FFmpeg
mpegaudio_tablegen.h
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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 #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 */
mpegaudio_tableinit
static av_cold void mpegaudio_tableinit(void)
Definition: mpegaudio_tablegen.h:48
cbrt
#define cbrt
Definition: tablegen.h:35
av_cold
#define av_cold
Definition: attributes.h:90
f
#define f(width, name)
Definition: cbs_vp9.c:255
expval_table_fixed
static uint32_t expval_table_fixed[512][16]
Definition: mpegaudio_tablegen.h:37
IMDCT_SCALAR
#define IMDCT_SCALAR
Definition: mpegaudio_tablegen.h:46
attributes.h
i
int i
Definition: input.c:406
value
it s the only field you need to keep assuming you have a context There is some magic you don t need to care about around this just let it vf default value
Definition: writing_filters.txt:86
exp_table_fixed
static uint32_t exp_table_fixed[512]
Definition: mpegaudio_tablegen.h:36
llrint
#define llrint(x)
Definition: libm.h:394
M_SQRT2
#define M_SQRT2
Definition: mathematics.h:61