Skip to content
This repository

HTTPS clone URL

Subversion checkout URL

You can clone with HTTPS or Subversion.

Download ZIP
tree: 1e9caf9c92
Fetching contributors…

Cannot retrieve contributors at this time

file 240 lines (212 sloc) 12.532 kb
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240
/*
* Common code between the AC-3 and E-AC-3 decoders
* Copyright (c) 2007 Bartlomiej Wolowiec <bartek.wolowiec@gmail.com>
*
* This file is part of FFmpeg.
*
* FFmpeg is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* License as published by the Free Software Foundation; either
* version 2.1 of the License, or (at your option) any later version.
*
* FFmpeg is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public
* License along with FFmpeg; if not, write to the Free Software
* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
*/

/**
* @file
* Common code between the AC-3 and E-AC-3 decoders.
*
* Summary of MDCT Coefficient Grouping:
* The individual MDCT coefficient indices are often referred to in the
* (E-)AC-3 specification as frequency bins. These bins are grouped together
* into subbands of 12 coefficients each. The subbands are grouped together
* into bands as defined in the bitstream by the band structures, which
* determine the number of bands and the size of each band. The full spectrum
* of 256 frequency bins is divided into 1 DC bin + 21 subbands = 253 bins.
* This system of grouping coefficients is used for channel bandwidth, stereo
* rematrixing, channel coupling, enhanced coupling, and spectral extension.
*
* +-+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+-+
* |1| |12| | [12|12|12|12] | | | | | | | | | | | | |3|
* +-+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+-+
* ~~~ ~~~~ ~~~~~~~~~~~~~ ~~~
* | | | |
* | | | 3 unused frequency bins--+
* | | |
* | | +--1 band containing 4 subbands
* | |
* | +--1 subband of 12 frequency bins
* |
* +--DC frequency bin
*/

#ifndef AVCODEC_AC3DEC_H
#define AVCODEC_AC3DEC_H

#include "libavutil/lfg.h"
#include "ac3.h"
#include "ac3dsp.h"
#include "get_bits.h"
#include "dsputil.h"
#include "fft.h"
#include "fmtconvert.h"

#define AC3_OUTPUT_LFEON 8

#define SPX_MAX_BANDS 17

/** Large enough for maximum possible frame size when the specification limit is ignored */
#define AC3_FRAME_BUFFER_SIZE 32768

typedef struct {
    AVClass *class; ///< class for AVOptions
    AVCodecContext *avctx; ///< parent context
    AVFrame frame; ///< AVFrame for decoded output
    GetBitContext gbc; ///< bitstream reader

///@name Bit stream information
///@{
    int frame_type; ///< frame type (strmtyp)
    int substreamid; ///< substream identification
    int frame_size; ///< current frame size, in bytes
    int bit_rate; ///< stream bit rate, in bits-per-second
    int sample_rate; ///< sample frequency, in Hz
    int num_blocks; ///< number of audio blocks
    int bitstream_mode; ///< bitstream mode (bsmod)
    int channel_mode; ///< channel mode (acmod)
    int channel_layout; ///< channel layout
    int lfe_on; ///< lfe channel in use
    int channel_map; ///< custom channel map
    int center_mix_level; ///< Center mix level index
    int surround_mix_level; ///< Surround mix level index
    int eac3; ///< indicates if current frame is E-AC-3
///@}

    int preferred_stereo_downmix;
    float ltrt_center_mix_level;
    float ltrt_surround_mix_level;
    float loro_center_mix_level;
    float loro_surround_mix_level;

///@name Frame syntax parameters
    int snr_offset_strategy; ///< SNR offset strategy (snroffststr)
    int block_switch_syntax; ///< block switch syntax enabled (blkswe)
    int dither_flag_syntax; ///< dither flag syntax enabled (dithflage)
    int bit_allocation_syntax; ///< bit allocation model syntax enabled (bamode)
    int fast_gain_syntax; ///< fast gain codes enabled (frmfgaincode)
    int dba_syntax; ///< delta bit allocation syntax enabled (dbaflde)
    int skip_syntax; ///< skip field syntax enabled (skipflde)
 ///@}

///@name Standard coupling
    int cpl_in_use[AC3_MAX_BLOCKS]; ///< coupling in use (cplinu)
    int cpl_strategy_exists[AC3_MAX_BLOCKS];///< coupling strategy exists (cplstre)
    int channel_in_cpl[AC3_MAX_CHANNELS]; ///< channel in coupling (chincpl)
    int phase_flags_in_use; ///< phase flags in use (phsflginu)
    int phase_flags[AC3_MAX_CPL_BANDS]; ///< phase flags (phsflg)
    int num_cpl_bands; ///< number of coupling bands (ncplbnd)
    uint8_t cpl_band_sizes[AC3_MAX_CPL_BANDS]; ///< number of coeffs in each coupling band
    int firstchincpl; ///< first channel in coupling
    int first_cpl_coords[AC3_MAX_CHANNELS]; ///< first coupling coordinates states (firstcplcos)
    int cpl_coords[AC3_MAX_CHANNELS][AC3_MAX_CPL_BANDS]; ///< coupling coordinates (cplco)
///@}

///@name Spectral extension
///@{
    int spx_in_use; ///< spectral extension in use (spxinu)
    uint8_t channel_uses_spx[AC3_MAX_CHANNELS]; ///< channel uses spectral extension (chinspx)
    int8_t spx_atten_code[AC3_MAX_CHANNELS]; ///< spx attenuation code (spxattencod)
    int spx_src_start_freq; ///< spx start frequency bin
    int spx_dst_end_freq; ///< spx end frequency bin
    int spx_dst_start_freq; ///< spx starting frequency bin for copying (copystartmant)
                                                ///< the copy region ends at the start of the spx region.
    int num_spx_bands; ///< number of spx bands (nspxbnds)
    uint8_t spx_band_sizes[SPX_MAX_BANDS]; ///< number of bins in each spx band
    uint8_t first_spx_coords[AC3_MAX_CHANNELS]; ///< first spx coordinates states (firstspxcos)
    float spx_noise_blend[AC3_MAX_CHANNELS][SPX_MAX_BANDS]; ///< spx noise blending factor (nblendfact)
    float spx_signal_blend[AC3_MAX_CHANNELS][SPX_MAX_BANDS];///< spx signal blending factor (sblendfact)
///@}

///@name Adaptive hybrid transform
    int channel_uses_aht[AC3_MAX_CHANNELS]; ///< channel AHT in use (chahtinu)
    int pre_mantissa[AC3_MAX_CHANNELS][AC3_MAX_COEFS][AC3_MAX_BLOCKS]; ///< pre-IDCT mantissas
///@}

///@name Channel
    int fbw_channels; ///< number of full-bandwidth channels
    int channels; ///< number of total channels
    int lfe_ch; ///< index of LFE channel
    float downmix_coeffs[AC3_MAX_CHANNELS][2]; ///< stereo downmix coefficients
    int downmixed; ///< indicates if coeffs are currently downmixed
    int output_mode; ///< output channel configuration
    int out_channels; ///< number of output channels
///@}

///@name Dynamic range
    float dynamic_range[2]; ///< dynamic range
    float drc_scale; ///< percentage of dynamic range compression to be applied
///@}

///@name Bandwidth
    int start_freq[AC3_MAX_CHANNELS]; ///< start frequency bin (strtmant)
    int end_freq[AC3_MAX_CHANNELS]; ///< end frequency bin (endmant)
///@}

///@name Rematrixing
    int num_rematrixing_bands; ///< number of rematrixing bands (nrematbnd)
    int rematrixing_flags[4]; ///< rematrixing flags (rematflg)
///@}

///@name Exponents
    int num_exp_groups[AC3_MAX_CHANNELS]; ///< Number of exponent groups (nexpgrp)
    int8_t dexps[AC3_MAX_CHANNELS][AC3_MAX_COEFS]; ///< decoded exponents
    int exp_strategy[AC3_MAX_BLOCKS][AC3_MAX_CHANNELS]; ///< exponent strategies (expstr)
///@}

///@name Bit allocation
    AC3BitAllocParameters bit_alloc_params; ///< bit allocation parameters
    int first_cpl_leak; ///< first coupling leak state (firstcplleak)
    int snr_offset[AC3_MAX_CHANNELS]; ///< signal-to-noise ratio offsets (snroffst)
    int fast_gain[AC3_MAX_CHANNELS]; ///< fast gain values/SMR's (fgain)
    uint8_t bap[AC3_MAX_CHANNELS][AC3_MAX_COEFS]; ///< bit allocation pointers
    int16_t psd[AC3_MAX_CHANNELS][AC3_MAX_COEFS]; ///< scaled exponents
    int16_t band_psd[AC3_MAX_CHANNELS][AC3_CRITICAL_BANDS]; ///< interpolated exponents
    int16_t mask[AC3_MAX_CHANNELS][AC3_CRITICAL_BANDS]; ///< masking curve values
    int dba_mode[AC3_MAX_CHANNELS]; ///< delta bit allocation mode
    int dba_nsegs[AC3_MAX_CHANNELS]; ///< number of delta segments
    uint8_t dba_offsets[AC3_MAX_CHANNELS][8]; ///< delta segment offsets
    uint8_t dba_lengths[AC3_MAX_CHANNELS][8]; ///< delta segment lengths
    uint8_t dba_values[AC3_MAX_CHANNELS][8]; ///< delta values for each segment
///@}

///@name Zero-mantissa dithering
    int dither_flag[AC3_MAX_CHANNELS]; ///< dither flags (dithflg)
    AVLFG dith_state; ///< for dither generation
///@}

///@name IMDCT
    int block_switch[AC3_MAX_CHANNELS]; ///< block switch flags (blksw)
    FFTContext imdct_512; ///< for 512 sample IMDCT
    FFTContext imdct_256; ///< for 256 sample IMDCT
///@}

///@name Optimization
    DSPContext dsp; ///< for optimization
    AC3DSPContext ac3dsp;
    FmtConvertContext fmt_conv; ///< optimized conversion functions
    float mul_bias; ///< scaling for float_to_int16 conversion
///@}

///@name Aligned arrays
    DECLARE_ALIGNED(16, int, fixed_coeffs)[AC3_MAX_CHANNELS][AC3_MAX_COEFS]; ///< fixed-point transform coefficients
    DECLARE_ALIGNED(32, float, transform_coeffs)[AC3_MAX_CHANNELS][AC3_MAX_COEFS]; ///< transform coefficients
    DECLARE_ALIGNED(32, float, delay)[AC3_MAX_CHANNELS][AC3_BLOCK_SIZE]; ///< delay - added to the next block
    DECLARE_ALIGNED(32, float, window)[AC3_BLOCK_SIZE]; ///< window coefficients
    DECLARE_ALIGNED(32, float, tmp_output)[AC3_BLOCK_SIZE]; ///< temporary storage for output before windowing
    DECLARE_ALIGNED(32, float, output)[AC3_MAX_CHANNELS][AC3_BLOCK_SIZE]; ///< output after imdct transform and windowing
    DECLARE_ALIGNED(32, uint8_t, input_buffer)[AC3_FRAME_BUFFER_SIZE + FF_INPUT_BUFFER_PADDING_SIZE]; ///< temp buffer to prevent overread
///@}
} AC3DecodeContext;

/**
* Parse the E-AC-3 frame header.
* This parses both the bit stream info and audio frame header.
*/
int ff_eac3_parse_header(AC3DecodeContext *s);

/**
* Decode mantissas in a single channel for the entire frame.
* This is used when AHT mode is enabled.
*/
void ff_eac3_decode_transform_coeffs_aht_ch(AC3DecodeContext *s, int ch);

void ff_ac3_downmix_c(float (*samples)[256], float (*matrix)[2],
                      int out_ch, int in_ch, int len);

/**
* Apply spectral extension to each channel by copying lower frequency
* coefficients to higher frequency bins and applying side information to
* approximate the original high frequency signal.
*/
void ff_eac3_apply_spectral_extension(AC3DecodeContext *s);

#endif /* AVCODEC_AC3DEC_H */
Something went wrong with that request. Please try again.