转载-java将pcm音频转换成wav格式

原文链接：https://blog.csdn.net/qq_25925973/article/details/90441386

PCM（Pulse Code Modulation）脉冲编码调制是数字通信的编码方式之一。主要过程是将话音、图像等模拟信号每隔一定时间进行取样，使其离散化，同时将抽样值按分层单位四舍五入取整量化，同时将抽样值按一组二进制码来表示抽样脉冲的幅值。

pcm音频想要直接听需要专业的软件才可以，这里我需要把pcm的音频转化为wav这种无损的格式，也就是需要在pcm文件添加wav的音频头，这样就可以直接使用音频软件打开了。使用Java实现的方式见下文

 

package com.test.shell;

import java.io.*;
import com.alibaba.druid.util.StringUtils;

public class ShellUtils {
    public static File tranPcmToWavFile(File pcmFile) {
        FileInputStream fis = null;
        FileOutputStream fos = null;
        try {
            fis = new FileInputStream(pcmFile);
            String wavfilepath = pcmFile.getAbsolutePath().substring(0, pcmFile.getAbsolutePath().lastIndexOf(".")) + "." + SysConstants.IVR_SPEAK_TYPE_WAV.toLowerCase();


            File file = new File(wavfilepath);
            if (!file.exists()) {
                file.createNewFile();
            }
            fos = new FileOutputStream(wavfilepath);


            int PCMSize = 0;
            byte[] buf = new byte[1024 * 4];
            int size = fis.read(buf);

            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 = 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(pcmFile);
            size = fis.read(buf);
            while (size != -1) {
                fos.write(buf, 0, size);
                size = fis.read(buf);
            }
            fis.close();
            fos.close();
            return new File(wavfilepath);
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            if (fis != null) {
                try {
                    fis.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
            if (fos != null) {
                try {
                    fos.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
        }
        return null;
    }
}

2、其中用到的WaveHeader 如下：

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);
        }
    }
}