Introduction

The Logic Pro X 10.1 Mixer allows for setting and displaying Core Audio device property values and listens to notifications when the value of a certain property has changed; for example, if a user turns the input gain knob on the audio device. This document contains a list of Core Audio device properties currently supported by the Logic Pro X Mixer.

Your Core Audio device driver may support the following device properties to gain this functionality from the Logic Pro X Mixer or any other audio application that also supports these hardware device properties.

Header File

The AudioHardware.h header file is part of the CoreAudio.framework and defines the HAL's object model for interacting with audio device objects including the properties, types, and constants that describe the property values. An audio device object represents an external device in the HAL.

For a further discussion of the audio HAL, Audio Objects and the Audio Device class, see the Overview section in AudioHardware.h.

Input Type

Pop-up button providing entries like: Mic, Instrument, -10dBV, +4dBu.

kAudioObjectPropertyElementName - A CFString that contains a human readable name for the given element in the given scope. The caller is responsible for releasing the returned CFObject.

kAudioDevicePropertyChannelNominalLineLevel - An array of UInt32s whose values are the item IDs for the currently selected nominal line levels. This property is implemented by an AudioControl object that is a subclass of AudioLineLevelControl.

kAudioDevicePropertyChannelNominalLineLevels - An array of UInt32s that represent all the IDs of all the nominal line levels currently available. This property is implemented by an AudioControl object that is a subclass of AudioLineLevelControl.

kAudioDevicePropertyChannelNominalLineLevelNameForIDCFString - This property translates the given nominal line level item ID into a human readable name using an AudioValueTranslation structure. The input data is the UInt32 containing the item ID to be translated and the output data is a CFString. The caller is responsible for releasing the returned CFObject. This property is implemented by an AudioControl object that is a subclass of AudioLineLevelControl.

Phantom Power

Toggle button to switch on/off phantom power.

kAudioDevicePropertyPhantomPower - A UInt32 where a value of 1 means that the AudioDevice has enabled phantom power for the given element. The property is implemented by an AudioControl object that is a subclass of AudioPhantomPowerControl.

High Pass Filter

Toggle button to switch on/off a high pass filter.

kAudioDevicePropertyHighPassFilterSetting - An array of UInt32s whose values are the item IDs for the currently selected high pass filter setting. This property is implemented by an AudioControl object that is a subclass of AudioHighPassFilterControl.

kAudioDevicePropertyHighPassFilterSettings - An array of UInt32s that represent all the IDs of all the high pass filter settings currently available. This property is implemented by an AudioControl object that is a subclass of AudioHighPassFilterControl.

kAudioDevicePropertyHighPassFilterSettingNameForIDCFString - This property translates the given high pass filter setting item ID into a human readable name using an AudioValueTranslation structure. The input data is the UInt32 containing the item ID to be translated and the output data is a CFString. The caller is responsible for releasing the returned CFObject. This property is implemented by an AudioControl object that is a subclass of AudioHighPassFilterControl.

Phase Invert

Toggle button to switch on/off phase invert.

kAudioDevicePropertyPhaseInvert - A UInt32 where a value of 1 means that phase of the signal for the given element has been flipped 180 degrees. The property is implemented by an AudioControl object that is a subclass of AudioPhaseInvertControl.

Input Gain

Display and knob to change the input gain.

kAudioDevicePropertyVolumeScalar - A Float32 that represents the value of the volume control. The range is between 0.0 and 1.0 (inclusive). Note that the set of all Float32 values between 0.0 and 1.0 inclusive is much larger than the set of actual values that the hardware can select. This means that the Float32 range has a many to one mapping with the underlying hardware values. As such, setting a scalar value will result in the control taking on the value nearest to what was set. This property is implemented by an AudioControl object that is a subclass of AudioVolumeControl.

kAudioDevicePropertyVolumeDecibels - A Float32 that represents the value of the volume control in dB. Note that the set of all Float32 values in the dB range for the control is much larger than the set of actual values that the hardware can select. This means that the Float32 range has a many to one mapping with the underlying hardware values. As such, setting a dB value will result in the control taking on the value nearest to what was set. This property is implemented by an AudioControl object that is a subclass of AudioVolumeControl.

Reference

Logic Pro X 10.1 Release Notes

Core Audio User-Space Driver Examples