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17ecb224e9
Also reduce neeeded temporary storage by half Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>
60 lines
1.8 KiB
C
60 lines
1.8 KiB
C
/*
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* This file is part of FFmpeg.
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*
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* FFmpeg is free software; you can redistribute it and/or
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* modify it under the terms of the GNU Lesser General Public
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* License as published by the Free Software Foundation; either
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* version 2.1 of the License, or (at your option) any later version.
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*
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* FFmpeg is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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* Lesser General Public License for more details.
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*
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* You should have received a copy of the GNU Lesser General Public
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* License along with FFmpeg; if not, write to the Free Software
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* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
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*/
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#include "libavutil/avassert.h"
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#include "libavutil/mathematics.h"
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#include "libavutil/attributes.h"
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#include "kbdwin.h"
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av_cold void ff_kbd_window_init(float *window, float alpha, int n)
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{
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int i;
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double sum = 0.0, tmp;
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double scale = 0.0;
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double temp[FF_KBD_WINDOW_MAX / 2 + 1];
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double alpha2 = 4 * (alpha * M_PI / n) * (alpha * M_PI / n);
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av_assert0(n <= FF_KBD_WINDOW_MAX);
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for (i = 0; i <= n / 2; i++) {
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tmp = i * (n - i) * alpha2;
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temp[i] = av_bessel_i0(sqrt(tmp));
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scale += temp[i] * (1 + (i && i<n/2));
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}
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scale = 1.0/(scale + 1);
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for (i = 0; i <= n / 2; i++) {
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sum += temp[i];
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window[i] = sqrt(sum * scale);
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}
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for (; i < n; i++) {
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sum += temp[n - i];
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window[i] = sqrt(sum * scale);
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}
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}
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av_cold void ff_kbd_window_init_fixed(int32_t *window, float alpha, int n)
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{
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int i;
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float local_window[FF_KBD_WINDOW_MAX];
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ff_kbd_window_init(local_window, alpha, n);
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for (i = 0; i < n; i++)
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window[i] = (int)floor(2147483647.0 * local_window[i] + 0.5);
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}
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