You specify an audio session category to express how you intend to use audio in your app. Table B-1 provides details about each of the available categories. For an explanation of how categories work, see Configuring an Audio Session.
Table B-1 Audio Session category behavior
Category
Silenced by the Ring/Silent switch and by screen locking see note
Interrupts nonmixable app’s audio
Allows audio input (recording) and output (playback)
AVAudioSessionCategoryAmbient
Yes
No
Output only
AVAudioSessionCategorySoloAmbient (Default)
Yes
Yes
Output only
AVAudioSessionCategoryPlayback
No
Yes by default; no by using override switch
Output only
AVAudioSessionCategoryRecord
No (recording continues with screen locked)
Yes
Input only
AVAudioSessionCategoryPlayAndRecord
No
Yes by default; no by using override switch
Input and output
AVAudioSessionCategoryMultiRoute
No
Yes
Input and output
Table B-2 provides a list of modes and the categories each mode can be used with.