PCM到WAV的转换（java）

来源：互联网发布：用友软件主要客户编辑：程序博客网时间：2024/05/01 08:37

其实WAV只是PCM文件加上相关的文件头和描述信息，不算复杂。这段程序参考了网上的一些实现(C/C++)，修改了其中的一些错误，比如转换后的文件能够播放但是时间长度是错误的；或者不能拖动等等。

代码见下。

private void convertAudioFiles(String src, String target) throws Exception {
   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 = 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!");
}

WavHeader辅助类。用于生成头部信息。

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);
   }
}
}

来源：http://hi.baidu.com/lff0305/blog/item/7d8ba938246f22cfd5622596.html

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