Apple example - demonstrateInputSelection

demonstrateInputSelection.m

#import <AVFoundation/AVAudioSession.h>
 
- (void) demonstrateInputSelection
{
    NSError* theError = nil;
    BOOL result = YES;
 
    AVAudioSession* myAudioSession = [AVAudioSession sharedInstance];
 
    result = [myAudioSession setCategory:AVAudioSessionCategoryPlayAndRecord error:&theError];
    if (!result)
    {
        NSLog(@"setCategory failed");
    }
 
    result = [myAudioSession setActive:YES error:&theError];
    if (!result)
    {
        NSLog(@"setActive failed");
    }
 
    // Get the set of available inputs. If there are no audio accessories attached, there will be
    // only one available input -- the built in microphone.
    NSArray* inputs = [myAudioSession availableInputs];
 
    // Locate the Port corresponding to the built-in microphone.
    AVAudioSessionPortDescription* builtInMicPort = nil;
    for (AVAudioSessionPortDescription* port in inputs)
    {
        if ([port.portType isEqualToString:AVAudioSessionPortBuiltInMic])
        {
            builtInMicPort = port;
            break;
        }
    }
 
    // Print out a description of the data sources for the built-in microphone
    NSLog(@"There are %u data sources for port :\"%@\"", (unsigned)[builtInMicPort.dataSources count], builtInMicPort);
    NSLog(@"%@", builtInMicPort.dataSources);
 
    // loop over the built-in mic's data sources and attempt to locate the front microphone
    AVAudioSessionDataSourceDescription* frontDataSource = nil;
    for (AVAudioSessionDataSourceDescription* source in builtInMicPort.dataSources)
    {
        if ([source.orientation isEqual:AVAudioSessionOrientationFront])
        {
            frontDataSource = source;
            break;
        }
    } // end data source iteration
 
    if (frontDataSource)
    {
        NSLog(@"Currently selected source is \"%@\" for port \"%@\"", builtInMicPort.selectedDataSource.dataSourceName, builtInMicPort.portName);
        NSLog(@"Attempting to select source \"%@\" on port \"%@\"", frontDataSource, builtInMicPort.portName);
 
        // Set a preference for the front data source.
        theError = nil;
        result = [builtInMicPort setPreferredDataSource:frontDataSource error:&theError];
        if (!result)
        {
            // an error occurred. Handle it!
            NSLog(@"setPreferredDataSource failed");
        }
    }
 
    // Make sure the built-in mic is selected for input. This will be a no-op if the built-in mic is
    // already the current input Port.
    theError = nil;
    result = [myAudioSession setPreferredInput:builtInMicPort error:&theError];
    if (!result)
    {
        // an error occurred. Handle it!
        NSLog(@"setPreferredInput failed");
    }
}