java - 我的应用程序 "find frequency of audio input from microphone"总是崩溃。但为什么？

Question

最后你会看到错误信息!!

import java.nio.ByteBuffer;  
import java.nio.ByteOrder;  

import javax.sound.sampled.AudioFormat;  
import javax.sound.sampled.AudioSystem;  
import javax.sound.sampled.DataLine;  
import javax.sound.sampled.TargetDataLine;

导入 Math3 以使用 fft。

import org.apache.commons.math3.complex.Complex;  
import org.apache.commons.math3.transform.DftNormalization;  
import org.apache.commons.math3.transform.FastFourierTransformer;  
import org.apache.commons.math3.transform.TransformType;  

public class AudioInput {  

    TargetDataLine  microphone;  

    final int       audioFrames= 8196;  //power ^ 2  

    final float     sampleRate= 8000.0f;  
    final int       bitsPerRecord= 16;  
    final int       channels= 1;  
    final boolean   bigEndian = true;  
    final boolean   signed= true;  

    byte            byteData[];     // length=audioFrames * 2  
    double          doubleData[];   // length=audioFrames only reals needed for apache lib.  
    AudioFormat     format;  
    FastFourierTransformer transformer;  

    public AudioInput () {  

        byteData= new byte[audioFrames * 2];  //two bytes per audio frame, 16 bits  

        //doubleData= new double[audioFrames * 2];  // real & imaginary  
        doubleData= new double[audioFrames];  // only real for apache  

        transformer = new FastFourierTransformer(DftNormalization.STANDARD);  

        System.out.print("Microphone initialization\n");  
        format = new AudioFormat(sampleRate, bitsPerRecord, channels, signed, bigEndian);  
        DataLine.Info info = new DataLine.Info(TargetDataLine.class, format); // format is an AudioFormat object  

        if (!AudioSystem.isLineSupported(info)) {  
            System.err.print("isLineSupported failed");  
            System.exit(1);  
        }  

        try {  
             microphone = (TargetDataLine) AudioSystem.getLine(info);  
             microphone.open(format);  
             System.out.print("Microphone opened with format: "+format.toString()+"\n");  
             microphone.start();  
        }catch(Exception ex){  
            System.out.println("Microphone failed: "+ex.getMessage());  
            System.exit(1);  
        }  

    }  

    public int readPcm(){  
        int numBytesRead=   
                microphone.read(byteData, 0, byteData.length);  
        if(numBytesRead!=byteData.length){  
            System.out.println("Warning: read less bytes than buffer size");  
            System.exit(1);  
        }  
        return numBytesRead;  
    }  


    public void byteToDouble(){  
        ByteBuffer buf= ByteBuffer.wrap(byteData);  
        buf.order(ByteOrder.BIG_ENDIAN);  
        int i=0;   

        while(buf.remaining()>2){  
            short s = buf.getShort();  
            doubleData[ i ] = (new Short(s)).doubleValue();  
            ++i;  
        }  
        //System.out.println("Parsed "+i+" doubles from "+byteData.length+" bytes");  
    }  


    public void findFrequency(){  
        double frequency;  
        Complex[] cmplx= transformer.transform(doubleData, TransformType.FORWARD);  
        double real;  
        double im;  
        double mag[] = new double[cmplx.length];  

        for(int i = 0; i < cmplx.length; i++){  
            real = cmplx[i].getReal();  
            im = cmplx[i].getImaginary();  
            mag[i] = Math.sqrt((real * real) + (im*im));  
        }  

        double peak = -1.0;  
        int index=-1;  
        for(int i = 0; i < cmplx.length; i++){  
            if(peak < mag[i]){  
                index=i;  
                peak= mag[i];  
            }  
        }  
        frequency = (sampleRate * index) / audioFrames;  
        System.out.print("Index: "+index+", Frequency: "+frequency+"\n");  
   }

/* * 打印第一个频率档以了解我们拥有的分辨率 */

    public void printFreqs(){  
        for (int i=0; i<audioFrames/4; i++){  
            System.out.println("bin "+i+", freq: "+(sampleRate*i)/audioFrames);  
        }  
    }  

    public static void main(String[] args) {  
        AudioInput ai= new AudioInput();  
        int turns=10000;  
        while(turns-- > 0){  
            ai.readPcm();  
            ai.byteToDouble();  
            ai.findFrequency();  
        }  


//ai.printFreqs();  
    }  
}  

以下是控制台中包含错误消息的内容:

麦克风初始化麦克风打开格式:PCM_SIGNED 8000.0 Hz，16 位，单声道，2 字节/帧，big-endian

Exception in thread "main" org.apache.commons.math3.exception.MathIllegalArgumentException: 8.196 is not a power of 2, consider padding for fix
    at org.apache.commons.math3.transform.FastFourierTransformer.transformInPlace(FastFourierTransformer.java:229)
    at org.apache.commons.math3.transform.FastFourierTransformer.transform(FastFourierTransformer.java:375)
    at AudioInput.findFrequency(AudioInput.java:88)
    at AudioInput.main(AudioInput.java:126)

Answer 1

8196 不是 2 的幂。尝试将变量 audioFrames 更改为 final int audioFrames= 8192;。 FFT 算法只能处理大小为 2 的幂的数组(2, 4, 8, 16, 32, 64, 128, 256, 512, 1024, 2048, 4096, 8192, ...)