FFmpeg
 All Data Structures Namespaces Files Functions Variables Typedefs Enumerations Enumerator Macros Groups Pages
mpegaudio_tablegen.h
Go to the documentation of this file.
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 
29 #define TABLE_4_3_SIZE (8191 + 16)*4
30 #if CONFIG_HARDCODED_TABLES
31 #define mpegaudio_tableinit()
32 #include "libavcodec/mpegaudio_tables.h"
33 #else
36 static uint32_t exp_table_fixed[512];
37 static uint32_t expval_table_fixed[512][16];
38 static float exp_table_float[512];
39 static float expval_table_float[512][16];
40 
41 #define FRAC_BITS 23
42 #define IMDCT_SCALAR 1.759
43 
44 static void mpegaudio_tableinit(void)
45 {
46  int i, value, exponent;
47  for (i = 1; i < TABLE_4_3_SIZE; i++) {
48  double value = i / 4;
49  double f, fm;
50  int e, m;
51  f = value / IMDCT_SCALAR * cbrtf(value) * pow(2, (i & 3) * 0.25);
52  fm = frexp(f, &e);
53  m = (uint32_t)(fm * (1LL << 31) + 0.5);
54  e += FRAC_BITS - 31 + 5 - 100;
55 
56  /* normalized to FRAC_BITS */
57  table_4_3_value[i] = m;
58  table_4_3_exp[i] = -e;
59  }
60  for (exponent = 0; exponent < 512; exponent++) {
61  for (value = 0; value < 16; value++) {
62  double f = (double)value * cbrtf(value) * pow(2, (exponent - 400) * 0.25 + FRAC_BITS + 5) / IMDCT_SCALAR;
63  expval_table_fixed[exponent][value] = llrint(f);
64  expval_table_float[exponent][value] = f;
65  }
66  exp_table_fixed[exponent] = expval_table_fixed[exponent][1];
67  exp_table_float[exponent] = expval_table_float[exponent][1];
68  }
69 }
70 #endif /* CONFIG_HARDCODED_TABLES */
71 
72 #endif /* AVCODEC_MPEGAUDIO_TABLEGEN_H */