Possiamo aumentare il guadagno del microfono di un telefono Android?

Question

Sto cercando di aumentare il guadagno del microfono di un telefono Android in modo che sia in grado di ascoltare suoni molto minuti. È possibile? Puoi per favore aiutarmi con questo.

Answer 1

this link dovrebbe portarti oltre. usa setStreamVolume (...) per impostare il volume più alto. ma nota che c'è un massimo che può essere richiesto chiamando getStreamMaxVolume (...). quindi il guadagno del microfono è probabilmente limitato dall'hardware che indovinerei. quindi è piuttosto impossibile farlo "on-fly" ma cosa dire della registrazione un po ', cercando di amplificare una frequenza speciale da equalizer e quindi riconoscere qualcosa come un battito cardiaco? sembra difficile ma forse possibile.

Answer 2

Audio controllo di guadagno

public class MainActivity extends Activity { 

public static final int SAMPLE_RATE = 16000; 

private AudioRecord mRecorder; 
private File mRecording; 
private short[] mBuffer; 
private final String startRecordingLabel = "Start recording"; 
private final String stopRecordingLabel = "Stop recording"; 
private boolean mIsRecording = false; 
private ProgressBar mProgressBar; 
float iGain = 1.0f; 
CheckBox gain; 

protected int bitsPerSamples = 16; 

@Override 
public void onCreate(final Bundle savedInstanceState) { 
    super.onCreate(savedInstanceState); 
    setContentView(R.layout.fragment_main); 

    initRecorder(); 

    Button bluetooth = (Button)findViewById(R.id.blue); 
    gain = (CheckBox) findViewById(R.id.checkBox1); 
    mProgressBar = (ProgressBar) findViewById(R.id.progressBar); 

    final Button button = (Button) findViewById(R.id.start); 
    button.setText(startRecordingLabel); 

    bluetooth.setOnClickListener(new View.OnClickListener() { 

     @Override 
     public void onClick(View v) { 
      // TODO Auto-generated method stub 
      Intent i = new Intent(""); 
     } 
    }); 
    gain.setOnCheckedChangeListener(new CompoundButton.OnCheckedChangeListener() { 

     @Override 
     public void onCheckedChanged(CompoundButton buttonView, 
       boolean isChecked) { 

      if (gain.isChecked()) { 
       iGain = 5.0f; 

      } else { 
       iGain = 2.0f; 
      } 
     } 
    }); 

    button.setOnClickListener(new View.OnClickListener() { 
     @Override 
     public void onClick(final View v) { 
      if (!mIsRecording) { 
       button.setText(stopRecordingLabel); 
       mIsRecording = true; 
       mRecorder.startRecording(); 
       mRecording = getFile("raw"); 
       startBufferedWrite(mRecording); 
      } else { 
       button.setText(startRecordingLabel); 
       mIsRecording = false; 
       mRecorder.stop(); 
       File waveFile = getFile("wav"); 
       try { 
        rawToWave(mRecording, waveFile); 
       } catch (IOException e) { 
        Toast.makeText(MainActivity.this, e.getMessage(), 
          Toast.LENGTH_SHORT).show(); 
       } 
       Toast.makeText(MainActivity.this, 
         "Recorded to " + waveFile.getName(), 
         Toast.LENGTH_SHORT).show(); 
      } 
     } 
    }); 
} 

@Override 
public void onDestroy() { 
    mRecorder.release(); 
    super.onDestroy(); 
} 

private void initRecorder() { 
    int bufferSize = AudioRecord.getMinBufferSize(SAMPLE_RATE, 
      AudioFormat.CHANNEL_IN_MONO, AudioFormat.ENCODING_PCM_16BIT); 
    mBuffer = new short[bufferSize]; 
    mRecorder = new AudioRecord(MediaRecorder.AudioSource.MIC, SAMPLE_RATE, 
      AudioFormat.CHANNEL_IN_MONO, AudioFormat.ENCODING_PCM_16BIT, 
      bufferSize); 
} 

private void startBufferedWrite(final File file) { 
    new Thread(new Runnable() { 
     @Override 
     public void run() { 
      DataOutputStream output = null; 
      try { 
       output = new DataOutputStream(new BufferedOutputStream(
         new FileOutputStream(file))); 
       while (mIsRecording) { 
        double sum = 0; 

        int readSize = mRecorder.read(mBuffer, 0, 
          mBuffer.length); 

        final int bytesPerSample = bitsPerSamples/8; 
        final int emptySpace = 64 - bitsPerSamples; 
        int byteIndex = 0; 
        int byteIndex2 = 0; 
        int temp = 0; 
        int mLeftTemp = 0; 
        int mRightTemp = 0; 
        int a = 0; 
        int x = 0; 

        for (int frameIndex = 0; frameIndex < readSize; frameIndex++) { 

         for (int c = 0; c < 1; c++) { 

          if (iGain != 1) { 

           long accumulator = 0; 
           for (int b = 0; b < bytesPerSample; b++) { 

            accumulator += ((long) (mBuffer[byteIndex++] & 0xFF)) << (b * 8 + emptySpace); 
           } 

           double sample = ((double) accumulator/(double) Long.MAX_VALUE); 
           sample *= iGain; 
           int intValue = (int) ((double) sample * (double) Integer.MAX_VALUE); 

           for (int i = 0; i < bytesPerSample; i++) { 
            mBuffer[i + byteIndex2] = (byte) (intValue >>> ((i + 2) * 8) & 0xff); 
           } 
           byteIndex2 += bytesPerSample; 

          } 
         }// end for(channel) 

         // mBuffer[frameIndex] *=iGain; 
         if (mBuffer[frameIndex] > 32765) { 
          mBuffer[frameIndex] = 32767; 

         } else if (mBuffer[frameIndex] < -32767) { 
          mBuffer[frameIndex] = -32767; 
         } 
         output.writeShort(mBuffer[frameIndex]); 
         sum += mBuffer[frameIndex] * mBuffer[frameIndex]; 

        } 

        if (readSize > 0) { 
         final double amplitude = sum/readSize; 
         mProgressBar.setProgress((int) Math.sqrt(amplitude)); 
        } 
       } 
      } catch (IOException e) { 
       Toast.makeText(MainActivity.this, e.getMessage(), 
         Toast.LENGTH_SHORT).show(); 
      } finally { 
       mProgressBar.setProgress(0); 
       if (output != null) { 
        try { 
         output.flush(); 
        } catch (IOException e) { 
         Toast.makeText(MainActivity.this, e.getMessage(), 
           Toast.LENGTH_SHORT).show(); 
        } finally { 
         try { 
          output.close(); 
         } catch (IOException e) { 
          Toast.makeText(MainActivity.this, e.getMessage(), 
            Toast.LENGTH_SHORT).show(); 
         } 
        } 
       } 
      } 
     } 
    }).start(); 
} 

private void rawToWave(final File rawFile, final File waveFile) 
     throws IOException { 

    byte[] rawData = new byte[(int) rawFile.length()]; 
    DataInputStream input = null; 
    try { 

     input = new DataInputStream(new FileInputStream(rawFile)); 
     input.read(rawData); 
    } finally { 
     if (input != null) { 
      input.close(); 
     } 
    } 

    DataOutputStream output = null; 
    try { 
     output = new DataOutputStream(new FileOutputStream(waveFile)); 
     // WAVE header 
     // see http://ccrma.stanford.edu/courses/422/projects/WaveFormat/ 
     writeString(output, "RIFF"); // chunk id 
     writeInt(output, 36 + rawData.length); // chunk size 
     writeString(output, "WAVE"); // format 
     writeString(output, "fmt "); // subchunk 1 id 
     writeInt(output, 16); // subchunk 1 size 
     writeShort(output, (short) 1); // audio format (1 = PCM) 
     writeShort(output, (short) 1); // number of channels 
     writeInt(output, SAMPLE_RATE); // sample rate 
     writeInt(output, SAMPLE_RATE * 2); // byte rate 
     writeShort(output, (short) 2); // block align 
     writeShort(output, (short) 16); // bits per sample 
     writeString(output, "data"); // subchunk 2 id 
     writeInt(output, rawData.length); // subchunk 2 size 
     // Audio data (conversion big endian -> little endian) 
     short[] shorts = new short[rawData.length/2]; 
     ByteBuffer.wrap(rawData).order(ByteOrder.LITTLE_ENDIAN) 
       .asShortBuffer().get(shorts); 
     ByteBuffer bytes = ByteBuffer.allocate(shorts.length * 2); 

     for (short s : shorts) { 

      // Apply Gain 
      /* 
      * s *= iGain; if(s>32767) { s=32767; } else if(s<-32768) { 
      * s=-32768; } 
      */ 
      bytes.putShort(s); 
     } 
     output.write(bytes.array()); 
    } finally { 
     if (output != null) { 
      output.close(); 
     } 
    } 
} 

private File getFile(final String suffix) { 
    Time time = new Time(); 
    time.setToNow(); 
    return new File(Environment.getExternalStorageDirectory(), 
      time.format("%Y%m%d%H%M%S") + "." + suffix); 
} 





private void writeInt(final DataOutputStream output, final int value) 
     throws IOException { 
    output.write(value >> 0); 
    output.write(value >> 8); 
    output.write(value >> 16); 
    output.write(value >> 24); 
} 

private void writeShort(final DataOutputStream output, final short value) 
     throws IOException { 
    output.write(value >> 0); 
    output.write(value >> 8); 
} 

private void writeString(final DataOutputStream output, final String value) 
     throws IOException { 
    for (int i = 0; i < value.length(); i++) { 
     output.write(value.charAt(i)); 
    } 
} 
}