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 */
62 #define FIXR(a) ((int)((a) * 0 + 0.5))
63 #define FIXR12(a) ((int)((a) * 4096 + 0.5))
64 #define FIXR15(a) ((int)((a) * 32768 + 0.5))
65 #define ROUND15(x) ((x) + 16384) >> 15
67 #define AC3_RENAME(x) x ## _fixed
68 #define AC3_NORM(norm) (1<<24)/(norm)
69 #define AC3_MUL(a,b) ((((int64_t) (a)) * (b))>>12)
70 #define AC3_RANGE(x) (x)
71 #define AC3_DYNAMIC_RANGE(x) (x)
72 #define AC3_SPX_BLEND(x) (x)
73 #define AC3_DYNAMIC_RANGE1 0
76 #define SHORTFLOAT int16_t
80 #define FIXR(x) ((float)(x))
81 #define FIXR12(x) ((float)(x))
82 #define FIXR15(x) ((float)(x))
83 #define ROUND15(x) (x)
85 #define AC3_RENAME(x) x
86 #define AC3_NORM(norm) (1.0f/(norm))
87 #define AC3_MUL(a,b) ((a) * (b))
88 #define AC3_RANGE(x) (dynamic_range_tab[(x)])
89 #define AC3_DYNAMIC_RANGE(x) (powf(x, s->drc_scale))
90 #define AC3_SPX_BLEND(x) (x)* (1.0f/32)
91 #define AC3_DYNAMIC_RANGE1 1.0f
93 #define INTFLOAT float
94 #define SHORTFLOAT float
96 #endif /* USE_FIXED */
98 #define AC3_LEVEL(x) ROUND15((x) * FIXR15(0.7071067811865476))
100 /* pre-defined gain values */
101 #define LEVEL_PLUS_3DB 1.4142135623730950
102 #define LEVEL_PLUS_1POINT5DB 1.1892071150027209
103 #define LEVEL_MINUS_1POINT5DB 0.8408964152537145
104 #define LEVEL_MINUS_3DB 0.7071067811865476
105 #define LEVEL_MINUS_4POINT5DB 0.5946035575013605
106 #define LEVEL_MINUS_6DB 0.5000000000000000
107 #define LEVEL_MINUS_9DB 0.3535533905932738
108 #define LEVEL_ZERO 0.0000000000000000
109 #define LEVEL_ONE 1.0000000000000000
111 /** Delta bit allocation strategy */
119 /** Channel mode (audio coding mode) */
121 AC3_CHMODE_DUALMONO = 0,
131 /** Dolby Surround mode */
132 typedef enum AC3DolbySurroundMode {
133 AC3_DSURMOD_NOTINDICATED = 0,
137 } AC3DolbySurroundMode;
139 /** Dolby Surround EX mode */
140 typedef enum AC3DolbySurroundEXMode {
141 AC3_DSUREXMOD_NOTINDICATED = 0,
145 } AC3DolbySurroundEXMode;
147 /** Dolby Headphone mode */
148 typedef enum AC3DolbyHeadphoneMode {
149 AC3_DHEADPHONMOD_NOTINDICATED = 0,
150 AC3_DHEADPHONMOD_OFF,
152 AC3_DHEADPHONMOD_RESERVED
153 } AC3DolbyHeadphoneMode;
155 /** Preferred Stereo Downmix mode */
156 typedef enum AC3PreferredStereoDownmixMode {
157 AC3_DMIXMOD_NOTINDICATED = 0,
160 AC3_DMIXMOD_DPLII // reserved value in A/52, but used by encoders to indicate DPL2
161 } AC3PreferredStereoDownmixMode;
163 typedef struct AC3BitAllocParameters {
166 int slow_gain, slow_decay, fast_decay, db_per_bit, floor;
167 int cpl_fast_leak, cpl_slow_leak;
168 } AC3BitAllocParameters;
171 * @struct AC3HeaderInfo
172 * Coded AC-3 header values up to the lfeon element, plus derived values.
174 typedef struct AC3HeaderInfo {
175 /** @name Coded elements
181 uint8_t bitstream_id;
182 uint8_t bitstream_mode;
183 uint8_t channel_mode;
186 int substreamid; ///< substream identification
187 int center_mix_level; ///< Center mix level index
188 int surround_mix_level; ///< Surround mix level index
189 uint16_t channel_map;
190 int num_blocks; ///< number of audio blocks
191 #if AV_HAVE_INCOMPATIBLE_LIBAV_ABI
192 int dolby_surround_mode;
196 /** @name Derived values
200 uint16_t sample_rate;
204 uint64_t channel_layout;
206 #if !AV_HAVE_INCOMPATIBLE_LIBAV_ABI
207 int dolby_surround_mode;
212 EAC3_FRAME_TYPE_INDEPENDENT = 0,
213 EAC3_FRAME_TYPE_DEPENDENT,
214 EAC3_FRAME_TYPE_AC3_CONVERT,
215 EAC3_FRAME_TYPE_RESERVED
218 void ff_ac3_common_init(void);
221 * Calculate the log power-spectral density of the input signal.
222 * This gives a rough estimate of signal power in the frequency domain by using
223 * the spectral envelope (exponents). The psd is also separately grouped
224 * into critical bands for use in the calculating the masking curve.
225 * 128 units in psd = -6 dB. The dbknee parameter in AC3BitAllocParameters
226 * determines the reference level.
228 * @param[in] exp frequency coefficient exponents
229 * @param[in] start starting bin location
230 * @param[in] end ending bin location
231 * @param[out] psd signal power for each frequency bin
232 * @param[out] band_psd signal power for each critical band
234 void ff_ac3_bit_alloc_calc_psd(int8_t *exp, int start, int end, int16_t *psd,
238 * Calculate the masking curve.
239 * First, the excitation is calculated using parameters in s and the signal
240 * power in each critical band. The excitation is compared with a predefined
241 * hearing threshold table to produce the masking curve. If delta bit
242 * allocation information is provided, it is used for adjusting the masking
243 * curve, usually to give a closer match to a better psychoacoustic model.
245 * @param[in] s adjustable bit allocation parameters
246 * @param[in] band_psd signal power for each critical band
247 * @param[in] start starting bin location
248 * @param[in] end ending bin location
249 * @param[in] fast_gain fast gain (estimated signal-to-mask ratio)
250 * @param[in] is_lfe whether or not the channel being processed is the LFE
251 * @param[in] dba_mode delta bit allocation mode (none, reuse, or new)
252 * @param[in] dba_nsegs number of delta segments
253 * @param[in] dba_offsets location offsets for each segment
254 * @param[in] dba_lengths length of each segment
255 * @param[in] dba_values delta bit allocation for each segment
256 * @param[out] mask calculated masking curve
257 * @return returns 0 for success, non-zero for error
259 int ff_ac3_bit_alloc_calc_mask(AC3BitAllocParameters *s, int16_t *band_psd,
260 int start, int end, int fast_gain, int is_lfe,
261 int dba_mode, int dba_nsegs, uint8_t *dba_offsets,
262 uint8_t *dba_lengths, uint8_t *dba_values,
265 #endif /* AVCODEC_AC3_H */