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https://gitee.com/openharmony/third_party_ffmpeg
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35 lines
1.2 KiB
C
35 lines
1.2 KiB
C
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/*
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* Copyright (c) 2011 Justin Ruggles
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*
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* This file is part of Libav.
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*
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* Libav 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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* Libav 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 Libav; 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/mathematics.h"
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#include "adx.h"
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void ff_adx_calculate_coeffs(int cutoff, int sample_rate, int bits, int *coeff)
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{
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double a, b, c;
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a = M_SQRT2 - cos(2.0 * M_PI * cutoff / sample_rate);
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b = M_SQRT2 - 1.0;
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c = (a - sqrt((a + b) * (a - b))) / b;
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coeff[0] = lrintf(c * 2.0 * (1 << bits));
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coeff[1] = lrintf(-(c * c) * (1 << bits));
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}
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