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
46
47 /* exponent encoding strategy */
50
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
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
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 */
121
122 /** Channel mode (audio coding mode) */
133
134 /** Dolby Surround mode */
141
142 /** Dolby Surround EX mode */
149
150 /** Dolby Headphone mode */
157
158 /** Preferred Stereo Downmix mode */
165
172
173 /**
174 * @struct AC3HeaderInfo
175 * Coded AC-3 header values up to the lfeon element, plus derived values.
176 */
178 /** @name Coded elements
179 * @{
180 */
195 /** @} */
196
197 /** @name Derived values
198 * @{
199 */
206 /** @} */
208
215
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 */
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 */
258 int start,
int end,
int fast_gain,
int is_lfe,
259 int dba_mode,
int dba_nsegs,
uint8_t *dba_offsets,
262
263 #endif /* AVCODEC_AC3_H */
AC3ChannelMode
Channel mode (audio coding mode)
AC3DolbySurroundEXMode
Dolby Surround EX mode.
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.
static av_cold int end(AVCodecContext *avctx)
void ff_ac3_common_init(void)
AC3DolbySurroundMode
Dolby Surround mode.
static const uint16_t mask[17]
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.
AC3PreferredStereoDownmixMode
Preferred Stereo Downmix mode.
Libavcodec external API header.
AC3DolbyHeadphoneMode
Dolby Headphone mode.
AC3DeltaStrategy
Delta bit allocation strategy.