1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
|
/*
* This file is part of Libav.
*
* Libav is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* License as published by the Free Software Foundation; either
* version 2.1 of the License, or (at your option) any later version.
*
* Libav is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public
* License along with Libav; if not, write to the Free Software
* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
*/
#include <math.h>
#include <stdint.h>
#include <stdio.h>
#include "libavutil/libm.h"
#include "iirfilter.h"
#define FILT_ORDER 4
#define SIZE 1024
int main(void)
{
struct FFIIRFilterCoeffs *fcoeffs = NULL;
struct FFIIRFilterState *fstate = NULL;
float cutoff_coeff = 0.4;
int16_t x[SIZE], y[SIZE];
int i;
fcoeffs = ff_iir_filter_init_coeffs(NULL, FF_FILTER_TYPE_BUTTERWORTH,
FF_FILTER_MODE_LOWPASS, FILT_ORDER,
cutoff_coeff, 0.0, 0.0);
fstate = ff_iir_filter_init_state(FILT_ORDER);
for (i = 0; i < SIZE; i++)
x[i] = lrint(0.75 * INT16_MAX * sin(0.5 * M_PI * i * i / SIZE));
ff_iir_filter(fcoeffs, fstate, SIZE, x, 1, y, 1);
for (i = 0; i < SIZE; i++)
printf("%6d %6d\n", x[i], y[i]);
ff_iir_filter_free_coeffs(fcoeffs);
ff_iir_filter_free_state(fstate);
return 0;
}
|
