fir_fixpt_ccs.c

用dsp解压mp3程序的算法

/*****************************************************************
*  fir_fixpt_ccs.c - C program for FIR filtering using CCS
*                    in Section 6.6.4     
******************************************************************
*  System configuration:
*
* 
* in(n) |----------------| out(n)
*  ---->| Bandpass filter|----->
*       |----------------|
*
******************************************************************
*  System simulation configuration:
*
*     in_buffer is used to store the input data
*     out_buffer is used to store the output filtered data
*
*****************************************************************/

#include <stdio.h>
#include <stdlib.h>
#include <math.h>
#include "coeff_ccs_16int.h"

int in_buffer[300];
int out_buffer[300];
#define TRUE 1

/*Function */
static int firproc(int *input, int *output);
static void dataIO(void);

void main()
{

/*****************************************************************
*    Declare file pointers
*****************************************************************/

int *input = &in_buffer[0];
int *output= &out_buffer[0];

/*****************************************************************
*    Start of main program
*****************************************************************/
 
  while(TRUE)
  {           /* read in x(n) from data file and processing it  */
   
    dataIO();
    firproc(input, output);  
  }
}

/* firproc - FIR filtering operations */
static int firproc(int *input, int *output)
{
/*****************************************************************
*    Define variable arrays, define and clear variables
*****************************************************************/

  long yn = 0;               /* y(n), output from IIR filter    */
  int xnbuf[96];
  int i,j,k;
  int size = 300;
  
  for(k=0;k<NL;k++)
  {
    xnbuf[k]=0;
  }

  while(size--){          
    for (i=NL-1;i>0;i--)
    {
	xnbuf[i]=xnbuf[i-1];
    }
	xnbuf[0]=*input++; 
        
    /*************************************************************
    *    FIR filtering:
    *         y(n) = Sum[x(n-i)*coeff(i)] for i = 0 to NL-1
    *************************************************************/
    yn = 0; 
    
    for (j=0; j< NL; j++)	
    {
      yn += (((long)(int)xnbuf[j] * (long)(int16_T)NUM[j])>>15);  
    } 
    *output++ = (int)(yn);
  }

  return(TRUE);
}

/* Function for dataIO */

static void dataIO()
{
  return;
}