filter.cpp

#include <stdio.h>
#include <string.h>
#include <stdlib.h>

#pragma warning(disable : 4996)  

#define LOW_B0 0.0605
#define LOW_B1 0.1210
#define LOW_B2 0.0605
#define LOW_A0 1.0000
#define LOW_A1 -1.1939
#define LOW_A2 0.4359

int main() {
	float x[3] = { 0 , 0, 0 }, y[3] = { 0, 0, 0 };

	FILE *fi, *fo;

	if ((fi = fopen("input_sound.snd", "rb")) == NULL)
	{
		printf("error");
		return -1;
	}
	fopen_s(&fo, "output_sound1.snd", "w");
	if (fo == NULL)
	{
		printf("output error");
		return -1;
	}

	fseek(fi, 0, SEEK_END);

	int fsize = ftell(fi) / 16 ;

	printf("%d\n", ftell(fi));


	fseek(fi, 0, SEEK_SET);

	printf("%d\n", fsize);

	for (int i = 0; i < fsize; i++)
	{
		x[2] = x[1];
		x[1] = x[0];
		y[2] = y[1];
		y[1] = y[0];

		__int16 inbuf;

		fread(&inbuf, sizeof(__int16), 1, fi);
		
		x[0] = inbuf;
		y[0] = LOW_B0 * x[0] + LOW_B1 * x[1] +LOW_B2 * x[2]
			- LOW_A1 * y[1] - LOW_A2 * y[2];

		__int16 outbuf = (__int16)x[0];

		printf("%d %d\n",inbuf, x[0]);
		fwrite(&outbuf, sizeof(__int16), 1, fo);
	}

	fclose(fi);
	fclose(fo);

	return 0;
}