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avcodec/kbdwin: Use av_bessel_i0()

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Old code used about 7 times as many cpu cycles as new

Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>
This commit is contained in:
Michael Niedermayer 2023-05-23 00:17:58 +02:00
parent 0c7a0514e3
commit 4ea87c0f73
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GPG Key ID: B18E8928B3948D64
1 changed files with 1 additions and 5 deletions
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6
libavcodec/kbdwin.c
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@ -21,8 +21,6 @@
#include "libavutil/attributes.h"
#include "kbdwin.h"
#define BESSEL_I0_ITER 50 // default: 50 iterations of Bessel I0 approximation
av_cold void ff_kbd_window_init(float *window, float alpha, int n)
{
int i, j;
@ -34,9 +32,7 @@ av_cold void ff_kbd_window_init(float *window, float alpha, int n)
for (i = 0; i < n; i++) {
tmp = i * (n - i) * alpha2;
bessel = 1.0;
for (j = BESSEL_I0_ITER; j > 0; j--)
bessel = bessel * tmp / (j * j) + 1;
bessel = av_bessel_i0(sqrt(tmp) * 2);
sum += bessel;
local_window[i] = sum;
}