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242 lines
12 KiB
C
242 lines
12 KiB
C
/*
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* Common code between the AC-3 and E-AC-3 decoders
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* Copyright (c) 2007 Bartlomiej Wolowiec <bartek.wolowiec@gmail.com>
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*
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* This file is part of FFmpeg.
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*
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* FFmpeg is free software; you can redistribute it and/or
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* modify it under the terms of the GNU Lesser General Public
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* License as published by the Free Software Foundation; either
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* version 2.1 of the License, or (at your option) any later version.
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*
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* FFmpeg is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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* Lesser General Public License for more details.
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*
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* You should have received a copy of the GNU Lesser General Public
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* License along with FFmpeg; if not, write to the Free Software
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* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
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*/
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/**
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* @file
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* Common code between the AC-3 and E-AC-3 decoders.
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*
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* Summary of MDCT Coefficient Grouping:
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* The individual MDCT coefficient indices are often referred to in the
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* (E-)AC-3 specification as frequency bins. These bins are grouped together
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* into subbands of 12 coefficients each. The subbands are grouped together
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* into bands as defined in the bitstream by the band structures, which
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* determine the number of bands and the size of each band. The full spectrum
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* of 256 frequency bins is divided into 1 DC bin + 21 subbands = 253 bins.
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* This system of grouping coefficients is used for channel bandwidth, stereo
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* rematrixing, channel coupling, enhanced coupling, and spectral extension.
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*
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* +-+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+-+
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* |1| |12| | [12|12|12|12] | | | | | | | | | | | | |3|
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* +-+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+-+
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* ~~~ ~~~~ ~~~~~~~~~~~~~ ~~~
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* | | | |
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* | | | 3 unused frequency bins--+
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* | | |
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* | | +--1 band containing 4 subbands
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* | |
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* | +--1 subband of 12 frequency bins
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* |
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* +--DC frequency bin
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*/
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#ifndef AVCODEC_AC3DEC_H
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#define AVCODEC_AC3DEC_H
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#include "libavutil/float_dsp.h"
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#include "libavutil/lfg.h"
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#include "ac3.h"
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#include "ac3dsp.h"
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#include "get_bits.h"
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#include "dsputil.h"
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#include "fft.h"
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#include "fmtconvert.h"
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#define AC3_OUTPUT_LFEON 8
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#define SPX_MAX_BANDS 17
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/** Large enough for maximum possible frame size when the specification limit is ignored */
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#define AC3_FRAME_BUFFER_SIZE 32768
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typedef struct AC3DecodeContext {
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AVClass *class; ///< class for AVOptions
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AVCodecContext *avctx; ///< parent context
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GetBitContext gbc; ///< bitstream reader
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///@name Bit stream information
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///@{
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int frame_type; ///< frame type (strmtyp)
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int substreamid; ///< substream identification
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int frame_size; ///< current frame size, in bytes
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int bit_rate; ///< stream bit rate, in bits-per-second
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int sample_rate; ///< sample frequency, in Hz
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int num_blocks; ///< number of audio blocks
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int bitstream_mode; ///< bitstream mode (bsmod)
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int channel_mode; ///< channel mode (acmod)
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int channel_layout; ///< channel layout
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int lfe_on; ///< lfe channel in use
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int channel_map; ///< custom channel map
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int center_mix_level; ///< Center mix level index
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int surround_mix_level; ///< Surround mix level index
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int eac3; ///< indicates if current frame is E-AC-3
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///@}
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int preferred_stereo_downmix;
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float ltrt_center_mix_level;
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float ltrt_surround_mix_level;
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float loro_center_mix_level;
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float loro_surround_mix_level;
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///@name Frame syntax parameters
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int snr_offset_strategy; ///< SNR offset strategy (snroffststr)
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int block_switch_syntax; ///< block switch syntax enabled (blkswe)
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int dither_flag_syntax; ///< dither flag syntax enabled (dithflage)
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int bit_allocation_syntax; ///< bit allocation model syntax enabled (bamode)
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int fast_gain_syntax; ///< fast gain codes enabled (frmfgaincode)
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int dba_syntax; ///< delta bit allocation syntax enabled (dbaflde)
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int skip_syntax; ///< skip field syntax enabled (skipflde)
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///@}
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///@name Standard coupling
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int cpl_in_use[AC3_MAX_BLOCKS]; ///< coupling in use (cplinu)
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int cpl_strategy_exists[AC3_MAX_BLOCKS];///< coupling strategy exists (cplstre)
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int channel_in_cpl[AC3_MAX_CHANNELS]; ///< channel in coupling (chincpl)
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int phase_flags_in_use; ///< phase flags in use (phsflginu)
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int phase_flags[AC3_MAX_CPL_BANDS]; ///< phase flags (phsflg)
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int num_cpl_bands; ///< number of coupling bands (ncplbnd)
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uint8_t cpl_band_sizes[AC3_MAX_CPL_BANDS]; ///< number of coeffs in each coupling band
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int firstchincpl; ///< first channel in coupling
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int first_cpl_coords[AC3_MAX_CHANNELS]; ///< first coupling coordinates states (firstcplcos)
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int cpl_coords[AC3_MAX_CHANNELS][AC3_MAX_CPL_BANDS]; ///< coupling coordinates (cplco)
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///@}
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///@name Spectral extension
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///@{
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int spx_in_use; ///< spectral extension in use (spxinu)
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uint8_t channel_uses_spx[AC3_MAX_CHANNELS]; ///< channel uses spectral extension (chinspx)
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int8_t spx_atten_code[AC3_MAX_CHANNELS]; ///< spx attenuation code (spxattencod)
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int spx_src_start_freq; ///< spx start frequency bin
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int spx_dst_end_freq; ///< spx end frequency bin
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int spx_dst_start_freq; ///< spx starting frequency bin for copying (copystartmant)
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///< the copy region ends at the start of the spx region.
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int num_spx_bands; ///< number of spx bands (nspxbnds)
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uint8_t spx_band_sizes[SPX_MAX_BANDS]; ///< number of bins in each spx band
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uint8_t first_spx_coords[AC3_MAX_CHANNELS]; ///< first spx coordinates states (firstspxcos)
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float spx_noise_blend[AC3_MAX_CHANNELS][SPX_MAX_BANDS]; ///< spx noise blending factor (nblendfact)
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float spx_signal_blend[AC3_MAX_CHANNELS][SPX_MAX_BANDS];///< spx signal blending factor (sblendfact)
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///@}
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///@name Adaptive hybrid transform
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int channel_uses_aht[AC3_MAX_CHANNELS]; ///< channel AHT in use (chahtinu)
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int pre_mantissa[AC3_MAX_CHANNELS][AC3_MAX_COEFS][AC3_MAX_BLOCKS]; ///< pre-IDCT mantissas
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///@}
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///@name Channel
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int fbw_channels; ///< number of full-bandwidth channels
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int channels; ///< number of total channels
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int lfe_ch; ///< index of LFE channel
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float downmix_coeffs[AC3_MAX_CHANNELS][2]; ///< stereo downmix coefficients
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int downmixed; ///< indicates if coeffs are currently downmixed
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int output_mode; ///< output channel configuration
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int out_channels; ///< number of output channels
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///@}
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///@name Dynamic range
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float dynamic_range[2]; ///< dynamic range
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float drc_scale; ///< percentage of dynamic range compression to be applied
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///@}
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///@name Bandwidth
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int start_freq[AC3_MAX_CHANNELS]; ///< start frequency bin (strtmant)
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int end_freq[AC3_MAX_CHANNELS]; ///< end frequency bin (endmant)
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///@}
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///@name Rematrixing
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int num_rematrixing_bands; ///< number of rematrixing bands (nrematbnd)
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int rematrixing_flags[4]; ///< rematrixing flags (rematflg)
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///@}
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///@name Exponents
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int num_exp_groups[AC3_MAX_CHANNELS]; ///< Number of exponent groups (nexpgrp)
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int8_t dexps[AC3_MAX_CHANNELS][AC3_MAX_COEFS]; ///< decoded exponents
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int exp_strategy[AC3_MAX_BLOCKS][AC3_MAX_CHANNELS]; ///< exponent strategies (expstr)
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///@}
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///@name Bit allocation
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AC3BitAllocParameters bit_alloc_params; ///< bit allocation parameters
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int first_cpl_leak; ///< first coupling leak state (firstcplleak)
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int snr_offset[AC3_MAX_CHANNELS]; ///< signal-to-noise ratio offsets (snroffst)
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int fast_gain[AC3_MAX_CHANNELS]; ///< fast gain values/SMR's (fgain)
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uint8_t bap[AC3_MAX_CHANNELS][AC3_MAX_COEFS]; ///< bit allocation pointers
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int16_t psd[AC3_MAX_CHANNELS][AC3_MAX_COEFS]; ///< scaled exponents
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int16_t band_psd[AC3_MAX_CHANNELS][AC3_CRITICAL_BANDS]; ///< interpolated exponents
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int16_t mask[AC3_MAX_CHANNELS][AC3_CRITICAL_BANDS]; ///< masking curve values
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int dba_mode[AC3_MAX_CHANNELS]; ///< delta bit allocation mode
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int dba_nsegs[AC3_MAX_CHANNELS]; ///< number of delta segments
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uint8_t dba_offsets[AC3_MAX_CHANNELS][8]; ///< delta segment offsets
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uint8_t dba_lengths[AC3_MAX_CHANNELS][8]; ///< delta segment lengths
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uint8_t dba_values[AC3_MAX_CHANNELS][8]; ///< delta values for each segment
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///@}
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///@name Zero-mantissa dithering
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int dither_flag[AC3_MAX_CHANNELS]; ///< dither flags (dithflg)
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AVLFG dith_state; ///< for dither generation
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///@}
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///@name IMDCT
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int block_switch[AC3_MAX_CHANNELS]; ///< block switch flags (blksw)
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FFTContext imdct_512; ///< for 512 sample IMDCT
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FFTContext imdct_256; ///< for 256 sample IMDCT
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///@}
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///@name Optimization
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DSPContext dsp; ///< for optimization
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AVFloatDSPContext fdsp;
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AC3DSPContext ac3dsp;
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FmtConvertContext fmt_conv; ///< optimized conversion functions
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///@}
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float *outptr[AC3_MAX_CHANNELS];
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float *xcfptr[AC3_MAX_CHANNELS];
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float *dlyptr[AC3_MAX_CHANNELS];
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///@name Aligned arrays
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DECLARE_ALIGNED(16, int32_t, fixed_coeffs)[AC3_MAX_CHANNELS][AC3_MAX_COEFS]; ///< fixed-point transform coefficients
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DECLARE_ALIGNED(32, float, transform_coeffs)[AC3_MAX_CHANNELS][AC3_MAX_COEFS]; ///< transform coefficients
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DECLARE_ALIGNED(32, float, delay)[AC3_MAX_CHANNELS][AC3_BLOCK_SIZE]; ///< delay - added to the next block
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DECLARE_ALIGNED(32, float, window)[AC3_BLOCK_SIZE]; ///< window coefficients
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DECLARE_ALIGNED(32, float, tmp_output)[AC3_BLOCK_SIZE]; ///< temporary storage for output before windowing
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DECLARE_ALIGNED(32, float, output)[AC3_MAX_CHANNELS][AC3_BLOCK_SIZE]; ///< output after imdct transform and windowing
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DECLARE_ALIGNED(32, uint8_t, input_buffer)[AC3_FRAME_BUFFER_SIZE + FF_INPUT_BUFFER_PADDING_SIZE]; ///< temp buffer to prevent overread
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///@}
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} AC3DecodeContext;
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/**
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* Parse the E-AC-3 frame header.
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* This parses both the bit stream info and audio frame header.
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*/
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int ff_eac3_parse_header(AC3DecodeContext *s);
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/**
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* Decode mantissas in a single channel for the entire frame.
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* This is used when AHT mode is enabled.
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*/
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void ff_eac3_decode_transform_coeffs_aht_ch(AC3DecodeContext *s, int ch);
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/**
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* Apply spectral extension to each channel by copying lower frequency
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* coefficients to higher frequency bins and applying side information to
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* approximate the original high frequency signal.
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*/
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void ff_eac3_apply_spectral_extension(AC3DecodeContext *s);
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#endif /* AVCODEC_AC3DEC_H */
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