AudioRecord录音出来的是原始文件PCM文件,有时候我们可能需要给转成G711格式的才能播放,最近我的项目就是需要把PCM格式转成G711格式,然后进行上传到服务器上,来实现声音的传递。我在网上查找资料也看了许久,还是觉得这个写的不错,所以发出来给大家参考一下。
public class G711Code {
private final static int SIGN_BIT = 0x80;
private final static int QUANT_MASK = 0xf;
private final static int SEG_SHIFT = 4;
private final static int SEG_MASK = 0x70;
static short[] seg_end = {0xFF, 0x1FF, 0x3FF, 0x7FF,0xFFF, 0x1FFF, 0x3FFF, 0x7FFF};
static short search(short val,short[] table,short size){
for (short i = 0 ; i < size; i++) {
if(val <= table[i]){
return i;
}
}
return size;
}
static byte linear2alaw(short pcm_val){
short mask;
short seg;
char aval;
if(pcm_val >= 0){
mask = 0xD5;
}else{
mask = 0x55;
pcm_val = (short) (-pcm_val - 1);
if(pcm_val < 0){
pcm_val = 32767;
}
}
/* Convert the scaled magnitude to segment number. */
seg = search(pcm_val, seg_end, (short) 8);
/* Combine the sign, segment, and quantization bits. */
if (seg >= 8) /* out of range, return maximum value. */
return (byte) (0x7F ^ mask);
else {
aval = (char) (seg << SEG_SHIFT);
if (seg < 2)
aval |= (pcm_val >> 4) & QUANT_MASK;
else
aval |= (pcm_val >> (seg + 3)) & QUANT_MASK;
return (byte) (aval ^ mask);
}
}
static short alaw2linear(byte a_val){
short t;
short seg;
a_val ^= 0x55;
t = (short) ((a_val & QUANT_MASK) << 4);
seg = (short) ((a_val & SEG_MASK) >> SEG_SHIFT);
switch (seg) {
case 0:
t += 8;
break;
case 1:
t += 0x108;
break;
default:
t += 0x108;
t <<= seg - 1;
}
return (a_val & SIGN_BIT) != 0 ? t : (short) -t;
}
/**
* pcm 转 G711 a率
* @param pcm
* @param code
* @param size
*/
public static void G711aEncoder(short[] pcm,byte[] code,int size){
for(int i=0;i<size;i++){
code[i]=linear2alaw(pcm[i]);
Log.e("-------------","数据编码");
}
}
/**
* G.711 转 PCM
* @param pcm
* @param code
* @param size
*/
public static void G711aDecoder(short[] pcm,byte[] code,int size)
{
for(int i=0;i<size;i++){
pcm[i]=alaw2linear(code[i]);
}
}
}
使用文件说明
//inG711Buffer为读取音频short类型,outG711Buffer为需要转换格式写入的byte类型,nReadBytes读取音频的长度
//调用G711编码
G711Code.G711aEncoder(inG711Buffer,outG711Buffer,nReadBytes);