java 使用 jtransforms 傅里叶库通过时域转频域实现wav 音频的加速与变慢效果

引入 maven 依赖：

 
      net.sourceforge.jtransforms
      jtransforms
      2.4.0
 

FourierTransformTest.java：

import edu.emory.mathcs.jtransforms.fft.DoubleFFT_1D;

import javax.sound.sampled.UnsupportedAudioFileException;
import java.io.File;
import java.io.IOException;
import java.util.Arrays;

public class FourierTransformTest {
    public static void main(String[] args) throws UnsupportedAudioFileException, IOException {
        fastTest();
        // slowTest();
    }

    public static void  fastTest() throws UnsupportedAudioFileException, IOException {
        double[] audio_src = AudioUtils.wavToDoubleArray( new File("C:\\E\\素材\\音频\\wav\\audio.wav") );

        // 将 audio_src 进行 时域转频域
        new DoubleFFT_1D(audio_src.length).realForward(audio_src);

        // 截取转换成频域以后得 audio_src 的前半部分 作为 audio_target
        // 这里拷贝频域模式下的 audio_src 的前半部分，因为是频域模式，所以前半部分和后半部分其实都包含 "完整" 的时域信息( 只是失真严重 )，如果是时域模式下直接砍一半，肯定会丢失一半的时域信息( 但是未丢失的时域信息的音质没有任何丢失 )
        // 所以频域下的double[]砍一半其实是音质砍一半( 即频率信息丢失一半 )
        // 这里 除以2实现了2x加速效果
        double[] audio_target = Arrays.copyOfRange(audio_src, 0, audio_src.length / 2);

        // 将 audio_target 进行频域转时域
        new DoubleFFT_1D( audio_target.length ).realInverse( audio_target, true );
        System.out.println("转换完毕");

        // 将audio_target 时域 double[] 转换成 wav 文件
        AudioUtils.doubleArrayToWAV( audio_target,new File( "C:\\E\\素材\\音频\\wav\\audio_target.wav" ) );
        System.out.println("生成完毕");
    }

    public static void slowTest() throws UnsupportedAudioFileException, IOException {
        double[] audio_src = AudioUtils.wavToDoubleArray( new File("C:\\E\\素材\\音频\\wav\\audio.wav") );

        // 将 audio_src 进行 时域转频域
        new DoubleFFT_1D(audio_src.length).realForward(audio_src);

        // 实现了 0.5X 变速效果
        double[] audio_zero = buildZeroDoubleValueArray( audio_src.length );
        // 将转换成频域以后的 audio_src 和一个等长度的 全是0的doublep[]合并( 可以把这个 audio_zero看做一个频域格式的 double[]，只是各个频率下的振幅全是0)
        double[] audio_target = combineArray( audio_src,audio_zero );

        // 将 audio_target 频域转时域
        new DoubleFFT_1D( audio_target.length ).realInverse( audio_target, true );
        System.out.println("转换完毕");

        // 将时域格式下的 audio_target 转成 wav 文件
        AudioUtils.doubleArrayToWAV( audio_target,new File( "C:\\E\\素材\\音频\\wav\\audio_target.wav" ) );
        System.out.println("生成完毕");
    }

    private static double[] buildZeroDoubleValueArray(int length) {
        double[] doubleArray = new double[length];
        for (int i = 0; i < length; i++) {
            doubleArray[i]=0d;
        }
        return doubleArray;
    }

    private static double[] combineArray(double[]... arrays) {
        int arrayCount = arrays.length;
        int totalLength = 0;
        for( int i=0;i

用到的工具类 AudioUtils.java：

import javax.sound.sampled.*;
import java.io.ByteArrayInputStream;
import java.io.File;
import java.io.IOException;
import java.util.Arrays;


public class AudioUtils {
    public static void main(String[] args) throws UnsupportedAudioFileException, IOException {
        File file = new File("C:\\E\\素材\\音频\\wav\\一生所爱.wav");
        double[] doubleArray = wavToDoubleArray(file);
        System.out.println( doubleArray.length );

        int partLength = doubleArray.length / 10;


        doubleArrayToWAV(  Arrays.copyOfRange(doubleArray, 0, partLength),new File( "C:\\E\\素材\\音频\\wav\\一生所爱_part1.wav" ) );
        doubleArrayToWAV(  Arrays.copyOfRange(doubleArray, partLength, partLength * 2),new File( "C:\\E\\素材\\音频\\wav\\一生所爱_part2.wav" ) );
        doubleArrayToWAV(  Arrays.copyOfRange(doubleArray, partLength * 2, partLength * 3),new File( "C:\\E\\素材\\音频\\wav\\一生所爱_part3.wav" ) );
        doubleArrayToWAV(  Arrays.copyOfRange(doubleArray, partLength * 3, partLength * 4),new File( "C:\\E\\素材\\音频\\wav\\一生所爱_part4.wav" ) );
        doubleArrayToWAV(  Arrays.copyOfRange(doubleArray, partLength * 4, partLength * 5),new File( "C:\\E\\素材\\音频\\wav\\一生所爱_part5.wav" ) );
        doubleArrayToWAV(  Arrays.copyOfRange(doubleArray, partLength * 5, partLength * 6),new File( "C:\\E\\素材\\音频\\wav\\一生所爱_part6.wav" ) );
    }

    public static double[] wavToDoubleArray(File mp3File) throws UnsupportedAudioFileException, IOException {
        AudioInputStream audioInputStream = AudioSystem.getAudioInputStream(mp3File);
        AudioFormat audioFormat = audioInputStream.getFormat();
        int numChannels = audioFormat.getChannels();
        int sampleSizeInBytes = audioFormat.getSampleSizeInBits() / 8;
        int frameSize = numChannels * sampleSizeInBytes;
        int bufferSize = (int) (audioInputStream.getFrameLength() * frameSize);
        byte[] audioBytes = new byte[bufferSize];
        audioInputStream.read(audioBytes);

        double[] audioData = new double[audioBytes.length / 2];
        for (int i = 0, j = 0; i < audioBytes.length; i += 2, j++) {
            int sample = (audioBytes[i + 1] << 8) | (audioBytes[i] & 0xFF);
            audioData[j] = sample / 32768.0;
        }

        return audioData;
    }

    public static void doubleArrayToWAV(double[] audioData, File outputFile) throws IOException, UnsupportedAudioFileException {
        AudioFormat audioFormat = new AudioFormat(44100, 16, 2, true, false);
        byte[] audioBytes = new byte[audioData.length * 2];
        for (int i = 0, j = 0; i < audioData.length; i++, j += 2) {
            short sample = (short) (audioData[i] * 32767);
            audioBytes[j] = (byte) (sample & 0xFF);
            audioBytes[j + 1] = (byte) ((sample >> 8) & 0xFF);
        }

        AudioInputStream audioInputStream = new AudioInputStream(new ByteArrayInputStream(audioBytes), audioFormat, audioData.length);
        AudioSystem.write(audioInputStream, AudioFileFormat.Type.WAVE, outputFile);
    }
}