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
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