2 * Common code between the AC-3 encoder and decoder
3 * Copyright (c) 2000, 2001, 2002 Fabrice Bellard
5 * This file is part of FFmpeg.
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.
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.
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
24 * Common code between the AC-3 encoder and decoder.
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 */
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
42 #include "libavutil/opt.h"
46 /* exponent encoding strategy */
54 /* pre-defined gain values */
55 #define LEVEL_PLUS_3DB 1.4142135623730950
56 #define LEVEL_PLUS_1POINT5DB 1.1892071150027209
57 #define LEVEL_MINUS_1POINT5DB 0.8408964152537145
58 #define LEVEL_MINUS_3DB 0.7071067811865476
59 #define LEVEL_MINUS_4POINT5DB 0.5946035575013605
60 #define LEVEL_MINUS_6DB 0.5000000000000000
61 #define LEVEL_MINUS_9DB 0.3535533905932738
62 #define LEVEL_ZERO 0.0000000000000000
63 #define LEVEL_ONE 1.0000000000000000
65 /** Delta bit allocation strategy */
73 /** Channel mode (audio coding mode) */
75 AC3_CHMODE_DUALMONO = 0,
85 /** Dolby Surround mode */
86 typedef enum AC3DolbySurroundMode {
87 AC3_DSURMOD_NOTINDICATED = 0,
91 } AC3DolbySurroundMode;
93 /** Dolby Surround EX mode */
94 typedef enum AC3DolbySurroundEXMode {
95 AC3_DSUREXMOD_NOTINDICATED = 0,
99 } AC3DolbySurroundEXMode;
101 /** Dolby Headphone mode */
102 typedef enum AC3DolbyHeadphoneMode {
103 AC3_DHEADPHONMOD_NOTINDICATED = 0,
104 AC3_DHEADPHONMOD_OFF,
106 AC3_DHEADPHONMOD_RESERVED
107 } AC3DolbyHeadphoneMode;
109 /** Preferred Stereo Downmix mode */
110 typedef enum AC3PreferredStereoDownmixMode {
111 AC3_DMIXMOD_NOTINDICATED = 0,
115 } AC3PreferredStereoDownmixMode;
117 typedef struct AC3BitAllocParameters {
120 int slow_gain, slow_decay, fast_decay, db_per_bit, floor;
121 int cpl_fast_leak, cpl_slow_leak;
122 } AC3BitAllocParameters;
125 * @struct AC3HeaderInfo
126 * Coded AC-3 header values up to the lfeon element, plus derived values.
128 typedef struct AC3HeaderInfo {
129 /** @name Coded elements
135 uint8_t bitstream_id;
136 uint8_t bitstream_mode;
137 uint8_t channel_mode;
140 int substreamid; ///< substream identification
141 int center_mix_level; ///< Center mix level index
142 int surround_mix_level; ///< Surround mix level index
143 uint16_t channel_map;
144 int num_blocks; ///< number of audio blocks
145 int dolby_surround_mode;
148 /** @name Derived values
152 uint16_t sample_rate;
156 uint64_t channel_layout;
161 EAC3_FRAME_TYPE_INDEPENDENT = 0,
162 EAC3_FRAME_TYPE_DEPENDENT,
163 EAC3_FRAME_TYPE_AC3_CONVERT,
164 EAC3_FRAME_TYPE_RESERVED
167 void ff_ac3_common_init(void);
170 * Calculate the log power-spectral density of the input signal.
171 * This gives a rough estimate of signal power in the frequency domain by using
172 * the spectral envelope (exponents). The psd is also separately grouped
173 * into critical bands for use in the calculating the masking curve.
174 * 128 units in psd = -6 dB. The dbknee parameter in AC3BitAllocParameters
175 * determines the reference level.
177 * @param[in] exp frequency coefficient exponents
178 * @param[in] start starting bin location
179 * @param[in] end ending bin location
180 * @param[out] psd signal power for each frequency bin
181 * @param[out] band_psd signal power for each critical band
183 void ff_ac3_bit_alloc_calc_psd(int8_t *exp, int start, int end, int16_t *psd,
187 * Calculate the masking curve.
188 * First, the excitation is calculated using parameters in s and the signal
189 * power in each critical band. The excitation is compared with a predefined
190 * hearing threshold table to produce the masking curve. If delta bit
191 * allocation information is provided, it is used for adjusting the masking
192 * curve, usually to give a closer match to a better psychoacoustic model.
194 * @param[in] s adjustable bit allocation parameters
195 * @param[in] band_psd signal power for each critical band
196 * @param[in] start starting bin location
197 * @param[in] end ending bin location
198 * @param[in] fast_gain fast gain (estimated signal-to-mask ratio)
199 * @param[in] is_lfe whether or not the channel being processed is the LFE
200 * @param[in] dba_mode delta bit allocation mode (none, reuse, or new)
201 * @param[in] dba_nsegs number of delta segments
202 * @param[in] dba_offsets location offsets for each segment
203 * @param[in] dba_lengths length of each segment
204 * @param[in] dba_values delta bit allocation for each segment
205 * @param[out] mask calculated masking curve
206 * @return returns 0 for success, non-zero for error
208 int ff_ac3_bit_alloc_calc_mask(AC3BitAllocParameters *s, int16_t *band_psd,
209 int start, int end, int fast_gain, int is_lfe,
210 int dba_mode, int dba_nsegs, uint8_t *dba_offsets,
211 uint8_t *dba_lengths, uint8_t *dba_values,
214 #endif /* AVCODEC_AC3_H */