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