Thursday, June 6, 2013

AVAudioSession setMode example in Objective C (iOS).

AVAudioSession setMode

Sets the audio session mode.

- (BOOL)setMode:(NSString *)theMode error:(NSError **)outError

Parameters of [AVAudioSession setMode]
The audio session mode you want to apply to the audio session. See “Audio Session Modes.”
On input, specify a pointer to an error object. If an error occurs, the pointer is set to an NSError object that describes the error. If you do not want error information, pass in nil.

Return Value of [AVAudioSession setMode]
Returns YES on success or NO on failure.

AVAudioSession setMode example.
appDelegate, applicationDidEnterBackground:

[[CDAudioManager sharedManager] setMode:kAMM_MediaPlayback];
[[CDAudioManager sharedManager] setResignBehavior:kAMRBDoNothing autoHandle:NO];
appDelegate, applicationWillEnterForeground: - just to get sure!

[[CDAudioManager sharedManager] setResignBehavior:kAMRBDoNothing autoHandle:NO];
playback, i also needed to know when a soundfile was done, to play the next, since i do not want to have built sentences in a mix of simult. words. like saying "Hello" then "world":

on initializing my Soundplayer:

[[AVAudioSession sharedInstance] setCategory:AVAudioSessionCategoryAmbient error:&err];
[[CDAudioManager sharedManager] setMode:kAMM_MediaPlayback];
soundEngine = [[CDAudioManager sharedManager] audioSourceForChannel:kASC_Right];
soundEngine.delegate = self; // ensure to implement <CDLongAudioSourceDelegate> 
playing sounds:

- (void)playSound:(NSString *)soundFile
 [soundEngine load:[NSString stringWithFormat:@"%@.caf",soundFile]];
 [soundEngine play];

Example of [AVAudioSession setMode].
// Configure the audio session
AVAudioSession *session = [AVAudioSession sharedInstance];
[session setCategory:AVAudioSessionCategoryRecord error:NULL];
[session setMode:AVAudioSessionModeMeasurement error:NULL];
[session setActive:YES error:NULL];
// Optional - default gives 1024 samples at 44.1kHz
//[session setPreferredIOBufferDuration:samplesPerSlice/session.sampleRate error:NULL];
// Configure the capture session (strongly-referenced instance variable, otherwise the capture stops after one slice)
_captureSession = [[AVCaptureSession alloc] init];
// Configure audio device input
AVCaptureDevice *device = [AVCaptureDevice defaultDeviceWithMediaType:AVMediaTypeAudio];
AVCaptureDeviceInput *input = [AVCaptureDeviceInput deviceInputWithDevice:device error:NULL];
[_captureSession addInput:input];
// Configure audio data output
AVCaptureAudioDataOutput *output = [[AVCaptureAudioDataOutput alloc] init];
dispatch_queue_t queue = dispatch_queue_create("My callback", DISPATCH_QUEUE_SERIAL);
[output setSampleBufferDelegate:self queue:queue];
[_captureSession addOutput:output];
// Start the capture session.  
[_captureSession startRunning];
(plus error checking, omitted here for readability).
Then I implement the following AVCaptureAudioDataOutputSampleBufferDelegate method:
- (void)captureOutput:(AVCaptureOutput *)captureOutput
       fromConnection:(AVCaptureConnection *)connection
    NSLog(@"Num samples: %ld", CMSampleBufferGetNumSamples(sampleBuffer));
    // Usually gives 1024 (except the first slice)

End of AVAudioSession setMode example article.