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/* ITU-T G.729 Software Package Release 2 (November 2006) */ 
/* 
   ITU-T G.729 Annex C - Reference C code for floating point 
                         implementation of G.729 Annex A 
                         Version 1.01 of 15.September.98 
*/ 
 
/* 
---------------------------------------------------------------------- 
                    COPYRIGHT NOTICE 
---------------------------------------------------------------------- 
   ITU-T G.729 Annex C ANSI C source code 
   Copyright (C) 1998, AT&T, France Telecom, NTT, University of 
   Sherbrooke.  All rights reserved. 
 
---------------------------------------------------------------------- 
*/ 
 
/* 
 File : LPCFUNCA.C 
 Used for the floating point version of G.729A only 
 (not for G.729 main body) 
*/ 
 
/*-------------------------------------------------------------* 
 *  Procedure lsp_az:                                          * 
 *            ~~~~~~                                           * 
 *   Compute the LPC coefficients from lsp (order=10)          * 
 *-------------------------------------------------------------*/ 
 
#include "typedef.h" 
#include "ld8a.h" 
#include "tab_ld8a.h" 
 
/* local function */ 
 
 
static void  get_lsp_pol(FLOAT lsf[],FLOAT f[]); 
static void  lsp_az(FLOAT *lsp, FLOAT *a); 
 
/*----------------------------------------------------------------------------- 
 * lsp_az - convert LSPs to predictor coefficients a[] 
 *----------------------------------------------------------------------------- 
 */ 
static void lsp_az( 
 FLOAT *lsp,            /* input : lsp[0:M-1] */ 
 FLOAT *a               /* output: predictor coeffs a[0:M], a[0] = 1. */ 
) 
{ 
 
  FLOAT f1[M], f2[M]; 
  int i,j; 
 
 
  get_lsp_pol(&lsp[0],f1); 
  get_lsp_pol(&lsp[1],f2); 
 
  for (i = NC; i > 0; i--) 
  { 
    f1[i] += f1[i-1]; 
    f2[i] -= f2[i-1]; 
  } 
  a[0] = (F)1.0; 
  for (i = 1, j = M; i <= NC; i++, j--) 
  { 
    a[i] = (F)0.5*(f1[i] + f2[i]); 
    a[j] = (F)0.5*(f1[i] - f2[i]); 
  } 
 
  return; 
} 
 
 
/*---------------------------------------------------------------------------- 
 * get_lsp_pol - find the polynomial F1(z) or F2(z) from the LSFs 
 *---------------------------------------------------------------------------- 
 */ 
static void get_lsp_pol( 
   FLOAT lsp[],           /* input : line spectral freq. (cosine domain)  */ 
   FLOAT f[]              /* output: the coefficients of F1 or F2 */ 
) 
{ 
  FLOAT b; 
  int   i,j; 
 
  f[0] = (F)1.0; 
  b = (F)-2.0*lsp[0]; 
  f[1] = b; 
  for (i = 2; i <= NC; i++) 
  { 
    b = (F)-2.0*lsp[2*i-2]; 
    f[i] = b*f[i-1] + (F)2.0*f[i-2]; 
    for (j = i-1; j > 1; j--) 
      f[j] += b*f[j-1] + f[j-2]; 
    f[1] += b; 
  } 
  return; 
} 
/*--------------------------------------------------------------------------- 
 * weight_az:  Weighting of LPC coefficients  ap[i]  =  a[i] * (gamma ** i) 
 *--------------------------------------------------------------------------- 
 */ 
void weight_az( 
 FLOAT *a,              /* input : lpc coefficients a[0:m]       */ 
 FLOAT gamma,           /* input : weighting factor              */ 
 int m,                 /* input : filter order                  */ 
 FLOAT *ap              /* output: weighted coefficients ap[0:m] */ 
) 
{ 
  FLOAT fac; 
  int i; 
 
  ap[0]=a[0]; 
  fac=gamma; 
  for (i = 1; i < m; i++) 
  { 
    ap[i] = fac*a[i]; 
    fac *= gamma; 
  } 
  ap[m] = fac*a[m]; 
 
  return; 
} 
 
/*----------------------------------------------------------------------------- 
 * int_qlpc -  interpolated M LSP parameters and convert to M+1 LPC coeffs 
 *----------------------------------------------------------------------------- 
 */ 
void int_qlpc( 
 FLOAT lsp_old[],       /* input : LSPs for past frame (0:M-1) */ 
 FLOAT lsp_new[],       /* input : LSPs for present frame (0:M-1) */ 
 FLOAT az[]             /* output: filter parameters in 2 subfr (dim 2(m+1)) */ 
) 
{ 
  int i; 
  FLOAT lsp[M]; 
 
  for (i = 0; i < M; i++) 
    lsp[i] = lsp_old[i]*(F)0.5 + lsp_new[i]*(F)0.5; 
 
  lsp_az(lsp, az); 
  lsp_az(lsp_new, &az[M+1]); 
 
  return; 
}