2 * Common code between the AC-3 encoder and decoder
3 * Copyright (c) 2000, 2001, 2002 Fabrice Bellard
5 * This file is part of Libav.
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.
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.
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
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
44 /* exponent encoding strategy */
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
63 /** Delta bit allocation strategy */
71 /** Channel mode (audio coding mode) */
73 AC3_CHMODE_DUALMONO = 0,
83 /** Dolby Surround mode */
84 typedef enum AC3DolbySurroundMode {
85 AC3_DSURMOD_NOTINDICATED = 0,
89 } AC3DolbySurroundMode;
91 /** Dolby Surround EX mode */
92 typedef enum AC3DolbySurroundEXMode {
93 AC3_DSUREXMOD_NOTINDICATED = 0,
97 } AC3DolbySurroundEXMode;
99 /** Dolby Headphone mode */
100 typedef enum AC3DolbyHeadphoneMode {
101 AC3_DHEADPHONMOD_NOTINDICATED = 0,
102 AC3_DHEADPHONMOD_OFF,
104 AC3_DHEADPHONMOD_RESERVED
105 } AC3DolbyHeadphoneMode;
107 typedef struct AC3BitAllocParameters {
110 int slow_gain, slow_decay, fast_decay, db_per_bit, floor;
111 int cpl_fast_leak, cpl_slow_leak;
112 } AC3BitAllocParameters;
115 * @struct AC3HeaderInfo
116 * Coded AC-3 header values up to the lfeon element, plus derived values.
118 typedef struct AC3HeaderInfo {
119 /** @name Coded elements
125 uint8_t bitstream_id;
126 uint8_t bitstream_mode;
127 uint8_t channel_mode;
130 int substreamid; ///< substream identification
131 int center_mix_level; ///< Center mix level index
132 int surround_mix_level; ///< Surround mix level index
133 uint16_t channel_map;
134 int num_blocks; ///< number of audio blocks
135 int dolby_surround_mode;
138 /** @name Derived values
142 uint16_t sample_rate;
146 uint64_t channel_layout;
151 EAC3_FRAME_TYPE_INDEPENDENT = 0,
152 EAC3_FRAME_TYPE_DEPENDENT,
153 EAC3_FRAME_TYPE_AC3_CONVERT,
154 EAC3_FRAME_TYPE_RESERVED
157 void ff_ac3_common_init(void);
160 * Calculate the log power-spectral density of the input signal.
161 * This gives a rough estimate of signal power in the frequency domain by using
162 * the spectral envelope (exponents). The psd is also separately grouped
163 * into critical bands for use in the calculating the masking curve.
164 * 128 units in psd = -6 dB. The dbknee parameter in AC3BitAllocParameters
165 * determines the reference level.
167 * @param[in] exp frequency coefficient exponents
168 * @param[in] start starting bin location
169 * @param[in] end ending bin location
170 * @param[out] psd signal power for each frequency bin
171 * @param[out] band_psd signal power for each critical band
173 void ff_ac3_bit_alloc_calc_psd(int8_t *exp, int start, int end, int16_t *psd,
177 * Calculate the masking curve.
178 * First, the excitation is calculated using parameters in s and the signal
179 * power in each critical band. The excitation is compared with a predefined
180 * hearing threshold table to produce the masking curve. If delta bit
181 * allocation information is provided, it is used for adjusting the masking
182 * curve, usually to give a closer match to a better psychoacoustic model.
184 * @param[in] s adjustable bit allocation parameters
185 * @param[in] band_psd signal power for each critical band
186 * @param[in] start starting bin location
187 * @param[in] end ending bin location
188 * @param[in] fast_gain fast gain (estimated signal-to-mask ratio)
189 * @param[in] is_lfe whether or not the channel being processed is the LFE
190 * @param[in] dba_mode delta bit allocation mode (none, reuse, or new)
191 * @param[in] dba_nsegs number of delta segments
192 * @param[in] dba_offsets location offsets for each segment
193 * @param[in] dba_lengths length of each segment
194 * @param[in] dba_values delta bit allocation for each segment
195 * @param[out] mask calculated masking curve
196 * @return returns 0 for success, non-zero for error
198 int ff_ac3_bit_alloc_calc_mask(AC3BitAllocParameters *s, int16_t *band_psd,
199 int start, int end, int fast_gain, int is_lfe,
200 int dba_mode, int dba_nsegs, uint8_t *dba_offsets,
201 uint8_t *dba_lengths, uint8_t *dba_values,
204 #endif /* AVCODEC_AC3_H */