FFT'd音頻的多峯值輪詢

Question

任何人都有一個很好的方法來輪詢音頻源數據的幾個頻率？如果我想得到500Hz，3500Hz，10kHz和20kHz（+ -1％）峯值的幅度，有沒有我可以參考的好的源庫呢？

謝謝！

Answer 1

這就是你如何做到的。

package com.example.frequencytest; 



import java.io.BufferedWriter; 
import java.io.File; 
import java.io.FileWriter; 
import java.io.IOException; 

import jfftpack.javasource.ca.uol.aig.fftpack.RealDoubleFFT; 
import android.app.Activity; 
import android.graphics.Bitmap; 
import android.graphics.Canvas; 
import android.graphics.Color; 
import android.graphics.Paint; 
import android.media.AudioFormat; 
import android.media.AudioRecord; 
import android.media.MediaRecorder; 
import android.os.AsyncTask; 
import android.os.Bundle; 
import android.util.Log; 
import android.view.Menu; 
import android.view.View; 
import android.view.View.OnClickListener; 
import android.widget.Button; 
import android.widget.ImageView; 
import android.widget.TextView; 

public class MainActivity extends Activity implements OnClickListener { 

    int frequency = 44100; 
    int channelConfiguration = AudioFormat.CHANNEL_IN_MONO; 
    int audioEncoding = AudioFormat.ENCODING_PCM_16BIT; 
    private RealDoubleFFT transformer; 
    int blockSize = 1024; 
    public double movingAvg = 0.0; 
    public int movingAvgCnt = 0; 
    public BufferedWriter buf = null; 
    File tempFile = new File("sdcard/Data_Log.txt"); 

    Button startStopButton; 
    boolean started = false; 

    RecordAudio recordTask; 
    TextView textView1; 

    ImageView imageView; 
    Bitmap bitmap; 
    Canvas canvas; 
    Paint paint; 

    //AudioRecord audioRecord; 

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

     startStopButton = (Button) this.findViewById(R.id.StartStopButton); 
     startStopButton.setOnClickListener(this); 

     transformer = new RealDoubleFFT(blockSize); 

     imageView = (ImageView) this.findViewById(R.id.ImageView01); 
     textView1 = (TextView) findViewById(R.id.textView1); 
     bitmap = Bitmap.createBitmap((int) 1024, (int) 300, 
       Bitmap.Config.ARGB_8888); 
     canvas = new Canvas(bitmap); 
     paint = new Paint(); 
     paint.setColor(Color.GREEN); 
     paint.setStrokeWidth(2); 
     imageView.setImageBitmap(bitmap); 

    } 

    public class RecordAudio extends AsyncTask<Void, double[], Void> { 

     @Override 
     protected Void doInBackground(Void... arg0) { 

      try { 
       int bufferSize = AudioRecord.getMinBufferSize(frequency, 
         channelConfiguration, audioEncoding); 
       AudioRecord audioRecord = new AudioRecord( 
         MediaRecorder.AudioSource.MIC, frequency, 
         channelConfiguration, audioEncoding, bufferSize); 

       short[] buffer = new short[blockSize]; 
       double[] toTransform = new double[blockSize]; 
       audioRecord.startRecording(); 

       // started = true; hopes this should true before calling 
       // following while loop 

       while (started) { 
        int bufferReadResult = audioRecord.read(buffer, 0, 
          blockSize); 

        for (int i = 0; i < blockSize && i < bufferReadResult; i++) { 
         toTransform[i] = (double) buffer[i]/32768.0; 
        } 
         toTransform = HanningWindow(toTransform,0,blockSize); 
         transformer.ft(toTransform); 
         publishProgress(toTransform); 
       } 

       audioRecord.stop(); 
       buf.close(); 

      } catch (Throwable t) { 
       t.printStackTrace(); 
       Log.e("AudioRecord", "Recording Failed"); 
      } 
      return null; 
     } 

     @Override 
     protected void onProgressUpdate(double[]... toTransform) { 

      canvas.drawColor(Color.BLACK); 

      double average = 0.0; 
      int averageCnt=1; 
      for (int i = 0; i < toTransform[0].length; i++) { 
       int x = i; 
       int downy = (int) (100 - (toTransform[0][i] * 10)); 
       int upy = 100; 

       if(i>2 && i<(toTransform[0].length/2)){ 
        average += Math.sqrt(Math.abs(toTransform[0][i])); 
        averageCnt++; 
       } 
       canvas.drawLine(x, downy, x, upy, paint);    
      } 
      average = average/averageCnt; 
      movingAvg += average; 
      movingAvgCnt++; 
      if(movingAvgCnt==5){ 
       movingAvg = movingAvg/movingAvgCnt; 

       textView1.setText(""+movingAvg); 
       try{ 
         buf.append("" + average + ","+movingAvg); 
         buf.newLine(); 
        }catch (IOException e) 
         { 
          e.printStackTrace(); 
         } 
       movingAvg = 0.0; 
       movingAvgCnt = 0; 
      } 
      imageView.invalidate(); 
     } 
    } 

    @Override 
    public boolean onCreateOptionsMenu(Menu menu) { 
     getMenuInflater().inflate(R.menu.main, menu); 
     return true; 
    } 

    public void onClick(View arg0) { 
     // TODO Auto-generated method stub 
     if (started) { 
      started = false; 
      startStopButton.setText("Start"); 
      recordTask.cancel(true); 
     } else { 
      started = true; 
      startStopButton.setText("Stop"); 
      setupTempFile(); 
      recordTask = new RecordAudio(); 
      recordTask.execute(); 
     } 
    } 

    public void setupTempFile(){ 
     Log.d("Process", "startRecording"); 

     if (tempFile.exists()){tempFile.delete();} 
     if (!tempFile.exists()) 
      { 
       try 
       { 
       tempFile.createNewFile(); 
       } 
       catch (IOException e) 
       { 
       // TODO Auto-generated catch block 
       e.printStackTrace(); 
       } 
       try 
       { 
        //BufferedWriter for performance, true to set append to file flag 
        buf = new BufferedWriter(new FileWriter(tempFile, true)); 
        buf.append("Data Val, Moving Average"); 
        buf.newLine(); 
       } 
       catch (IOException e) 
       { 
        // TODO Auto-generated catch block 
        e.printStackTrace(); 
       } 

      } 
    } 
    public short[] HanningWindow(short[] signal_in, int pos, int size) 
    { 
     for (int i = pos; i < pos + size; i++) 
     { 
      int j = i - pos; // j = index into Hann window function 
      signal_in[i] = (short) (signal_in[i] * 0.5 * (1.0 - Math.cos(2.0 * Math.PI * j/size))); 
     } 
     return signal_in; 
    } 

    public double[] HanningWindow(double[] signal_in, int pos, int size) 
    { 
     for (int i = pos; i < pos + size; i++) 
     { 
      int j = i - pos; // j = index into Hann window function 
      signal_in[i] = (double) (signal_in[i] * 0.5 * (1.0 - Math.cos(2.0 * Math.PI * j/size))); 
     } 
     return signal_in; 
    } 

}