Android - AudioRecord：通過音頻插孔（麥克風）檢測脈寬調製信號

我試圖通過音頻插孔近乎實時地檢測出方波信號（麥克風）。出於這個原因，我在流模式下使用AudioRecord類。但我的問題是，我的手機（麥克風）總是工作不同。有時我使用20,000的閾值，有時我必須將閾值調整爲1'000以檢測（第一個脈衝的）邊緣。信號的電壓範圍是0到3V。我不確定我的麥克風是否工作不正常，或者adc是否使用不同的參考電壓？Android - AudioRecord：通過音頻插孔（麥克風）檢測脈寬調製信號

我還沒有任何想法如何解決這個問題。我真的希望你能幫助我。

這裏我的源代碼：

公共類ReceiveCom擴展的AsyncTask實現對MIC層{

private AudioRecord audioRecord; 
private int sampleRate = 44100; 

private short[] audioData; 
private int sizeInShorts; 

private boolean isRunning=false; 
private int receiveBuffer; 

private int minBuffersize; 
private boolean ready=false; 

private int audioResult,dataCounter=0; 
private short[] dataBits = new short[8]; 

@TargetApi(Build.VERSION_CODES.JELLY_BEAN) 
public ReceiveCom(){ 
    try{ 
     minBuffersize = AudioRecord.getMinBufferSize(sampleRate, AudioFormat.CHANNEL_IN_MONO, 
                AudioFormat.ENCODING_PCM_16BIT); 


     audioRecord = new AudioRecord(AudioSource.MIC, sampleRate, AudioFormat.CHANNEL_IN_MONO, 
             AudioFormat.ENCODING_PCM_16BIT, minBuffersize); 


     if (audioRecord.getState() != AudioRecord.STATE_INITIALIZED){ 
      throw new Exception("AudioRecord init failed"); 
     } 

     audioData = new short[2*minBuffersize]; 
     Log.e("ERROR", "ReceiveCom constructor: OK "); 
    } 
    catch(IllegalArgumentException e){ 
     Log.e("ERROR", "IllegalArgumentException: " + e); 
    } 
    catch(Exception e){ 
     Log.e("ERROR", "ConstructorException: " + e);   
    } 
    finally{ 
     Log.e("ERROR", "ReceiveCom constructor: END "); 
    } 

    if(Build.VERSION.SDK_INT >= 17){ 
     if(AutomaticGainControl.isAvailable()){ 
      Log.e("INFO", "AGC is available"); 
      //AutomaticGainControl.create(audioRecord.getAudioSessionId()); 
     } 
    } 
} 


protected Void doInBackground(Void... arg0) {  
    audioRecord.setPositionNotificationPeriod(minBuffersize); 
    audioRecord.setRecordPositionUpdateListener(new OnRecordPositionUpdateListener(){ 

     @Override 
     public void onPeriodicNotification(AudioRecord myRecorder) { 
      int timeCounter=0,bitCounter=0,i=0; 
      boolean edgeTriggered=false, bitReady=false; 
      int dB,edgeThreshold=10000,idleThreshold=edgeThreshold/5; 

      for(i=2; i<audioResult; i=i+1){ 
       if(edgeTriggered==false && audioData[i-2]<=idleThreshold && audioData[i-1]>=edgeThreshold && audioData[i]>=edgeThreshold){ 
        Log.e("DEBUG","audioData["+i+"]: "+audioData[i]); 
        timeCounter++; 
        edgeTriggered=true; 
        bitReady=false; 
       } 
      } 
     } 
     @Override 
     public void onMarkerReached(AudioRecord recorder) { } 
    }); 

    audioRecord.startRecording(); 
    while(isRunning){ 
     audioResult = audioRecord.read(audioData, 0, minBuffersize);  
    } 

    audioRecord.stop(); 
    audioRecord.release(); 
    return null; 
}

來源

2013-04-29 user2279797

您不應該期望音頻通道通過信號的DC分量，但輸入上出現的任何恆定偏移電壓可能會短暫出現然後衰減。可能你需要爲你的解碼器建立幅度和偏移的跟蹤方案。 – 2014-01-30 16:48:16