初始化 AVAudio 会话模式测量

Question

嘿，我在这里肯定超出了我的深度，但不幸的是，由于讲师向我提供了该项目，现在回头已经太晚了。

我试图通过在我的项目中使用 AVAudio Session Mode Measurement 来禁用系统提供的信号处理应用于我的输入。

但是，我正在努力寻找有关执行此操作的任何资源。

我想要的结果是，通过启用此功能，我将能够在我的应用程序中获得更准确的读数。

代码如下：

#import "ViewController.h"

@import AudioToolbox;
@import AVFoundation;


#define kOutputBus 0
#define kInputBus 1

@interface ViewController () 

@property (nonatomic, weak) IBOutlet UILabel *dBSPLView2;

@end



@implementation ViewController

static AudioComponentInstance audioUnit;

- (void)viewDidLoad {
    [super viewDidLoad];
    // Do any additional setup after loading the view, typically from a nib.


    [self setupAudio];
}

- (void) setupAudio {


    AudioComponentDescription desc;


    desc.componentType = kAudioUnitType_Output;
    desc.componentSubType = kAudioUnitSubType_RemoteIO;
    desc.componentManufacturer = kAudioUnitManufacturer_Apple;
    desc.componentFlags = 0;
    desc.componentFlagsMask = 0;

    AudioComponent comp = AudioComponentFindNext(NULL, &desc);

    OSStatus status = AudioComponentInstanceNew(comp, &audioUnit);
    if (status != noErr) {
        NSAssert(status == noErr,@"Error");
    }

    AudioStreamBasicDescription audioFormat;

    audioFormat.mSampleRate = 96000.00;
    audioFormat.mFormatID = kAudioFormatLinearPCM;
    audioFormat.mFormatFlags = kAudioFormatFlagIsSignedInteger | kAudioFormatFlagIsPacked;
    audioFormat.mFramesPerPacket = 1;
    audioFormat.mChannelsPerFrame = 1;
    audioFormat.mBitsPerChannel = 16;
    audioFormat.mBytesPerFrame = audioFormat.mChannelsPerFrame * sizeof(SInt16);
    audioFormat.mBytesPerPacket = audioFormat.mFramesPerPacket * audioFormat.mBytesPerFrame;


    UInt32 flag = 1;
    status = AudioUnitSetProperty(audioUnit, kAudioOutputUnitProperty_EnableIO, kAudioUnitScope_Input, kInputBus, &flag, sizeof(flag));
    if (status != noErr) {
        NSAssert(status == noErr,@"Error");
    }

    flag = 0;
    status = AudioUnitSetProperty(audioUnit, kAudioOutputUnitProperty_EnableIO, kAudioUnitScope_Output, kOutputBus, &flag, sizeof(flag));
    if (status != noErr) {
        NSAssert(status == noErr,@"Error");
    }

    status = AudioUnitSetProperty(audioUnit , kAudioUnitProperty_StreamFormat, kAudioUnitScope_Output, kInputBus, &audioFormat, sizeof(audioFormat));
    if (status != noErr) {
        NSAssert(status == noErr,@"Error");
    }

    AURenderCallbackStruct callbackStruct;
    callbackStruct.inputProc = recordingCallback;
    callbackStruct.inputProcRefCon = (__bridge void*)self;

    status = AudioUnitSetProperty(audioUnit , kAudioOutputUnitProperty_SetInputCallback, kAudioUnitScope_Global, kInputBus, &callbackStruct, sizeof(callbackStruct));
    if (status != noErr) {
        NSAssert(status == noErr,@"Error");
    }

    status = AudioUnitInitialize(audioUnit);
    if (status != noErr) {
        NSAssert(status == noErr,@"Error");
    }

}

static OSStatus recordingCallback(

                                  void *inRefCon,
                                  AudioUnitRenderActionFlags *ioActionFlags,
                                  const AudioTimeStamp *inTimeStamp,
                                  UInt32 inBusNumber,
                                  UInt32 inNumberFrames,
                                  AudioBufferList *ioData

                            ) {

    AudioBuffer buffer;

    buffer.mNumberChannels = 1;
    buffer.mDataByteSize = inNumberFrames * sizeof(SInt16);
    buffer.mData = malloc(buffer.mDataByteSize);

    AudioBufferList bufferList;
    bufferList.mNumberBuffers = 1;
    bufferList.mBuffers[0] = buffer;

    OSStatus status = AudioUnitRender(audioUnit , ioActionFlags, inTimeStamp, inBusNumber, inNumberFrames, &bufferList);
    if (status != noErr) {
        printf("Error\n");
        return -1;
    }

    SInt16 *frameBuffer = buffer.mData;

    double totalAmplitude = 0;

    for (int i = 0; i < inNumberFrames; i++) {
       // printf("%i\n",frameBuffer[i]);

        totalAmplitude += frameBuffer[i] * frameBuffer[i];
    }

    totalAmplitude /= inNumberFrames;

    totalAmplitude = sqrt(totalAmplitude);

    //Creates a negative number that goes no higher than zero
    //float SPLFloat = totalAmplitude / (float)SHRT_MAX * 2;

    float dBFloat = (20 * log10(totalAmplitude)) + 11;



    dispatch_async(dispatch_get_main_queue(), ^{
        ViewController *viewController = (__bridge ViewController*)inRefCon;
        viewController.dBSPLView2.text = [NSString stringWithFormat:@"%.f", dBFloat];
    });

    return noErr;
}

- (IBAction)recordButtonPressed:(id)sender {
    NSError *error;
    [[AVAudioSession sharedInstance] setActive:YES error:&error];
    if (error != nil) {
        NSAssert(error == nil, @"Error");
    }
    [[AVAudioSession sharedInstance] setCategory:AVAudioSessionCategoryRecord error:&error];
    if (error != nil) {
        NSAssert(error == nil, @"Error");
    }

    [[AVAudioSession sharedInstance] requestRecordPermission:^(BOOL granted) {
        if (granted) {
            OSStatus status = AudioOutputUnitStart(audioUnit);
            if (status != noErr) {
                NSAssert(status == noErr,@"Error");
            }
        } else {
            NSAssert(NO, @"Error");
        }
    }];
}



- (IBAction)stopButtonPressed:(id)sender {
    OSStatus status = AudioOutputUnitStop(audioUnit);
    if (status != noErr) {
        NSAssert(status == noErr,@"Error");
    }
    NSError *error;
    [[AVAudioSession sharedInstance] setActive:NO error:&error];
    if (error != nil) {
        NSAssert(error == nil, @"Error");
    }

}

- (void)didReceiveMemoryWarning {
    [super didReceiveMemoryWarning];
    // Dispose of any resources that can be recreated.
}

- (void) dealloc {
    OSStatus status = AudioComponentInstanceDispose(audioUnit);
    if (status != noErr) {
        NSAssert(status == noErr,@"Error");
    }
}

@end

Answer 1

为会话配置类别后：

[[AVAudioSession sharedInstance] setMode:AVAudioSessionModeMeasurement error:&error];
if (error != nil) {
    NSAssert(error == nil, @"Error");
}

此外，您的错误处理没有遵循既定模式。您应该检查 setMode:error: 的 return 值。 error in/out 参数仅在方法的 return 值为 NO 时保证有效。（实际上，在大多数情况下，检查错误是否为 nil 可能工作正常，但没有记录以这种方式工作 - 所以你不应该依赖它。）

初始化 AVAudio 会话模式测量

Initialising AVAudioSessionModeMeasurement

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初始化 AVAudio 会话 模式 测量

Initialising AVAudio​Session​Mode​Measurement

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初始化 AVAudio 会话模式测量

Initialising AVAudioSessionModeMeasurement