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ffmpeg / libavcodec / mpegaudio_tablegen.h @ 6bb6fb05

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/*
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 * Header file for hardcoded mpegaudiodec tables
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 *
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 * Copyright (c) 2009 Reimar Döffinger <Reimar.Doeffinger@gmx.de>
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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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#ifndef MPEGAUDIO_TABLEGEN_H
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#define MPEGAUDIO_TABLEGEN_H
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#include <stdint.h>
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#include <math.h>
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#define TABLE_4_3_SIZE (8191 + 16)*4
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#if CONFIG_HARDCODED_TABLES
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#define mpegaudio_tableinit()
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#include "libavcodec/mpegaudio_tables.h"
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#else
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static int8_t   table_4_3_exp[TABLE_4_3_SIZE];
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static uint32_t table_4_3_value[TABLE_4_3_SIZE];
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static uint32_t exp_table[512];
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static uint32_t expval_table[512][16];
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static float exp_table_float[512];
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static float expval_table_float[512][16];
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#define FRAC_BITS 23
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static void mpegaudio_tableinit(void)
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{
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    int i, value, exponent;
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    for (i = 1; i < TABLE_4_3_SIZE; i++) {
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        double value = i / 4;
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        double f, fm;
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        int e, m;
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        f  = value * cbrtf(value) * pow(2, (i & 3) * 0.25);
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        fm = frexp(f, &e);
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        m  = (uint32_t)(fm * (1LL << 31) + 0.5);
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        e += FRAC_BITS - 31 + 5 - 100;
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        /* normalized to FRAC_BITS */
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        table_4_3_value[i] =  m;
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        table_4_3_exp[i]   = -e;
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    }
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    for (exponent = 0; exponent < 512; exponent++) {
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        for (value = 0; value < 16; value++) {
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            double f = (double)value * cbrtf(value) * pow(2, (exponent - 400) * 0.25 + FRAC_BITS + 5);
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            expval_table[exponent][value] = llrint(f);
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            expval_table_float[exponent][value] = f;
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        }
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        exp_table[exponent] = expval_table[exponent][1];
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        exp_table_float[exponent] = expval_table_float[exponent][1];
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    }
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}
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#endif /* CONFIG_HARDCODED_TABLES */
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#endif /* MPEGAUDIO_TABLEGEN_H */