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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/lfg.h"
54 #include "ac3.h"
55 #include "ac3dsp.h"
56 #include "get_bits.h"
57 #include "dsputil.h"
58 #include "fft.h"
59 #include "fmtconvert.h"
60 
61 #define AC3_OUTPUT_LFEON 8
62 
63 #define SPX_MAX_BANDS 17
64 
65 /** Large enough for maximum possible frame size when the specification limit is ignored */
66 #define AC3_FRAME_BUFFER_SIZE 32768
67 
68 typedef struct AC3DecodeContext {
69  AVClass *class; ///< class for AVOptions
70  AVCodecContext *avctx; ///< parent context
71  AVFrame frame; ///< AVFrame for decoded output
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 
92  int preferred_stereo_downmix;
93  float ltrt_center_mix_level;
94  float ltrt_surround_mix_level;
95  float loro_center_mix_level;
96  float loro_surround_mix_level;
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)
139  int pre_mantissa[AC3_MAX_CHANNELS][AC3_MAX_COEFS][AC3_MAX_BLOCKS]; ///< pre-IDCT mantissas
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
202  AC3DSPContext ac3dsp;
203  FmtConvertContext fmt_conv; ///< optimized conversion functions
204 ///@}
205 
206  float *outptr[AC3_MAX_CHANNELS];
207  float *xcfptr[AC3_MAX_CHANNELS];
208  float *dlyptr[AC3_MAX_CHANNELS];
209 
210 ///@name Aligned arrays
211  DECLARE_ALIGNED(16, int, fixed_coeffs)[AC3_MAX_CHANNELS][AC3_MAX_COEFS]; ///< fixed-point transform coefficients
212  DECLARE_ALIGNED(32, float, transform_coeffs)[AC3_MAX_CHANNELS][AC3_MAX_COEFS]; ///< transform coefficients
213  DECLARE_ALIGNED(32, float, delay)[AC3_MAX_CHANNELS][AC3_BLOCK_SIZE]; ///< delay - added to the next block
214  DECLARE_ALIGNED(32, float, window)[AC3_BLOCK_SIZE]; ///< window coefficients
215  DECLARE_ALIGNED(32, float, tmp_output)[AC3_BLOCK_SIZE]; ///< temporary storage for output before windowing
216  DECLARE_ALIGNED(32, float, output)[AC3_MAX_CHANNELS][AC3_BLOCK_SIZE]; ///< output after imdct transform and windowing
217  DECLARE_ALIGNED(32, uint8_t, input_buffer)[AC3_FRAME_BUFFER_SIZE + FF_INPUT_BUFFER_PADDING_SIZE]; ///< temp buffer to prevent overread
218 ///@}
219 } AC3DecodeContext;
220 
221 /**
222  * Parse the E-AC-3 frame header.
223  * This parses both the bit stream info and audio frame header.
224  */
225 int ff_eac3_parse_header(AC3DecodeContext *s);
226 
227 /**
228  * Decode mantissas in a single channel for the entire frame.
229  * This is used when AHT mode is enabled.
230  */
231 void ff_eac3_decode_transform_coeffs_aht_ch(AC3DecodeContext *s, int ch);
232 
233 /**
234  * Apply spectral extension to each channel by copying lower frequency
235  * coefficients to higher frequency bins and applying side information to
236  * approximate the original high frequency signal.
237  */
238 void ff_eac3_apply_spectral_extension(AC3DecodeContext *s);
239 
240 #endif /* AVCODEC_AC3DEC_H */
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