repositories / deb_ffmpeg.git / blame
| Commit | Line | Data |
|---|---|---|
| 2ba45a60 DM |
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 | } |