iirfilter_7.c

来自「用于TM1300/PNX1300系列DSP（主要用于视频处理）的各种滤波器源码」· C语言 代码 · 共 44 行

    
#include <stdlib.h>
#include <math.h>
#include <ops/custom_defs.h>

#define SHIFT 3  /* see case study on IIR filter in Cookbook */

int iirFilter_7( int *inputData, int *outputData, 
                 int *coeff, int *state, int sampleNumber )
{
    int i;
    int * restrict input, * restrict output;
    int temp1, temp2, temp3, temp4, temp5;
    int coeff_a0, coeff_a1, coeff_a2, coeff_b1, coeff_b2;
    int state_0, state_1, state_2, state_3;

    input = inputData; output = outputData;
    coeff_a0 = coeff[0]; coeff_a1 = coeff[1]; coeff_a2 = coeff[2];
    coeff_b1 = coeff[3]; coeff_b2 = coeff[4];
    state_0 = state[0]; state_1 = state[1]; 
    state_2 = state[2]; state_3 = state[3];

    for( i=0; i < sampleNumber; i++ )
    {
        temp1 = IMULM( coeff_a0, input[i] );
        temp2 = IMULM( coeff_a1, state_0 );
        temp3 = IMULM( coeff_a2, state_1 );
        temp4 = IMULM( coeff_b1, state_2 );
        temp5 = IMULM( coeff_b2, state_3 );
        
        output[i] = ( temp1 + temp2 + temp3 - temp4 - temp5 ) << SHIFT;

        state_1 = state_0;
        state_0 = input[i];
        state_3 = state_2;
        state_2 = output[i];
    } 

    state[0] = state_0; state[1] = state_1; 
    state[2] = state_2; state[3] = state_3;

    return 0;  
}