mirror of
https://github.com/FFmpeg/FFmpeg.git
synced 2024-12-28 20:53:54 +02:00
49 lines
1.5 KiB
C
49 lines
1.5 KiB
C
/*
|
|
* This file is part of FFmpeg.
|
|
*
|
|
* FFmpeg 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.
|
|
*
|
|
* FFmpeg 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 FFmpeg; if not, write to the Free Software
|
|
* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
|
|
*/
|
|
|
|
#include <assert.h>
|
|
#include <libavutil/mathematics.h>
|
|
#include "libavutil/attributes.h"
|
|
#include "kbdwin.h"
|
|
|
|
#define BESSEL_I0_ITER 50 // default: 50 iterations of Bessel I0 approximation
|
|
|
|
av_cold void ff_kbd_window_init(float *window, float alpha, int n)
|
|
{
|
|
int i, j;
|
|
double sum = 0.0, bessel, tmp;
|
|
double local_window[FF_KBD_WINDOW_MAX];
|
|
double alpha2 = (alpha * M_PI / n) * (alpha * M_PI / n);
|
|
|
|
assert(n <= FF_KBD_WINDOW_MAX);
|
|
|
|
for (i = 0; i < n; i++) {
|
|
tmp = i * (n - i) * alpha2;
|
|
bessel = 1.0;
|
|
for (j = BESSEL_I0_ITER; j > 0; j--)
|
|
bessel = bessel * tmp / (j * j) + 1;
|
|
sum += bessel;
|
|
local_window[i] = sum;
|
|
}
|
|
|
|
sum++;
|
|
for (i = 0; i < n; i++)
|
|
window[i] = sqrt(local_window[i] / sum);
|
|
}
|
|
|