| /* |
| * 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); |
| } |