1/*
2 * Common code between the AC-3 encoder and decoder
3 * Copyright (c) 2000, 2001, 2002 Fabrice Bellard
4 *
5 * This file is part of Libav.
6 *
7 * Libav 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 * Libav 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 Libav; 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 * Common code between the AC-3 encoder and decoder.
25 */
26
27#ifndef AVCODEC_AC3_H
28#define AVCODEC_AC3_H
29
30#define AC3_MAX_CODED_FRAME_SIZE 3840 /* in bytes */
31#define AC3_MAX_CHANNELS 7            /**< maximum number of channels, including coupling channel */
32#define CPL_CH 0                      /**< coupling channel index */
33
34#define AC3_MAX_COEFS   256
35#define AC3_BLOCK_SIZE  256
36#define AC3_MAX_BLOCKS    6
37#define AC3_FRAME_SIZE (AC3_MAX_BLOCKS * 256)
38#define AC3_WINDOW_SIZE (AC3_BLOCK_SIZE * 2)
39#define AC3_CRITICAL_BANDS 50
40#define AC3_MAX_CPL_BANDS  18
41
42#include "ac3tab.h"
43
44/* exponent encoding strategy */
45#define EXP_REUSE 0
46#define EXP_NEW   1
47
48#define EXP_D15   1
49#define EXP_D25   2
50#define EXP_D45   3
51
52/* pre-defined gain values */
53#define LEVEL_PLUS_3DB          1.4142135623730950
54#define LEVEL_PLUS_1POINT5DB    1.1892071150027209
55#define LEVEL_MINUS_1POINT5DB   0.8408964152537145
56#define LEVEL_MINUS_3DB         0.7071067811865476
57#define LEVEL_MINUS_4POINT5DB   0.5946035575013605
58#define LEVEL_MINUS_6DB         0.5000000000000000
59#define LEVEL_MINUS_9DB         0.3535533905932738
60#define LEVEL_ZERO              0.0000000000000000
61#define LEVEL_ONE               1.0000000000000000
62
63/** Delta bit allocation strategy */
64typedef enum {
65    DBA_REUSE = 0,
66    DBA_NEW,
67    DBA_NONE,
68    DBA_RESERVED
69} AC3DeltaStrategy;
70
71/** Channel mode (audio coding mode) */
72typedef enum {
73    AC3_CHMODE_DUALMONO = 0,
74    AC3_CHMODE_MONO,
75    AC3_CHMODE_STEREO,
76    AC3_CHMODE_3F,
77    AC3_CHMODE_2F1R,
78    AC3_CHMODE_3F1R,
79    AC3_CHMODE_2F2R,
80    AC3_CHMODE_3F2R
81} AC3ChannelMode;
82
83typedef struct AC3BitAllocParameters {
84    int sr_code;
85    int sr_shift;
86    int slow_gain, slow_decay, fast_decay, db_per_bit, floor;
87    int cpl_fast_leak, cpl_slow_leak;
88} AC3BitAllocParameters;
89
90/**
91 * @struct AC3HeaderInfo
92 * Coded AC-3 header values up to the lfeon element, plus derived values.
93 */
94typedef struct {
95    /** @name Coded elements
96     * @{
97     */
98    uint16_t sync_word;
99    uint16_t crc1;
100    uint8_t sr_code;
101    uint8_t bitstream_id;
102    uint8_t bitstream_mode;
103    uint8_t channel_mode;
104    uint8_t lfe_on;
105    uint8_t frame_type;
106    int substreamid;                        ///< substream identification
107    int center_mix_level;                   ///< Center mix level index
108    int surround_mix_level;                 ///< Surround mix level index
109    uint16_t channel_map;
110    int num_blocks;                         ///< number of audio blocks
111    /** @} */
112
113    /** @name Derived values
114     * @{
115     */
116    uint8_t sr_shift;
117    uint16_t sample_rate;
118    uint32_t bit_rate;
119    uint8_t channels;
120    uint16_t frame_size;
121    uint64_t channel_layout;
122    /** @} */
123} AC3HeaderInfo;
124
125typedef enum {
126    EAC3_FRAME_TYPE_INDEPENDENT = 0,
127    EAC3_FRAME_TYPE_DEPENDENT,
128    EAC3_FRAME_TYPE_AC3_CONVERT,
129    EAC3_FRAME_TYPE_RESERVED
130} EAC3FrameType;
131
132void ff_ac3_common_init(void);
133
134/**
135 * Calculate the log power-spectral density of the input signal.
136 * This gives a rough estimate of signal power in the frequency domain by using
137 * the spectral envelope (exponents).  The psd is also separately grouped
138 * into critical bands for use in the calculating the masking curve.
139 * 128 units in psd = -6 dB.  The dbknee parameter in AC3BitAllocParameters
140 * determines the reference level.
141 *
142 * @param[in]  exp        frequency coefficient exponents
143 * @param[in]  start      starting bin location
144 * @param[in]  end        ending bin location
145 * @param[out] psd        signal power for each frequency bin
146 * @param[out] band_psd   signal power for each critical band
147 */
148void ff_ac3_bit_alloc_calc_psd(int8_t *exp, int start, int end, int16_t *psd,
149                               int16_t *band_psd);
150
151/**
152 * Calculate the masking curve.
153 * First, the excitation is calculated using parameters in s and the signal
154 * power in each critical band.  The excitation is compared with a predefined
155 * hearing threshold table to produce the masking curve.  If delta bit
156 * allocation information is provided, it is used for adjusting the masking
157 * curve, usually to give a closer match to a better psychoacoustic model.
158 *
159 * @param[in]  s            adjustable bit allocation parameters
160 * @param[in]  band_psd     signal power for each critical band
161 * @param[in]  start        starting bin location
162 * @param[in]  end          ending bin location
163 * @param[in]  fast_gain    fast gain (estimated signal-to-mask ratio)
164 * @param[in]  is_lfe       whether or not the channel being processed is the LFE
165 * @param[in]  dba_mode     delta bit allocation mode (none, reuse, or new)
166 * @param[in]  dba_nsegs    number of delta segments
167 * @param[in]  dba_offsets  location offsets for each segment
168 * @param[in]  dba_lengths  length of each segment
169 * @param[in]  dba_values   delta bit allocation for each segment
170 * @param[out] mask         calculated masking curve
171 * @return returns 0 for success, non-zero for error
172 */
173int ff_ac3_bit_alloc_calc_mask(AC3BitAllocParameters *s, int16_t *band_psd,
174                               int start, int end, int fast_gain, int is_lfe,
175                               int dba_mode, int dba_nsegs, uint8_t *dba_offsets,
176                               uint8_t *dba_lengths, uint8_t *dba_values,
177                               int16_t *mask);
178
179#endif /* AVCODEC_AC3_H */
180