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# Audio Session Errors

## Topics

### Constants

[`var kAudioSessionNoError: Int`](/documentation/AudioToolbox/kAudioSessionNoError)

No error has occurred.

[`var kAudioSessionNotInitialized: Int`](/documentation/AudioToolbox/kAudioSessionNotInitialized)

An Audio Session function was called without first initializing the session. To avoid this error, call the `AudioSessionInitialize` function before attempting to use the session.

[`var kAudioSessionAlreadyInitialized: Int`](/documentation/AudioToolbox/kAudioSessionAlreadyInitialized)

The `AudioSessionInitialize` function was called more than once during the lifetime of your application.

[`var kAudioSessionInitializationError: Int`](/documentation/AudioToolbox/kAudioSessionInitializationError)

There was an error during audio session initialization.

[`var kAudioSessionUnsupportedPropertyError: Int`](/documentation/AudioToolbox/kAudioSessionUnsupportedPropertyError)

The audio session property is not supported.

[`var kAudioSessionBadPropertySizeError: Int`](/documentation/AudioToolbox/kAudioSessionBadPropertySizeError)

The size of the audio session property data was not correct.

[`var kAudioSessionNotActiveError: Int`](/documentation/AudioToolbox/kAudioSessionNotActiveError)

The audio operation failed because your application’s audio session was not active.

[`var kAudioServicesNoHardwareError: Int`](/documentation/AudioToolbox/kAudioServicesNoHardwareError)

The audio operation failed because the device has no audio input available.

[`var kAudioSessionNoCategorySet: Int`](/documentation/AudioToolbox/kAudioSessionNoCategorySet)

The audio operation failed because it requires the audio session to have an explicitly-set category, but none was set. To use a hardware codec you must explicitly initialize the audio session and explicitly set an audio session category.

[`var kAudioSessionIncompatibleCategory: Int`](/documentation/AudioToolbox/kAudioSessionIncompatibleCategory)

The specified audio session category cannot be used for the attempted audio operation. For example, you attempted to play or record audio with the audio session category set to `kAudioSessionCategory_AudioProcessing`.

[`var kAudioSessionUnspecifiedError: Int`](/documentation/AudioToolbox/kAudioSessionUnspecifiedError)

An unspecified audio session error has occurred. This typically results from the audio system being in an inconsistent state.


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