FFmpeg coverage

Directory: ../../../ffmpeg/
File: src/libavcodec/ac3dec_data.c
Date: 2026-07-21 08:37:06
Exec Total Coverage
Lines: 21 21 100.0%
Functions: 3 3 100.0%
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1 /*
2 * AC-3 and E-AC-3 decoder tables
3 * Copyright (c) 2007 Bartlomiej Wolowiec <bartek.wolowiec@gmail.com>
4 *
5 * This file is part of FFmpeg.
6 *
7 * FFmpeg is free software; you can redistribute it and/or
8 * modify it under the terms of the GNU Lesser General Public
9 * License as published by the Free Software Foundation; either
10 * version 2.1 of the License, or (at your option) any later version.
11 *
12 * FFmpeg is distributed in the hope that it will be useful,
13 * but WITHOUT ANY WARRANTY; without even the implied warranty of
14 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
15 * Lesser General Public License for more details.
16 *
17 * You should have received a copy of the GNU Lesser General Public
18 * License along with FFmpeg; if not, write to the Free Software
19 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
20 */
21
22 /**
23 * @file
24 * Tables taken directly from the AC-3 spec or derived from it.
25 */
26
27 #include "ac3dec_data.h"
28 #include "libavutil/thread.h"
29
30 /**
31 * Table used to ungroup 3 values stored in 5 bits.
32 * Used by bap=1 mantissas and GAQ.
33 * ff_ac3_ungroup_3_in_5_bits_tab[i] = { i/9, (i%9)/3, (i%9)%3 }
34 */
35 const uint8_t ff_ac3_ungroup_3_in_5_bits_tab[32][3] = {
36 { 0, 0, 0 }, { 0, 0, 1 }, { 0, 0, 2 }, { 0, 1, 0 },
37 { 0, 1, 1 }, { 0, 1, 2 }, { 0, 2, 0 }, { 0, 2, 1 },
38 { 0, 2, 2 }, { 1, 0, 0 }, { 1, 0, 1 }, { 1, 0, 2 },
39 { 1, 1, 0 }, { 1, 1, 1 }, { 1, 1, 2 }, { 1, 2, 0 },
40 { 1, 2, 1 }, { 1, 2, 2 }, { 2, 0, 0 }, { 2, 0, 1 },
41 { 2, 0, 2 }, { 2, 1, 0 }, { 2, 1, 1 }, { 2, 1, 2 },
42 { 2, 2, 0 }, { 2, 2, 1 }, { 2, 2, 2 }, { 3, 0, 0 },
43 { 3, 0, 1 }, { 3, 0, 2 }, { 3, 1, 0 }, { 3, 1, 1 }
44 };
45
46 /**
47 * table for ungrouping 3 values in 7 bits.
48 * used for exponents and bap=2 mantissas
49 */
50 uint8_t ff_ac3_ungroup_3_in_7_bits_tab[128][3];
51
52 /**
53 * Symmetrical Dequantization
54 * reference: Section 7.3.3 Expansion of Mantissas for Symmetrical Quantization
55 * Tables 7.19 to 7.23
56 */
57 #define SYMMETRIC_DEQUANT(code, levels) (((code - (levels >> 1)) * (1 << 24)) / levels)
58 /**
59 * Ungrouped mantissa tables; the extra entry is padding to avoid range checks
60 */
61 /**
62 * Table 7.21
63 */
64 const int ff_ac3_bap3_mantissas[7 + 1] = {
65 SYMMETRIC_DEQUANT(0, 7),
66 SYMMETRIC_DEQUANT(1, 7),
67 SYMMETRIC_DEQUANT(2, 7),
68 SYMMETRIC_DEQUANT(3, 7),
69 SYMMETRIC_DEQUANT(4, 7),
70 SYMMETRIC_DEQUANT(5, 7),
71 SYMMETRIC_DEQUANT(6, 7),
72 };
73 /**
74 * Table 7.23
75 */
76 const int ff_ac3_bap5_mantissas[15 + 1] = {
77 SYMMETRIC_DEQUANT(0, 15),
78 SYMMETRIC_DEQUANT(1, 15),
79 SYMMETRIC_DEQUANT(2, 15),
80 SYMMETRIC_DEQUANT(3, 15),
81 SYMMETRIC_DEQUANT(4, 15),
82 SYMMETRIC_DEQUANT(5, 15),
83 SYMMETRIC_DEQUANT(6, 15),
84 SYMMETRIC_DEQUANT(7, 15),
85 SYMMETRIC_DEQUANT(8, 15),
86 SYMMETRIC_DEQUANT(9, 15),
87 SYMMETRIC_DEQUANT(10, 15),
88 SYMMETRIC_DEQUANT(11, 15),
89 SYMMETRIC_DEQUANT(12, 15),
90 SYMMETRIC_DEQUANT(13, 15),
91 SYMMETRIC_DEQUANT(14, 15),
92 };
93
94 int ff_ac3_bap1_mantissas[32][3];
95 int ff_ac3_bap2_mantissas[128][3];
96 int ff_ac3_bap4_mantissas[128][2];
97
98 static inline int
99 32384 symmetric_dequant(int code, int levels)
100 {
101 32384 return SYMMETRIC_DEQUANT(code, levels);
102 }
103
104 44 static av_cold void ac3_init_static(void)
105 {
106 /* generate table for ungrouping 3 values in 7 bits
107 reference: Section 7.1.3 Exponent Decoding */
108
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 5676 for (int i = 0; i < 128; ++i) {
109 5632 ff_ac3_ungroup_3_in_7_bits_tab[i][0] = i / 25;
110 5632 ff_ac3_ungroup_3_in_7_bits_tab[i][1] = (i % 25) / 5;
111 5632 ff_ac3_ungroup_3_in_7_bits_tab[i][2] = (i % 25) % 5;
112 }
113
114 /* generate grouped mantissa tables
115 reference: Section 7.3.5 Ungrouping of Mantissas */
116
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 1452 for (int i = 0; i < 32; ++i) {
117 /* bap=1 mantissas */
118 1408 ff_ac3_bap1_mantissas[i][0] = symmetric_dequant(ff_ac3_ungroup_3_in_5_bits_tab[i][0], 3);
119 1408 ff_ac3_bap1_mantissas[i][1] = symmetric_dequant(ff_ac3_ungroup_3_in_5_bits_tab[i][1], 3);
120 1408 ff_ac3_bap1_mantissas[i][2] = symmetric_dequant(ff_ac3_ungroup_3_in_5_bits_tab[i][2], 3);
121 }
122
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 5676 for (int i = 0; i < 128; ++i) {
123 /* bap=2 mantissas */
124 5632 ff_ac3_bap2_mantissas[i][0] = symmetric_dequant(ff_ac3_ungroup_3_in_7_bits_tab[i][0], 5);
125 5632 ff_ac3_bap2_mantissas[i][1] = symmetric_dequant(ff_ac3_ungroup_3_in_7_bits_tab[i][1], 5);
126 5632 ff_ac3_bap2_mantissas[i][2] = symmetric_dequant(ff_ac3_ungroup_3_in_7_bits_tab[i][2], 5);
127
128 /* bap=4 mantissas */
129 5632 ff_ac3_bap4_mantissas[i][0] = symmetric_dequant(i / 11, 11);
130 5632 ff_ac3_bap4_mantissas[i][1] = symmetric_dequant(i % 11, 11);
131 }
132 44 }
133
134 48 av_cold void ff_ac3_init_static(void)
135 {
136 static AVOnce ac3_init_static_once = AV_ONCE_INIT;
137 48 ff_thread_once(&ac3_init_static_once, ac3_init_static);
138 48 }
139
140 /**
141 * Quantization table: levels for symmetric. bits for asymmetric.
142 * reference: Table 7.18 Mapping of bap to Quantizer
143 */
144 const uint8_t ff_ac3_quantization_tab[16] = {
145 0, 3, 5, 7, 11, 15,
146 5, 6, 7, 8, 9, 10, 11, 12, 14, 16
147 };
148
149 /**
150 * Table for default stereo downmixing coefficients
151 * reference: Section 7.8.2 Downmixing Into Two Channels
152 */
153 const uint8_t ff_ac3_default_coeffs[8][5][2] = {
154 { { 2, 7 }, { 7, 2 }, },
155 { { 4, 4 }, },
156 { { 2, 7 }, { 7, 2 }, },
157 { { 2, 7 }, { 5, 5 }, { 7, 2 }, },
158 { { 2, 7 }, { 7, 2 }, { 6, 6 }, },
159 { { 2, 7 }, { 5, 5 }, { 7, 2 }, { 8, 8 }, },
160 { { 2, 7 }, { 7, 2 }, { 6, 7 }, { 7, 6 }, },
161 { { 2, 7 }, { 5, 5 }, { 7, 2 }, { 6, 7 }, { 7, 6 }, },
162 };
163
164 const uint8_t ff_eac3_hebap_tab[64] = {
165 0, 1, 2, 3, 4, 5, 6, 7, 8, 8,
166 8, 8, 9, 9, 9, 10, 10, 10, 10, 11,
167 11, 11, 11, 12, 12, 12, 12, 13, 13, 13,
168 13, 14, 14, 14, 14, 15, 15, 15, 15, 16,
169 16, 16, 16, 17, 17, 17, 17, 18, 18, 18,
170 18, 18, 18, 18, 18, 19, 19, 19, 19, 19,
171 19, 19, 19, 19,
172 };
173
174 /**
175 * Table E2.15 Default Spectral Extension Banding Structure
176 */
177 const uint8_t ff_eac3_default_spx_band_struct[17] =
178 { 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1 };
179
180 /** Adjustments in dB gain (LFE, +10 to -21 dB) */
181 const float ff_eac3_gain_levels_lfe[32] = {
182 3.162275, 2.818382, 2.511886, 2.238719, 1.995261, 1.778278, 1.584893,
183 1.412536, 1.258924, 1.122018, 1.000000, 0.891251, 0.794328, 0.707946,
184 0.630957, 0.562341, 0.501187, 0.446683, 0.398107, 0.354813, 0.316227,
185 0.281838, 0.251188, 0.223872, 0.199526, 0.177828, 0.158489, 0.141253,
186 0.125892, 0.112201, 0.100000, 0.089125
187 };
188