do_zfilt.c

4.8k/s速率FS1016标准语音压缩源码

/**************************************************************************
*
* ROUTINE
*		do_zfilt
*		do_zfilt_dynamic
*
* FUNCTION
*		pole filter - given a filter structure
*		do_zfilt assumes static coefficients
*		do_zfilt_dynamic assumes changing coefficients
*
* SYNOPSIS
*		subroutine do_zfilt(flt, coef, data)
*
*   formal 
*
*                       data    I/O
*       name            type    type    function
*       -------------------------------------------------------------------	
*	flt		FILTER	i/o	FILTER structure
*	coef		float	 i	coefficients
*	data		float	i/o	input/filtered output data	
*
***************************************************************************
*       
* DESCRIPTION
*
*	Nonrecursive all-zero in-place time-domain filter.
*	The filter is implemented in a direct form realisation.
*
*               N       -i
*       H(z) = SUM b(i)z
*              i=0
*
*       x(t) ->---(z0)----- b0 >------+-----> y(t)
*                  |                  |
*                  z1------ b1 >------+
*                  |                  |
*                  z2------ b2 >------+
*                  |                  |
*                  :                  :
*                  |                  |
*                  zN------ bN >------+
*
*
***************************************************************************
*
* CALLED BY
*
*	FindAdaptResidual FindLPCResidual UpdateEverything
*	HPF_InSpeech HPF_OutSpeech PostFilter 
*
***************************************************************************/

#include "celpfilt.h"

void do_zfilt(
FILTER *flt,
float data[])
{
  register float ar;
  int t, j;

  for (t = 0; t < flt->data_length; t++)
  {
    flt->memory[0] = data[t];
    ar   = 0.0;
    for (j = flt->order; j > 0; j--)
    {
      ar  += flt->memory[j] * flt->coef[j];
      flt->memory[j] = flt->memory[j-1];
    }
    data[t] = ar + flt->memory[0] * flt->coef[0];
  }
}

void do_zfilt_dynamic(
FILTER 	*flt,
float	coef[],
float 	data[])
{
  register float ar;
  int t, j;

  for (t = 0; t < flt->data_length; t++)
  {
    flt->memory[0] = data[t];
    ar   = 0.0;
    for (j = flt->order; j > 0; j--)
    {
      ar  += flt->memory[j] * coef[j];
      flt->memory[j] = flt->memory[j-1];
    }
    data[t] = ar + flt->memory[0] * coef[0];
  }
}