FFmpeg: libavcodec/kbdwin.c Source File

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kbdwin.c

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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 */

19 #include "libavutil/avassert.h"

20 #include "libavutil/libm.h"

21 #include "libavutil/mathematics.h"

22 #include "libavutil/attributes.h"

23 #include "kbdwin.h"

25 av_cold static void kbd_window_init(float *float_window, int *int_window, float alpha, int n)

26 {

27 int i;

28 double sum = 0.0, tmp;

29 double scale = 0.0;

30 double temp[FF_KBD_WINDOW_MAX / 2 + 1];

31 double alpha2 = 4 * (alpha * M_PI / n) * (alpha * M_PI / n);

33 av_assert0(n <= FF_KBD_WINDOW_MAX);

35 for (i = 0; i <= n / 2; i++) {

36 tmp = i * (n - i) * alpha2;

37 temp[i] = av_bessel_i0(sqrt(tmp));

38 scale += temp[i] * (1 + (i && i<n/2));

39 }

40 scale = 1.0/(scale + 1);

42 for (i = 0; i <= n / 2; i++) {

43 sum += temp[i];

44 if (float_window) float_window[i] = sqrt(sum * scale);

45 else int_window[i] = lrint(2147483647 * sqrt(sum * scale));

46 }

47 for (; i < n; i++) {

48 sum += temp[n - i];

49 if (float_window) float_window[i] = sqrt(sum * scale);

50 else int_window[i] = lrint(2147483647 * sqrt(sum * scale));

51 }

52 }

54 av_cold void ff_kbd_window_init(float *window, float alpha, int n)

55 {

56 kbd_window_init(window, NULL, alpha, n);

57 }

59 av_cold void ff_kbd_window_init_fixed(int32_t *window, float alpha, int n)

60 {

61 kbd_window_init(NULL, window, alpha, n);

62 }

libm.h

FF_KBD_WINDOW_MAX

#define FF_KBD_WINDOW_MAX

Maximum window size for ff_kbd_window_init.

Definition: kbdwin.h:27

ff_kbd_window_init_fixed

av_cold void ff_kbd_window_init_fixed(int32_t *window, float alpha, int n)

Definition: kbdwin.c:59

av_bessel_i0

double av_bessel_i0(double x)

0th order modified bessel function of the first kind.

Definition: mathematics.c:257

mathematics.h

window

static SDL_Window * window

Definition: ffplay.c:361

avassert.h

lrint

#define lrint

Definition: tablegen.h:53

av_cold

#define av_cold

Definition: attributes.h:106

av_assert0

#define av_assert0(cond)

assert() equivalent, that is always enabled.

Definition: avassert.h:41

kbdwin.h

tmp

static uint8_t tmp[40]

Definition: aes_ctr.c:52

NULL

#define NULL

Definition: coverity.c:32

attributes.h

M_PI

#define M_PI

Definition: mathematics.h:67

#define i(width, name, range_min, range_max)

Definition: cbs_h2645.c:256

ff_kbd_window_init

av_cold void ff_kbd_window_init(float *window, float alpha, int n)

Generate a Kaiser-Bessel Derived Window.

Definition: kbdwin.c:54

temp

else temp

Definition: vf_mcdeint.c:271

kbd_window_init

static av_cold void kbd_window_init(float *float_window, int *int_window, float alpha, int n)

Definition: kbdwin.c:25

scale

static void scale(int *out, const int *in, const int w, const int h, const int shift)

Definition: intra.c:273

alpha

static const int16_t alpha[]

Definition: ilbcdata.h:55

int32_t

Definition: audioconvert.c:56

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