如何從iPhone上的錄音中獲取線性PCM？

Question

我想在iPhone上做一些演講者驗證（作爲課程項目）。我想知道如何從揚聲器獲得線性PCM。我閱讀關於隊列服務的文檔，似乎它會記錄聲音，然後將其存儲到文件中。有沒有辦法直接從這個線性PCM？文檔中提到了一些有關緩衝區的內容，但我不太明白。也許這是做到這一點的關鍵？

Answer 1

音頻隊列服務是這樣做的。只需在回撥功能中輸入您需要的代碼即可。 http://developer.apple.com/library/ios/#documentation/MusicAudio/Conceptual/AudioQueueProgrammingGuide/Introduction/Introduction.html#//apple_ref/doc/uid/TP40005343

Answer 2

 AVAudioRecorder *audioRecorder = [[AVAudioRecorder alloc] 
        initWithURL:soundFileURL 
        settings:recordSettings 
        error:&error]; 
     audioRecorder.delegate = self; 
     audioRecorder.meteringEnabled = YES; 

然後開始使用的NSTimer如調用定時器拍攝時，你點擊錄音鍵

-(IBAction)record:(id)sender{ 
     NSTimer *recordTimer = [NSTimer scheduledTimerWithTimeInterval:.01 target:self 
     selector:@selector(recordTimerAction:) userInfo:nil repeats:YES];  
    } 

    -(void)recordTimerAction:(id)sender { 

      [audioRecorder updateMeters]; 
      const double ALPHA = 0.05; 
      double peakPowerForChannel = pow(10, (0.05 * [audioRecorder peakPowerForChannel:0])); 
      lowPassResults = ALPHA * peakPowerForChannel + (1.0 - ALPHA) * lowPassResults; 
      NSLog(@"The Amplitude of the recording Sound is %f",lowPassResults); 
      NSLog(@"The Normal Linear PCM Value is %f",[audioRecorder peakPowerForChannel:0]); 
    } 

//委託方法

-(void)audioRecorderDidFinishRecording: (AVAudioRecorder *)recorder successfully:(BOOL)flag{ 

     [recordTimer invalidate]; 

    }