PCM与G711 转换

加密解码代码如下：

提供以下接口，提供一段数据和一个目标数据地址及数据长度及类型，成功返回加密解密后的数据长度；

音频的转换方法参考：链接；

一个在线转化网址：G711 File Converter

#include <stdio.h>   #define bool char#define false 0#define true  1#define G711ALAW 0#define G711ULAW 1#define SIGN_BIT    (0x80)      /* Sign bit for a A-law byte. */  #define QUANT_MASK  (0xf)       /* Quantization field mask. */  #define NSEGS       (8)     /* Number of A-law segments. */  #define SEG_SHIFT   (4)     /* Left shift for segment number. */  #define SEG_MASK    (0x70)      /* Segment field mask. */    static short seg_end[8] = {0xFF, 0x1FF, 0x3FF, 0x7FF,                  0xFFF, 0x1FFF, 0x3FFF, 0x7FFF};    /* copy from CCITT G.711 specifications */  unsigned char _u2a[128] = {         /* u- to A-law conversions */      1,  1,  2,  2,  3,  3,  4,  4,      5,  5,  6,  6,  7,  7,  8,  8,      9,  10, 11, 12, 13, 14, 15, 16,      17, 18, 19, 20, 21, 22, 23, 24,      25, 27, 29, 31, 33, 34, 35, 36,      37, 38, 39, 40, 41, 42, 43, 44,      46, 48, 49, 50, 51, 52, 53, 54,      55, 56, 57, 58, 59, 60, 61, 62,      64, 65, 66, 67, 68, 69, 70, 71,      72, 73, 74, 75, 76, 77, 78, 79,      81, 82, 83, 84, 85, 86, 87, 88,      89, 90, 91, 92, 93, 94, 95, 96,      97, 98, 99, 100,    101,    102,    103,    104,      105,    106,    107,    108,    109,    110,    111,    112,      113,    114,    115,    116,    117,    118,    119,    120,      121,    122,    123,    124,    125,    126,    127,    128};    unsigned char _a2u[128] = {         /* A- to u-law conversions */      1,  3,  5,  7,  9,  11, 13, 15,      16, 17, 18, 19, 20, 21, 22, 23,      24, 25, 26, 27, 28, 29, 30, 31,      32, 32, 33, 33, 34, 34, 35, 35,      36, 37, 38, 39, 40, 41, 42, 43,      44, 45, 46, 47, 48, 48, 49, 49,      50, 51, 52, 53, 54, 55, 56, 57,      58, 59, 60, 61, 62, 63, 64, 64,      65, 66, 67, 68, 69, 70, 71, 72,      73, 74, 75, 76, 77, 78, 79, 79,      80, 81, 82, 83, 84, 85, 86, 87,      88, 89, 90, 91, 92, 93, 94, 95,      96, 97, 98, 99, 100,    101,    102,    103,      104,    105,    106,    107,    108,    109,    110,    111,      112,    113,    114,    115,    116,    117,    118,    119,      120,    121,    122,    123,    124,    125,    126,    127};   //Encodeint G711EnCode(char* pCodecBits, char* pBuffer, int BufferSize, int type)  {      if(pCodecBits == NULL || pBuffer == NULL || BufferSize <= 0)        return -1;    unsigned char* codecbits = (unsigned char*)pCodecBits;    short* buffer = (short*)pBuffer;    if(type == 0){        for(int i=0; i<nBufferSize/2; i++)  {              codecbits[i] = linear2alaw(buffer[i]);          }      } else {        for(int i=0; i<nBufferSize/2; i++)  {              codecbits[i] = linear2ulaw(buffer[i]);          }     }        return BufferSize/2;  }     //Decodeint G711Decode(char* pRawData, char* pBuffer, int BufferSize, int type)  {      if(pRawData == NULL || pBuffer == NULL || BufferSize <= 0)        return -1;    short *out_data = (short*)pRawData;      unsigned char* buffer = (unsigned char*)pBuffer;    if(type == 0) {        for(int i=0; i<nBufferSize; i++){              out_data[i] = alaw2linear(buffer[i]);          }      } else {        for(int i=0; i<nBufferSize; i++){              out_data[i] = ulaw2linear(buffer[i]);          }    }           return BufferSize*2;  }bool G711TypeChange(unsigned char* alawdata, unsigned char* ulawdata, int datasize, int type){    if(alawdata == NULL || ulawdata == NULL || datasize <= 0)        return false;    if(type == 0) {        for(int i = 0; i < datasize; i++) {            alawdata[i] = ulaw2alaw(ulawdata[i]);        }    } else {        for(int i = 0; i < datasize; i++) {            ulawdata[i] = alaw2ulaw(alawdata[i]);        }    }    return true;}     static short search(short val, short *table, short size)  {      short i;      for (i = 0; i < size; i++) {          if (val <= *table++)              return (i);      }      return (size);  }    /*  * linear2alaw() - Convert a 16-bit linear PCM value to 8-bit A-law  *  * linear2alaw() accepts an 16-bit integer and encodes it as A-law data.  *  *      Linear Input Code   Compressed Code  *  ------------------------    ---------------  *  0000000wxyza            000wxyz  *  0000001wxyza            001wxyz  *  000001wxyzab            010wxyz  *  00001wxyzabc            011wxyz  *  0001wxyzabcd            100wxyz  *  001wxyzabcde            101wxyz  *  01wxyzabcdef            110wxyz  *  1wxyzabcdefg            111wxyz  *  * For further information see John C. Bellamy's Digital Telephony, 1982,  * John Wiley & Sons, pps 98-111 and 472-476.  */  unsigned char linear2alaw(short pcm_val)    /* 2's complement (16-bit range) */  {      short     mask;      short     seg;      unsigned char   aval;        if (pcm_val >= 0) {          mask = 0xD5;        /* sign (7th) bit = 1 */      } else {          mask = 0x55;        /* sign bit = 0 */          pcm_val = -pcm_val - 8;      }        /* Convert the scaled magnitude to segment number. */      seg = search(pcm_val, seg_end, 8);        /* Combine the sign, segment, and quantization bits. */        if (seg >= 8)        /* out of range, return maximum value. */          return (0x7F ^ mask);      else {          aval = seg << SEG_SHIFT;          if (seg < 2)              aval |= (pcm_val >> 4) & QUANT_MASK;          else              aval |= (pcm_val >> (seg + 3)) & QUANT_MASK;          return (aval ^ mask);      }  }    /*  * alaw2linear() - Convert an A-law value to 16-bit linear PCM  *  */  short alaw2linear(unsigned char  a_val)  {      short     t;      short     seg;        a_val ^= 0x55;        t = (a_val & QUANT_MASK) << 4;      seg = ((unsigned)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) ? t : -t);  }    #define BIAS        (0x84)      /* Bias for linear code. */    /*  * linear2ulaw() - Convert a linear PCM value to u-law  *  * In order to simplify the encoding process, the original linear magnitude  * is biased by adding 33 which shifts the encoding range from (0 - 8158) to  * (33 - 8191). The result can be seen in the following encoding table:  *  *  Biased Linear Input Code    Compressed Code  *  ------------------------    ---------------  *  00000001wxyza           000wxyz  *  0000001wxyzab           001wxyz  *  000001wxyzabc           010wxyz  *  00001wxyzabcd           011wxyz  *  0001wxyzabcde           100wxyz  *  001wxyzabcdef           101wxyz  *  01wxyzabcdefg           110wxyz  *  1wxyzabcdefgh           111wxyz  *  * Each biased linear code has a leading 1 which identifies the segment  * number. The value of the segment number is equal to 7 minus the number  * of leading 0's. The quantization interval is directly available as the  * four bits wxyz.  * The trailing bits (a - h) are ignored.  *  * Ordinarily the complement of the resulting code word is used for  * transmission, and so the code word is complemented before it is returned.  *  * For further information see John C. Bellamy's Digital Telephony, 1982,  * John Wiley & Sons, pps 98-111 and 472-476.  */  unsigned char linear2ulaw(int pcm_val)    /* 2's complement (16-bit range) */  {      short     mask;      short     seg;      unsigned char   uval;        /* Get the sign and the magnitude of the value. */      if (pcm_val < 0) {          pcm_val = BIAS - pcm_val;          mask = 0x7F;      } else {          pcm_val += BIAS;          mask = 0xFF;      }        /* Convert the scaled magnitude to segment number. */      seg = search(pcm_val, seg_end, 8);        /*      * Combine the sign, segment, quantization bits;      * and complement the code word.      */      if (seg >= 8)        /* out of range, return maximum value. */          return (0x7F ^ mask);      else {          uval = (seg << 4) | ((pcm_val >> (seg + 3)) & 0xF);          return (uval ^ mask);      }    }    /*  * ulaw2linear() - Convert a u-law value to 16-bit linear PCM  *  * First, a biased linear code is derived from the code word. An unbiased  * output can then be obtained by subtracting 33 from the biased code.  *  * Note that this function expects to be passed the complement of the  * original code word. This is in keeping with ISDN conventions.  */  int  ulaw2linear(unsigned char u_val)  {      short     t;        /* Complement to obtain normal u-law value. */      u_val = ~u_val;        /*      * Extract and bias the quantization bits. Then      * shift up by the segment number and subtract out the bias.      */      t = ((u_val & QUANT_MASK) << 3) + BIAS;      t <<= ((unsigned)u_val & SEG_MASK) >> SEG_SHIFT;        return ((u_val & SIGN_BIT) ? (BIAS - t) : (t - BIAS));  }/* A-law to u-law conversion */  unsigned char alaw2ulaw(unsigned char aval)  {      aval &= 0xff;      return ((aval & 0x80) ? (0xFF ^ _a2u[aval ^ 0xD5]) :          (0x7F ^ _a2u[aval ^ 0x55]));  }    /* u-law to A-law conversion */  unsigned char ulaw2alaw(unsigned char uval)  {      uval &= 0xff;      return ((uval & 0x80) ? (0xD5 ^ (_u2a[0xFF ^ uval] - 1)) :          (0x55 ^ (_u2a[0x7F ^ uval] - 1)));  }