FFT 音频的多峰值轮询

Posted 2023-02-25

【中文标题】FFT 音频的多峰值轮询

【英文标题】：Multiple Peak Polling of FFT'd Audio

【发布时间】：2013-12-15 17:38:27

【问题描述】：

任何人有一个很好的快速方法来轮询几个频率的音频源数据？

即 - 如果我想获得 500Hz、3500Hz、10kHz 和 20kHz (+-1%) 峰值的幅度，是否有任何好的源库可供我参考？

谢谢！

【问题讨论】：

有很多关于 SO 的相关问题。我写了这么多这篇博文，可能会对你有所帮助：blog.bjornroche.com/2012/07/…

由于您只查看 4 个频率，您可能希望使用带通滤波器或 goertzel 算法进行过滤，但 FFT 可以正常工作：en.wikipedia.org/wiki/Goertzel_algorithm

是的，我已经阅读（我还在阅读）那些博客，非常棒的信息。我只是在钓鱼，看看是否有人开发了复制和粘贴功能，可以节省大量使用时间。

我开始工作了，现在在主线程中发布了一个关于音频捕获机制的问题。感谢您的帮助。

【参考方案1】：

这就是你的做法。

 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;