Android pcm转wav格式方法

程序中的录音文件之前直接保存的是 .pcm格式，一直也相安无事，用的挺好。最近有一个webview中需要加载录音文件，出现了不兼容的问题，所以需要把 .pcm格式文件转换为 .wav格式。

PCM

PCM（Pulse Code Modulation----脉码调制录音)。所谓PCM录音就是将声音等模拟信号变成符号化的脉冲列，再予以记录。PCM信号是由[1]、[0]等符号构成的数字信号，而未经过任何编码和压缩处理。与模拟信号比，它不易受传送系统的杂波及失真的影响。动态范围宽，可得到音质相当好的效果。简单的说，pcm就是没有压缩的音频格式。

wav

wav全称是WAVE，.wav是其扩展名，它是一种无损的音频文件格式，WAV符合 RIFF(Resource Interchange File Format)规范。所有的WAV都有一个文件头，这个文件头是音频流的编码参数。WAV对音频流的编码没有硬性规定，除了PCM之外，还有几乎所有支持ACM规范的编码都可以为WAV的音频流进行编码。

pcm和wav关系 pcm是无损wav文件中音频数据的一种编码方式，pcm加上wav文件头就可以转为wav格式，但wav还可以用其它方式编码。

PcmToWavUtil

package com.hgb.mytest;
import android.media.AudioFormat;
import android.media.AudioRecord;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;
/**
 * Created by HaoGuibao
 * Date 2016/8/26.
 * Description :pcm格式的音频转换为wav格式的工具类
 */
public class PcmToWavUtil {
 private int mBufferSize; //缓存的音频大小
 private int mSampleRate = 8000;// 8000|16000
 private int mChannel = AudioFormat.CHANNEL_IN_STEREO; //立体声
 private int mEncoding = AudioFormat.ENCODING_PCM_16BIT;

 public PcmToWavUtil() {
  this.mBufferSize = AudioRecord.getMinBufferSize(mSampleRate, mChannel, mEncoding);
 }
 /**
  * @param sampleRate sample rate、采样率
  * @param channel channel、声道
  * @param encoding Audio data format、音频格式
  */
 public PcmToWavUtil(int sampleRate, int channel, int encoding) {
  this.mSampleRate = sampleRate;
  this.mChannel = channel;
  this.mEncoding = encoding;
  this.mBufferSize = AudioRecord.getMinBufferSize(mSampleRate, mChannel, mEncoding);
 }
 /**
  * pcm文件转wav文件
  *
  * @param inFilename 源文件路径
  * @param outFilename 目标文件路径
  */
 public void pcmToWav(String inFilename, String outFilename) {
  FileInputStream in;
  FileOutputStream out;
  long totalAudioLen;
  long totalDataLen;
  long longSampleRate = mSampleRate;
  int channels = 2;
  long byteRate = 16 * mSampleRate * channels / 8;
  byte[] data = new byte[mBufferSize];
  try {
   in = new FileInputStream(inFilename);
   out = new FileOutputStream(outFilename);
   totalAudioLen = in.getChannel().size();
   totalDataLen = totalAudioLen + 36;

   writeWaveFileHeader(out, totalAudioLen, totalDataLen,
     longSampleRate, channels, byteRate);
   while (in.read(data) != -1) {
    out.write(data);
   }
   in.close();
   out.close();
  } catch (IOException e) {
   e.printStackTrace();
  }
 }
 /**
  * 加入wav文件头
  */
 private void writeWaveFileHeader(FileOutputStream out, long totalAudioLen,
          long totalDataLen, long longSampleRate, int channels, long byteRate)
   throws IOException {
  byte[] header = new byte[44];
  header[0] = 'R'; // RIFF/WAVE header
  header[1] = 'I';
  header[2] = 'F';
  header[3] = 'F';
  header[4] = (byte) (totalDataLen & 0xff);
  header[5] = (byte) ((totalDataLen >> 8) & 0xff);
  header[6] = (byte) ((totalDataLen >> 16) & 0xff);
  header[7] = (byte) ((totalDataLen >> 24) & 0xff);
  header[8] = 'W'; //WAVE
  header[9] = 'A';
  header[10] = 'V';
  header[11] = 'E';
  header[12] = 'f'; // 'fmt ' chunk
  header[13] = 'm';
  header[14] = 't';
  header[15] = ' ';
  header[16] = 16; // 4 bytes: size of 'fmt ' chunk
  header[17] = 0;
  header[18] = 0;
  header[19] = 0;
  header[20] = 1; // format = 1
  header[21] = 0;
  header[22] = (byte) channels;
  header[23] = 0;
  header[24] = (byte) (longSampleRate & 0xff);
  header[25] = (byte) ((longSampleRate >> 8) & 0xff);
  header[26] = (byte) ((longSampleRate >> 16) & 0xff);
  header[27] = (byte) ((longSampleRate >> 24) & 0xff);
  header[28] = (byte) (byteRate & 0xff);
  header[29] = (byte) ((byteRate >> 8) & 0xff);
  header[30] = (byte) ((byteRate >> 16) & 0xff);
  header[31] = (byte) ((byteRate >> 24) & 0xff);
  header[32] = (byte) (2 * 16 / 8); // block align
  header[33] = 0;
  header[34] = 16; // bits per sample
  header[35] = 0;
  header[36] = 'd'; //data
  header[37] = 'a';
  header[38] = 't';
  header[39] = 'a';
  header[40] = (byte) (totalAudioLen & 0xff);
  header[41] = (byte) ((totalAudioLen >> 8) & 0xff);
  header[42] = (byte) ((totalAudioLen >> 16) & 0xff);
  header[43] = (byte) ((totalAudioLen >> 24) & 0xff);
  out.write(header, 0, 44);
 }
}

Demo 把手机内存卡上 /sdcard/yxck/treamentRecord/ 的123.pcm转换为123.wav文件。

public class MainActivity extends AppCompatActivity {
 /**
  * pcm格式转wav格式工具类
  */
 private PcmToWavUtil pcmToWavUtil = new PcmToWavUtil();

 @Override
 protected void onCreate(Bundle savedInstanceState) {
  super.onCreate(savedInstanceState);
  setContentView(R.layout.activity_main);

  final String path = "/sdcard/yxck/treamentRecord/123.pcm";
  //按原路径把音频文件后缀改一下;
  final String outpath = path.replace(".pcm", ".wav");

  Button button = (Button) findViewById(R.id.button);
  button.setOnClickListener(new View.OnClickListener() {
   @Override
   public void onClick(View view) {
    pcmToWavUtil.pcmToWav(path, outpath);
   }
  });
 }
}

pcm转换wav格式成功