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  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. #define TABLE_4_3_SIZE (8191 + 16)*4
  31. #if CONFIG_HARDCODED_TABLES
  32. #define mpegaudio_tableinit()
  33. #include "libavcodec/mpegaudio_tables.h"
  34. #else
  35. static int8_t   table_4_3_exp[TABLE_4_3_SIZE];
  36. static uint32_t table_4_3_value[TABLE_4_3_SIZE];
  37. static uint32_t exp_table_fixed[512];
  38. static uint32_t expval_table_fixed[512][16];
  39. static float exp_table_float[512];
  40. static float expval_table_float[512][16];
  41.  
  42. #define FRAC_BITS 23
  43. #define IMDCT_SCALAR 1.759
  44.  
  45. static av_cold void mpegaudio_tableinit(void)
  46. {
  47.     int i, value, exponent;
  48.     for (i = 1; i < TABLE_4_3_SIZE; i++) {
  49.         double value = i / 4;
  50.         double f, fm;
  51.         int e, m;
  52.         /* cbrtf() isn't available on all systems, so we use powf(). */
  53.         f  = value / IMDCT_SCALAR * pow(value, 1.0 / 3.0) * pow(2, (i & 3) * 0.25);
  54.         fm = frexp(f, &e);
  55.         m  = (uint32_t)(fm * (1LL << 31) + 0.5);
  56.         e += FRAC_BITS - 31 + 5 - 100;
  57.  
  58.         /* normalized to FRAC_BITS */
  59.         table_4_3_value[i] =  m;
  60.         table_4_3_exp[i]   = -e;
  61.     }
  62.     for (exponent = 0; exponent < 512; exponent++) {
  63.         for (value = 0; value < 16; value++) {
  64.             /* cbrtf() isn't available on all systems, so we use powf(). */
  65.             double f = (double)value * pow(value, 1.0 / 3.0) * pow(2, (exponent - 400) * 0.25 + FRAC_BITS + 5) / IMDCT_SCALAR;
  66.             /* llrint() isn't always available, so round and cast manually. */
  67.             expval_table_fixed[exponent][value] = (long long int) (f < 0xFFFFFFFF ? floor(f + 0.5) : 0xFFFFFFFF);
  68.             expval_table_float[exponent][value] = f;
  69.         }
  70.         exp_table_fixed[exponent] = expval_table_fixed[exponent][1];
  71.         exp_table_float[exponent] = expval_table_float[exponent][1];
  72.     }
  73. }
  74. #endif /* CONFIG_HARDCODED_TABLES */
  75.  
  76. #endif /* AVCODEC_MPEGAUDIO_TABLEGEN_H */
  77.