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[FFmpeg-devel,4/6] avcodec/kbdwin: Use av_bessel_i0()

Message ID 20230522233601.20552-4-michael@niedermayer.cc
State Accepted
Commit 4ea87c0f73d4178fd5dd60cf8ec19e5e71508c9c
Headers show
Series [FFmpeg-devel,1/6] Move bessel_i0() from swresample/resample to avutil/mathematics | expand

Checks

Context Check Description
andriy/make_fate_x86 success Make fate finished
andriy/make_x86 warning New warnings during build

Commit Message

Michael Niedermayer May 22, 2023, 11:35 p.m. UTC 
Old code used about 7 times as many cpu cycles as new

Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>
---
 libavcodec/kbdwin.c | 6 +-----
 1 file changed, 1 insertion(+), 5 deletions(-)
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Patch

diff --git a/libavcodec/kbdwin.c b/libavcodec/kbdwin.c
index bf32aeb317..5dff334250 100644
--- a/libavcodec/kbdwin.c
+++ b/libavcodec/kbdwin.c
@@ -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;
    }