iir_fixpt_c55x.c

用dsp解压mp3程序的算法

/*****************************************************************
*  iir_fixpt_c55x.c- Fixed-point C program for IIR filtering using
*                direct-form II biquads in C55x assembly functions
*                in Section 7.7.6.2
******************************************************************
*  System configuration:
* 
* in(n) |----------------| out(n)
*  ---->| Bandpass filter|----->
*       |----------------|
*
*     in(n) is the input data from data file "in_int_ccs.dat"
*  This C program called two functions written in C55x assembly
*
*****************************************************************/
#include <stdio.h>
#include <stdlib.h>
#include <math.h>
#include "iircoeff_ccs_16.h"  // coefficient header file  

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

extern void gain_c55x(int *,int *,int );
extern void iir_c55x(int *,const int16_T *,const int16_T *,int *);
 
/*Function */
static int iirproc(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();
    iirproc(input, output);  
  }
}


/*    Function for IIR filtering    */
static int iirproc(int *input, int *output)
{
  /***************************************************************
  *    Define variable arrays, define and clear variables
  ***************************************************************/
  const int section = 3;
  int out = 0;          /* y(n), output from IIR filter         */
  int delay[9] = {0,0,0,0,0,0,0,0,0};
  int gain = 17;
  int j,i;
  int size = 300;

  for(i=0;i<size;i++)
  {          	
    gain_c55x(&out,&in_buffer[i],gain); /* gain function        */  
    /*************************************************************
    *    IIR filtering: feedback follow by feedforward and repeat
    *         for three sections.
    *************************************************************/
    
    for (j=0; j<section; j++)	
    {
        iir_c55x(&out,&NUM[j][1],&DEN[j][1],&delay[1+(3*j)]);
    }       
    *output++ = (int)(out*8);	
  }
  return(TRUE);
}


/* Function for dataIO */

static void dataIO()
{
  return;
}