libavcodec/mpegaudio_tablegen.h

   1 /*
   2  * Header file for hardcoded mpegaudiodec tables
   3  *
   4  * Copyright (c) 2009 Reimar Döffinger <Reimar.Doeffinger@gmx.de>
   5  *
   6  * This file is part of FFmpeg.
   7  *
   8  * FFmpeg is free software; you can redistribute it and/or
   9  * modify it under the terms of the GNU Lesser General Public
  10  * License as published by the Free Software Foundation; either
  11  * version 2.1 of the License, or (at your option) any later version.
  12  *
  13  * FFmpeg is distributed in the hope that it will be useful,
  14  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  15  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  16  * Lesser General Public License for more details.
  17  *
  18  * You should have received a copy of the GNU Lesser General Public
  19  * License along with FFmpeg; if not, write to the Free Software
  20  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
  21  */
  22
  23 #ifndef AVCODEC_MPEGAUDIO_TABLEGEN_H
  24 #define AVCODEC_MPEGAUDIO_TABLEGEN_H
  25
  26 #include <stdint.h>
  27 #include <math.h>
  28 #include "libavutil/attributes.h"
  29
  30 #if CONFIG_HARDCODED_TABLES
  31 #define mpegaudio_tableinit()
  32 #include "libavcodec/mpegaudio_tables.h"
  33 #else
  34 #if defined(BUILD_TABLES) || !USE_FLOATS
  35 #define FIXED_TABLE
  36 static uint32_t exp_table_fixed[512];
  37 static uint32_t expval_table_fixed[512][16];
  38 #endif
  39
  40 #if defined(BUILD_TABLES) || USE_FLOATS
  41 #define FLOAT_TABLE
  42 static float exp_table_float[512];
  43 static float expval_table_float[512][16];
  44 #endif
  45
  46 #define IMDCT_SCALAR 1.759
  47
  48 static av_cold void mpegaudio_tableinit(void)
  49 {
  50     int i, value, exponent;
  51     static const double exp2_lut[4] = {
  52         1.00000000000000000000, /* 2 ^ (0 * 0.25) */
  53         1.18920711500272106672, /* 2 ^ (1 * 0.25) */
  54         M_SQRT2               , /* 2 ^ (2 * 0.25) */
  55         1.68179283050742908606, /* 2 ^ (3 * 0.25) */
  56     };
  57     double pow43_lut[16];
  58     double exp2_base = 2.11758236813575084767080625169910490512847900390625e-22; // 2^(-72)
  59     double exp2_val;
  60
  61     for (i = 0; i < 16; ++i)
  62         pow43_lut[i] = i * cbrt(i);
  63
  64     for (exponent = 0; exponent < 512; exponent++) {
  65         if (exponent && (exponent & 3) == 0)
  66             exp2_base *= 2;
  67         exp2_val = exp2_base * exp2_lut[exponent & 3] / IMDCT_SCALAR;
  68         for (value = 0; value < 16; value++) {
  69             double f = pow43_lut[value] * exp2_val;
  70 #ifdef FIXED_TABLE
  71             expval_table_fixed[exponent][value] = (f < 0xFFFFFFFF ? llrint(f) : 0xFFFFFFFF);
  72 #endif
  73 #ifdef FLOAT_TABLE
  74             expval_table_float[exponent][value] = f;
  75 #endif
  76         }
  77 #ifdef FIXED_TABLE
  78         exp_table_fixed[exponent] = expval_table_fixed[exponent][1];
  79 #endif
  80 #ifdef FLOAT_TABLE
  81         exp_table_float[exponent] = expval_table_float[exponent][1];
  82 #endif
  83     }
  84 }
  85 #undef FLOAT_TABLE
  86 #undef FIXED_TABLE
  87 #endif /* CONFIG_HARDCODED_TABLES */
  88
  89 #endif /* AVCODEC_MPEGAUDIO_TABLEGEN_H */