FFmpeg  2.1.1
ac3dec.h
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1 /*
2  * Common code between the AC-3 and E-AC-3 decoders
3  * Copyright (c) 2007 Bartlomiej Wolowiec <bartek.wolowiec@gmail.com>
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 and E-AC-3 decoders.
25  *
26  * Summary of MDCT Coefficient Grouping:
27  * The individual MDCT coefficient indices are often referred to in the
28  * (E-)AC-3 specification as frequency bins. These bins are grouped together
29  * into subbands of 12 coefficients each. The subbands are grouped together
30  * into bands as defined in the bitstream by the band structures, which
31  * determine the number of bands and the size of each band. The full spectrum
32  * of 256 frequency bins is divided into 1 DC bin + 21 subbands = 253 bins.
33  * This system of grouping coefficients is used for channel bandwidth, stereo
34  * rematrixing, channel coupling, enhanced coupling, and spectral extension.
35  *
36  * +-+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+-+
37  * |1| |12| | [12|12|12|12] | | | | | | | | | | | | |3|
38  * +-+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+-+
39  * ~~~ ~~~~ ~~~~~~~~~~~~~ ~~~
40  * | | | |
41  * | | | 3 unused frequency bins--+
42  * | | |
43  * | | +--1 band containing 4 subbands
44  * | |
45  * | +--1 subband of 12 frequency bins
46  * |
47  * +--DC frequency bin
48  */
49 
50 #ifndef AVCODEC_AC3DEC_H
51 #define AVCODEC_AC3DEC_H
52 
53 #include "libavutil/float_dsp.h"
54 #include "libavutil/lfg.h"
55 #include "ac3.h"
56 #include "ac3dsp.h"
57 #include "get_bits.h"
58 #include "dsputil.h"
59 #include "fft.h"
60 #include "fmtconvert.h"
61 
62 #define AC3_OUTPUT_LFEON 8
63 
64 #define SPX_MAX_BANDS 17
65 
66 /** Large enough for maximum possible frame size when the specification limit is ignored */
67 #define AC3_FRAME_BUFFER_SIZE 32768
68 
69 typedef struct AC3DecodeContext {
70  AVClass *class; ///< class for AVOptions
71  AVCodecContext *avctx; ///< parent context
72  GetBitContext gbc; ///< bitstream reader
73 
74 ///@name Bit stream information
75 ///@{
76  int frame_type; ///< frame type (strmtyp)
77  int substreamid; ///< substream identification
78  int frame_size; ///< current frame size, in bytes
79  int bit_rate; ///< stream bit rate, in bits-per-second
80  int sample_rate; ///< sample frequency, in Hz
81  int num_blocks; ///< number of audio blocks
82  int bitstream_mode; ///< bitstream mode (bsmod)
83  int channel_mode; ///< channel mode (acmod)
84  int channel_layout; ///< channel layout
85  int lfe_on; ///< lfe channel in use
86  int channel_map; ///< custom channel map
87  int center_mix_level; ///< Center mix level index
88  int surround_mix_level; ///< Surround mix level index
89  int eac3; ///< indicates if current frame is E-AC-3
90 ///@}
91 
97 
98 ///@name Frame syntax parameters
99  int snr_offset_strategy; ///< SNR offset strategy (snroffststr)
100  int block_switch_syntax; ///< block switch syntax enabled (blkswe)
101  int dither_flag_syntax; ///< dither flag syntax enabled (dithflage)
102  int bit_allocation_syntax; ///< bit allocation model syntax enabled (bamode)
103  int fast_gain_syntax; ///< fast gain codes enabled (frmfgaincode)
104  int dba_syntax; ///< delta bit allocation syntax enabled (dbaflde)
105  int skip_syntax; ///< skip field syntax enabled (skipflde)
106  ///@}
107 
108 ///@name Standard coupling
109  int cpl_in_use[AC3_MAX_BLOCKS]; ///< coupling in use (cplinu)
110  int cpl_strategy_exists[AC3_MAX_BLOCKS];///< coupling strategy exists (cplstre)
111  int channel_in_cpl[AC3_MAX_CHANNELS]; ///< channel in coupling (chincpl)
112  int phase_flags_in_use; ///< phase flags in use (phsflginu)
113  int phase_flags[AC3_MAX_CPL_BANDS]; ///< phase flags (phsflg)
114  int num_cpl_bands; ///< number of coupling bands (ncplbnd)
115  uint8_t cpl_band_sizes[AC3_MAX_CPL_BANDS]; ///< number of coeffs in each coupling band
116  int firstchincpl; ///< first channel in coupling
117  int first_cpl_coords[AC3_MAX_CHANNELS]; ///< first coupling coordinates states (firstcplcos)
118  int cpl_coords[AC3_MAX_CHANNELS][AC3_MAX_CPL_BANDS]; ///< coupling coordinates (cplco)
119 ///@}
120 
121 ///@name Spectral extension
122 ///@{
123  int spx_in_use; ///< spectral extension in use (spxinu)
124  uint8_t channel_uses_spx[AC3_MAX_CHANNELS]; ///< channel uses spectral extension (chinspx)
125  int8_t spx_atten_code[AC3_MAX_CHANNELS]; ///< spx attenuation code (spxattencod)
126  int spx_src_start_freq; ///< spx start frequency bin
127  int spx_dst_end_freq; ///< spx end frequency bin
128  int spx_dst_start_freq; ///< spx starting frequency bin for copying (copystartmant)
129  ///< the copy region ends at the start of the spx region.
130  int num_spx_bands; ///< number of spx bands (nspxbnds)
131  uint8_t spx_band_sizes[SPX_MAX_BANDS]; ///< number of bins in each spx band
132  uint8_t first_spx_coords[AC3_MAX_CHANNELS]; ///< first spx coordinates states (firstspxcos)
133  float spx_noise_blend[AC3_MAX_CHANNELS][SPX_MAX_BANDS]; ///< spx noise blending factor (nblendfact)
134  float spx_signal_blend[AC3_MAX_CHANNELS][SPX_MAX_BANDS];///< spx signal blending factor (sblendfact)
135 ///@}
136 
137 ///@name Adaptive hybrid transform
138  int channel_uses_aht[AC3_MAX_CHANNELS]; ///< channel AHT in use (chahtinu)
140 ///@}
141 
142 ///@name Channel
143  int fbw_channels; ///< number of full-bandwidth channels
144  int channels; ///< number of total channels
145  int lfe_ch; ///< index of LFE channel
146  float downmix_coeffs[AC3_MAX_CHANNELS][2]; ///< stereo downmix coefficients
147  int downmixed; ///< indicates if coeffs are currently downmixed
148  int output_mode; ///< output channel configuration
149  int out_channels; ///< number of output channels
150 ///@}
151 
152 ///@name Dynamic range
153  float dynamic_range[2]; ///< dynamic range
154  float drc_scale; ///< percentage of dynamic range compression to be applied
155 ///@}
156 
157 ///@name Bandwidth
158  int start_freq[AC3_MAX_CHANNELS]; ///< start frequency bin (strtmant)
159  int end_freq[AC3_MAX_CHANNELS]; ///< end frequency bin (endmant)
160 ///@}
161 
162 ///@name Rematrixing
163  int num_rematrixing_bands; ///< number of rematrixing bands (nrematbnd)
164  int rematrixing_flags[4]; ///< rematrixing flags (rematflg)
165 ///@}
166 
167 ///@name Exponents
168  int num_exp_groups[AC3_MAX_CHANNELS]; ///< Number of exponent groups (nexpgrp)
169  int8_t dexps[AC3_MAX_CHANNELS][AC3_MAX_COEFS]; ///< decoded exponents
170  int exp_strategy[AC3_MAX_BLOCKS][AC3_MAX_CHANNELS]; ///< exponent strategies (expstr)
171 ///@}
172 
173 ///@name Bit allocation
174  AC3BitAllocParameters bit_alloc_params; ///< bit allocation parameters
175  int first_cpl_leak; ///< first coupling leak state (firstcplleak)
176  int snr_offset[AC3_MAX_CHANNELS]; ///< signal-to-noise ratio offsets (snroffst)
177  int fast_gain[AC3_MAX_CHANNELS]; ///< fast gain values/SMR's (fgain)
178  uint8_t bap[AC3_MAX_CHANNELS][AC3_MAX_COEFS]; ///< bit allocation pointers
179  int16_t psd[AC3_MAX_CHANNELS][AC3_MAX_COEFS]; ///< scaled exponents
180  int16_t band_psd[AC3_MAX_CHANNELS][AC3_CRITICAL_BANDS]; ///< interpolated exponents
181  int16_t mask[AC3_MAX_CHANNELS][AC3_CRITICAL_BANDS]; ///< masking curve values
182  int dba_mode[AC3_MAX_CHANNELS]; ///< delta bit allocation mode
183  int dba_nsegs[AC3_MAX_CHANNELS]; ///< number of delta segments
184  uint8_t dba_offsets[AC3_MAX_CHANNELS][8]; ///< delta segment offsets
185  uint8_t dba_lengths[AC3_MAX_CHANNELS][8]; ///< delta segment lengths
186  uint8_t dba_values[AC3_MAX_CHANNELS][8]; ///< delta values for each segment
187 ///@}
188 
189 ///@name Zero-mantissa dithering
190  int dither_flag[AC3_MAX_CHANNELS]; ///< dither flags (dithflg)
191  AVLFG dith_state; ///< for dither generation
192 ///@}
193 
194 ///@name IMDCT
195  int block_switch[AC3_MAX_CHANNELS]; ///< block switch flags (blksw)
196  FFTContext imdct_512; ///< for 512 sample IMDCT
197  FFTContext imdct_256; ///< for 256 sample IMDCT
198 ///@}
199 
200 ///@name Optimization
201  DSPContext dsp; ///< for optimization
204  FmtConvertContext fmt_conv; ///< optimized conversion functions
205 ///@}
206 
210 
211 ///@name Aligned arrays
212  DECLARE_ALIGNED(16, int32_t, fixed_coeffs)[AC3_MAX_CHANNELS][AC3_MAX_COEFS]; ///< fixed-point transform coefficients
213  DECLARE_ALIGNED(32, float, transform_coeffs)[AC3_MAX_CHANNELS][AC3_MAX_COEFS]; ///< transform coefficients
214  DECLARE_ALIGNED(32, float, delay)[AC3_MAX_CHANNELS][AC3_BLOCK_SIZE]; ///< delay - added to the next block
215  DECLARE_ALIGNED(32, float, window)[AC3_BLOCK_SIZE]; ///< window coefficients
216  DECLARE_ALIGNED(32, float, tmp_output)[AC3_BLOCK_SIZE]; ///< temporary storage for output before windowing
217  DECLARE_ALIGNED(32, float, output)[AC3_MAX_CHANNELS][AC3_BLOCK_SIZE]; ///< output after imdct transform and windowing
219 ///@}
221 
222 /**
223  * Parse the E-AC-3 frame header.
224  * This parses both the bit stream info and audio frame header.
225  */
227 
228 /**
229  * Decode mantissas in a single channel for the entire frame.
230  * This is used when AHT mode is enabled.
231  */
233 
234 /**
235  * Apply spectral extension to each channel by copying lower frequency
236  * coefficients to higher frequency bins and applying side information to
237  * approximate the original high frequency signal.
238  */
240 
241 #endif /* AVCODEC_AC3DEC_H */
Definition: lfg.h:25
int dba_nsegs[AC3_MAX_CHANNELS]
number of delta segments
Definition: ac3dec.h:183
const char * s
Definition: avisynth_c.h:668
float * dlyptr[AC3_MAX_CHANNELS]
Definition: ac3dec.h:209
int16_t psd[AC3_MAX_CHANNELS][AC3_MAX_COEFS]
scaled exponents
Definition: ac3dec.h:179
int spx_in_use
spectral extension in use (spxinu)
Definition: ac3dec.h:123
uint8_t dba_offsets[AC3_MAX_CHANNELS][8]
delta segment offsets
Definition: ac3dec.h:184
int dither_flag[AC3_MAX_CHANNELS]
dither flags (dithflg)
Definition: ac3dec.h:190
int16_t mask[AC3_MAX_CHANNELS][AC3_CRITICAL_BANDS]
masking curve values
Definition: ac3dec.h:181
#define AC3_MAX_COEFS
Definition: ac3.h:34
AVFloatDSPContext fdsp
Definition: ac3dec.h:202
int channels
number of total channels
Definition: ac3dec.h:144
#define DECLARE_ALIGNED(n, t, v)
Definition: avcodec.h:5102
int spx_dst_end_freq
spx end frequency bin
Definition: ac3dec.h:127
int exp_strategy[AC3_MAX_BLOCKS][AC3_MAX_CHANNELS]
exponent strategies (expstr)
Definition: ac3dec.h:170
float dynamic_range[2]
dynamic range
Definition: ac3dec.h:153
int lfe_on
lfe channel in use
Definition: ac3dec.h:85
float spx_signal_blend[AC3_MAX_CHANNELS][SPX_MAX_BANDS]
spx signal blending factor (sblendfact)
Definition: ac3dec.h:134
int block_switch[AC3_MAX_CHANNELS]
block switch flags (blksw)
Definition: ac3dec.h:195
float * xcfptr[AC3_MAX_CHANNELS]
Definition: ac3dec.h:208
int dba_syntax
delta bit allocation syntax enabled (dbaflde)
Definition: ac3dec.h:104
int preferred_stereo_downmix
Definition: ac3dec.h:92
int spx_src_start_freq
spx start frequency bin
Definition: ac3dec.h:126
uint8_t cpl_band_sizes[AC3_MAX_CPL_BANDS]
number of coeffs in each coupling band
Definition: ac3dec.h:115
#define AC3_FRAME_BUFFER_SIZE
Large enough for maximum possible frame size when the specification limit is ignored.
Definition: ac3dec.h:67
float downmix_coeffs[AC3_MAX_CHANNELS][2]
stereo downmix coefficients
Definition: ac3dec.h:146
float ltrt_center_mix_level
Definition: ac3dec.h:93
uint8_t
int first_cpl_coords[AC3_MAX_CHANNELS]
first coupling coordinates states (firstcplcos)
Definition: ac3dec.h:117
float output[AC3_MAX_CHANNELS][AC3_BLOCK_SIZE]
output after imdct transform and windowing
Definition: ac3dec.h:217
int num_rematrixing_bands
number of rematrixing bands (nrematbnd)
Definition: ac3dec.h:163
int fast_gain[AC3_MAX_CHANNELS]
fast gain values/SMR&#39;s (fgain)
Definition: ac3dec.h:177
float ltrt_surround_mix_level
Definition: ac3dec.h:94
int ff_eac3_parse_header(AC3DecodeContext *s)
Parse the E-AC-3 frame header.
Definition: eac3dec.c:291
int cpl_coords[AC3_MAX_CHANNELS][AC3_MAX_CPL_BANDS]
coupling coordinates (cplco)
Definition: ac3dec.h:118
int num_exp_groups[AC3_MAX_CHANNELS]
Number of exponent groups (nexpgrp)
Definition: ac3dec.h:168
bitstream reader API header.
float delay[AC3_MAX_CHANNELS][AC3_BLOCK_SIZE]
delay - added to the next block
Definition: ac3dec.h:214
int bit_allocation_syntax
bit allocation model syntax enabled (bamode)
Definition: ac3dec.h:102
int phase_flags_in_use
phase flags in use (phsflginu)
Definition: ac3dec.h:112
int phase_flags[AC3_MAX_CPL_BANDS]
phase flags (phsflg)
Definition: ac3dec.h:113
int out_channels
number of output channels
Definition: ac3dec.h:149
int channel_map
custom channel map
Definition: ac3dec.h:86
int substreamid
substream identification
Definition: ac3dec.h:77
FFTContext imdct_256
for 256 sample IMDCT
Definition: ac3dec.h:197
DSPContext dsp
for optimization
Definition: ac3dec.h:201
int bit_rate
stream bit rate, in bits-per-second
Definition: ac3dec.h:79
float * outptr[AC3_MAX_CHANNELS]
Definition: ac3dec.h:207
int lfe_ch
index of LFE channel
Definition: ac3dec.h:145
uint8_t first_spx_coords[AC3_MAX_CHANNELS]
first spx coordinates states (firstspxcos)
Definition: ac3dec.h:132
AC3BitAllocParameters bit_alloc_params
bit allocation parameters
Definition: ac3dec.h:174
GetBitContext gbc
bitstream reader
Definition: ac3dec.h:72
AC3DSPContext ac3dsp
Definition: ac3dec.h:203
#define AC3_MAX_CHANNELS
maximum number of channels, including coupling channel
Definition: ac3.h:31
float loro_center_mix_level
Definition: ac3dec.h:95
int block_switch_syntax
block switch syntax enabled (blkswe)
Definition: ac3dec.h:100
int fast_gain_syntax
fast gain codes enabled (frmfgaincode)
Definition: ac3dec.h:103
int16_t band_psd[AC3_MAX_CHANNELS][AC3_CRITICAL_BANDS]
interpolated exponents
Definition: ac3dec.h:180
uint8_t channel_uses_spx[AC3_MAX_CHANNELS]
channel uses spectral extension (chinspx)
Definition: ac3dec.h:124
#define AC3_BLOCK_SIZE
Definition: ac3.h:35
#define FF_INPUT_BUFFER_PADDING_SIZE
Required number of additionally allocated bytes at the end of the input bitstream for decoding...
Definition: avcodec.h:580
uint8_t input_buffer[AC3_FRAME_BUFFER_SIZE+FF_INPUT_BUFFER_PADDING_SIZE]
temp buffer to prevent overread
Definition: ac3dec.h:218
Definition: fft.h:77
float loro_surround_mix_level
Definition: ac3dec.h:96
int dither_flag_syntax
dither flag syntax enabled (dithflage)
Definition: ac3dec.h:101
int end_freq[AC3_MAX_CHANNELS]
end frequency bin (endmant)
Definition: ac3dec.h:159
uint8_t dba_values[AC3_MAX_CHANNELS][8]
delta values for each segment
Definition: ac3dec.h:186
FFTContext imdct_512
for 512 sample IMDCT
Definition: ac3dec.h:196
int32_t
void ff_eac3_decode_transform_coeffs_aht_ch(AC3DecodeContext *s, int ch)
Decode mantissas in a single channel for the entire frame.
Definition: eac3dec.c:198
float drc_scale
percentage of dynamic range compression to be applied
Definition: ac3dec.h:154
int32_t fixed_coeffs[AC3_MAX_CHANNELS][AC3_MAX_COEFS]
fixed-point transform coefficients
Definition: ac3dec.h:212
AVCodecContext * avctx
parent context
Definition: ac3dec.h:71
int channel_in_cpl[AC3_MAX_CHANNELS]
channel in coupling (chincpl)
Definition: ac3dec.h:111
int fbw_channels
number of full-bandwidth channels
Definition: ac3dec.h:143
int8_t spx_atten_code[AC3_MAX_CHANNELS]
spx attenuation code (spxattencod)
Definition: ac3dec.h:125
uint8_t bap[AC3_MAX_CHANNELS][AC3_MAX_COEFS]
bit allocation pointers
Definition: ac3dec.h:178
main external API structure.
Definition: avcodec.h:1146
#define AC3_CRITICAL_BANDS
Definition: ac3.h:39
int num_cpl_bands
number of coupling bands (ncplbnd)
Definition: ac3dec.h:114
int num_spx_bands
number of spx bands (nspxbnds)
Definition: ac3dec.h:130
float tmp_output[AC3_BLOCK_SIZE]
temporary storage for output before windowing
Definition: ac3dec.h:216
void ff_eac3_apply_spectral_extension(AC3DecodeContext *s)
Apply spectral extension to each channel by copying lower frequency coefficients to higher frequency ...
Definition: eac3dec.c:66
Describe the class of an AVClass context structure.
Definition: log.h:50
int bitstream_mode
bitstream mode (bsmod)
Definition: ac3dec.h:82
int frame_type
frame type (strmtyp)
Definition: ac3dec.h:76
#define AC3_MAX_BLOCKS
Definition: ac3.h:36
int eac3
indicates if current frame is E-AC-3
Definition: ac3dec.h:89
int channel_uses_aht[AC3_MAX_CHANNELS]
channel AHT in use (chahtinu)
Definition: ac3dec.h:138
uint8_t dba_lengths[AC3_MAX_CHANNELS][8]
delta segment lengths
Definition: ac3dec.h:185
int cpl_in_use[AC3_MAX_BLOCKS]
coupling in use (cplinu)
Definition: ac3dec.h:109
int firstchincpl
first channel in coupling
Definition: ac3dec.h:116
int dba_mode[AC3_MAX_CHANNELS]
delta bit allocation mode
Definition: ac3dec.h:182
int first_cpl_leak
first coupling leak state (firstcplleak)
Definition: ac3dec.h:175
int surround_mix_level
Surround mix level index.
Definition: ac3dec.h:88
int snr_offset[AC3_MAX_CHANNELS]
signal-to-noise ratio offsets (snroffst)
Definition: ac3dec.h:176
int downmixed
indicates if coeffs are currently downmixed
Definition: ac3dec.h:147
float window[AC3_BLOCK_SIZE]
window coefficients
Definition: ac3dec.h:215
#define AC3_MAX_CPL_BANDS
Definition: ac3.h:40
int num_blocks
number of audio blocks
Definition: ac3dec.h:81
FmtConvertContext fmt_conv
optimized conversion functions
Definition: ac3dec.h:204
float transform_coeffs[AC3_MAX_CHANNELS][AC3_MAX_COEFS]
transform coefficients
Definition: ac3dec.h:213
#define SPX_MAX_BANDS
Definition: ac3dec.h:64
DSP utils.
int pre_mantissa[AC3_MAX_CHANNELS][AC3_MAX_COEFS][AC3_MAX_BLOCKS]
pre-IDCT mantissas
Definition: ac3dec.h:139
float spx_noise_blend[AC3_MAX_CHANNELS][SPX_MAX_BANDS]
spx noise blending factor (nblendfact)
Definition: ac3dec.h:133
int rematrixing_flags[4]
rematrixing flags (rematflg)
Definition: ac3dec.h:164
uint8_t spx_band_sizes[SPX_MAX_BANDS]
number of bins in each spx band
Definition: ac3dec.h:131
int snr_offset_strategy
SNR offset strategy (snroffststr)
Definition: ac3dec.h:99
int start_freq[AC3_MAX_CHANNELS]
start frequency bin (strtmant)
Definition: ac3dec.h:158
int sample_rate
sample frequency, in Hz
Definition: ac3dec.h:80
int center_mix_level
Center mix level index.
Definition: ac3dec.h:87
int output_mode
output channel configuration
Definition: ac3dec.h:148
int frame_size
current frame size, in bytes
Definition: ac3dec.h:78
int channel_layout
channel layout
Definition: ac3dec.h:84
AVLFG dith_state
for dither generation
Definition: ac3dec.h:191
int cpl_strategy_exists[AC3_MAX_BLOCKS]
coupling strategy exists (cplstre)
Definition: ac3dec.h:110
Common code between the AC-3 encoder and decoder.
int channel_mode
channel mode (acmod)
Definition: ac3dec.h:83
int spx_dst_start_freq
spx starting frequency bin for copying (copystartmant) the copy region ends at the start of the spx r...
Definition: ac3dec.h:128
int skip_syntax
skip field syntax enabled (skipflde)
Definition: ac3dec.h:105
DSPContext.
Definition: dsputil.h:124
int8_t dexps[AC3_MAX_CHANNELS][AC3_MAX_COEFS]
decoded exponents
Definition: ac3dec.h:169