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FFmpeg/libavcodec/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 Libav.

  6.  *

  7.  * Libav 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.  * Libav 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 Libav; 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/lfg.h"

  55. #include "ac3.h"

  56. #include "ac3dsp.h"

  57. #include "bswapdsp.h"

  58. #include "get_bits.h"

  59. #include "fft.h"

  60. #include "fmtconvert.h"

  61. 

  62. #define AC3_OUTPUT_LFEON  8

  63. 

  64. #define SPX_MAX_BANDS    17

  65. 

  66. /** Large enough for maximum possible frame size when the specification limit is ignored */

  67. #define AC3_FRAME_BUFFER_SIZE 32768

  68. 

  69. typedef struct AC3DecodeContext {

  70.     AVClass        *class;                  ///< class for AVOptions

  71.     AVCodecContext *avctx;                  ///< parent context

  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_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 eac3_frame_dependent_found;         ///< bitstream has E-AC-3 dependent frame(s)

  96.     int eac3_subsbtreamid_found;            ///< bitstream has E-AC-3 additional substream(s)

  97.     int dolby_surround_mode;                ///< dolby surround mode                    (dsurmod)

  98.     int dolby_surround_ex_mode;             ///< dolby surround ex mode                 (dsurexmod)

  99.     int dolby_headphone_mode;               ///< dolby headphone mode                   (dheadphonmod)

  100. ///@}

  101. 

  102. ///@name Frame syntax parameters

  103.     int snr_offset_strategy;                ///< SNR offset strategy                    (snroffststr)

  104.     int block_switch_syntax;                ///< block switch syntax enabled            (blkswe)

  105.     int dither_flag_syntax;                 ///< dither flag syntax enabled             (dithflage)

  106.     int bit_allocation_syntax;              ///< bit allocation model syntax enabled    (bamode)

  107.     int fast_gain_syntax;                   ///< fast gain codes enabled                (frmfgaincode)

  108.     int dba_syntax;                         ///< delta bit allocation syntax enabled    (dbaflde)

  109.     int skip_syntax;                        ///< skip field syntax enabled              (skipflde)

  110.  ///@}

  111. 

  112. ///@name Standard coupling

  113.     int cpl_in_use[AC3_MAX_BLOCKS];         ///< coupling in use                        (cplinu)

  114.     int cpl_strategy_exists[AC3_MAX_BLOCKS];///< coupling strategy exists               (cplstre)

  115.     int channel_in_cpl[AC3_MAX_CHANNELS];   ///< channel in coupling                    (chincpl)

  116.     int phase_flags_in_use;                 ///< phase flags in use                     (phsflginu)

  117.     int phase_flags[AC3_MAX_CPL_BANDS];     ///< phase flags                            (phsflg)

  118.     int num_cpl_bands;                      ///< number of coupling bands               (ncplbnd)

  119.     uint8_t cpl_band_sizes[AC3_MAX_CPL_BANDS]; ///< number of coeffs in each coupling band

  120.     int firstchincpl;                       ///< first channel in coupling

  121.     int first_cpl_coords[AC3_MAX_CHANNELS]; ///< first coupling coordinates states      (firstcplcos)

  122.     int cpl_coords[AC3_MAX_CHANNELS][AC3_MAX_CPL_BANDS]; ///< coupling coordinates      (cplco)

  123. ///@}

  124. 

  125. ///@name Spectral extension

  126. ///@{

  127.     int spx_in_use;                             ///< spectral extension in use              (spxinu)

  128.     uint8_t channel_uses_spx[AC3_MAX_CHANNELS]; ///< channel uses spectral extension        (chinspx)

  129.     int8_t spx_atten_code[AC3_MAX_CHANNELS];    ///< spx attenuation code                   (spxattencod)

  130.     int spx_src_start_freq;                     ///< spx start frequency bin

  131.     int spx_dst_end_freq;                       ///< spx end frequency bin

  132.     int spx_dst_start_freq;                     ///< spx starting frequency bin for copying (copystartmant)

  133.                                                 ///< the copy region ends at the start of the spx region.

  134.     int num_spx_bands;                          ///< number of spx bands                    (nspxbnds)

  135.     uint8_t spx_band_sizes[SPX_MAX_BANDS];      ///< number of bins in each spx band

  136.     uint8_t first_spx_coords[AC3_MAX_CHANNELS]; ///< first spx coordinates states           (firstspxcos)

  137.     float spx_noise_blend[AC3_MAX_CHANNELS][SPX_MAX_BANDS]; ///< spx noise blending factor  (nblendfact)

  138.     float spx_signal_blend[AC3_MAX_CHANNELS][SPX_MAX_BANDS];///< spx signal blending factor (sblendfact)

  139. ///@}

  140. 

  141. ///@name Adaptive hybrid transform

  142.     int channel_uses_aht[AC3_MAX_CHANNELS];                         ///< channel AHT in use (chahtinu)

  143.     int pre_mantissa[AC3_MAX_CHANNELS][AC3_MAX_COEFS][AC3_MAX_BLOCKS];  ///< pre-IDCT mantissas

  144. ///@}

  145. 

  146. ///@name Channel

  147.     int fbw_channels;                           ///< number of full-bandwidth channels

  148.     int channels;                               ///< number of total channels

  149.     int lfe_ch;                                 ///< index of LFE channel

  150.     float *downmix_coeffs[2];                   ///< stereo downmix coefficients

  151.     int downmixed;                              ///< indicates if coeffs are currently downmixed

  152.     int output_mode;                            ///< output channel configuration

  153.     int out_channels;                           ///< number of output channels

  154. ///@}

  155. 

  156. ///@name Dynamic range

  157.     float dynamic_range[2];                 ///< dynamic range

  158.     float drc_scale;                        ///< percentage of dynamic range compression to be applied

  159. ///@}

  160. 

  161. ///@name Bandwidth

  162.     int start_freq[AC3_MAX_CHANNELS];       ///< start frequency bin                    (strtmant)

  163.     int end_freq[AC3_MAX_CHANNELS];         ///< end frequency bin                      (endmant)

  164. ///@}

  165. 

  166. ///@name Rematrixing

  167.     int num_rematrixing_bands;              ///< number of rematrixing bands            (nrematbnd)

  168.     int rematrixing_flags[4];               ///< rematrixing flags                      (rematflg)

  169. ///@}

  170. 

  171. ///@name Exponents

  172.     int num_exp_groups[AC3_MAX_CHANNELS];           ///< Number of exponent groups      (nexpgrp)

  173.     int8_t dexps[AC3_MAX_CHANNELS][AC3_MAX_COEFS];  ///< decoded exponents

  174.     int exp_strategy[AC3_MAX_BLOCKS][AC3_MAX_CHANNELS]; ///< exponent strategies        (expstr)

  175. ///@}

  176. 

  177. ///@name Bit allocation

  178.     AC3BitAllocParameters bit_alloc_params;         ///< bit allocation parameters

  179.     int first_cpl_leak;                             ///< first coupling leak state      (firstcplleak)

  180.     int snr_offset[AC3_MAX_CHANNELS];               ///< signal-to-noise ratio offsets  (snroffst)

  181.     int fast_gain[AC3_MAX_CHANNELS];                ///< fast gain values/SMR's         (fgain)

  182.     uint8_t bap[AC3_MAX_CHANNELS][AC3_MAX_COEFS];   ///< bit allocation pointers

  183.     int16_t psd[AC3_MAX_CHANNELS][AC3_MAX_COEFS];   ///< scaled exponents

  184.     int16_t band_psd[AC3_MAX_CHANNELS][AC3_CRITICAL_BANDS]; ///< interpolated exponents

  185.     int16_t mask[AC3_MAX_CHANNELS][AC3_CRITICAL_BANDS];     ///< masking curve values

  186.     int dba_mode[AC3_MAX_CHANNELS];                 ///< delta bit allocation mode

  187.     int dba_nsegs[AC3_MAX_CHANNELS];                ///< number of delta segments

  188.     uint8_t dba_offsets[AC3_MAX_CHANNELS][8];       ///< delta segment offsets

  189.     uint8_t dba_lengths[AC3_MAX_CHANNELS][8];       ///< delta segment lengths

  190.     uint8_t dba_values[AC3_MAX_CHANNELS][8];        ///< delta values for each segment

  191. ///@}

  192. 

  193. ///@name Zero-mantissa dithering

  194.     int dither_flag[AC3_MAX_CHANNELS];      ///< dither flags                           (dithflg)

  195.     AVLFG dith_state;                       ///< for dither generation

  196. ///@}

  197. 

  198. ///@name IMDCT

  199.     int block_switch[AC3_MAX_CHANNELS];     ///< block switch flags                     (blksw)

  200.     FFTContext imdct_512;                   ///< for 512 sample IMDCT

  201.     FFTContext imdct_256;                   ///< for 256 sample IMDCT

  202. ///@}

  203. 

  204. ///@name Optimization

  205.     BswapDSPContext bdsp;

  206.     AVFloatDSPContext fdsp;

  207.     AC3DSPContext ac3dsp;

  208.     FmtConvertContext fmt_conv;             ///< optimized conversion functions

  209. ///@}

  210. 

  211.     float *outptr[AC3_MAX_CHANNELS];

  212.     float *xcfptr[AC3_MAX_CHANNELS];

  213.     float *dlyptr[AC3_MAX_CHANNELS];

  214. 

  215. ///@name Aligned arrays

  216.     DECLARE_ALIGNED(16, int32_t, fixed_coeffs)[AC3_MAX_CHANNELS][AC3_MAX_COEFS];     ///< fixed-point transform coefficients

  217.     DECLARE_ALIGNED(32, float, transform_coeffs)[AC3_MAX_CHANNELS][AC3_MAX_COEFS];   ///< transform coefficients

  218.     DECLARE_ALIGNED(32, float, delay)[AC3_MAX_CHANNELS][AC3_BLOCK_SIZE];             ///< delay - added to the next block

  219.     DECLARE_ALIGNED(32, float, window)[AC3_BLOCK_SIZE];                              ///< window coefficients

  220.     DECLARE_ALIGNED(32, float, tmp_output)[AC3_BLOCK_SIZE];                          ///< temporary storage for output before windowing

  221.     DECLARE_ALIGNED(32, float, output)[AC3_MAX_CHANNELS][AC3_BLOCK_SIZE];            ///< output after imdct transform and windowing

  222.     DECLARE_ALIGNED(32, uint8_t, input_buffer)[AC3_FRAME_BUFFER_SIZE + AV_INPUT_BUFFER_PADDING_SIZE]; ///< temp buffer to prevent overread

  223. ///@}

  224. } AC3DecodeContext;

  225. 

  226. /**

  227.  * Parse the E-AC-3 frame header.

  228.  * This parses both the bit stream info and audio frame header.

  229.  */

  230. int ff_eac3_parse_header(AC3DecodeContext *s);

  231. 

  232. /**

  233.  * Decode mantissas in a single channel for the entire frame.

  234.  * This is used when AHT mode is enabled.

  235.  */

  236. void ff_eac3_decode_transform_coeffs_aht_ch(AC3DecodeContext *s, int ch);

  237. 

  238. /**

  239.  * Apply spectral extension to each channel by copying lower frequency

  240.  * coefficients to higher frequency bins and applying side information to

  241.  * approximate the original high frequency signal.

  242.  */

  243. void ff_eac3_apply_spectral_extension(AC3DecodeContext *s);

  244. 

  245. #endif /* AVCODEC_AC3DEC_H */