www.pudn.com > g729.rar > post_pro.c

/* 
   ITU-T G.729A Speech Coder    ANSI-C Source Code 
   Version 1.1    Last modified: September 1996 
 
   Copyright (c) 1996, 
   AT&T, France Telecom, NTT, Universite de Sherbrooke 
   All rights reserved. 
*/ 
 
/*------------------------------------------------------------------------* 
 * Function Post_Process()                                                * 
 *                                                                        * 
 * Post-processing of output speech.                                      * 
 *   - 2nd order high pass filter with cut off frequency at 100 Hz.       * 
 *   - Multiplication by two of output speech with saturation.            * 
 *-----------------------------------------------------------------------*/ 
 
#include "typedef.h" 
#include "basic_op.h" 
#include "oper_32b.h" 
 
#include "ld8a.h" 
#include "tab_ld8a.h" 
 
/*------------------------------------------------------------------------* 
 * 2nd order high pass filter with cut off frequency at 100 Hz.           * 
 * Designed with SPPACK efi command -40 dB att, 0.25 ri.                  * 
 *                                                                        * 
 * Algorithm:                                                             * 
 *                                                                        * 
 *  y[i] = b[0]*x[i]   + b[1]*x[i-1]   + b[2]*x[i-2]                      * 
 *                     + a[1]*y[i-1]   + a[2]*y[i-2];                     * 
 *                                                                        * 
 *     b[3] = {0.93980581E+00, -0.18795834E+01, 0.93980581E+00};          * 
 *     a[3] = {0.10000000E+01, 0.19330735E+01, -0.93589199E+00};          * 
 *-----------------------------------------------------------------------*/ 
 
/* Static values to be preserved between calls */ 
/* y[] values is keep in double precision      */ 
 
static Word16 y2_hi, y2_lo, y1_hi, y1_lo, x0, x1; 
 
 
/* Initialization of static values */ 
 
void Init_Post_Process(void) 
{ 
  y2_hi = 0; 
  y2_lo = 0; 
  y1_hi = 0; 
  y1_lo = 0; 
  x0   = 0; 
  x1   = 0; 
} 
 
 
void Post_Process( 
  Word16 signal[],    /* input/output signal */ 
  Word16 lg)          /* length of signal    */ 
{ 
  Word16 i, x2; 
  Word32 L_tmp; 
 
  for(i=0; i Q31 (Q13 --> Q15) */ 
 
     /* Multiplication by two of output speech with saturation. */ 
     signal[i] = round(L_shl(L_tmp, 1)); 
 
     y2_hi = y1_hi; 
     y2_lo = y1_lo; 
     L_Extract(L_tmp, &y1_hi, &y1_lo); 
  } 
  return; 
}