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Core Audio Frameworks

Core Audio consists of a number of separate frameworks, which you can find in /System/Library/Frameworks. These frameworks are not grouped under an umbrella framework, so finding particular headers can sometimes be tricky. This appendix describes each of the Core Audio frameworks and their associated header files.

In this section:

AudioToolbox.framework
AudioUnit.framework
CoreAudioKit.framework
CoreAudio.framework
CoreMIDI.framework
CoreMIDIServer.framework
OpenAL.framework

AudioToolbox.framework

The Audio Toolbox framework contains the APIs that provide application-level services:

• AudioToolbox.h: Top-level include file for the Audio Toolbox framework.

• AudioConverter.h: Audio Converter API. Defines the interface used to create and use audio converters.

• AudioFile.h: Audio File API. Defines the interface used to read and write audio data in files.

• ExtendedAudioFile.h: Extended Audio File API. Defines the interface used to translate audio data from files directly into linear PCM, and vice versa.

• AudioFormat.h: Audio Format API. Defines the interface used to assign and read audio format metadata in audio files.

• CoreAudioClock.h: The Core Audio Clock interface lets you designate a timing source for synchronizing applications or devices.

• MusicPlayer.h: Music Player API. Defines the interface used to manage and play event tracks in music sequences.

• AUGraph.h: Audio Processing Graph API. Defines the interface used to create and use audio processing graphs.

• DefaultAudioOutput.h: Deprecated: Do not use. Defines an older interface for accessing the default output unit (deprecated in Mac OS X v10.3 and later).

• AudioUnitUtilities.h: Some utility functions for interacting with audio units. Includes audio unit parameter conversion functions, and audio unit event functions to create listener objects, which invoke a callback when specified audio unit parameters have changed.

• AUMIDIController.h: Deprecated: Do not use. An interface to allow audio units to receive data from a designated MIDI source. Standard MIDI messages are translated into audio unit parameter values. This interface is superseded by functions in the Music Player API.

• CAFFile.h: Defines the Core Audio file format, which provides many advantages over other audio file formats. See Apple Core Audio Format Specification 1.0 for more information.

• AudioFileComponents.h: Defines the interface for Audio File Component Manager components. You use an audio file component to implement reading and writing a custom file format.

AudioUnit.framework

The Audio Unit framework contains the APIs used specifically for audio units and audio codecs.

• AudioUnit.h: Top-level include file for the Audio Unit framework.

• AUComponent.h: Defines the basic interface for audio unit components.

• AudioCodec.h: Defines the interface used specifically for creating audio codec components..

• AudioOutputUnit.h: Defines the interface used to turn an output unit on or off.

• AudioUnitParameters.h: Predefined parameter constants used by Apple's audio units. Third parties can also use these constants for their own audio units.

• AudioUnitProperties.h: Predefined audio unit properties for common audio unit types as well as Apple's audio units.

• AudioUnitCarbonView.h: Defines the interface for loading and interacting with a Carbon-based audio unit user interface. A Carbon interface is packaged as a Component Manager component and appears as an HIView.

• AUCocoaUIView.h: Defines the protocol for a custom Cocoa view you can use to hold your audio unit's user interface. See also CoreAudioKit.framework/AUGenericView.h.

• AUNTComponent.h: Deprecated: Do not use. Defines the interface for older "v1" audio units. Deprecated in Mac OS X v10.3 and later. Replaced by AUComponent.h.

• MusicDevice.h: An interface for creating instrument units (that is, software-based music synthesizers).

CoreAudioKit.framework

The Core Audio Kit framework contains APIs used for creating a Cocoa user interface for an audio unit.

• CoreAudioKit.h: Top-level include file for the Core Audio Kit framework.

• AUGenericView.h: Defines a generic Cocoa view class for use with audio units. This is the bare-bones user interface that is displayed if an audio unit doesn't create its own custom interface.

CoreAudio.framework

The Core Audio framework contains lower-level APIs used to interact with hardware, as well as data types common to all Core Audio services. This framework contains all the APIs that make up Hardware Abstraction Layer (HAL) Services.

• CoreAudio.h: Top-level include file for the Core Audio framework.

• CoreAudioTypes.h: Defines data types used by all of Core Audio.

• HostTime.h: Contains functions to obtain and convert the host's time base.

• AudioDriverPlugin.h: Defines the interface used to communicate with an audio driver plug-in.

• AudioHardware.h: Defines the interface for interacting with audio device objects. An audio device object represents an external device in the hardware abstraction layer (HAL).

• AudioHardwarePlugin.h: Defines the CFPlugin interface required for a HAL plug-in. An instance of a plug-in appears as an audio device object in the HAL.

CoreMIDI.framework

The Core MIDI framework contains all Core MIDI Services APIs used to implement MIDI support in applications.

• CoreMIDI.h: Top-level include file for the Core MIDI framework.

• MIDIServices.h: Defines the interface used to set up and configure an application to communicate with MIDI devices (through MIDI endpoints, notifications, and so on).

• MIDISetup.h: Defines the interface used to configure or customize the global state of the MIDI system (that is, available MIDI devices, MIDI endpoints, and so on).

• MIDIThruConnection.h: Defines functions to create MIDI play-through connections between MIDI sources and destinations. A MIDI thru connection allows you to daisy-chain MIDI devices, allowing input to one device to pass through to another device as well.

CoreMIDIServer.framework

The Core MIDI Server framework contains interfaces for MIDI drivers.

• CoreMIDIServer.h: Top-level include file for the Core MIDI Server framework.

• MIDIDriver.h: Defines the CFPlugin interface used by MIDI drivers to interact with the Core MIDI Server.

OpenAL.framework

The OpenAL framework provides the Mac OS X implementation of the the OpenAL specification. For more details about OpenAL APIs, see openal.org.

• al.h

• alc.h

• alctypes.h

• altypes.h

• alut.h

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