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2611874a50
Namely the part that creates a temporary LUT. Reviewed-by: Zhao Zhili <quinkblack@foxmail.com> Reviewed-by: Lynne <dev@lynne.ee> Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@outlook.com>
67 lines
2.4 KiB
C
67 lines
2.4 KiB
C
/*
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* Header file for hardcoded AAC cube-root table
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*
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* Copyright (c) 2010 Reimar Döffinger <Reimar.Doeffinger@gmx.de>
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*
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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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#ifndef AVCODEC_CBRT_TABLEGEN_H
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#define AVCODEC_CBRT_TABLEGEN_H
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#include <assert.h>
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#include <stdint.h>
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#include <math.h>
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#include "libavutil/attributes.h"
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#include "libavutil/intfloat.h"
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#include "libavcodec/aac_defines.h"
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#include "cbrt_data.h"
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#if USE_FIXED
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#define CBRT(x) lrint((x) * 8192)
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#else
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#define CBRT(x) av_float2int((float)(x))
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#endif
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union CBRT AAC_RENAME(ff_cbrt_tab_internal);
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av_cold void AAC_RENAME(ff_cbrt_tableinit)(void)
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{
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static_assert(2 * sizeof(AAC_RENAME(ff_cbrt_tab_internal).cbrt_tab[0])
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>= sizeof(AAC_RENAME(ff_cbrt_tab_internal).tmp[0]),
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"unexpected sizeofs");
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// We reuse ff_cbrt_tab_internal.tmp as a LUT (of doubles) for the roots
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// of the odd integers: tmp[idx] contains (2 * idx + 1)^{4/3}.
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ff_cbrt_dbl_tableinit(AAC_RENAME(ff_cbrt_tab_internal).tmp);
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double cbrt_2 = 2 * cbrt(2);
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for (int idx = TMP_LUT_SIZE - 1; idx >= 0; --idx) {
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double cbrt_val = AAC_RENAME(ff_cbrt_tab_internal).tmp[idx];
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// Due to i * sizeof(ff_cbrt_tab_internal.cbrt_tab[0]) >=
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// 2 * idx * sizeof(ff_cbrt_tab_internal.cbrt_tab[0]) >= idx * sizeof(double)
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// we don't clobber the double-LUT entries with index < idx
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// in the loop below. This is why we process idx in descending order.
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for (int i = 2 * idx + 1; i < LUT_SIZE; i *= 2) {
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AAC_RENAME(ff_cbrt_tab_internal).cbrt_tab[i] = CBRT(cbrt_val);
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cbrt_val *= cbrt_2;
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}
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}
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AAC_RENAME(ff_cbrt_tab_internal).cbrt_tab[0] = CBRT(0);
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}
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#endif /* AVCODEC_CBRT_TABLEGEN_H */
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