Java实现PCM格式音频转MP3或WAV——CV即用，质量保证

本文介绍了一种将PCM格式音频文件转换为MP3和WAV格式的方法，通过Java编程实现，详细展示了文件读取、参数设置、头部信息填充及数据流写入过程，适用于音视频处理和音频格式转换的初学者。

import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;
 
/**
 * PCM 转 MP3
 *
 * @author laowang
 * @since 2020-04-02
 */
public class PcmToMp3 {
    /**
     * @param src    待转换文件路径
     * @param target 目标文件路径(这个工具是在源文件的基础上再形成一个文件，target样例：D:/landscape/music/25745664665456.mp3,必须写全否则报io‘无法访问错误’)
     * @throws IOException 抛出异常
     */
    public static String convertAudioFiles(String src, String target) throws IOException {
        FileInputStream fis = new FileInputStream(src);
        FileOutputStream fos = new FileOutputStream(target);
 
        //计算长度
        byte[] buf = new byte[1024 * 4];
        int size = fis.read(buf);
        int PCMSize = 0;
        while (size != -1) {
            PCMSize += size;
            size = fis.read(buf);
        }
        fis.close();
        
        //填入参数，比特率等等。这里用的是16位单声道 8000 hz
        WaveHeader header = new WaveHeader();
        //长度字段 = 内容的大小（PCMSize) + 头部字段的大小(不包括前面4字节的标识符RIFF以及fileLength本身的4字节)
        header.fileLength = PCMSize + (44 - 8);
        header.FmtHdrLeth = 16;
        header.BitsPerSample = 16;
        header.Channels = 1;
        header.FormatTag = 0x0001;
        header.SamplesPerSec = 16000;
        header.BlockAlign = (short) (header.Channels * header.BitsPerSample / 8);
        header.AvgBytesPerSec = header.BlockAlign * header.SamplesPerSec;
        header.DataHdrLeth = PCMSize;
 
        byte[] h = header.getHeader();
 
        assert h.length == 44; //WAV标准，头部应该是44字节
        //write header
        fos.write(h, 0, h.length);
        //write data stream
        fis = new FileInputStream(src);
        size = fis.read(buf);
        while (size != -1) {
            fos.write(buf, 0, size);
            size = fis.read(buf);
        }
        fis.close();
        fos.close();
        System.out.println("PCM Convert to MP3 OK!");
        return "ok";
    }
}

 
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;
 
/**
 * PCM 转 WAV
 *
 * @author laowang
 * @since 2020-04-02
 */
public class PcmToWav {
    /**
     * @param src    待转换文件路径
     * @param target 目标文件路径
     * @throws IOException 抛出异常
     */
    public static void convertAudioFiles(String src, String target) throws IOException {
 
        FileInputStream fis = new FileInputStream(src);
        FileOutputStream fos = new FileOutputStream(target);
 
        //计算长度
        byte[] buf = new byte[1024 * 4];
        int size = fis.read(buf);
        int PCMSize = 0;
        while (size != -1) {
            PCMSize += size;
            size = fis.read(buf);
        }
        fis.close();
 
        //填入参数，比特率等等。这里用的是16位单声道 8000 hz
        WaveHeader header = new WaveHeader();
        //长度字段 = 内容的大小（PCMSize) + 头部字段的大小(不包括前面4字节的标识符RIFF以及fileLength本身的4字节)
        header.fileLength = PCMSize + (44 - 8);
        header.FmtHdrLeth = 16;
        header.BitsPerSample = 16;
        header.Channels = 2;
        header.FormatTag = 0x0001;
        header.SamplesPerSec = 8000;
        header.BlockAlign = (short) (header.Channels * header.BitsPerSample / 8);
        header.AvgBytesPerSec = header.BlockAlign * header.SamplesPerSec;
        header.DataHdrLeth = PCMSize;
 
        byte[] h = header.getHeader();
 
        assert h.length == 44; //WAV标准，头部应该是44字节
        // write header
        fos.write(h, 0, h.length);
        // write data stream
        fis = new FileInputStream(src);
        size = fis.read(buf);
        while (size != -1) {
            fos.write(buf, 0, size);
            size = fis.read(buf);
        }
        fis.close();
        fos.close();
        System.out.println("Convert OK!");
    }
}

处理函数waveHeader




package com.test.shell;

import java.io.ByteArrayOutputStream;
import java.io.IOException;

public class WaveHeader {

    public final char fileID[] = {'R', 'I', 'F', 'F'};
    public int fileLength;
    public char wavTag[] = {'W', 'A', 'V', 'E'};;
    public char FmtHdrID[] = {'f', 'm', 't', ' '};
    public int FmtHdrLeth;
    public short FormatTag;
    public short Channels;
    public int SamplesPerSec;
    public int AvgBytesPerSec;
    public short BlockAlign;
    public short BitsPerSample;
    public char DataHdrID[] = {'d','a','t','a'};
    public int DataHdrLeth;

    public byte[] getHeader() throws IOException {
        ByteArrayOutputStream bos = new ByteArrayOutputStream();
        WriteChar(bos, fileID);
        WriteInt(bos, fileLength);
        WriteChar(bos, wavTag);
        WriteChar(bos, FmtHdrID);
        WriteInt(bos,FmtHdrLeth);
        WriteShort(bos,FormatTag);
        WriteShort(bos,Channels);
        WriteInt(bos,SamplesPerSec);
        WriteInt(bos,AvgBytesPerSec);
        WriteShort(bos,BlockAlign);
        WriteShort(bos,BitsPerSample);
        WriteChar(bos,DataHdrID);
        WriteInt(bos,DataHdrLeth);
        bos.flush();
        byte[] r = bos.toByteArray();
        bos.close();
        return r;
    }

    private void WriteShort(ByteArrayOutputStream bos, int s) throws IOException {
        byte[] mybyte = new byte[2];
        mybyte[1] =(byte)( (s << 16) >> 24 );
        mybyte[0] =(byte)( (s << 24) >> 24 );
        bos.write(mybyte);
    }


    private void WriteInt(ByteArrayOutputStream bos, int n) throws IOException {
        byte[] buf = new byte[4];
        buf[3] =(byte)( n >> 24 );
        buf[2] =(byte)( (n << 8) >> 24 );
        buf[1] =(byte)( (n << 16) >> 24 );
        buf[0] =(byte)( (n << 24) >> 24 );
        bos.write(buf);
    }

    private void WriteChar(ByteArrayOutputStream bos, char[] id) {
        for (int i=0; i<id.length; i++) {
            char c = id[i];
            bos.write(c);
        }
    }
}

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