User guide

To set the audio session category, call the setCategory:error: method as shown in Listing 2-1. For

descriptions of all the categories, refer to Choosing the Best Category (page 18).

Listing 2-1 Setting the audio session category using the AV Foundation framework

NSError *setCategoryError = nil;

BOOL success = [[AVAudioSession sharedInstance]

setCategory: AVAudioSessionCategoryAmbient

error: &setCategoryError];

if (!success) { /* handle the error in setCategoryError */ }

Using Modes to Specialize the Category

While categories set the base behaviors for your app, modes are used to specialize an audio session category.

Set the mode for a category to further define the audio behaviors of your app. There are seven modes to choose

from:

●

AVAudioSessionModeDefault—Default mode that works with all categories and configures the device

for general usage.

●

AVAudioSessionModeVoiceChat—For Voice over IP (VoIP) apps. This mode can be used only with the

AVAudioSessionCategoryPlayAndRecord category. Signals are optimized for voice through

system-supplied signal processing, and the mode sets

AVAudioSessionCategoryOptionAllowBluetooth.

The set of allowable audio routes are optimized for voice chat experience. When the built-in microphones

are used, the system automatically chooses the best combination of built-in microphones for the voice

chat.

●

AVAudioSessionModeVideoChat—For video chat apps such as FaceTime. The video chat mode can

only be used with the AVAudioSessionCategoryPlayAndRecord category. Signals are optimized for

voice through system-supplied signal processing and sets

AVAudioSessionCategoryOptionAllowBluetooth and

AVAudioSessionCategoryOptionDefaultToSpeaker.

The set of allowable audio routes are optimized for video chat experience. When the built-in microphones

are used, the system automatically chooses the best combination of built-in microphones for the video

chat.

Working with Categories

Using Modes to Specialize the Category