Android系统wav和amr的互转

来源：长沙it培训|发布时间：2017-04-17|浏览量：

　　1、wav和amr文件都有头文件，AudioRecord录制出来的文件是raw格式的就不能播放，加上wav头文件就变成wav文件就可以播放。

　　给raw文件添加wav头文件

/**       * 这里提供一个头信息。插入这些信息就可以得到可以播放的文件。       * 为我为啥插入这44个字节，这个还真没深入研究，不过你随便打开一个wav       * 音频的文件，可以发现前面的头文件可以说基本一样哦。每种格式的文件都有       * 自己特有的头文件。       */      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';          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';          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);      }

　　amr头文件

[java] view plain copy final private static byte[] header = new byte[]{0x23, 0x21, 0x41, 0x4D, 0x52, 0x0A};

 

　　2、wav或raw转amr

　　2.1 通过Android系统自带的AmrInputStream类，因为它被隐藏了，只有通过反射来操作。

public class AmrInputStream extends InputStream  {          static {          System.loadLibrary("media");      }            private final static String TAG = "AmrInputStream";            // frame is 20 msec at 8.000 khz      private final static int SAMPLES_PER_FRAME = 8000 * 20 / 1000;            // pcm input stream      private InputStream mInputStream;            // native handle      private int mGae;            // result amr stream      private final byte[] mBuf = new byte[SAMPLES_PER_FRAME * 2];      private int mBufIn = 0;      private int mBufOut = 0;            // helper for bytewise read()      private byte[] mOneByte = new byte[1];            /**      * Create a new AmrInputStream, which converts 16 bit PCM to AMR      * @param inputStream InputStream containing 16 bit PCM.      */      public AmrInputStream(InputStream inputStream) {          mInputStream = inputStream;          mGae = GsmAmrEncoderNew();          GsmAmrEncoderInitialize(mGae);      }        @Override      public int read() throws IOException {          int rtn = read(mOneByte, 0, 1);          return rtn == 1 ? (0xff & mOneByte[0]) : -1;      }            @Override      public int read(byte[] b) throws IOException {          return read(b, 0, b.length);      }        @Override      public int read(byte[] b, int offset, int length) throws IOException {          if (mGae == 0) throw new IllegalStateException("not open");                    // local buffer of amr encoded audio empty          if (mBufOut >= mBufIn) {              // reset the buffer              mBufOut = 0;              mBufIn = 0;                            // fetch a 20 msec frame of pcm              for (int i = 0; i < SAMPLES_PER_FRAME * 2; ) {                  int n = mInputStream.read(mBuf, i, SAMPLES_PER_FRAME * 2 - i);                  if (n == -1) return -1;                  i += n;              }                            // encode it              mBufIn = GsmAmrEncoderEncode(mGae, mBuf, 0, mBuf, 0);          }                    // return encoded audio to user          if (length > mBufIn - mBufOut) length = mBufIn - mBufOut;          System.arraycopy(mBuf, mBufOut, b, offset, length);          mBufOut += length;                    return length;      }        @Override      public void close() throws IOException {          try {              if (mInputStream != null) mInputStream.close();          } finally {              mInputStream = null;              try {                  if (mGae != 0) GsmAmrEncoderCleanup(mGae);              } finally {                  try {                      if (mGae != 0) GsmAmrEncoderDelete(mGae);                  } finally {                      mGae = 0;                  }              }          }      }        @Override      protected void finalize() throws Throwable {          if (mGae != 0) {              close();              throw new IllegalStateException("someone forgot to close AmrInputStream");          }      }            //      // AudioRecord JNI interface      //      public static native int GsmAmrEncoderNew();      public static native void GsmAmrEncoderInitialize(int gae);      public static native int GsmAmrEncoderEncode(int gae,              byte[] pcm, int pcmOffset, byte[] amr, int amrOffset) throws IOException;      public static native void GsmAmrEncoderCleanup(int gae);      public static native void GsmAmrEncoderDelete(int gae);    }

　　JNI位于源代码下的frameworks\base\media\jni目录，对应的libmedia_jni.so文件文件在system/lib,打开File Exploer就可以看到。

　　下面是通过反射进行文件转换

/**     * 通过反射调用android系统自身AmrInputStream类进行转换     * @param inPath 源文件     * @param outPath 目标文件     */     public void systemWav2Amr(String inPath,String outPath){      try {          FileInputStream fileInputStream = new FileInputStream(inPath);          FileOutputStream fileoutputStream = new FileOutputStream(outPath);          // 获得Class          Class<?> cls = Class.forName("android.media.AmrInputStream");          // 通过Class获得所对应对象的方法          Method[] methods = cls.getMethods();          // 输出每个方法名          fileoutputStream.write(header);          Constructor<?> con = cls.getConstructor(InputStream.class);          Object obj = con.newInstance(fileInputStream);          for (Method method : methods) {              Class<?>[] parameterTypes = method.getParameterTypes();              if ("read".equals(method.getName())                      && parameterTypes.length == 3) {                  byte[] buf = new byte[1024];                  int len = 0;                  while ((len = (int) method.invoke(obj, buf, 0, 1024)) > 0) {                      fileoutputStream.write(buf, 0, len);                  }                  break;              }          }          for (Method method : methods) {              if ("close".equals(method.getName())) {                  method.invoke(obj);                  break;              }          }          fileoutputStream.close();      } catch (Exception e) {          e.printStackTrace();      }     }

　　2.2 通过开源库opencore进行转换，下面是jni部分

public class AmrEncoder {        public enum Mode {          MR475,/* 4.75 kbps */          MR515,    /* 5.15 kbps */          MR59,     /* 5.90 kbps */          MR67,     /* 6.70 kbps */          MR74,     /* 7.40 kbps */          MR795,    /* 7.95 kbps */          MR102,    /* 10.2 kbps */          MR122,    /* 12.2 kbps */          MRDTX,    /* DTX       */          N_MODES   /* Not Used  */      }        public static native void init(int dtx);        public static native int encode(int mode, short[] in, byte[] out);        public static native void reset();        public static native void exit();        static {          System.loadLibrary("amr-codec");      }  }

　　转换操作，里面也有解码的部分

private void wav2amr(final String inpath,final String outpath){          //  Random random = new Random();  //      File file = new File(root + "/RawAudio.raw");  //      file.getAbsolutePath(),root + "/test" + random.nextInt(120) + ".amr"          new Thread(new Runnable() {              @Override              public void run() {                  convertAMR(inpath,outpath);              }          }).start();      }      /**      * 将wav或raw文件转换成amr      * @param inpath 源文件      * @param outpath 目标文件      */      private void convertAMR(String inpath,String outpath){          try {              AmrEncoder.init(0);              File inFile = new File(inpath);              List<short[]> armsList = new ArrayList<short[]>();              FileInputStream inputStream = new FileInputStream(inFile);              FileOutputStream outStream = new FileOutputStream(outpath);              //写入Amr头文件              outStream.write(header);                int byteSize = 320;              byte[] buff = new byte[byteSize];              int rc = 0;              while ((rc = inputStream.read(buff, 0, byteSize)) > 0) {                  short[] shortTemp = new short[160];                  //将byte[]转换成short[]                  ByteBuffer.wrap(buff).order(ByteOrder.LITTLE_ENDIAN).asShortBuffer().get(shortTemp);                    //将short[]转换成byte[]   //              ByteBuffer.wrap(buff).order(ByteOrder.LITTLE_ENDIAN).asShortBuffer().put(shortTemp);                    armsList.add(shortTemp);              }                             for (int i = 0; i < armsList.size(); i++) {                  int size = armsList.get(i).length;                  byte[] encodedData = new byte[size*2];                  int len = AmrEncoder.encode(AmrEncoder.Mode.MR122.ordinal(), armsList.get(i), encodedData);                  if (len>0) {                      byte[] tempBuf = new byte[len];                      System.arraycopy(encodedData, 0, tempBuf, 0, len);                      outStream.write(tempBuf, 0, len);                  }              }              AmrEncoder.reset();              AmrEncoder.exit();                            outStream.close();              inputStream.close();              System.out.println("convert success ... "+outpath);          } catch (Exception e) {              e.printStackTrace();          }      }

 

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