fir_fixpt_c55x.c

用dsp解压mp3程序的算法

/*****************************************************************
*  fir_fixpt_c55x.c - Fixed-point C for FIR filtering using CCS  *
*                     the FIR function is in C55x assembly       *
*                     in Section 6.6.6.2                         *
******************************************************************
*  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"   /* coefficient header file       */

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

/*   Functions   */
static int firproc(int *input, int *output);
static void dataIO(void);
extern int fir_c55(int *,int ,const int16_T *);  
                               /* C55x asm file for FIR filter  */
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);  
  }
}

/*  C function firproc for FIR filtering    */
static int firproc(int *input, int *output)
{
/*****************************************************************
*    Define variable arrays, define and clear variables
*****************************************************************/
 
  long yn = 0;            /* y(n), output of FIR filter         */
  int xnbuf[96];          /* signal buffer for FIR filter       */
  int i,k;
  int size = 300;
  
  for(k=0;k<NL;k++)       /* BL is defined in coeff_ccs_16int.h */
  {
    xnbuf[k]=0;           /* clear signal buffer                */
  }

  while(size--){          
    for (i=NL-1;i>0;i--)
    {
	xnbuf[i]=xnbuf[i-1];  /* refresh signal buffer          */
    }
	xnbuf[0]=*input++;    /*insert newest sample into buffer*/

    /*************************************************************
    *    FIR filtering:
    *         y(n) = sum[x(n-i)*b(i)] for i = 0 to BL-1
    *************************************************************/
    yn = 0; 
    
    yn = fir_c55(xnbuf,NL,NUM); /* FIR filtering in assembly    */
           
    *output++ = (int)(yn);
  }
  return(TRUE);
}

/*   Function for dataIO   */

static void dataIO()
{
  return;
}