初始化AVAudio會話模式測量

Question

嘿，在這裏我肯定沒有深度，但不幸的是，由於我是由講師提供了項目，所以太遲了。

我試圖通過在我的項目中使用AVAudio會話模式測量來禁用應用於我的輸入的系統提供的信號處理。

但是我很努力地找到任何消息來源。

我希望的結果是，通過啓用此功能，我將能夠在我的應用程序中製作更準確的讀數。

下面是代碼：

#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

配置的類別後的會話：

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

此外，您的錯誤處理不遵循既定的模式。您應該檢查setMode:error:的返回值。當方法的返回值爲NO時，error輸入/輸出參數僅保證有效。 （實際上，在大多數情況下，檢查錯誤爲零可能工作正常，但它沒有記錄工作的方式 - 所以你不應該依靠它。）