asterisk/codecs/ilbc/LPCencode.c

 
/****************************************************************** 
 
    iLBC Speech Coder ANSI-C Source Code 
 
    LPCencode.c  
 
    Copyright (c) 2001, 
    Global IP Sound AB. 
    All rights reserved. 
 
******************************************************************/ 
 
#include <string.h> 
 
#include "iLBC_define.h" 
#include "helpfun.h" 
#include "lsf.h" 
#include "constants.h" 
#include "LPCencode.h"
 
/*----------------------------------------------------------------* 
 *  lpc analysis (subrutine to LPCencode)                            
 *---------------------------------------------------------------*/ 
 
static void SimpleAnalysis( 
    float *lsf,         /* (o) lsf coefficients */ 
    float *data,    /* (i) new data vector */ 
    float *lpc_buffer   /* (i) buffer containing old data */  
){ 
    int k, is; 
    float temp[BLOCKL], lp[LPC_FILTERORDER + 1]; 
    float lp2[LPC_FILTERORDER + 1]; 
    float r[LPC_FILTERORDER + 1]; 
 
    memcpy(lpc_buffer+LPC_LOOKBACK,data,BLOCKL*sizeof(float)); 
     
    /* No lookahead, last window is asymmetric */ 
     
    for (k = 0; k < LPC_N; k++) { 
         
        is = LPC_LOOKBACK; 
 
        if (k < (LPC_N - 1)) { 
            lbc_window(temp, lpc_winTbl, lpc_buffer, BLOCKL); 
        } else { 
            lbc_window(temp, lpc_asymwinTbl, lpc_buffer + is, BLOCKL); 
        } 
         
        autocorr(r, temp, BLOCKL, LPC_FILTERORDER); 
        lbc_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); 
    } 
    memcpy(lpc_buffer, lpc_buffer+BLOCKL,  
        LPC_LOOKBACK*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 FILTERORDER */ 
){ 
    int    i, pos, lp_length; 
    float  lp[LPC_FILTERORDER + 1], *lsf2, *lsfdeq2; 
     
    lsf2 = lsf + length; 
    lsfdeq2 = lsfdeq + length; 
    lp_length = length + 1; 
     
    /* subframe 1: Interpolation between old and first set of  
    lsf coefficients */ 
 
    LSFinterpolate2a_enc(lp, lsfdeqold, lsfdeq,  
        lsf_weightTbl[0], length); 
    memcpy(syntdenum,lp,lp_length*sizeof(float)); 
    LSFinterpolate2a_enc(lp, lsfold, lsf, lsf_weightTbl[0], length); 
    bwexpand(weightdenum, lp, LPC_CHIRP_WEIGHTDENUM, lp_length); 
 
    /* subframe 2 to 6: Interpolation between first and second  
    set of lsf coefficients */ 
     
    pos = lp_length; 
    for (i = 1; i < NSUB; i++) { 
        LSFinterpolate2a_enc(lp, lsfdeq, lsfdeq2,  
            lsf_weightTbl[i], length); 
        memcpy(syntdenum + pos,lp,lp_length*sizeof(float)); 
         
        LSFinterpolate2a_enc(lp, lsf, lsf2,  
            lsf_weightTbl[i], length); 
        bwexpand(weightdenum + pos, lp,  
            LPC_CHIRP_WEIGHTDENUM, lp_length); 
        pos += lp_length; 
    } 
     
    /* update memory */ 
 
    memcpy(lsfold, lsf2, length*sizeof(float)); 
    memcpy(lsfdeqold, lsfdeq2, 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 ) */ 
){     
    /* Quantize first LSF with memoryless split VQ */ 
    SplitVQ(lsfdeq, index, lsf, lsfCbTbl, LSF_NSPLIT,  
        dim_lsfCbTbl, size_lsfCbTbl); 
 
    /* 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]; 
    float lsfdeq[LPC_FILTERORDER * LPC_N]; 
    int change=0; 
     
    SimpleAnalysis(lsf, data, (*iLBCenc_inst).lpc_buffer);  
    SimplelsfQ(lsfdeq, lsf_index, lsf); 
    change=LSF_check(lsfdeq, LPC_FILTERORDER, LPC_N); 
    SimpleInterpolateLSF(syntdenum, weightdenum,  
        lsf, lsfdeq, (*iLBCenc_inst).lsfold,  
        (*iLBCenc_inst).lsfdeqold, LPC_FILTERORDER); 
}