icbconstruct.c

来自「Asterisk-1.4.4最新内核源代码」· C语言 代码 · 共 109 行

/******************************************************************

    iLBC Speech Coder ANSI-C Source Code

    iCBConstruct.c 

    Copyright (C) The Internet Society (2004). 
    All Rights Reserved.

******************************************************************/

#include <math.h>

#include "iLBC_define.h"
#include "iCBConstruct.h"
#include "gainquant.h"
#include "getCBvec.h"

/*----------------------------------------------------------------*
 *  Convert the codebook indexes to make the search easier
 *---------------------------------------------------------------*/



void index_conv_enc(
    int *index          /* (i/o) Codebook indexes */
){
    int k;

    for (k=1; k<CB_NSTAGES; k++) {
        
        if ((index[k]>=108)&&(index[k]<172)) {
            index[k]-=64;
        } else if (index[k]>=236) {
            index[k]-=128;
        } else {
            /* ERROR */
        }
    }
}

void index_conv_dec(
    int *index          /* (i/o) Codebook indexes */
){
    int k;

    for (k=1; k<CB_NSTAGES; k++) {
        
        if ((index[k]>=44)&&(index[k]<108)) {
            index[k]+=64;
        } else if ((index[k]>=108)&&(index[k]<128)) {
            index[k]+=128;
        } else {
            /* ERROR */
        }
    }
}

/*----------------------------------------------------------------*
 *  Construct decoded vector from codebook and gains.
 *---------------------------------------------------------------*/

void iCBConstruct(
    float *decvector,   /* (o) Decoded vector */
    int *index,         /* (i) Codebook indices */
    int *gain_index,/* (i) Gain quantization indices */
    float *mem,         /* (i) Buffer for codevector construction */
    int lMem,           /* (i) Length of buffer */
    int veclen,         /* (i) Length of vector */
    int nStages         /* (i) Number of codebook stages */
){
    int j,k;
    float gain[CB_NSTAGES];
    float cbvec[SUBL];

    /* gain de-quantization */

    gain[0] = gaindequant(gain_index[0], 1.0, 32);


    if (nStages > 1) {
        gain[1] = gaindequant(gain_index[1], 
            (float)fabs(gain[0]), 16);  
    }
    if (nStages > 2) {
        gain[2] = gaindequant(gain_index[2], 
            (float)fabs(gain[1]), 8);
    }

    /* codebook vector construction and construction of 
    total vector */

    getCBvec(cbvec, mem, index[0], lMem, veclen);
    for (j=0;j<veclen;j++){
        decvector[j] = gain[0]*cbvec[j];
    }
    if (nStages > 1) {
        for (k=1; k<nStages; k++) {
            getCBvec(cbvec, mem, index[k], lMem, veclen);
            for (j=0;j<veclen;j++) {
                decvector[j] += gain[k]*cbvec[j];
            }
        }
    }
}