

kAUNBandEQFilterType_ResonantLowPass

Low pass filter with resonance support (via bandwidth parameter).

Applicable parameters when using this filter type:

Available in iOS 5.0 and later.

Declared in AudioUnitParameters.h.

kAUNBandEQFilterType_ResonantHighPass

High pass filter with resonance support (via bandwidth parameter).

Applicable parameters when using this filter type:

Available in iOS 5.0 and later.

Declared in AudioUnitParameters.h.

kAUNBandEQFilterType_BandPass

Bandpass filter.

Applicable parameters when using this filter type:

Available in iOS 5.0 and later.

Declared in AudioUnitParameters.h.

kAUNBandEQFilterType_BandStop

Band stop (also called notch) filter.

Applicable parameters when using this filter type:

Available in iOS 5.0 and later.

Declared in AudioUnitParameters.h.

kAUNBandEQFilterType_LowShelf

Low shelf filter.

Applicable parameters when using this filter type:

Available in iOS 5.0 and later.

Declared in AudioUnitParameters.h.

kAUNBandEQFilterType_HighShelf

High shelf filter.

Applicable parameters when using this filter type:

Available in iOS 5.0 and later.

Declared in AudioUnitParameters.h.

kAUNBandEQFilterType_ResonantLowShelf

Low shelf filter with resonance support (via bandwidth parameter).

Applicable parameters when using this filter type:

Available in iOS 5.0 and later.

Declared in AudioUnitParameters.h.

kAUNBandEQFilterType_ResonantHighShelf

High shelf filter with resonance support (via bandwidth parameter).

Applicable parameters when using this filter type:

Available in iOS 5.0 and later.

Declared in AudioUnitParameters.h.

kNumAUNBandEQFilterTypes

The available filter types.

Available in iOS 5.0 and later.

Declared in AudioUnitParameters.h.

Dynamics Processor Unit Parameters

Parameters for the Dynamics Processor unit.

enum {
   kDynamicsProcessorParam_Threshold          = 0,
   kDynamicsProcessorParam_HeadRoom           = 1,
   kDynamicsProcessorParam_ExpansionRatio     = 2,
   kDynamicsProcessorParam_ExpansionThreshold = 3,
   kDynamicsProcessorParam_AttackTime         = 4,
   kDynamicsProcessorParam_ReleaseTime        = 5,
   kDynamicsProcessorParam_MasterGain         = 6,
   kDynamicsProcessorParam_CompressionAmount  = 1000,
   kDynamicsProcessorParam_InputAmplitude     = 2000,
   kDynamicsProcessorParam_OutputAmplitude    = 3000
};
Constants
kDynamicsProcessorParam_Threshold

Range is from –40 through +20 dB. Default value is –20 dB. Used on the Global scope.

Available in iOS 5.0 and later.

Declared in AudioUnitParameters.h.

kDynamicsProcessorParam_HeadRoom

Range is from 0.1 through 40 dB. Default value is 5 dB. Used on the Global scope.

Available in iOS 5.0 and later.

Declared in AudioUnitParameters.h.

kDynamicsProcessorParam_ExpansionRatio

Range is from 1.0 through 50.0. Default value is 2. Used on the Global scope.

Available in iOS 5.0 and later.

Declared in AudioUnitParameters.h.

kDynamicsProcessorParam_ExpansionThreshold

Units are dB. Used on the Global scope.

Available in iOS 5.0 and later.

Declared in AudioUnitParameters.h.

kDynamicsProcessorParam_AttackTime

Range is from 0.0001 through 0.2 seconds. Default value is 0.001 s. Used on the Global scope.

Available in iOS 5.0 and later.

Declared in AudioUnitParameters.h.

kDynamicsProcessorParam_ReleaseTime

Range is from 0.01 through 3.0 seconds. Default value is 0.05 s. Used on the Global scope.

Available in iOS 5.0 and later.

Declared in AudioUnitParameters.h.

kDynamicsProcessorParam_MasterGain

Range is from –40 through +40 dB. Default value is 0 dB. Used on the Global scope.

Available in iOS 5.0 and later.

Declared in AudioUnitParameters.h.

kDynamicsProcessorParam_CompressionAmount

Units are dB. Used on the Global scope. Read-only.

Available in iOS 5.0 and later.

Declared in AudioUnitParameters.h.

kDynamicsProcessorParam_InputAmplitude

Units are dB. Used on the Global scope. Read-only.

Available in iOS 5.0 and later.

Declared in AudioUnitParameters.h.

kDynamicsProcessorParam_OutputAmplitude

Units are dB. Used on the Global scope. Read-only.

Available in iOS 5.0 and later.

Declared in AudioUnitParameters.h.

Peak Limiter Unit Parameters

Parameters for the Peak Limiter unit.

enum {
   kLimiterParam_AttackTime  = 0,
   kLimiterParam_DecayTime   = 1,
   kLimiterParam_PreGain     = 2
};
Constants
kLimiterParam_AttackTime

Range is from 0.001 through 0.03 seconds. Default value is 0.012 s. Used on the Global scope.

Available in iOS 5.0 and later.

Declared in AudioUnitParameters.h.

kLimiterParam_DecayTime

Range is from 0.001 through 0.06 seconds. Default value is 0.024 s. Used on the Global scope.

Available in iOS 5.0 and later.

Declared in AudioUnitParameters.h.

kLimiterParam_PreGain

Range is from –40 through +40 dB. Default value is 0 dB. Used on the Global scope.

Available in iOS 5.0 and later.

Declared in AudioUnitParameters.h.

Reverb Unit Parameters

Parameters for the Reverb unit.

enum {
   kReverb2Param_DryWetMix            = 0,
   kReverb2Param_Gain                 = 1,
   kReverb2Param_MinDelayTime         = 2,
   kReverb2Param_MaxDelayTime         = 3,
   kReverb2Param_DecayTimeAt0Hz       = 4,
   kReverb2Param_DecayTimeAtNyquist   = 5,
   kReverb2Param_RandomizeReflections = 6,
};
Constants
kReverb2Param_DryWetMix

Range is from 0 through 100%. Default value is 100% (full reverb). Used on the Global scope.

Available in iOS 5.0 and later.

Declared in AudioUnitParameters.h.

kReverb2Param_Gain

Range is from –20 through +20 dB. Default value is 0 dB. Used on the Global scope.

Available in iOS 5.0 and later.

Declared in AudioUnitParameters.h.

kReverb2Param_MinDelayTime

Range is from 0.0001 through 1.0 seconds. Default value is 0.008 s. Used on the Global scope.

Available in iOS 5.0 and later.

Declared in AudioUnitParameters.h.

kReverb2Param_MaxDelayTime

Range is from 0.0001 through 1.0 seconds. Default value is 0.050 s. Used on the Global scope.

Available in iOS 5.0 and later.

Declared in AudioUnitParameters.h.

kReverb2Param_DecayTimeAt0Hz

Range is from 0.001 through 20.0 seconds. Default value is 1.0 s. Used on the Global scope.

Available in iOS 5.0 and later.

Declared in AudioUnitParameters.h.

kReverb2Param_DecayTimeAtNyquist

Range is from 0.001 through 20.0 seconds. Default value is 0.5 s. Used on the Global scope.

Available in iOS 5.0 and later.

Declared in AudioUnitParameters.h.

kReverb2Param_RandomizeReflections

Range is from 1 through 1000 (unitless). Used on the Global scope.

Available in iOS 5.0 and later.

Declared in AudioUnitParameters.h.

Additional Reverb Parameters

Additional reverb parameters.

enum {
   kReverbParam_FilterFrequency  = 14,
   kReverbParam_FilterBandwidth  = 15,
   kReverbParam_FilterGain       = 16
};
Constants
kReverbParam_FilterFrequency

Range is from 10.0 through 20000.0 Hz. Default value is 800.0 Hz. Used on the Global scope.

Available in iOS 5.0 and later.

Declared in AudioUnitParameters.h.

kReverbParam_FilterBandwidth

Range is from 0.05 through 4.0 octaves. Default value is 3.0 octaves. Used on the Global scope.

Available in iOS 5.0 and later.

Declared in AudioUnitParameters.h.

kReverbParam_FilterGain

Range is from –18.0 through +18.0 dB. Default value is 0.0 dB. Used on the Global scope.

Available in iOS 5.0 and later.

Declared in AudioUnitParameters.h.

Varispeed Unit Parameters

Parameters for the Varispeed unit.

enum {
   kVarispeedParam_PlaybackRate   = 0,
   kVarispeedParam_PlaybackCents  = 1
};
Constants
kVarispeedParam_PlaybackRate

Available in iOS 5.0 and later.

Declared in AudioUnitParameters.h.

kVarispeedParam_PlaybackCents

Available in iOS 5.0 and later.

Declared in AudioUnitParameters.h.

MIDI Audio Unit Parameters

Parameters for instrument units.

enum {
   kAUGroupParameterID_Volume               = 7,    // value 0 < 128
   kAUGroupParameterID_Sustain              = 64,   // value 0-63 (off),
   64-127 (on)
   kAUGroupParameterID_AllNotesOff          = 123,  // value ignored
   kAUGroupParameterID_ModWheel             = 1,    // value 0 < 128
   kAUGroupParameterID_PitchBend            = 0xE0, // value -8192 - 8191
   kAUGroupParameterID_AllSoundOff          = 120,  // value ignored
   kAUGroupParameterID_ResetAllControllers  = 121,  // value ignored
   kAUGroupParameterID_Pan                  = 10,   // value 0 < 128
   kAUGroupParameterID_Foot                 = 4,    // value 0 < 128
   kAUGroupParameterID_ChannelPressure      = 0xD0, // value 0 < 128
   kAUGroupParameterID_KeyPressure          = 0xA0, // values 0 < 128
   kAUGroupParameterID_Expression           = 11,   // value 0 < 128
   kAUGroupParameterID_DataEntry            = 6,    // value 0 < 128
   
   kAUGroupParameterID_Volume_LSB           = kAUGroupParameterID_Volume + 32,     // value 0 < 128
   kAUGroupParameterID_ModWheel_LSB         = kAUGroupParameterID_ModWheel + 32,   // value 0 < 128
   kAUGroupParameterID_Pan_LSB              = kAUGroupParameterID_Pan + 32,        // value 0 < 128
   kAUGroupParameterID_Foot_LSB             = kAUGroupParameterID_Foot + 32,       // value 0 < 128
   kAUGroupParameterID_Expression_LSB       = kAUGroupParameterID_Expression + 32, // value 0 < 128
   kAUGroupParameterID_DataEntry_LSB        = kAUGroupParameterID_DataEntry + 32,  // value 0 < 128
   
   kAUGroupParameterID_KeyPressure_FirstKey = 256,  // value 0 < 128
   kAUGroupParameterID_KeyPressure_LastKey  = 383   // value 0 < 128
};
Constants
kAUGroupParameterID_Volume

The output volume of the audio unit.

Available in iOS 5.0 and later.

Declared in AudioUnitParameters.h.

kAUGroupParameterID_Sustain

The sustain characteristic for notes produced by the audio unit.

Available in iOS 5.0 and later.

Declared in AudioUnitParameters.h.

kAUGroupParameterID_AllNotesOff

Unused.

Available in iOS 5.0 and later.

Declared in AudioUnitParameters.h.

kAUGroupParameterID_ModWheel

The amount of mod wheel effect to apply to notes produced by the audio unit.

Available in iOS 5.0 and later.

Declared in AudioUnitParameters.h.

kAUGroupParameterID_PitchBend

The amount of pitch bend to apply to notes produced by the audio unit.

Available in iOS 5.0 and later.

Declared in AudioUnitParameters.h.

kAUGroupParameterID_AllSoundOff

Unused.

Available in iOS 5.0 and later.

Declared in AudioUnitParameters.h.

kAUGroupParameterID_ResetAllControllers

Unused.

Available in iOS 5.0 and later.

Declared in AudioUnitParameters.h.

kAUGroupParameterID_Pan

The left/right pan position for notes produced by the audio unit.

Available in iOS 5.0 and later.

Declared in AudioUnitParameters.h.

kAUGroupParameterID_Foot

The amount of foot pedal effect to apply to notes produced by the audio unit.

Available in iOS 5.0 and later.

Declared in AudioUnitParameters.h.

kAUGroupParameterID_ChannelPressure

The amount of channel pressure to apply to notes produced by the audio unit.

Available in iOS 5.0 and later.

Declared in AudioUnitParameters.h.

kAUGroupParameterID_KeyPressure

The amount of key pressure to apply to notes produced by the audio unit.

Available in iOS 5.0 and later.

Declared in AudioUnitParameters.h.

kAUGroupParameterID_Expression

The expression value to apply to notes produced by the audio unit.

Available in iOS 5.0 and later.

Declared in AudioUnitParameters.h.

kAUGroupParameterID_DataEntry

The data entry value to apply to notes produced by the audio unit.

Available in iOS 5.0 and later.

Declared in AudioUnitParameters.h.

kAUGroupParameterID_Volume_LSB

The least significant byte portion of the kAUGroupParameterID_Volume parameter value.

Available in iOS 5.0 and later.

Declared in AudioUnitParameters.h.

kAUGroupParameterID_ModWheel_LSB

The least significant byte portion of the kAUGroupParameterID_ModWheel parameter value.

Available in iOS 5.0 and later.

Declared in AudioUnitParameters.h.

kAUGroupParameterID_Pan_LSB

The least significant byte portion of the kAUGroupParameterID_Pan parameter value.

Available in iOS 5.0 and later.

Declared in AudioUnitParameters.h.

kAUGroupParameterID_Foot_LSB

The least significant byte portion of the kAUGroupParameterID_Foot parameter value.

Available in iOS 5.0 and later.

Declared in AudioUnitParameters.h.

kAUGroupParameterID_Expression_LSB

The least significant byte portion of the kAUGroupParameterID_Expression parameter value.

Available in iOS 5.0 and later.

Declared in AudioUnitParameters.h.

kAUGroupParameterID_DataEntry_LSB

The least significant byte portion of the kAUGroupParameterID_DataEntry parameter value.

Available in iOS 5.0 and later.

Declared in AudioUnitParameters.h.

kAUGroupParameterID_KeyPressure_FirstKey

The first key key pressure.

Available in iOS 5.0 and later.

Declared in AudioUnitParameters.h.

kAUGroupParameterID_KeyPressure_LastKey

The last key key pressure.

Available in iOS 5.0 and later.

Declared in AudioUnitParameters.h.

Discussion

These parameters correspond to the Group scope for standard MIDI Controllers.

Group scope parameter IDs from 0 through 511 are reserved for mapping MIDI controllers.

AUTimePitch, AUTimePitch (offline), and AUPitch Unit Parameters

enum {
   kTimePitchParam_Rate        = 0,
   kTimePitchParam_Pitch       = 1,
   kTimePitchParam_EffectBlend = 2 // only for the AUPitch unit
};
Constants
kTimePitchParam_Rate

Available in iOS 2.0 and later.

Declared in AudioUnitParameters.h.

kTimePitchParam_Pitch

Available in iOS 2.0 through iOS 2.0.

Declared in AudioUnitParameters.h.

kTimePitchParam_EffectBlend

Available in iOS 2.0 through iOS 2.0.

Declared in AudioUnitParameters.h.

Discussion

These parameters are not used in iPhone OS.

Output Unit Parameters

enum {
   kHALOutputParam_Volume = 14
};
Constants
kHALOutputParam_Volume

Applies to the audio unit global scope. Linear gain from 0 through 1. Default value is 1.

Available in iOS 2.0 and later.

Declared in AudioUnitParameters.h.

Discussion