www.pudn.com > g729_audio_encode.rar > filter.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. 
*/ 
 
/*-------------------------------------------------------------------* 
 * Function  Convolve:                                               * 
 *           ~~~~~~~~~                                               * 
 *-------------------------------------------------------------------* 
 * Perform the convolution between two vectors x[] and h[] and       * 
 * write the result in the vector y[].                               * 
 * All vectors are of length N.                                      * 
 *-------------------------------------------------------------------*/ 
 
#include "typedef.h" 
#include "basic_op.h" 
#include "ld8k.h" 
 
void Convolve( 
  Word16 x[],      /* (i)     : input vector                           */ 
  Word16 h[],      /* (i) Q12 : impulse response                       */ 
  Word16 y[],      /* (o)     : output vector                          */ 
  Word16 L         /* (i)     : vector size                            */ 
) 
{ 
   Word16 i, n; 
   Word32 s; 
 
   for (n = 0; n < L; n++) 
   { 
     s = 0; 
     for (i = 0; i <= n; i++) 
       s = L_mac(s, x[i], h[n-i]); 
 
     s    = L_shl(s, 3);                   /* h is in Q12 and saturation */ 
     y[n] = extract_h(s); 
   } 
 
   return; 
} 
 
/*-----------------------------------------------------* 
 * procedure Syn_filt:                                 * 
 *           ~~~~~~~~                                  * 
 * Do the synthesis filtering 1/A(z).                  * 
 *-----------------------------------------------------*/ 
 
 
void Syn_filt( 
  Word16 a[],     /* (i) Q12 : a[m+1] prediction coefficients   (m=10)  */ 
  Word16 x[],     /* (i)     : input signal                             */ 
  Word16 y[],     /* (o)     : output signal                            */ 
  Word16 lg,      /* (i)     : size of filtering                        */ 
  Word16 mem[],   /* (i/o)   : memory associated with this filtering.   */ 
  Word16 update   /* (i)     : 0=no update, 1=update of memory.         */ 
) 
{ 
  Word16 i, j; 
  Word32 s; 
  Word16 tmp[80];     /* This is usually done by memory allocation (lg+M) */ 
  Word16 *yy; 
 
  /* Copy mem[] to yy[] */ 
 
  yy = tmp; 
 
  for(i=0; i