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/*
* 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 "libavutil/avassert.h"
#include "libavutil/libm.h"
#include "libavutil/mathematics.h"
#include "libavutil/attributes.h"
#include "kbdwin.h"
av_cold static void kbd_window_init(float *float_window, int *int_window, float alpha, int n)
{
int i;
double sum = 0.0, tmp;
double scale = 0.0;
double temp[FF_KBD_WINDOW_MAX / 2 + 1];
double alpha2 = 4 * (alpha * M_PI / n) * (alpha * M_PI / n);
av_assert0(n <= FF_KBD_WINDOW_MAX);
for (i = 0; i <= n / 2; i++) {
tmp = i * (n - i) * alpha2;
temp[i] = av_bessel_i0(sqrt(tmp));
scale += temp[i] * (1 + (i && i<n/2));
}
scale = 1.0/(scale + 1);
for (i = 0; i <= n / 2; i++) {
sum += temp[i];
if (float_window) float_window[i] = sqrt(sum * scale);
else int_window[i] = lrint(2147483647 * sqrt(sum * scale));
}
for (; i < n; i++) {
sum += temp[n - i];
if (float_window) float_window[i] = sqrt(sum * scale);
else int_window[i] = lrint(2147483647 * sqrt(sum * scale));
}
}
av_cold void ff_kbd_window_init(float *window, float alpha, int n)
{
kbd_window_init(window, NULL, alpha, n);
}
av_cold void ff_kbd_window_init_fixed(int32_t *window, float alpha, int n)
{
kbd_window_init(NULL, window, alpha, n);
}
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