dacelpcp.c

来自「语音编码G.729 语音编码G.729」· C语言 代码 · 共 68 行

/*
   ITU-T G.729 Annex C+ - Reference C code for floating point
                         implementation of G.729 Annex C+
                         (integration of Annexes B, D and E)
                          Version 2.1 of October 1999
*/

/*
File : DACELPCP.C
*/
#include "typedef.h"
#include "ld8k.h"
#include "ld8cp.h"
#include "tabld8cp.h"

/*-----------------------------------------------------------*
*  Function  decod_ACELP()                                  *
*  ~~~~~~~~~~~~~~~~~~~~~~~                                  *
*   Algebraic codebook decoder.                             *
*----------------------------------------------------------*/
void decod_ACELP(
    int sign,              /* input : signs of 4 pulses     */
    int index,             /* input : positions of 4 pulses */
    FLOAT cod[]            /* output: innovative codevector */
)
{
    int pos[4];
    int i, j;
    
    /* decode the positions of 4 pulses */
    i = index & 7;
    pos[0] = i*5;
    
    index >>= 3;
    i = index & 7;
    pos[1] = i*5 + 1;
    
    index >>= 3;
    i = index & 7;
    pos[2] = i*5 + 2;
    
    index >>= 3;
    j = index & 1;
    index >>= 1;
    i = index & 7;
    pos[3] = i*5 + 3 + j;
    
    /* find the algebraic codeword */
    /*for (i = 0; i < L_SUBFR; i++) cod[i] = 0;*/
	set_zero(cod, L_SUBFR);
    
    /* decode the signs of 4 pulses */
    
    for (j=0; j<4; j++)
    {
        
        i = sign & 1;
        sign >>= 1;
        
        if (i != 0) {
            cod[pos[j]] = (F)1.0;
        }
        else {
            cod[pos[j]] = (F)-1.0;
        }
    }
}