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 #include <math.h>
31 #include <stdint.h>
32 
33 #include "ac3tab.h"
34 
35 #ifndef USE_FIXED
36 #define USE_FIXED 0
37 #endif
38 
39 #if USE_FIXED
40 
41 #define FIXR(a) ((int)((a) * 0 + 0.5))
42 #define FIXR12(a) ((int)((a) * 4096 + 0.5))
43 #define FIXR15(a) ((int)((a) * 32768 + 0.5))
44 #define ROUND15(x) ((x) + 16384) >> 15
45 
46 #define AC3_RENAME(x) x ## _fixed
47 #define AC3_NORM(norm) (1<<24)/(norm)
48 #define AC3_MUL(a,b) ((((int64_t) (a)) * (b))>>12)
49 #define AC3_RANGE(x) ((x)|(((x)&128)<<1))
50 #define AC3_HEAVY_RANGE(x) ((x)<<1)
51 #define AC3_DYNAMIC_RANGE(x) (x)
52 #define AC3_SPX_BLEND(x) (x)
53 #define AC3_DYNAMIC_RANGE1 0
54 
55 typedef int INTFLOAT;
56 typedef int16_t SHORTFLOAT;
57 
58 #else /* USE_FIXED */
59 #include "libavutil/libm.h"
60 
61 #define FIXR(x) ((float)(x))
62 #define FIXR12(x) ((float)(x))
63 #define FIXR15(x) ((float)(x))
64 #define ROUND15(x) (x)
65 
66 #define AC3_RENAME(x) x
67 #define AC3_NORM(norm) (1.0f/(norm))
68 #define AC3_MUL(a,b) ((a) * (b))
69 #define AC3_RANGE(x) (dynamic_range_tab[(x)])
70 #define AC3_HEAVY_RANGE(x) (ff_ac3_heavy_dynamic_range_tab[(x)])
71 #define AC3_DYNAMIC_RANGE(x) (powf(x, s->drc_scale))
72 #define AC3_SPX_BLEND(x) (x)* (1.0f/32)
73 #define AC3_DYNAMIC_RANGE1 1.0f
74 
75 typedef float INTFLOAT;
76 typedef float SHORTFLOAT;
77 
78 #endif /* USE_FIXED */
79 
80 #define AC3_LEVEL(x) ROUND15((x) * FIXR15(M_SQRT1_2))
81 
82 /* pre-defined gain values */
83 #define LEVEL_PLUS_3DB M_SQRT2
84 #define LEVEL_PLUS_1POINT5DB 1.1892071150027209
85 #define LEVEL_MINUS_1POINT5DB 0.8408964152537145
86 #define LEVEL_MINUS_3DB M_SQRT1_2
87 #define LEVEL_MINUS_4POINT5DB 0.5946035575013605
88 #define LEVEL_MINUS_6DB 0.5000000000000000
89 #define LEVEL_MINUS_9DB 0.3535533905932738
90 #define LEVEL_ZERO 0.0000000000000000
91 #define LEVEL_ONE 1.0000000000000000
92 
93 typedef struct AC3BitAllocParameters {
94  int sr_code;
95  int sr_shift;
99 
100 /**
101  * Calculate the log power-spectral density of the input signal.
102  * This gives a rough estimate of signal power in the frequency domain by using
103  * the spectral envelope (exponents). The psd is also separately grouped
104  * into critical bands for use in the calculating the masking curve.
105  * 128 units in psd = -6 dB. The dbknee parameter in AC3BitAllocParameters
106  * determines the reference level.
107  *
108  * @param[in] exp frequency coefficient exponents
109  * @param[in] start starting bin location
110  * @param[in] end ending bin location
111  * @param[out] psd signal power for each frequency bin
112  * @param[out] band_psd signal power for each critical band
113  */
114 void ff_ac3_bit_alloc_calc_psd(int8_t *exp, int start, int end, int16_t *psd,
115  int16_t *band_psd);
116 
117 /**
118  * Calculate the masking curve.
119  * First, the excitation is calculated using parameters in s and the signal
120  * power in each critical band. The excitation is compared with a predefined
121  * hearing threshold table to produce the masking curve. If delta bit
122  * allocation information is provided, it is used for adjusting the masking
123  * curve, usually to give a closer match to a better psychoacoustic model.
124  *
125  * @param[in] s adjustable bit allocation parameters
126  * @param[in] band_psd signal power for each critical band
127  * @param[in] start starting bin location
128  * @param[in] end ending bin location
129  * @param[in] fast_gain fast gain (estimated signal-to-mask ratio)
130  * @param[in] is_lfe whether or not the channel being processed is the LFE
131  * @param[in] dba_mode delta bit allocation mode (none, reuse, or new)
132  * @param[in] dba_nsegs number of delta segments
133  * @param[in] dba_offsets location offsets for each segment
134  * @param[in] dba_lengths length of each segment
135  * @param[in] dba_values delta bit allocation for each segment
136  * @param[out] mask calculated masking curve
137  * @return returns 0 for success, non-zero for error
138  */
139 int ff_ac3_bit_alloc_calc_mask(AC3BitAllocParameters *s, int16_t *band_psd,
140  int start, int end, int fast_gain, int is_lfe,
141  int dba_mode, int dba_nsegs, uint8_t *dba_offsets,
142  uint8_t *dba_lengths, uint8_t *dba_values,
143  int16_t *mask);
144 
145 #endif /* AVCODEC_AC3_H */
libm.h
AC3BitAllocParameters::slow_decay
int slow_decay
Definition: ac3.h:96
SHORTFLOAT
float SHORTFLOAT
Definition: ac3.h:76
INTFLOAT
float INTFLOAT
Definition: ac3.h:75
AC3BitAllocParameters::cpl_slow_leak
int cpl_slow_leak
Definition: ac3.h:97
ff_ac3_bit_alloc_calc_mask
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:201
mask
static const uint16_t mask[17]
Definition: lzw.c:38
s
#define s(width, name)
Definition: cbs_vp9.c:256
AC3BitAllocParameters::slow_gain
int slow_gain
Definition: ac3.h:96
AC3BitAllocParameters::floor
int floor
Definition: ac3.h:96
AC3BitAllocParameters::fast_decay
int fast_decay
Definition: ac3.h:96
AC3BitAllocParameters::db_per_bit
int db_per_bit
Definition: ac3.h:96
exp
int8_t exp
Definition: eval.c:72
AC3BitAllocParameters::cpl_fast_leak
int cpl_fast_leak
Definition: ac3.h:97
AC3BitAllocParameters::sr_code
int sr_code
Definition: ac3.h:94
ff_ac3_bit_alloc_calc_psd
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:175
AC3BitAllocParameters
Definition: ac3.h:93
AC3BitAllocParameters::sr_shift
int sr_shift
Definition: ac3.h:95
ac3tab.h