FFmpeg
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/fixed_dsp.h"
55 #include "libavutil/lfg.h"
56 #include "libavutil/mem_internal.h"
57 
58 #include "ac3.h"
59 #include "ac3dsp.h"
60 #include "bswapdsp.h"
61 #include "get_bits.h"
62 #include "fft.h"
63 #include "fmtconvert.h"
64 
65 #define AC3_OUTPUT_LFEON 8
66 
67 #define SPX_MAX_BANDS 17
68 
69 /** Large enough for maximum possible frame size when the specification limit is ignored */
70 #define AC3_FRAME_BUFFER_SIZE 32768
71 
72 typedef struct AC3DecodeContext {
73  AVClass *class; ///< class for AVOptions
74  AVCodecContext *avctx; ///< parent context
75  GetBitContext gbc; ///< bitstream reader
76 
77 ///@name Bit stream information
78 ///@{
79  int frame_type; ///< frame type (strmtyp)
80  int substreamid; ///< substream identification
81  int superframe_size; ///< current superframe size, in bytes
82  int frame_size; ///< current frame size, in bytes
83  int bit_rate; ///< stream bit rate, in bits-per-second
84  int sample_rate; ///< sample frequency, in Hz
85  int num_blocks; ///< number of audio blocks
86  int bitstream_id; ///< bitstream id (bsid)
87  int bitstream_mode; ///< bitstream mode (bsmod)
88  int channel_mode; ///< channel mode (acmod)
89  int lfe_on; ///< lfe channel in use
90  int dialog_normalization[2]; ///< dialog level in dBFS (dialnorm)
91  int compression_exists[2]; ///< compression field is valid for frame (compre)
92  int compression_gain[2]; ///< gain to apply for heavy compression (compr)
93  int channel_map; ///< custom channel map (chanmap)
94  int preferred_downmix; ///< Preferred 2-channel downmix mode (dmixmod)
95  int center_mix_level; ///< Center mix level index
96  int center_mix_level_ltrt; ///< Center mix level index for Lt/Rt (ltrtcmixlev)
97  int surround_mix_level; ///< Surround mix level index
98  int surround_mix_level_ltrt; ///< Surround mix level index for Lt/Rt (ltrtsurmixlev)
99  int lfe_mix_level_exists; ///< indicates if lfemixlevcod is specified (lfemixlevcode)
100  int lfe_mix_level; ///< LFE mix level index (lfemixlevcod)
101  int eac3; ///< indicates if current frame is E-AC-3
102  int eac3_frame_dependent_found; ///< bitstream has E-AC-3 dependent frame(s)
103  int eac3_subsbtreamid_found; ///< bitstream has E-AC-3 additional substream(s)
104  int dolby_surround_mode; ///< dolby surround mode (dsurmod)
105  int dolby_surround_ex_mode; ///< dolby surround ex mode (dsurexmod)
106  int dolby_headphone_mode; ///< dolby headphone mode (dheadphonmod)
107 ///@}
108 
109  int preferred_stereo_downmix;
110  float ltrt_center_mix_level;
111  float ltrt_surround_mix_level;
112  float loro_center_mix_level;
113  float loro_surround_mix_level;
114  int target_level; ///< target level in dBFS
115  float level_gain[2];
116 
117 ///@name Frame syntax parameters
118  int snr_offset_strategy; ///< SNR offset strategy (snroffststr)
119  int block_switch_syntax; ///< block switch syntax enabled (blkswe)
120  int dither_flag_syntax; ///< dither flag syntax enabled (dithflage)
121  int bit_allocation_syntax; ///< bit allocation model syntax enabled (bamode)
122  int fast_gain_syntax; ///< fast gain codes enabled (frmfgaincode)
123  int dba_syntax; ///< delta bit allocation syntax enabled (dbaflde)
124  int skip_syntax; ///< skip field syntax enabled (skipflde)
125  ///@}
126 
127 ///@name Standard coupling
128  int cpl_in_use[AC3_MAX_BLOCKS]; ///< coupling in use (cplinu)
129  int cpl_strategy_exists[AC3_MAX_BLOCKS];///< coupling strategy exists (cplstre)
130  int channel_in_cpl[AC3_MAX_CHANNELS]; ///< channel in coupling (chincpl)
131  int phase_flags_in_use; ///< phase flags in use (phsflginu)
132  int phase_flags[AC3_MAX_CPL_BANDS]; ///< phase flags (phsflg)
133  int num_cpl_bands; ///< number of coupling bands (ncplbnd)
134  uint8_t cpl_band_struct[AC3_MAX_CPL_BANDS];
135  uint8_t cpl_band_sizes[AC3_MAX_CPL_BANDS]; ///< number of coeffs in each coupling band
136  int firstchincpl; ///< first channel in coupling
137  int first_cpl_coords[AC3_MAX_CHANNELS]; ///< first coupling coordinates states (firstcplcos)
138  int cpl_coords[AC3_MAX_CHANNELS][AC3_MAX_CPL_BANDS]; ///< coupling coordinates (cplco)
139 ///@}
140 
141 ///@name Spectral extension
142 ///@{
143  int spx_in_use; ///< spectral extension in use (spxinu)
144  uint8_t channel_uses_spx[AC3_MAX_CHANNELS]; ///< channel uses spectral extension (chinspx)
145  int8_t spx_atten_code[AC3_MAX_CHANNELS]; ///< spx attenuation code (spxattencod)
146  int spx_src_start_freq; ///< spx start frequency bin
147  int spx_dst_end_freq; ///< spx end frequency bin
148  int spx_dst_start_freq; ///< spx starting frequency bin for copying (copystartmant)
149  ///< the copy region ends at the start of the spx region.
150  int num_spx_bands; ///< number of spx bands (nspxbnds)
151  uint8_t spx_band_struct[SPX_MAX_BANDS];
152  uint8_t spx_band_sizes[SPX_MAX_BANDS]; ///< number of bins in each spx band
153  uint8_t first_spx_coords[AC3_MAX_CHANNELS]; ///< first spx coordinates states (firstspxcos)
154  INTFLOAT spx_noise_blend[AC3_MAX_CHANNELS][SPX_MAX_BANDS]; ///< spx noise blending factor (nblendfact)
155  INTFLOAT spx_signal_blend[AC3_MAX_CHANNELS][SPX_MAX_BANDS];///< spx signal blending factor (sblendfact)
156 ///@}
157 
158 ///@name Adaptive hybrid transform
159  int channel_uses_aht[AC3_MAX_CHANNELS]; ///< channel AHT in use (chahtinu)
160  int pre_mantissa[AC3_MAX_CHANNELS][AC3_MAX_COEFS][AC3_MAX_BLOCKS]; ///< pre-IDCT mantissas
161 ///@}
162 
163 ///@name Channel
164  int fbw_channels; ///< number of full-bandwidth channels
165  int channels; ///< number of total channels
166  int lfe_ch; ///< index of LFE channel
167  SHORTFLOAT *downmix_coeffs[2]; ///< stereo downmix coefficients
168  int downmixed; ///< indicates if coeffs are currently downmixed
169  int output_mode; ///< output channel configuration
170  int prev_output_mode; ///< output channel configuration for previous frame
171  int out_channels; ///< number of output channels
172  int prev_bit_rate; ///< stream bit rate, in bits-per-second for previous frame
173 ///@}
174 
175 ///@name Dynamic range
176  INTFLOAT dynamic_range[2]; ///< dynamic range
177  INTFLOAT drc_scale; ///< percentage of dynamic range compression to be applied
178  int heavy_compression; ///< apply heavy compression
179  INTFLOAT heavy_dynamic_range[2]; ///< heavy dynamic range compression
180 ///@}
181 
182 ///@name Bandwidth
183  int start_freq[AC3_MAX_CHANNELS]; ///< start frequency bin (strtmant)
184  int end_freq[AC3_MAX_CHANNELS]; ///< end frequency bin (endmant)
185 ///@}
186 
187 ///@name Consistent noise generation
188  int consistent_noise_generation; ///< seed noise generation with AC-3 frame on decode
189 ///@}
190 
191 ///@name Rematrixing
192  int num_rematrixing_bands; ///< number of rematrixing bands (nrematbnd)
193  int rematrixing_flags[4]; ///< rematrixing flags (rematflg)
194 ///@}
195 
196 ///@name Exponents
197  int num_exp_groups[AC3_MAX_CHANNELS]; ///< Number of exponent groups (nexpgrp)
198  int8_t dexps[AC3_MAX_CHANNELS][AC3_MAX_COEFS]; ///< decoded exponents
199  int exp_strategy[AC3_MAX_BLOCKS][AC3_MAX_CHANNELS]; ///< exponent strategies (expstr)
200 ///@}
201 
202 ///@name Bit allocation
203  AC3BitAllocParameters bit_alloc_params; ///< bit allocation parameters
204  int first_cpl_leak; ///< first coupling leak state (firstcplleak)
205  int snr_offset[AC3_MAX_CHANNELS]; ///< signal-to-noise ratio offsets (snroffst)
206  int fast_gain[AC3_MAX_CHANNELS]; ///< fast gain values/SMR's (fgain)
207  uint8_t bap[AC3_MAX_CHANNELS][AC3_MAX_COEFS]; ///< bit allocation pointers
208  int16_t psd[AC3_MAX_CHANNELS][AC3_MAX_COEFS]; ///< scaled exponents
209  int16_t band_psd[AC3_MAX_CHANNELS][AC3_CRITICAL_BANDS]; ///< interpolated exponents
210  int16_t mask[AC3_MAX_CHANNELS][AC3_CRITICAL_BANDS]; ///< masking curve values
211  int dba_mode[AC3_MAX_CHANNELS]; ///< delta bit allocation mode
212  int dba_nsegs[AC3_MAX_CHANNELS]; ///< number of delta segments
213  uint8_t dba_offsets[AC3_MAX_CHANNELS][8]; ///< delta segment offsets
214  uint8_t dba_lengths[AC3_MAX_CHANNELS][8]; ///< delta segment lengths
215  uint8_t dba_values[AC3_MAX_CHANNELS][8]; ///< delta values for each segment
216 ///@}
217 
218 ///@name Zero-mantissa dithering
219  int dither_flag[AC3_MAX_CHANNELS]; ///< dither flags (dithflg)
220  AVLFG dith_state; ///< for dither generation
221 ///@}
222 
223 ///@name IMDCT
224  int block_switch[AC3_MAX_CHANNELS]; ///< block switch flags (blksw)
225  FFTContext imdct_512; ///< for 512 sample IMDCT
226  FFTContext imdct_256; ///< for 256 sample IMDCT
227 ///@}
228 
229 ///@name Optimization
230  BswapDSPContext bdsp;
231 #if USE_FIXED
232  AVFixedDSPContext *fdsp;
233 #else
234  AVFloatDSPContext *fdsp;
235 #endif
236  AC3DSPContext ac3dsp;
237  FmtConvertContext fmt_conv; ///< optimized conversion functions
238 ///@}
239 
240  SHORTFLOAT *outptr[AC3_MAX_CHANNELS];
241  INTFLOAT *xcfptr[AC3_MAX_CHANNELS];
242  INTFLOAT *dlyptr[AC3_MAX_CHANNELS];
243 
244 ///@name Aligned arrays
245  DECLARE_ALIGNED(16, int, fixed_coeffs)[AC3_MAX_CHANNELS][AC3_MAX_COEFS]; ///< fixed-point transform coefficients
246  DECLARE_ALIGNED(32, INTFLOAT, transform_coeffs)[AC3_MAX_CHANNELS][AC3_MAX_COEFS]; ///< transform coefficients
247  DECLARE_ALIGNED(32, INTFLOAT, delay)[EAC3_MAX_CHANNELS][AC3_BLOCK_SIZE]; ///< delay - added to the next block
248  DECLARE_ALIGNED(32, INTFLOAT, window)[AC3_BLOCK_SIZE]; ///< window coefficients
249  DECLARE_ALIGNED(32, INTFLOAT, tmp_output)[AC3_BLOCK_SIZE]; ///< temporary storage for output before windowing
250  DECLARE_ALIGNED(32, SHORTFLOAT, output)[EAC3_MAX_CHANNELS][AC3_BLOCK_SIZE]; ///< output after imdct transform and windowing
251  DECLARE_ALIGNED(32, uint8_t, input_buffer)[AC3_FRAME_BUFFER_SIZE + AV_INPUT_BUFFER_PADDING_SIZE]; ///< temp buffer to prevent overread
252  DECLARE_ALIGNED(32, SHORTFLOAT, output_buffer)[EAC3_MAX_CHANNELS][AC3_BLOCK_SIZE * 6]; ///< final output buffer
253 ///@}
254 } AC3DecodeContext;
255 
256 /**
257  * Parse the E-AC-3 frame header.
258  * This parses both the bit stream info and audio frame header.
259  */
260 static int ff_eac3_parse_header(AC3DecodeContext *s);
261 
262 /**
263  * Decode mantissas in a single channel for the entire frame.
264  * This is used when AHT mode is enabled.
265  */
266 static void ff_eac3_decode_transform_coeffs_aht_ch(AC3DecodeContext *s, int ch);
267 
268 /**
269  * Apply spectral extension to each channel by copying lower frequency
270  * coefficients to higher frequency bins and applying side information to
271  * approximate the original high frequency signal.
272  */
273 static void ff_eac3_apply_spectral_extension(AC3DecodeContext *s);
274 
275 #if (!USE_FIXED)
276 extern float ff_ac3_heavy_dynamic_range_tab[256];
277 #endif
278 
279 #endif /* AVCODEC_AC3DEC_H */
bswapdsp.h
ff_eac3_parse_header
static int ff_eac3_parse_header(AC3DecodeContext *s)
Definition: eac3dec.c:289
mem_internal.h
output
filter_frame For filters that do not use the this method is called when a frame is pushed to the filter s input It can be called at any time except in a reentrant way If the input frame is enough to produce output
Definition: filter_design.txt:225
AC3DSPContext
Definition: ac3dsp.h:33
AC3_MAX_COEFS
#define AC3_MAX_COEFS
Definition: ac3.h:37
AC3_CRITICAL_BANDS
#define AC3_CRITICAL_BANDS
Definition: ac3.h:42
AVFixedDSPContext
Definition: fixed_dsp.h:56
ff_eac3_decode_transform_coeffs_aht_ch
static void ff_eac3_decode_transform_coeffs_aht_ch(AC3DecodeContext *s, int ch)
Definition: eac3dec.c:196
sample_rate
sample_rate
Definition: ffmpeg_filter.c:156
fmtconvert.h
window
static SDL_Window * window
Definition: ffplay.c:364
AC3_MAX_BLOCKS
#define AC3_MAX_BLOCKS
Definition: ac3.h:39
fixed_coeffs
static const int fixed_coeffs[][3]
Definition: shorten.c:343
GetBitContext
Definition: get_bits.h:62
AC3_MAX_CHANNELS
#define AC3_MAX_CHANNELS
maximum number of channels, including coupling channel
Definition: ac3.h:34
AC3_MAX_CPL_BANDS
#define AC3_MAX_CPL_BANDS
Definition: ac3.h:43
mask
static const uint16_t mask[17]
Definition: lzw.c:38
s
#define s(width, name)
Definition: cbs_vp9.c:257
frame_size
int frame_size
Definition: mxfenc.c:2205
lfg.h
channels
channels
Definition: aptx.h:33
get_bits.h
fixed_dsp.h
ff_ac3_heavy_dynamic_range_tab
float ff_ac3_heavy_dynamic_range_tab[256]
Definition: ac3dec.c:70
SHORTFLOAT
float SHORTFLOAT
Definition: aac_defines.h:89
AVClass
Describe the class of an AVClass context structure.
Definition: log.h:66
ac3dsp.h
float_dsp.h
AVLFG
Context structure for the Lagged Fibonacci PRNG.
Definition: lfg.h:33
AVFloatDSPContext
Definition: float_dsp.h:24
EAC3_MAX_CHANNELS
#define EAC3_MAX_CHANNELS
maximum number of channels in EAC3
Definition: ac3.h:33
DECLARE_ALIGNED
#define DECLARE_ALIGNED(n, t, v)
Definition: mem.h:116
FFTContext
Definition: fft.h:75
frame_type
frame_type
Definition: jpeg2000_parser.c:31
ff_eac3_apply_spectral_extension
static void ff_eac3_apply_spectral_extension(AC3DecodeContext *s)
Definition: eac3dec.c:59
AV_INPUT_BUFFER_PADDING_SIZE
#define AV_INPUT_BUFFER_PADDING_SIZE
Definition: defs.h:40
AC3BitAllocParameters
Definition: ac3.h:166
AVCodecContext
main external API structure.
Definition: avcodec.h:383
FmtConvertContext
Definition: fmtconvert.h:28
ac3.h
BswapDSPContext
Definition: bswapdsp.h:24
INTFLOAT
float INTFLOAT
Definition: aac_defines.h:86
AC3_BLOCK_SIZE
#define AC3_BLOCK_SIZE
Definition: ac3.h:38