iOS Developer Library


Audio Toolbox Framework Reference Audio Session Services Reference

Document Revision History

This table describes the changes to Audio Session Services Reference.




Deprecated entire class for iOS 7.0.


Added information on equivalencies between C and Objective-C APIs for categories and modes. See Audio Session Categories and Audio Session Modes.


Added descriptions for Audio Session Modes.

Added descriptions for the kAudioSessionProperty_InputGainAvailable and kAudioSessionProperty_InputGainScalar properties, which support programmatically adjusting input gain.

Added descriptions for new constants and properties that indicate audio hardware routes in Audio Route Description Dictionary Keys, USB Accessory Audio Source Dictionary Keys, USB Accessory Audio Destination Dictionary Keys, Audio Input Routes, Audio Output Routes, and Audio Session Property Identifiers.

Improved the descriptions for the kAudioSessionProperty_OverrideAudioRoute and kAudioSessionProperty_OverrideCategoryEnableBluetoothInput properties.


Added memory management information to the description of the AudioSessionGetProperty function.


Added a description for the “kAudioSessionUnspecifiedError” result code.


Updated for iOS 4.0.

Added a description for the AudioSessionSetActiveWithFlags function.

Added descriptions for the Audio Session Activation Flags and Audio Session Interruption Types enumerations.

Added a description for the kAudioSessionProperty_InterruptionType property.


Improved description for the kAudioSessionProperty_PreferredHardwareIOBufferDuration property.


Added descriptions for new properties kAudioSessionProperty_OtherMixableAudioShouldDuck, kAudioSessionProperty_OverrideCategoryMixWithOthers, kAudioSessionProperty_OverrideCategoryDefaultToSpeaker, and kAudioSessionProperty_OverrideCategoryEnableBluetoothInput.

Improved and updated descriptions in the Audio Session Categories enumeration; added description for new category kAudioSessionCategory_AudioProcessing.

Clarified description of Alternative Audio Route Change Reason Dictionary Key.

Added descriptions for new result codes “kAudioSessionNoCategorySet” and “kAudioSessionIncompatibleCategory”. Added links to Result Codes chapter in each function description.


Updated for iOS 3.0.

Added descriptions for kAudioSessionProperty_ServerDied property and for “kAudioServicesNoHardwareError” result code.


Improved description of the interruptionListener parameter in the AudioSessionInitialize function.

Added descriptions for Alternative Audio Route Change Reason Dictionary Key defines.


Updated for iOS 2.2.

Clarified description of AudioSessionAddPropertyListener function.


New document that describes the C interface for working with an iOS application's audio session object.