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 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 * Common code between the AC-3 encoder and decoder.
25 */
26
27#ifndef AVCODEC_AC3_H
28#define AVCODEC_AC3_H
29
30#include "ac3tab.h"
31
32#define AC3_MAX_CODED_FRAME_SIZE 3840 /* in bytes */
33#define AC3_MAX_CHANNELS 6 /* including LFE channel */
34
35#define NB_BLOCKS 6 /* number of PCM blocks inside an AC-3 frame */
36#define AC3_FRAME_SIZE (NB_BLOCKS * 256)
37
38/* exponent encoding strategy */
39#define EXP_REUSE 0
40#define EXP_NEW   1
41
42#define EXP_D15   1
43#define EXP_D25   2
44#define EXP_D45   3
45
46/** Delta bit allocation strategy */
47typedef enum {
48    DBA_REUSE = 0,
49    DBA_NEW,
50    DBA_NONE,
51    DBA_RESERVED
52} AC3DeltaStrategy;
53
54/** Channel mode (audio coding mode) */
55typedef enum {
56    AC3_CHMODE_DUALMONO = 0,
57    AC3_CHMODE_MONO,
58    AC3_CHMODE_STEREO,
59    AC3_CHMODE_3F,
60    AC3_CHMODE_2F1R,
61    AC3_CHMODE_3F1R,
62    AC3_CHMODE_2F2R,
63    AC3_CHMODE_3F2R
64} AC3ChannelMode;
65
66typedef struct AC3BitAllocParameters {
67    int sr_code;
68    int sr_shift;
69    int slow_gain, slow_decay, fast_decay, db_per_bit, floor;
70    int cpl_fast_leak, cpl_slow_leak;
71} AC3BitAllocParameters;
72
73/**
74 * @struct AC3HeaderInfo
75 * Coded AC-3 header values up to the lfeon element, plus derived values.
76 */
77typedef struct {
78    /** @defgroup coded Coded elements
79     * @{
80     */
81    uint16_t sync_word;
82    uint16_t crc1;
83    uint8_t sr_code;
84    uint8_t bitstream_id;
85    uint8_t channel_mode;
86    uint8_t lfe_on;
87    uint8_t frame_type;
88    int substreamid;                        ///< substream identification
89    int center_mix_level;                   ///< Center mix level index
90    int surround_mix_level;                 ///< Surround mix level index
91    uint16_t channel_map;
92    int num_blocks;                         ///< number of audio blocks
93    /** @} */
94
95    /** @defgroup derived Derived values
96     * @{
97     */
98    uint8_t sr_shift;
99    uint16_t sample_rate;
100    uint32_t bit_rate;
101    uint8_t channels;
102    uint16_t frame_size;
103    int64_t channel_layout;
104    /** @} */
105} AC3HeaderInfo;
106
107typedef enum {
108    EAC3_FRAME_TYPE_INDEPENDENT = 0,
109    EAC3_FRAME_TYPE_DEPENDENT,
110    EAC3_FRAME_TYPE_AC3_CONVERT,
111    EAC3_FRAME_TYPE_RESERVED
112} EAC3FrameType;
113
114void ac3_common_init(void);
115
116/**
117 * Calculates the log power-spectral density of the input signal.
118 * This gives a rough estimate of signal power in the frequency domain by using
119 * the spectral envelope (exponents).  The psd is also separately grouped
120 * into critical bands for use in the calculating the masking curve.
121 * 128 units in psd = -6 dB.  The dbknee parameter in AC3BitAllocParameters
122 * determines the reference level.
123 *
124 * @param[in]  exp        frequency coefficient exponents
125 * @param[in]  start      starting bin location
126 * @param[in]  end        ending bin location
127 * @param[out] psd        signal power for each frequency bin
128 * @param[out] band_psd   signal power for each critical band
129 */
130void ff_ac3_bit_alloc_calc_psd(int8_t *exp, int start, int end, int16_t *psd,
131                               int16_t *band_psd);
132
133/**
134 * Calculates the masking curve.
135 * First, the excitation is calculated using parameters in s and the signal
136 * power in each critical band.  The excitation is compared with a predefined
137 * hearing threshold table to produce the masking curve.  If delta bit
138 * allocation information is provided, it is used for adjusting the masking
139 * curve, usually to give a closer match to a better psychoacoustic model.
140 *
141 * @param[in]  s            adjustable bit allocation parameters
142 * @param[in]  band_psd     signal power for each critical band
143 * @param[in]  start        starting bin location
144 * @param[in]  end          ending bin location
145 * @param[in]  fast_gain    fast gain (estimated signal-to-mask ratio)
146 * @param[in]  is_lfe       whether or not the channel being processed is the LFE
147 * @param[in]  dba_mode     delta bit allocation mode (none, reuse, or new)
148 * @param[in]  dba_nsegs    number of delta segments
149 * @param[in]  dba_offsets  location offsets for each segment
150 * @param[in]  dba_lengths  length of each segment
151 * @param[in]  dba_values   delta bit allocation for each segment
152 * @param[out] mask         calculated masking curve
153 * @return returns 0 for success, non-zero for error
154 */
155int ff_ac3_bit_alloc_calc_mask(AC3BitAllocParameters *s, int16_t *band_psd,
156                               int start, int end, int fast_gain, int is_lfe,
157                               int dba_mode, int dba_nsegs, uint8_t *dba_offsets,
158                               uint8_t *dba_lengths, uint8_t *dba_values,
159                               int16_t *mask);
160
161/**
162 * Calculates bit allocation pointers.
163 * The SNR is the difference between the masking curve and the signal.  AC-3
164 * uses this value for each frequency bin to allocate bits.  The snroffset
165 * parameter is a global adjustment to the SNR for all bins.
166 *
167 * @param[in]  mask       masking curve
168 * @param[in]  psd        signal power for each frequency bin
169 * @param[in]  start      starting bin location
170 * @param[in]  end        ending bin location
171 * @param[in]  snr_offset SNR adjustment
172 * @param[in]  floor      noise floor
173 * @param[in]  bap_tab    look-up table for bit allocation pointers
174 * @param[out] bap        bit allocation pointers
175 */
176void ff_ac3_bit_alloc_calc_bap(int16_t *mask, int16_t *psd, int start, int end,
177                               int snr_offset, int floor,
178                               const uint8_t *bap_tab, uint8_t *bap);
179
180void ac3_parametric_bit_allocation(AC3BitAllocParameters *s, uint8_t *bap,
181                                   int8_t *exp, int start, int end,
182                                   int snr_offset, int fast_gain, int is_lfe,
183                                   int dba_mode, int dba_nsegs,
184                                   uint8_t *dba_offsets, uint8_t *dba_lengths,
185                                   uint8_t *dba_values);
186
187#endif /* AVCODEC_AC3_H */
188