ffmpeg/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 #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 */