www.pudn.com > g729_audio_encode.rar > lpcfunc.c

/* 
   ITU-T G.729 Speech Coder ANSI-C Source Code 
   Version 3.3    Last modified: December 26, 1995 
 
   Copyright (c) 1996, 
   AT&T, France Telecom, NTT, Universite de Sherbrooke, Lucent Technologies 
   All rights reserved. 
*/ 
 
/*-------------------------------------------------------------* 
 *  Procedure Lsp_Az:                                          * 
 *            ~~~~~~                                           * 
 *   Compute the LPC coefficients from lsp (order=10)          * 
 *-------------------------------------------------------------*/ 
 
#include "typedef.h" 
#include "basic_op.h" 
#include "oper_32b.h" 
 
#include "ld8k.h" 
#include "tab_ld8k.h" 
 
/* local function */ 
 
static void Get_lsp_pol(Word16 *lsp, Word32 *f); 
 
void Lsp_Az( 
  Word16 lsp[],    /* (i) Q15 : line spectral frequencies            */ 
  Word16 a[]       /* (o) Q12 : predictor coefficients (order = 10)  */ 
) 
{ 
  Word16 i, j; 
  Word32 f1[6], f2[6]; 
  Word32 t0; 
 
  Get_lsp_pol(&lsp[0],f1); 
  Get_lsp_pol(&lsp[1],f2); 
 
  for (i = 5; i > 0; i--) 
  { 
    f1[i] = L_add(f1[i], f1[i-1]);        /* f1[i] += f1[i-1]; */ 
    f2[i] = L_sub(f2[i], f2[i-1]);        /* f2[i] -= f2[i-1]; */ 
  } 
 
  a[0] = 4096; 
  for (i = 1, j = 10; i <= 5; i++, j--) 
  { 
    t0   = L_add(f1[i], f2[i]);                 /* f1[i] + f2[i]             */ 
    a[i] = extract_l( L_shr_r(t0, 13) );        /* from Q24 to Q12 and * 0.5 */ 
 
    t0   = L_sub(f1[i], f2[i]);                 /* f1[i] - f2[i]             */ 
    a[j] = extract_l( L_shr_r(t0, 13) );        /* from Q24 to Q12 and * 0.5 */ 
 
  } 
 
  return; 
} 
 
/*-----------------------------------------------------------* 
 * procedure Get_lsp_pol:                                    * 
 *           ~~~~~~~~~~~                                     * 
 *   Find the polynomial F1(z) or F2(z) from the LSPs        * 
 *-----------------------------------------------------------* 
 *                                                           * 
 * Parameters:                                               * 
 *  lsp[]   : line spectral freq. (cosine domain)    in Q15  * 
 *  f[]     : the coefficients of F1 or F2           in Q24  * 
 *-----------------------------------------------------------*/ 
 
static void Get_lsp_pol(Word16 *lsp, Word32 *f) 
{ 
  Word16 i,j, hi, lo; 
  Word32 t0; 
 
   /* All computation in Q24 */ 
 
   *f = L_mult(4096, 2048);             /* f[0] = 1.0;             in Q24  */ 
   f++; 
   *f = L_msu((Word32)0, *lsp, 512);    /* f[1] =  -2.0 * lsp[0];  in Q24  */ 
 
   f++; 
   lsp += 2;                            /* Advance lsp pointer             */ 
 
   for(i=2; i<=5; i++) 
   { 
     *f = f[-2]; 
 
     for(j=1; j= 0; i--) 
  { 
    /* find value in table that is just greater than lsp[i] */ 
    while( sub(table[ind], lsp[i]) < 0 ) 
    { 
      ind = sub(ind,1); 
    } 
 
    /* acos(lsp[i])= ind*256 + ( ( lsp[i]-table[ind] ) * slope[ind] )/4096 */ 
 
    L_tmp  = L_mult( sub(lsp[i], table[ind]) , slope[ind] ); 
    tmp = round(L_shl(L_tmp, 3));     /*(lsp[i]-table[ind])*slope[ind])>>12*/ 
    lsf[i] = add(tmp, shl(ind, 8)); 
  } 
  return; 
} 
 
/*___________________________________________________________________________ 
 |                                                                           | 
 |   Functions : Lsp_lsf and Lsf_lsp                                         | 
 |                                                                           | 
 |      Lsp_lsf   Transformation lsp to lsf                                  | 
 |      Lsf_lsp   Transformation lsf to lsp                                  | 
 |---------------------------------------------------------------------------| 
 |  Algorithm:                                                               | 
 |                                                                           | 
 |   The transformation from lsp[i] to lsf[i] and lsf[i] to lsp[i] are       | 
 |   approximated by a look-up table and interpolation.                      | 
 |___________________________________________________________________________| 
*/ 
 
void Lsf_lsp2( 
  Word16 lsf[],    /* (i) Q13 : lsf[m] (range: 0.0<=val0 ){ 
      ind = 63;                 /* 0 <= ind <= 63 */ 
    } 
 
    /* lsp[i] = table2[ind]+ (slope_cos[ind]*offset >> 12) */ 
 
    L_tmp   = L_mult(slope_cos[ind], offset);   /* L_tmp in Q28 */ 
    lsp[i] = add(table2[ind], extract_l(L_shr(L_tmp, 13))); 
 
  } 
  return; 
} 
 
 
 
void Lsp_lsf2( 
  Word16 lsp[],    /* (i) Q15 : lsp[m] (range: -1<=val<1)   */ 
  Word16 lsf[],    /* (o) Q13 : lsf[m] (range: 0.0<=val= 0; i--) 
  { 
    /* find value in table2 that is just greater than lsp[i] */ 
    while( sub(table2[ind], lsp[i]) < 0 ) 
    { 
      ind = sub(ind,1); 
      if ( ind <= 0 ) 
        break; 
    } 
 
    offset = sub(lsp[i], table2[ind]); 
 
    /* acos(lsp[i])= ind*512 + (slope_acos[ind]*offset >> 11) */ 
 
    L_tmp  = L_mult( slope_acos[ind], offset );   /* L_tmp in Q28 */ 
    freq = add(shl(ind, 9), extract_l(L_shr(L_tmp, 12))); 
    lsf[i] = mult(freq, 25736);           /* 25736: 2.0*PI in Q12 */ 
 
  } 
  return; 
} 
 
/*-------------------------------------------------------------* 
 *  procedure Weight_Az                                        * 
 *            ~~~~~~~~~                                        * 
 * Weighting of LPC coefficients.                              * 
 *   ap[i]  =  a[i] * (gamma ** i)                             * 
 *                                                             * 
 *-------------------------------------------------------------*/ 
 
 
void Weight_Az( 
  Word16 a[],      /* (i) Q12 : a[m+1]  LPC coefficients             */ 
  Word16 gamma,    /* (i) Q15 : Spectral expansion factor.           */ 
  Word16 m,        /* (i)     : LPC order.                           */ 
  Word16 ap[]      /* (o) Q12 : Spectral expanded LPC coefficients   */ 
) 
{ 
  Word16 i, fac; 
 
  ap[0] = a[0]; 
  fac   = gamma; 
  for(i=1; i