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/*
* Header file for hardcoded AAC tables
*
* Copyright (c) 2010 Alex Converse <alex.converse@gmail.com>
*
* This file is part of FFmpeg.
*
* FFmpeg is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* License as published by the Free Software Foundation; either
* version 2.1 of the License, or (at your option) any later version.
*
* FFmpeg is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public
* License along with FFmpeg; if not, write to the Free Software
* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
*/
#ifndef AVCODEC_AAC_TABLEGEN_H
#define AVCODEC_AAC_TABLEGEN_H
#include "aac_tablegen_decl.h"
#if CONFIG_HARDCODED_TABLES
#include "libavcodec/aac_tables.h"
#else
#include "libavutil/mathematics.h"
float ff_aac_pow2sf_tab[428];
float ff_aac_pow34sf_tab[428];
av_cold void ff_aac_tableinit(void)
{
int i;
/* 2^(i/16) for 0 <= i <= 15 */
const float exp2_lut[] = {
1.00000000000000000000,
1.04427378242741384032,
1.09050773266525765921,
1.13878863475669165370,
1.18920711500272106672,
1.24185781207348404859,
1.29683955465100966593,
1.35425554693689272830,
1.41421356237309504880,
1.47682614593949931139,
1.54221082540794082361,
1.61049033194925430818,
1.68179283050742908606,
1.75625216037329948311,
1.83400808640934246349,
1.91520656139714729387,
};
float t1 = 8.8817841970012523233890533447265625e-16; // 2^(-50)
float t2 = 3.63797880709171295166015625e-12; // 2^(-38)
int t1_inc_cur, t2_inc_cur;
int t1_inc_prev = 0;
int t2_inc_prev = 8;
for (i = 0; i < 428; i++) {
t1_inc_cur = 4 * (i % 4);
t2_inc_cur = (8 + 3*i) % 16;
if (t1_inc_cur < t1_inc_prev)
t1 *= 2;
if (t2_inc_cur < t2_inc_prev)
t2 *= 2;
// A much more efficient and accurate way of doing:
// ff_aac_pow2sf_tab[i] = pow(2, (i - POW_SF2_ZERO) / 4.0);
// ff_aac_pow34sf_tab[i] = pow(ff_aac_pow2sf_tab[i], 3.0/4.0);
ff_aac_pow2sf_tab[i] = t1 * exp2_lut[t1_inc_cur];
ff_aac_pow34sf_tab[i] = t2 * exp2_lut[t2_inc_cur];
t1_inc_prev = t1_inc_cur;
t2_inc_prev = t2_inc_cur;
}
}
#endif /* CONFIG_HARDCODED_TABLES */
#endif /* AVCODEC_AAC_TABLEGEN_H */
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