#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");
}
}
清单1将在iPhone 5上运行时生成以下控制台输出：
There are 3 data sources for port :"<AVAudioSessionPortDescription: 0x14d935a0, type = MicrophoneBuiltIn; name = iPhone Microphone; UID = Built-In Microphone; selectedDataSource = Bottom>"
(
"<AVAudioSessionDataSourceDescription: 0x14d93800, ID = 1835216945; name = Bottom>",
"<AVAudioSessionDataSourceDescription: 0x14d938d0, ID = 1835216946; name = Front>",
"<AVAudioSessionDataSourceDescription: 0x14d93a10, ID = 1835216947; name = Back>"
)
Currently selected source is "Bottom" for port "iPhone Microphone"
Attempting to select source "<AVAudioSessionDataSourceDescription: 0x14d938d0, ID = 1835216946; name = Front>" on port "iPhone Microphone”
2 回答
操作系统目前仅允许应用程序一次连接到一个音频源路由 . 在iOS设备上录制2声道的唯一方法是使用带有标准USB立体声ADC的Aple USB to Lightning接口（较旧型号的相机连接套件）或具有多个麦克风输入的音频混合面板 .
我在Apple库上找到了一些关于如何从不同的麦克风端口选择数据源的常见问题解答，这些可能会有所帮助：
https://developer.apple.com/library/ios/qa/qa1799/_index.html
清单1演示了应用程序如何找到代表内置麦克风的AVAudioSessionPortDescription，找到前麦克风（在iPhone 5或其他具有前置麦克风的设备上），将前麦克风设置为首选数据源并设置内置麦克风在麦克风端口作为首选输入 .
清单1演示输入选择 .
清单1将在iPhone 5上运行时生成以下控制台输出：
UPDATE 14 Nov使用前面的代码我可以在iPhone上设置特定的内置麦克风来录制声音，现在我正在尝试经常更换iPhone上的特定麦克风来模拟立体声录音 .