PCM转G711的JAVA代码

  private final static short SHORT_MAX = 0x7FFF;
  public static byte[] convertPcmToG711(byte[] pcmBuffer, int length, byte[] g711Buffer)
  {
    length = length/2;
    if (pcmBuffer == null)
    {
      pcmBuffer = new byte[length];
    }
    for (int i=0; i<length; i++)
    {
      short pcm = ToolKit.getShort(pcmBuffer, i*2);
      int sign = (pcm & 0x8000) >> 8;
        if (sign != 0)
        {
            pcm = (short)-pcm;
        }
        if (pcm > SHORT_MAX)
        {
          pcm = SHORT_MAX;
        }
        int exponent = 7;
        int expMask;
        //有的使用数组来代替这个步骤。
        for (expMask = 0x4000; (pcm & expMask) == 0 && exponent>0; exponent--, expMask >>= 1)
        {
          //
        }
        int mantissa = (pcm >> ((exponent == 0) ? 4 : (exponent + 3))) & 0x0F;
        byte alaw = (byte)(sign | exponent << 4 | mantissa);
        g711Buffer[i] = (byte)(alaw^0xD5);
    }
    return g711Buffer;
  }