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ac3.h
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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 #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 "libavutil/opt.h"
43 #include "avcodec.h"
44 #include "ac3tab.h"
45 
46 /* exponent encoding strategy */
47 #define EXP_REUSE 0
48 #define EXP_NEW 1
49 
50 #define EXP_D15 1
51 #define EXP_D25 2
52 #define EXP_D45 3
53 
54 #ifndef USE_FIXED
55 #define USE_FIXED 0
56 #endif
57 
58 #if USE_FIXED
59 
60 #define FFT_FLOAT 0
61 
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
66 
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)|(((x)&128)<<1))
71 #define AC3_HEAVY_RANGE(x) ((x)<<1)
72 #define AC3_DYNAMIC_RANGE(x) (x)
73 #define AC3_SPX_BLEND(x) (x)
74 #define AC3_DYNAMIC_RANGE1 0
75 
76 #define INTFLOAT int
77 #define SHORTFLOAT int16_t
78 
79 #else /* USE_FIXED */
80 
81 #define FIXR(x) ((float)(x))
82 #define FIXR12(x) ((float)(x))
83 #define FIXR15(x) ((float)(x))
84 #define ROUND15(x) (x)
85 
86 #define AC3_RENAME(x) x
87 #define AC3_NORM(norm) (1.0f/(norm))
88 #define AC3_MUL(a,b) ((a) * (b))
89 #define AC3_RANGE(x) (dynamic_range_tab[(x)])
90 #define AC3_HEAVY_RANGE(x) (heavy_dynamic_range_tab[(x)])
91 #define AC3_DYNAMIC_RANGE(x) (powf(x, s->drc_scale))
92 #define AC3_SPX_BLEND(x) (x)* (1.0f/32)
93 #define AC3_DYNAMIC_RANGE1 1.0f
94 
95 #define INTFLOAT float
96 #define SHORTFLOAT float
97 
98 #endif /* USE_FIXED */
99 
100 #define AC3_LEVEL(x) ROUND15((x) * FIXR15(0.7071067811865476))
101 
102 /* pre-defined gain values */
103 #define LEVEL_PLUS_3DB 1.4142135623730950
104 #define LEVEL_PLUS_1POINT5DB 1.1892071150027209
105 #define LEVEL_MINUS_1POINT5DB 0.8408964152537145
106 #define LEVEL_MINUS_3DB 0.7071067811865476
107 #define LEVEL_MINUS_4POINT5DB 0.5946035575013605
108 #define LEVEL_MINUS_6DB 0.5000000000000000
109 #define LEVEL_MINUS_9DB 0.3535533905932738
110 #define LEVEL_ZERO 0.0000000000000000
111 #define LEVEL_ONE 1.0000000000000000
112 
113 /** Delta bit allocation strategy */
114 typedef enum {
115  DBA_REUSE = 0,
116  DBA_NEW,
117  DBA_NONE,
118  DBA_RESERVED
119 } AC3DeltaStrategy;
120 
121 /** Channel mode (audio coding mode) */
122 typedef enum {
123  AC3_CHMODE_DUALMONO = 0,
124  AC3_CHMODE_MONO,
125  AC3_CHMODE_STEREO,
126  AC3_CHMODE_3F,
127  AC3_CHMODE_2F1R,
128  AC3_CHMODE_3F1R,
129  AC3_CHMODE_2F2R,
130  AC3_CHMODE_3F2R
131 } AC3ChannelMode;
132 
133 /** Dolby Surround mode */
134 typedef enum AC3DolbySurroundMode {
135  AC3_DSURMOD_NOTINDICATED = 0,
136  AC3_DSURMOD_OFF,
137  AC3_DSURMOD_ON,
138  AC3_DSURMOD_RESERVED
139 } AC3DolbySurroundMode;
140 
141 /** Dolby Surround EX mode */
142 typedef enum AC3DolbySurroundEXMode {
143  AC3_DSUREXMOD_NOTINDICATED = 0,
144  AC3_DSUREXMOD_OFF,
145  AC3_DSUREXMOD_ON,
146  AC3_DSUREXMOD_PLIIZ
147 } AC3DolbySurroundEXMode;
148 
149 /** Dolby Headphone mode */
150 typedef enum AC3DolbyHeadphoneMode {
151  AC3_DHEADPHONMOD_NOTINDICATED = 0,
152  AC3_DHEADPHONMOD_OFF,
153  AC3_DHEADPHONMOD_ON,
154  AC3_DHEADPHONMOD_RESERVED
155 } AC3DolbyHeadphoneMode;
156 
157 /** Preferred Stereo Downmix mode */
158 typedef enum AC3PreferredStereoDownmixMode {
159  AC3_DMIXMOD_NOTINDICATED = 0,
160  AC3_DMIXMOD_LTRT,
161  AC3_DMIXMOD_LORO,
162  AC3_DMIXMOD_DPLII // reserved value in A/52, but used by encoders to indicate DPL2
163 } AC3PreferredStereoDownmixMode;
164 
165 typedef struct AC3BitAllocParameters {
166  int sr_code;
167  int sr_shift;
168  int slow_gain, slow_decay, fast_decay, db_per_bit, floor;
169  int cpl_fast_leak, cpl_slow_leak;
170 } AC3BitAllocParameters;
171 
172 /**
173  * @struct AC3HeaderInfo
174  * Coded AC-3 header values up to the lfeon element, plus derived values.
175  */
176 typedef struct AC3HeaderInfo {
177  /** @name Coded elements
178  * @{
179  */
180  uint16_t sync_word;
181  uint16_t crc1;
182  uint8_t sr_code;
183  uint8_t bitstream_id;
184  uint8_t bitstream_mode;
185  uint8_t channel_mode;
186  uint8_t lfe_on;
187  uint8_t frame_type;
188  int substreamid; ///< substream identification
189  int center_mix_level; ///< Center mix level index
190  int surround_mix_level; ///< Surround mix level index
191  uint16_t channel_map;
192  int num_blocks; ///< number of audio blocks
193 #if AV_HAVE_INCOMPATIBLE_LIBAV_ABI
194  int dolby_surround_mode;
195 #endif
196  /** @} */
197 
198  /** @name Derived values
199  * @{
200  */
201  uint8_t sr_shift;
202  uint16_t sample_rate;
203  uint32_t bit_rate;
204  uint8_t channels;
205  uint16_t frame_size;
206  uint64_t channel_layout;
207  /** @} */
208 #if !AV_HAVE_INCOMPATIBLE_LIBAV_ABI
209  int dolby_surround_mode;
210 #endif
211 } AC3HeaderInfo;
212 
213 typedef enum {
214  EAC3_FRAME_TYPE_INDEPENDENT = 0,
215  EAC3_FRAME_TYPE_DEPENDENT,
216  EAC3_FRAME_TYPE_AC3_CONVERT,
217  EAC3_FRAME_TYPE_RESERVED
218 } EAC3FrameType;
219 
220 void ff_ac3_common_init(void);
221 
222 /**
223  * Calculate the log power-spectral density of the input signal.
224  * This gives a rough estimate of signal power in the frequency domain by using
225  * the spectral envelope (exponents). The psd is also separately grouped
226  * into critical bands for use in the calculating the masking curve.
227  * 128 units in psd = -6 dB. The dbknee parameter in AC3BitAllocParameters
228  * determines the reference level.
229  *
230  * @param[in] exp frequency coefficient exponents
231  * @param[in] start starting bin location
232  * @param[in] end ending bin location
233  * @param[out] psd signal power for each frequency bin
234  * @param[out] band_psd signal power for each critical band
235  */
236 void ff_ac3_bit_alloc_calc_psd(int8_t *exp, int start, int end, int16_t *psd,
237  int16_t *band_psd);
238 
239 /**
240  * Calculate the masking curve.
241  * First, the excitation is calculated using parameters in s and the signal
242  * power in each critical band. The excitation is compared with a predefined
243  * hearing threshold table to produce the masking curve. If delta bit
244  * allocation information is provided, it is used for adjusting the masking
245  * curve, usually to give a closer match to a better psychoacoustic model.
246  *
247  * @param[in] s adjustable bit allocation parameters
248  * @param[in] band_psd signal power for each critical band
249  * @param[in] start starting bin location
250  * @param[in] end ending bin location
251  * @param[in] fast_gain fast gain (estimated signal-to-mask ratio)
252  * @param[in] is_lfe whether or not the channel being processed is the LFE
253  * @param[in] dba_mode delta bit allocation mode (none, reuse, or new)
254  * @param[in] dba_nsegs number of delta segments
255  * @param[in] dba_offsets location offsets for each segment
256  * @param[in] dba_lengths length of each segment
257  * @param[in] dba_values delta bit allocation for each segment
258  * @param[out] mask calculated masking curve
259  * @return returns 0 for success, non-zero for error
260  */
261 int ff_ac3_bit_alloc_calc_mask(AC3BitAllocParameters *s, int16_t *band_psd,
262  int start, int end, int fast_gain, int is_lfe,
263  int dba_mode, int dba_nsegs, uint8_t *dba_offsets,
264  uint8_t *dba_lengths, uint8_t *dba_values,
265  int16_t *mask);
266 
267 #endif /* AVCODEC_AC3_H */
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