2 * Common code between the AC-3 and E-AC-3 decoders
3 * Copyright (c) 2007 Bartlomiej Wolowiec <bartek.wolowiec@gmail.com>
5 * This file is part of FFmpeg.
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.
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.
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
24 * Common code between the AC-3 and E-AC-3 decoders.
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.
36 * +-+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+-+
37 * |1| |12| | [12|12|12|12] | | | | | | | | | | | | |3|
38 * +-+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+-+
39 * ~~~ ~~~~ ~~~~~~~~~~~~~ ~~~
41 * | | | 3 unused frequency bins--+
43 * | | +--1 band containing 4 subbands
45 * | +--1 subband of 12 frequency bins
50 #ifndef AVCODEC_AC3DEC_H
51 #define AVCODEC_AC3DEC_H
53 #include "libavutil/float_dsp.h"
54 #include "libavutil/lfg.h"
60 #include "fmtconvert.h"
62 #define AC3_OUTPUT_LFEON 8
64 #define SPX_MAX_BANDS 17
66 /** Large enough for maximum possible frame size when the specification limit is ignored */
67 #define AC3_FRAME_BUFFER_SIZE 32768
69 typedef struct AC3DecodeContext {
70 AVClass *class; ///< class for AVOptions
71 AVCodecContext *avctx; ///< parent context
72 GetBitContext gbc; ///< bitstream reader
74 ///@name Bit stream information
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_id; ///< bitstream id (bsid)
83 int bitstream_mode; ///< bitstream mode (bsmod)
84 int channel_mode; ///< channel mode (acmod)
85 int lfe_on; ///< lfe channel in use
86 int channel_map; ///< custom channel map
87 int preferred_downmix; ///< Preferred 2-channel downmix mode (dmixmod)
88 int center_mix_level; ///< Center mix level index
89 int center_mix_level_ltrt; ///< Center mix level index for Lt/Rt (ltrtcmixlev)
90 int surround_mix_level; ///< Surround mix level index
91 int surround_mix_level_ltrt; ///< Surround mix level index for Lt/Rt (ltrtsurmixlev)
92 int lfe_mix_level_exists; ///< indicates if lfemixlevcod is specified (lfemixlevcode)
93 int lfe_mix_level; ///< LFE mix level index (lfemixlevcod)
94 int eac3; ///< indicates if current frame is E-AC-3
95 int dolby_surround_mode; ///< dolby surround mode (dsurmod)
96 int dolby_surround_ex_mode; ///< dolby surround ex mode (dsurexmod)
97 int dolby_headphone_mode; ///< dolby headphone mode (dheadphonmod)
100 int preferred_stereo_downmix;
101 float ltrt_center_mix_level;
102 float ltrt_surround_mix_level;
103 float loro_center_mix_level;
104 float loro_surround_mix_level;
106 ///@name Frame syntax parameters
107 int snr_offset_strategy; ///< SNR offset strategy (snroffststr)
108 int block_switch_syntax; ///< block switch syntax enabled (blkswe)
109 int dither_flag_syntax; ///< dither flag syntax enabled (dithflage)
110 int bit_allocation_syntax; ///< bit allocation model syntax enabled (bamode)
111 int fast_gain_syntax; ///< fast gain codes enabled (frmfgaincode)
112 int dba_syntax; ///< delta bit allocation syntax enabled (dbaflde)
113 int skip_syntax; ///< skip field syntax enabled (skipflde)
116 ///@name Standard coupling
117 int cpl_in_use[AC3_MAX_BLOCKS]; ///< coupling in use (cplinu)
118 int cpl_strategy_exists[AC3_MAX_BLOCKS];///< coupling strategy exists (cplstre)
119 int channel_in_cpl[AC3_MAX_CHANNELS]; ///< channel in coupling (chincpl)
120 int phase_flags_in_use; ///< phase flags in use (phsflginu)
121 int phase_flags[AC3_MAX_CPL_BANDS]; ///< phase flags (phsflg)
122 int num_cpl_bands; ///< number of coupling bands (ncplbnd)
123 uint8_t cpl_band_sizes[AC3_MAX_CPL_BANDS]; ///< number of coeffs in each coupling band
124 int firstchincpl; ///< first channel in coupling
125 int first_cpl_coords[AC3_MAX_CHANNELS]; ///< first coupling coordinates states (firstcplcos)
126 int cpl_coords[AC3_MAX_CHANNELS][AC3_MAX_CPL_BANDS]; ///< coupling coordinates (cplco)
129 ///@name Spectral extension
131 int spx_in_use; ///< spectral extension in use (spxinu)
132 uint8_t channel_uses_spx[AC3_MAX_CHANNELS]; ///< channel uses spectral extension (chinspx)
133 int8_t spx_atten_code[AC3_MAX_CHANNELS]; ///< spx attenuation code (spxattencod)
134 int spx_src_start_freq; ///< spx start frequency bin
135 int spx_dst_end_freq; ///< spx end frequency bin
136 int spx_dst_start_freq; ///< spx starting frequency bin for copying (copystartmant)
137 ///< the copy region ends at the start of the spx region.
138 int num_spx_bands; ///< number of spx bands (nspxbnds)
139 uint8_t spx_band_sizes[SPX_MAX_BANDS]; ///< number of bins in each spx band
140 uint8_t first_spx_coords[AC3_MAX_CHANNELS]; ///< first spx coordinates states (firstspxcos)
141 float spx_noise_blend[AC3_MAX_CHANNELS][SPX_MAX_BANDS]; ///< spx noise blending factor (nblendfact)
142 float spx_signal_blend[AC3_MAX_CHANNELS][SPX_MAX_BANDS];///< spx signal blending factor (sblendfact)
145 ///@name Adaptive hybrid transform
146 int channel_uses_aht[AC3_MAX_CHANNELS]; ///< channel AHT in use (chahtinu)
147 int pre_mantissa[AC3_MAX_CHANNELS][AC3_MAX_COEFS][AC3_MAX_BLOCKS]; ///< pre-IDCT mantissas
151 int fbw_channels; ///< number of full-bandwidth channels
152 int channels; ///< number of total channels
153 int lfe_ch; ///< index of LFE channel
154 float downmix_coeffs[AC3_MAX_CHANNELS][2]; ///< stereo downmix coefficients
155 int downmixed; ///< indicates if coeffs are currently downmixed
156 int output_mode; ///< output channel configuration
157 int out_channels; ///< number of output channels
160 ///@name Dynamic range
161 float dynamic_range[2]; ///< dynamic range
162 float drc_scale; ///< percentage of dynamic range compression to be applied
166 int start_freq[AC3_MAX_CHANNELS]; ///< start frequency bin (strtmant)
167 int end_freq[AC3_MAX_CHANNELS]; ///< end frequency bin (endmant)
171 int num_rematrixing_bands; ///< number of rematrixing bands (nrematbnd)
172 int rematrixing_flags[4]; ///< rematrixing flags (rematflg)
176 int num_exp_groups[AC3_MAX_CHANNELS]; ///< Number of exponent groups (nexpgrp)
177 int8_t dexps[AC3_MAX_CHANNELS][AC3_MAX_COEFS]; ///< decoded exponents
178 int exp_strategy[AC3_MAX_BLOCKS][AC3_MAX_CHANNELS]; ///< exponent strategies (expstr)
181 ///@name Bit allocation
182 AC3BitAllocParameters bit_alloc_params; ///< bit allocation parameters
183 int first_cpl_leak; ///< first coupling leak state (firstcplleak)
184 int snr_offset[AC3_MAX_CHANNELS]; ///< signal-to-noise ratio offsets (snroffst)
185 int fast_gain[AC3_MAX_CHANNELS]; ///< fast gain values/SMR's (fgain)
186 uint8_t bap[AC3_MAX_CHANNELS][AC3_MAX_COEFS]; ///< bit allocation pointers
187 int16_t psd[AC3_MAX_CHANNELS][AC3_MAX_COEFS]; ///< scaled exponents
188 int16_t band_psd[AC3_MAX_CHANNELS][AC3_CRITICAL_BANDS]; ///< interpolated exponents
189 int16_t mask[AC3_MAX_CHANNELS][AC3_CRITICAL_BANDS]; ///< masking curve values
190 int dba_mode[AC3_MAX_CHANNELS]; ///< delta bit allocation mode
191 int dba_nsegs[AC3_MAX_CHANNELS]; ///< number of delta segments
192 uint8_t dba_offsets[AC3_MAX_CHANNELS][8]; ///< delta segment offsets
193 uint8_t dba_lengths[AC3_MAX_CHANNELS][8]; ///< delta segment lengths
194 uint8_t dba_values[AC3_MAX_CHANNELS][8]; ///< delta values for each segment
197 ///@name Zero-mantissa dithering
198 int dither_flag[AC3_MAX_CHANNELS]; ///< dither flags (dithflg)
199 AVLFG dith_state; ///< for dither generation
203 int block_switch[AC3_MAX_CHANNELS]; ///< block switch flags (blksw)
204 FFTContext imdct_512; ///< for 512 sample IMDCT
205 FFTContext imdct_256; ///< for 256 sample IMDCT
208 ///@name Optimization
209 DSPContext dsp; ///< for optimization
210 AVFloatDSPContext fdsp;
211 AC3DSPContext ac3dsp;
212 FmtConvertContext fmt_conv; ///< optimized conversion functions
215 float *outptr[AC3_MAX_CHANNELS];
216 float *xcfptr[AC3_MAX_CHANNELS];
217 float *dlyptr[AC3_MAX_CHANNELS];
219 ///@name Aligned arrays
220 DECLARE_ALIGNED(16, int32_t, fixed_coeffs)[AC3_MAX_CHANNELS][AC3_MAX_COEFS]; ///< fixed-point transform coefficients
221 DECLARE_ALIGNED(32, float, transform_coeffs)[AC3_MAX_CHANNELS][AC3_MAX_COEFS]; ///< transform coefficients
222 DECLARE_ALIGNED(32, float, delay)[AC3_MAX_CHANNELS][AC3_BLOCK_SIZE]; ///< delay - added to the next block
223 DECLARE_ALIGNED(32, float, window)[AC3_BLOCK_SIZE]; ///< window coefficients
224 DECLARE_ALIGNED(32, float, tmp_output)[AC3_BLOCK_SIZE]; ///< temporary storage for output before windowing
225 DECLARE_ALIGNED(32, float, output)[AC3_MAX_CHANNELS][AC3_BLOCK_SIZE]; ///< output after imdct transform and windowing
226 DECLARE_ALIGNED(32, uint8_t, input_buffer)[AC3_FRAME_BUFFER_SIZE + FF_INPUT_BUFFER_PADDING_SIZE]; ///< temp buffer to prevent overread
231 * Parse the E-AC-3 frame header.
232 * This parses both the bit stream info and audio frame header.
234 int ff_eac3_parse_header(AC3DecodeContext *s);
237 * Decode mantissas in a single channel for the entire frame.
238 * This is used when AHT mode is enabled.
240 void ff_eac3_decode_transform_coeffs_aht_ch(AC3DecodeContext *s, int ch);
243 * Apply spectral extension to each channel by copying lower frequency
244 * coefficients to higher frequency bins and applying side information to
245 * approximate the original high frequency signal.
247 void ff_eac3_apply_spectral_extension(AC3DecodeContext *s);
249 #endif /* AVCODEC_AC3DEC_H */