g711enc.c

linux下的sip voip程序

#include <stdio.h>

#define BIAS    132    /* バイアスの猛 */
#define CLIP	32635  /* 惧嘎、布嘎の冷滦猛 ( 0x7fff - BIAS ) */

void disp_c(unsigned char value);
void disp_s(short value);
unsigned char g711encode(short audio_sample);


int main(int argv, char **argc){
    int i;
    unsigned char mu_val;

    /* テスト脱サンプル猛 */
    short a_smp[8] ={
                /* 恃垂涟     掐蜗+バイアス   |  XOR涟   | エンコ〖ド猛 */
        0,      /* 0 00000001 0000 100        | 00000000 | 11111111 */
        140,    /* 0 0000001  0001 0000       | 00010001 | 11101110 */
        444,    /* 0 000001   0010 00000      | 00100010 | 11011101 */
        1084,   /* 0 00001    0011 000000     | 00110011 | 11001100 */
        -2460,  /* 0 0001     0100 0100000    | 01000100 | 00111011 */
        -5372,  /* 0 001      0101 10000000   | 01010101 | 00101010 */
        -11420, /* 0 01       0110 100100000  | 01100110 | 00011001 */
        -24060  /* 0 1        0111 1010000000 | 01110111 | 00001000 */
    };

    for (i = 0; i < 8; i++ ){
        mu_val = g711encode( a_smp[i] );
        disp_c( mu_val );
        printf("\n");
    }
    return 0;
}

/* エンコ〖ド簇眶 */
unsigned char g711encode(short audio_sample){
    int i;
    int mask;
    int range;
    unsigned char mulaw_val;

    if( audio_sample > 0 && audio_sample > CLIP ) audio_sample = CLIP;
    if( audio_sample < 0 && audio_sample < -CLIP ) audio_sample = -CLIP;
    if( audio_sample < 0 ){
       mask = 0x7f;
       audio_sample = -audio_sample;
    }else{
       mask = 0xff;
    }
       audio_sample += BIAS;
    for( i = 7, range = 0x4000; range >= 0x80; range >>= 1, i-- ){
       if( range & audio_sample ) break;
    }
    mulaw_val = (i << 4) +  (( audio_sample >> ( i + 3 )) & 0x0f);
    disp_c(mulaw_val);
    return mulaw_val ^ mask;
}

/* shortの2渴眶山绩簇眶 */
void disp_s(short value){
    int i;

    printf("\t");
    for( i = 0x8000; i > 0; i >>= 1 ){
       if(value & i ){
           printf("1");
       }else{
           printf("0");
       }
    }
}

/* unsigned char の2渴眶山绩簇眶 */
void disp_c(unsigned char value){
    int i;

    printf("\t");
    for( i = 0x80; i > 0; i >>= 1 ){
        if(value & i ){
            printf("1");
        }else{
            printf("0");
        }
    }
}