FFmpeg
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 EAC3_MAX_CHANNELS 16 /**< maximum number of channels in EAC3 */
32 #define AC3_MAX_CHANNELS 7 /**< maximum number of channels, including coupling channel */
33 #define CPL_CH 0 /**< coupling channel index */
34 
35 #define AC3_MAX_COEFS 256
36 #define AC3_BLOCK_SIZE 256
37 #define AC3_MAX_BLOCKS 6
38 #define AC3_FRAME_SIZE (AC3_MAX_BLOCKS * 256)
39 #define AC3_WINDOW_SIZE (AC3_BLOCK_SIZE * 2)
40 #define AC3_CRITICAL_BANDS 50
41 #define AC3_MAX_CPL_BANDS 18
42 
43 #include "libavutil/opt.h"
44 #include "avcodec.h"
45 #include "ac3tab.h"
46 
47 /* exponent encoding strategy */
48 #define EXP_REUSE 0
49 #define EXP_NEW 1
50 
51 #define EXP_D15 1
52 #define EXP_D25 2
53 #define EXP_D45 3
54 
55 #ifndef USE_FIXED
56 #define USE_FIXED 0
57 #endif
58 
59 #if USE_FIXED
60 
61 #define FFT_FLOAT 0
62 
63 #define FIXR(a) ((int)((a) * 0 + 0.5))
64 #define FIXR12(a) ((int)((a) * 4096 + 0.5))
65 #define FIXR15(a) ((int)((a) * 32768 + 0.5))
66 #define ROUND15(x) ((x) + 16384) >> 15
67 
68 #define AC3_RENAME(x) x ## _fixed
69 #define AC3_NORM(norm) (1<<24)/(norm)
70 #define AC3_MUL(a,b) ((((int64_t) (a)) * (b))>>12)
71 #define AC3_RANGE(x) ((x)|(((x)&128)<<1))
72 #define AC3_HEAVY_RANGE(x) ((x)<<1)
73 #define AC3_DYNAMIC_RANGE(x) (x)
74 #define AC3_SPX_BLEND(x) (x)
75 #define AC3_DYNAMIC_RANGE1 0
76 
77 typedef int INTFLOAT;
78 typedef int16_t SHORTFLOAT;
79 
80 #else /* USE_FIXED */
81 
82 #define FIXR(x) ((float)(x))
83 #define FIXR12(x) ((float)(x))
84 #define FIXR15(x) ((float)(x))
85 #define ROUND15(x) (x)
86 
87 #define AC3_RENAME(x) x
88 #define AC3_NORM(norm) (1.0f/(norm))
89 #define AC3_MUL(a,b) ((a) * (b))
90 #define AC3_RANGE(x) (dynamic_range_tab[(x)])
91 #define AC3_HEAVY_RANGE(x) (ff_ac3_heavy_dynamic_range_tab[(x)])
92 #define AC3_DYNAMIC_RANGE(x) (powf(x, s->drc_scale))
93 #define AC3_SPX_BLEND(x) (x)* (1.0f/32)
94 #define AC3_DYNAMIC_RANGE1 1.0f
95 
96 typedef float INTFLOAT;
97 typedef float SHORTFLOAT;
98 
99 #endif /* USE_FIXED */
100 
101 #define AC3_LEVEL(x) ROUND15((x) * FIXR15(M_SQRT1_2))
102 
103 /* pre-defined gain values */
104 #define LEVEL_PLUS_3DB M_SQRT2
105 #define LEVEL_PLUS_1POINT5DB 1.1892071150027209
106 #define LEVEL_MINUS_1POINT5DB 0.8408964152537145
107 #define LEVEL_MINUS_3DB M_SQRT1_2
108 #define LEVEL_MINUS_4POINT5DB 0.5946035575013605
109 #define LEVEL_MINUS_6DB 0.5000000000000000
110 #define LEVEL_MINUS_9DB 0.3535533905932738
111 #define LEVEL_ZERO 0.0000000000000000
112 #define LEVEL_ONE 1.0000000000000000
113 
114 /** Delta bit allocation strategy */
115 typedef enum {
121 
122 /** Channel mode (audio coding mode) */
123 typedef enum {
133 
134 /** Dolby Surround mode */
135 typedef enum AC3DolbySurroundMode {
141 
142 /** Dolby Surround EX mode */
149 
150 /** Dolby Headphone mode */
151 typedef enum AC3DolbyHeadphoneMode {
157 
158 /** Preferred Stereo Downmix mode */
163  AC3_DMIXMOD_DPLII // reserved value in A/52, but used by encoders to indicate DPL2
165 
166 typedef struct AC3BitAllocParameters {
167  int sr_code;
168  int sr_shift;
172 
173 /**
174  * @struct AC3HeaderInfo
175  * Coded AC-3 header values up to the lfeon element, plus derived values.
176  */
177 typedef struct AC3HeaderInfo {
178  /** @name Coded elements
179  * @{
180  */
181  uint16_t sync_word;
182  uint16_t crc1;
189  int substreamid; ///< substream identification
190  int center_mix_level; ///< Center mix level index
191  int surround_mix_level; ///< Surround mix level index
192  uint16_t channel_map;
193  int num_blocks; ///< number of audio blocks
195  /** @} */
196 
197  /** @name Derived values
198  * @{
199  */
201  uint16_t sample_rate;
202  uint32_t bit_rate;
204  uint16_t frame_size;
205  uint64_t channel_layout;
206  /** @} */
207 } AC3HeaderInfo;
208 
209 typedef enum {
214 } EAC3FrameType;
215 
216 void ff_ac3_common_init(void);
217 
218 /**
219  * Calculate the log power-spectral density of the input signal.
220  * This gives a rough estimate of signal power in the frequency domain by using
221  * the spectral envelope (exponents). The psd is also separately grouped
222  * into critical bands for use in the calculating the masking curve.
223  * 128 units in psd = -6 dB. The dbknee parameter in AC3BitAllocParameters
224  * determines the reference level.
225  *
226  * @param[in] exp frequency coefficient exponents
227  * @param[in] start starting bin location
228  * @param[in] end ending bin location
229  * @param[out] psd signal power for each frequency bin
230  * @param[out] band_psd signal power for each critical band
231  */
232 void ff_ac3_bit_alloc_calc_psd(int8_t *exp, int start, int end, int16_t *psd,
233  int16_t *band_psd);
234 
235 /**
236  * Calculate the masking curve.
237  * First, the excitation is calculated using parameters in s and the signal
238  * power in each critical band. The excitation is compared with a predefined
239  * hearing threshold table to produce the masking curve. If delta bit
240  * allocation information is provided, it is used for adjusting the masking
241  * curve, usually to give a closer match to a better psychoacoustic model.
242  *
243  * @param[in] s adjustable bit allocation parameters
244  * @param[in] band_psd signal power for each critical band
245  * @param[in] start starting bin location
246  * @param[in] end ending bin location
247  * @param[in] fast_gain fast gain (estimated signal-to-mask ratio)
248  * @param[in] is_lfe whether or not the channel being processed is the LFE
249  * @param[in] dba_mode delta bit allocation mode (none, reuse, or new)
250  * @param[in] dba_nsegs number of delta segments
251  * @param[in] dba_offsets location offsets for each segment
252  * @param[in] dba_lengths length of each segment
253  * @param[in] dba_values delta bit allocation for each segment
254  * @param[out] mask calculated masking curve
255  * @return returns 0 for success, non-zero for error
256  */
257 int ff_ac3_bit_alloc_calc_mask(AC3BitAllocParameters *s, int16_t *band_psd,
258  int start, int end, int fast_gain, int is_lfe,
259  int dba_mode, int dba_nsegs, uint8_t *dba_offsets,
260  uint8_t *dba_lengths, uint8_t *dba_values,
261  int16_t *mask);
262 
263 #endif /* AVCODEC_AC3_H */
uint8_t bitstream_mode
Definition: ac3.h:185
uint64_t channel_layout
Definition: ac3.h:205
AC3ChannelMode
Channel mode (audio coding mode)
Definition: ac3.h:123
uint16_t crc1
Definition: ac3.h:182
AC3DolbySurroundEXMode
Dolby Surround EX mode.
Definition: ac3.h:143
int ff_ac3_bit_alloc_calc_mask(AC3BitAllocParameters *s, int16_t *band_psd, int start, int end, int fast_gain, int is_lfe, int dba_mode, int dba_nsegs, uint8_t *dba_offsets, uint8_t *dba_lengths, uint8_t *dba_values, int16_t *mask)
Calculate the masking curve.
Definition: ac3.c:118
Definition: ac3.h:116
uint8_t
AVOptions.
uint8_t lfe_on
Definition: ac3.h:187
float SHORTFLOAT
Definition: ac3.h:97
static av_cold int end(AVCodecContext *avctx)
Definition: avrndec.c:90
void ff_ac3_common_init(void)
uint8_t sr_shift
Definition: ac3.h:200
uint8_t bitstream_id
Definition: ac3.h:184
uint16_t sync_word
Definition: ac3.h:181
AC3DolbySurroundMode
Dolby Surround mode.
Definition: ac3.h:135
uint8_t frame_type
Definition: ac3.h:188
static const uint16_t mask[17]
Definition: lzw.c:38
uint8_t sr_code
Definition: ac3.h:183
Definition: ac3.h:117
Coded AC-3 header values up to the lfeon element, plus derived values.
Definition: ac3.h:177
uint16_t sample_rate
Definition: ac3.h:201
int8_t exp
Definition: eval.c:72
void ff_ac3_bit_alloc_calc_psd(int8_t *exp, int start, int end, int16_t *psd, int16_t *band_psd)
Calculate the log power-spectral density of the input signal.
Definition: ac3.c:92
AC3PreferredStereoDownmixMode
Preferred Stereo Downmix mode.
Definition: ac3.h:159
uint32_t bit_rate
Definition: ac3.h:202
uint16_t channel_map
Definition: ac3.h:192
#define s(width, name)
Definition: cbs_vp9.c:257
Definition: ac3.h:118
int dolby_surround_mode
Definition: ac3.h:194
Libavcodec external API header.
EAC3FrameType
Definition: ac3.h:209
AC3DolbyHeadphoneMode
Dolby Headphone mode.
Definition: ac3.h:151
uint16_t frame_size
Definition: ac3.h:204
int surround_mix_level
Surround mix level index.
Definition: ac3.h:191
int center_mix_level
Center mix level index.
Definition: ac3.h:190
AC3DeltaStrategy
Delta bit allocation strategy.
Definition: ac3.h:115
int substreamid
substream identification
Definition: ac3.h:189
uint8_t channels
Definition: ac3.h:203
void INT64 start
Definition: avisynth_c.h:766
int num_blocks
number of audio blocks
Definition: ac3.h:193
uint8_t channel_mode
Definition: ac3.h:186
float INTFLOAT
Definition: ac3.h:96