g711dec.c

来自「linux下的sip voip程序」· C语言 代码 · 共 73 行

#include <stdio.h>

#define BIAS    132    /* バイアスの猛 */

void disp_c(unsigned char value);
void disp_s(short value);
short g711decode(unsigned char ulaw_sample);

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

    unsigned char mu[8]={
            /* デコ〖ド涟 | デコ〖ド稿 */
         0, /* 0 000 0000 | 1000001010000100 */
        17, /* 0 001 0001 | 1100001110000100 */
        34, /* 0 010 0010 | 1110001100000100 */
        51, /* 0 011 0011 | 1111001001000100 */
        68, /* 0 100 0100 | 1111100110100100 */
        89, /* 0 101 1001 | 1111110110110100 */
       108, /* 0 110 1100 | 1111111101001100 */
       123  /* 0 111 1011 | 1111111111100000 */
    };

    /* テスト */
    for (i = 0; i < 8; i++ ){
        disp_c(mu[i]);
        g711decode( mu[i] ); 
        printf("\n");
    }
    return 0;
}

/* デコ〖ド簇眶 */
short g711decode(unsigned char ulaw_sample){
    short audio_sample;
    int t;

    ulaw_sample = ~ulaw_sample;
    t = ((ulaw_sample & 0x0f) << 3) + BIAS;
    t <<= (ulaw_sample & 0x70) >> 4;
    audio_sample = ((ulaw_sample & 0x80) ? (BIAS - t) : (t - BIAS));
    return audio_sample;
}

/* 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");
        }
    }
}