lpcencode.c

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

    iLBC Speech Coder ANSI-C Source Code

    LPCencode.c 

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

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

#include <string.h>



#include "iLBC_define.h"
#include "LPCencode.h"
#include "helpfun.h"
#include "lsf.h"
#include "constants.h"

/*----------------------------------------------------------------*
 *  lpc analysis (subrutine to LPCencode)
 *---------------------------------------------------------------*/

static void SimpleAnalysis(
    float *lsf,         /* (o) lsf coefficients */
    float *data,    /* (i) new data vector */
    iLBC_Enc_Inst_t *iLBCenc_inst 
                        /* (i/o) the encoder state structure */
){
    int k, is;
    float temp[BLOCKL_MAX], lp[LPC_FILTERORDER + 1];
    float lp2[LPC_FILTERORDER + 1];
    float r[LPC_FILTERORDER + 1];

    is=LPC_LOOKBACK+BLOCKL_MAX-iLBCenc_inst->blockl;
    memcpy(iLBCenc_inst->lpc_buffer+is,data,
        iLBCenc_inst->blockl*sizeof(float));
    
    /* No lookahead, last window is asymmetric */
    
    for (k = 0; k < iLBCenc_inst->lpc_n; k++) {
        
        is = LPC_LOOKBACK;

        if (k < (iLBCenc_inst->lpc_n - 1)) {
            window(temp, lpc_winTbl, 
                iLBCenc_inst->lpc_buffer, BLOCKL_MAX);
        } else {
            window(temp, lpc_asymwinTbl, 
                iLBCenc_inst->lpc_buffer + is, BLOCKL_MAX);
        }
        
        autocorr(r, temp, BLOCKL_MAX, LPC_FILTERORDER);
        window(r, r, lpc_lagwinTbl, LPC_FILTERORDER + 1);
        
        levdurb(lp, temp, r, LPC_FILTERORDER);
        bwexpand(lp2, lp, LPC_CHIRP_SYNTDENUM, LPC_FILTERORDER+1);

        a2lsf(lsf + k*LPC_FILTERORDER, lp2);
    }
    is=LPC_LOOKBACK+BLOCKL_MAX-iLBCenc_inst->blockl;
    memmove(iLBCenc_inst->lpc_buffer, 
        iLBCenc_inst->lpc_buffer+LPC_LOOKBACK+BLOCKL_MAX-is, 
        is*sizeof(float));
}

/*----------------------------------------------------------------*


 *  lsf interpolator and conversion from lsf to a coefficients
 *  (subrutine to SimpleInterpolateLSF)
 *---------------------------------------------------------------*/

static void LSFinterpolate2a_enc(
    float *a,       /* (o) lpc coefficients */ 
    float *lsf1,/* (i) first set of lsf coefficients */
    float *lsf2,/* (i) second set of lsf coefficients */
    float coef,     /* (i) weighting coefficient to use between 
                           lsf1 and lsf2 */
    long length      /* (i) length of coefficient vectors */
){  
    float  lsftmp[LPC_FILTERORDER];
    
    interpolate(lsftmp, lsf1, lsf2, coef, length);
    lsf2a(a, lsftmp);
}

/*----------------------------------------------------------------*
 *  lsf interpolator (subrutine to LPCencode)
 *---------------------------------------------------------------*/

static void SimpleInterpolateLSF(
    float *syntdenum,   /* (o) the synthesis filter denominator 
                               resulting from the quantized 
                               interpolated lsf */
    float *weightdenum, /* (o) the weighting filter denominator 
                               resulting from the unquantized 
                               interpolated lsf */
    float *lsf,         /* (i) the unquantized lsf coefficients */
    float *lsfdeq,      /* (i) the dequantized lsf coefficients */
    float *lsfold,      /* (i) the unquantized lsf coefficients of 
                               the previous signal frame */
    float *lsfdeqold, /* (i) the dequantized lsf coefficients of 
                               the previous signal frame */
    int length,         /* (i) should equate LPC_FILTERORDER */
    iLBC_Enc_Inst_t *iLBCenc_inst 
                        /* (i/o) the encoder state structure */
){
    int    i, pos, lp_length;
    float  lp[LPC_FILTERORDER + 1], *lsf2, *lsfdeq2;
    
    lsf2 = lsf + length;
    lsfdeq2 = lsfdeq + length;
    lp_length = length + 1; 
 
    if (iLBCenc_inst->mode==30) {
        /* sub-frame 1: Interpolation between old and first 
           set of lsf coefficients */

        LSFinterpolate2a_enc(lp, lsfdeqold, lsfdeq, 
            lsf_weightTbl_30ms[0], length);
        memcpy(syntdenum,lp,lp_length*sizeof(float));
        LSFinterpolate2a_enc(lp, lsfold, lsf, 


            lsf_weightTbl_30ms[0], length);
        bwexpand(weightdenum, lp, LPC_CHIRP_WEIGHTDENUM, lp_length);

        /* sub-frame 2 to 6: Interpolation between first 
           and second set of lsf coefficients */
    
        pos = lp_length;
        for (i = 1; i < iLBCenc_inst->nsub; i++) {
            LSFinterpolate2a_enc(lp, lsfdeq, lsfdeq2, 
                lsf_weightTbl_30ms[i], length);
            memcpy(syntdenum + pos,lp,lp_length*sizeof(float));
        
            LSFinterpolate2a_enc(lp, lsf, lsf2, 
                lsf_weightTbl_30ms[i], length);
            bwexpand(weightdenum + pos, lp, 
                LPC_CHIRP_WEIGHTDENUM, lp_length);
            pos += lp_length;
        }
    }
    else {
        pos = 0;
        for (i = 0; i < iLBCenc_inst->nsub; i++) {
            LSFinterpolate2a_enc(lp, lsfdeqold, lsfdeq, 
                lsf_weightTbl_20ms[i], length);
            memcpy(syntdenum+pos,lp,lp_length*sizeof(float));
            LSFinterpolate2a_enc(lp, lsfold, lsf, 
                lsf_weightTbl_20ms[i], length);
            bwexpand(weightdenum+pos, lp, 
                LPC_CHIRP_WEIGHTDENUM, lp_length);
            pos += lp_length;
        }
    }
    
    /* update memory */

    if (iLBCenc_inst->mode==30) {
        memcpy(lsfold, lsf2, length*sizeof(float));
        memcpy(lsfdeqold, lsfdeq2, length*sizeof(float));
    }
    else {
        memcpy(lsfold, lsf, length*sizeof(float));
        memcpy(lsfdeqold, lsfdeq, length*sizeof(float));
    }
}

/*----------------------------------------------------------------*
 *  lsf quantizer (subrutine to LPCencode)
 *---------------------------------------------------------------*/

static void SimplelsfQ(
    float *lsfdeq,    /* (o) dequantized lsf coefficients
                           (dimension FILTERORDER) */
    int *index,     /* (o) quantization index */
    float *lsf,      /* (i) the lsf coefficient vector to be 


                           quantized (dimension FILTERORDER ) */
    int lpc_n     /* (i) number of lsf sets to quantize */
){    
    /* Quantize first LSF with memoryless split VQ */
    SplitVQ(lsfdeq, index, lsf, lsfCbTbl, LSF_NSPLIT, 
        dim_lsfCbTbl, size_lsfCbTbl);

    if (lpc_n==2) {
        /* Quantize second LSF with memoryless split VQ */
        SplitVQ(lsfdeq + LPC_FILTERORDER, index + LSF_NSPLIT, 
            lsf + LPC_FILTERORDER, lsfCbTbl, LSF_NSPLIT, 
            dim_lsfCbTbl, size_lsfCbTbl);
    }
}

/*----------------------------------------------------------------*
 *  lpc encoder
 *---------------------------------------------------------------*/

void LPCencode( 
    float *syntdenum, /* (i/o) synthesis filter coefficients 
                               before/after encoding */
    float *weightdenum, /* (i/o) weighting denumerator 
                               coefficients before/after 
                               encoding */
    int *lsf_index,     /* (o) lsf quantization index */
    float *data,    /* (i) lsf coefficients to quantize */
    iLBC_Enc_Inst_t *iLBCenc_inst 
                        /* (i/o) the encoder state structure */
){
    float lsf[LPC_FILTERORDER * LPC_N_MAX];
    float lsfdeq[LPC_FILTERORDER * LPC_N_MAX];
    int change=0;
    
    SimpleAnalysis(lsf, data, iLBCenc_inst);
    SimplelsfQ(lsfdeq, lsf_index, lsf, iLBCenc_inst->lpc_n);
    change=LSF_check(lsfdeq, LPC_FILTERORDER, iLBCenc_inst->lpc_n);
    SimpleInterpolateLSF(syntdenum, weightdenum, 
        lsf, lsfdeq, iLBCenc_inst->lsfold, 
        iLBCenc_inst->lsfdeqold, LPC_FILTERORDER, iLBCenc_inst);
}