blob: bf32aeb31767b4bd6be1460ac6d38f8ad8905194
1 | /* |
2 | * This file is part of FFmpeg. |
3 | * |
4 | * FFmpeg is free software; you can redistribute it and/or |
5 | * modify it under the terms of the GNU Lesser General Public |
6 | * License as published by the Free Software Foundation; either |
7 | * version 2.1 of the License, or (at your option) any later version. |
8 | * |
9 | * FFmpeg is distributed in the hope that it will be useful, |
10 | * but WITHOUT ANY WARRANTY; without even the implied warranty of |
11 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU |
12 | * Lesser General Public License for more details. |
13 | * |
14 | * You should have received a copy of the GNU Lesser General Public |
15 | * License along with FFmpeg; if not, write to the Free Software |
16 | * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA |
17 | */ |
18 | |
19 | #include "libavutil/avassert.h" |
20 | #include "libavutil/mathematics.h" |
21 | #include "libavutil/attributes.h" |
22 | #include "kbdwin.h" |
23 | |
24 | #define BESSEL_I0_ITER 50 // default: 50 iterations of Bessel I0 approximation |
25 | |
26 | av_cold void ff_kbd_window_init(float *window, float alpha, int n) |
27 | { |
28 | int i, j; |
29 | double sum = 0.0, bessel, tmp; |
30 | double local_window[FF_KBD_WINDOW_MAX]; |
31 | double alpha2 = (alpha * M_PI / n) * (alpha * M_PI / n); |
32 | |
33 | av_assert0(n <= FF_KBD_WINDOW_MAX); |
34 | |
35 | for (i = 0; i < n; i++) { |
36 | tmp = i * (n - i) * alpha2; |
37 | bessel = 1.0; |
38 | for (j = BESSEL_I0_ITER; j > 0; j--) |
39 | bessel = bessel * tmp / (j * j) + 1; |
40 | sum += bessel; |
41 | local_window[i] = sum; |
42 | } |
43 | |
44 | sum++; |
45 | for (i = 0; i < n; i++) |
46 | window[i] = sqrt(local_window[i] / sum); |
47 | } |
48 | |
49 | av_cold void ff_kbd_window_init_fixed(int32_t *window, float alpha, int n) |
50 | { |
51 | int i; |
52 | float local_window[FF_KBD_WINDOW_MAX]; |
53 | |
54 | ff_kbd_window_init(local_window, alpha, n); |
55 | for (i = 0; i < n; i++) |
56 | window[i] = (int)floor(2147483647.0 * local_window[i] + 0.5); |
57 | } |
58 |