PCM与G711 转换

朴灿烈づ我的快乐病毒、 2022-06-07 10:13 345阅读 0赞

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][Link 1]；

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};  
     
    //Encode
    int 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;  
    }   
      
    //Decode
    int 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)));  
    }

[Link 1]: http://read.pudn.com/downloads63/sourcecode/embed/219523/g711.cpp__.htm
[G711 File Converter]: http://g711.org/