如何从iPhone上的录音中获取线性PCM？

Question

我想在iPhone上做一些演讲者验证（作为课程项目）。我想知道如何从扬声器获得线性PCM。我阅读关于队列服务的文档，似乎它会记录声音，然后将其存储到文件中。有没有办法直接从这个线性PCM？文档中提到了一些有关缓冲区的内容，但我不太明白。也许这是做到这一点的关键？

Answer 1

音频队列服务是这样做的。只需在回拨功能中输入您需要的代码即可。 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; 

然后开始使用的NSTimer如调用定时器拍摄时，你点击录音键

-(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]); 
    } 

//委托方法

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

     [recordTimer invalidate]; 

    }