libavcodec/ac3.h

   1 /*
   2  * Common code between the AC-3 encoder and decoder
   3  * Copyright (c) 2000, 2001, 2002 Fabrice Bellard
   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 encoder and decoder.
  25  */
  26
  27 #ifndef AVCODEC_AC3_H
  28 #define AVCODEC_AC3_H
  29
  30 #define AC3_MAX_CODED_FRAME_SIZE 3840 /* in bytes */
  31 #define AC3_MAX_CHANNELS 7            /**< maximum number of channels, including coupling channel */
  32 #define CPL_CH 0                      /**< coupling channel index */
  33
  34 #define AC3_MAX_COEFS   256
  35 #define AC3_BLOCK_SIZE  256
  36 #define AC3_MAX_BLOCKS    6
  37 #define AC3_FRAME_SIZE (AC3_MAX_BLOCKS * 256)
  38 #define AC3_WINDOW_SIZE (AC3_BLOCK_SIZE * 2)
  39 #define AC3_CRITICAL_BANDS 50
  40 #define AC3_MAX_CPL_BANDS  18
  41
  42 #include "ac3tab.h"
  43
  44 /* exponent encoding strategy */
  45 #define EXP_REUSE 0
  46 #define EXP_NEW   1
  47
  48 #define EXP_D15   1
  49 #define EXP_D25   2
  50 #define EXP_D45   3
  51
  52 /* pre-defined gain values */
  53 #define LEVEL_PLUS_3DB          1.4142135623730950
  54 #define LEVEL_PLUS_1POINT5DB    1.1892071150027209
  55 #define LEVEL_MINUS_1POINT5DB   0.8408964152537145
  56 #define LEVEL_MINUS_3DB         0.7071067811865476
  57 #define LEVEL_MINUS_4POINT5DB   0.5946035575013605
  58 #define LEVEL_MINUS_6DB         0.5000000000000000
  59 #define LEVEL_MINUS_9DB         0.3535533905932738
  60 #define LEVEL_ZERO              0.0000000000000000
  61 #define LEVEL_ONE               1.0000000000000000
  62
  63 /** Delta bit allocation strategy */
  64 typedef enum {
  65     DBA_REUSE = 0,
  66     DBA_NEW,
  67     DBA_NONE,
  68     DBA_RESERVED
  69 } AC3DeltaStrategy;
  70
  71 /** Channel mode (audio coding mode) */
  72 typedef enum {
  73     AC3_CHMODE_DUALMONO = 0,
  74     AC3_CHMODE_MONO,
  75     AC3_CHMODE_STEREO,
  76     AC3_CHMODE_3F,
  77     AC3_CHMODE_2F1R,
  78     AC3_CHMODE_3F1R,
  79     AC3_CHMODE_2F2R,
  80     AC3_CHMODE_3F2R
  81 } AC3ChannelMode;
  82
  83 /** Dolby Surround mode */
  84 typedef enum AC3DolbySurroundMode {
  85     AC3_DSURMOD_NOTINDICATED = 0,
  86     AC3_DSURMOD_OFF,
  87     AC3_DSURMOD_ON,
  88     AC3_DSURMOD_RESERVED
  89 } AC3DolbySurroundMode;
  90
  91 /** Dolby Surround EX mode */
  92 typedef enum AC3DolbySurroundEXMode {
  93     AC3_DSUREXMOD_NOTINDICATED = 0,
  94     AC3_DSUREXMOD_OFF,
  95     AC3_DSUREXMOD_ON,
  96     AC3_DSUREXMOD_PLIIZ
  97 } AC3DolbySurroundEXMode;
  98
  99 /** Dolby Headphone mode */
 100 typedef enum AC3DolbyHeadphoneMode {
 101     AC3_DHEADPHONMOD_NOTINDICATED = 0,
 102     AC3_DHEADPHONMOD_OFF,
 103     AC3_DHEADPHONMOD_ON,
 104     AC3_DHEADPHONMOD_RESERVED
 105 } AC3DolbyHeadphoneMode;
 106
 107 /** Preferred Stereo Downmix mode */
 108 typedef enum AC3PreferredStereoDownmixMode {
 109     AC3_DMIXMOD_NOTINDICATED = 0,
 110     AC3_DMIXMOD_LTRT,
 111     AC3_DMIXMOD_LORO,
 112     AC3_DMIXMOD_DPLII // reserved value in A/52, but used by encoders to indicate DPL2
 113 } AC3PreferredStereoDownmixMode;
 114
 115 typedef struct AC3BitAllocParameters {
 116     int sr_code;
 117     int sr_shift;
 118     int slow_gain, slow_decay, fast_decay, db_per_bit, floor;
 119     int cpl_fast_leak, cpl_slow_leak;
 120 } AC3BitAllocParameters;
 121
 122 /**
 123  * @struct AC3HeaderInfo
 124  * Coded AC-3 header values up to the lfeon element, plus derived values.
 125  */
 126 typedef struct AC3HeaderInfo {
 127     /** @name Coded elements
 128      * @{
 129      */
 130     uint16_t sync_word;
 131     uint16_t crc1;
 132     uint8_t sr_code;
 133     uint8_t bitstream_id;
 134     uint8_t bitstream_mode;
 135     uint8_t channel_mode;
 136     uint8_t lfe_on;
 137     uint8_t frame_type;
 138     int substreamid;                        ///< substream identification
 139     int center_mix_level;                   ///< Center mix level index
 140     int surround_mix_level;                 ///< Surround mix level index
 141     uint16_t channel_map;
 142     int num_blocks;                         ///< number of audio blocks
 143     int dolby_surround_mode;
 144     /** @} */
 145
 146     /** @name Derived values
 147      * @{
 148      */
 149     uint8_t sr_shift;
 150     uint16_t sample_rate;
 151     uint32_t bit_rate;
 152     uint8_t channels;
 153     uint16_t frame_size;
 154     uint64_t channel_layout;
 155     /** @} */
 156 } AC3HeaderInfo;
 157
 158 typedef enum {
 159     EAC3_FRAME_TYPE_INDEPENDENT = 0,
 160     EAC3_FRAME_TYPE_DEPENDENT,
 161     EAC3_FRAME_TYPE_AC3_CONVERT,
 162     EAC3_FRAME_TYPE_RESERVED
 163 } EAC3FrameType;
 164
 165 void ff_ac3_common_init(void);
 166
 167 /**
 168  * Calculate the log power-spectral density of the input signal.
 169  * This gives a rough estimate of signal power in the frequency domain by using
 170  * the spectral envelope (exponents).  The psd is also separately grouped
 171  * into critical bands for use in the calculating the masking curve.
 172  * 128 units in psd = -6 dB.  The dbknee parameter in AC3BitAllocParameters
 173  * determines the reference level.
 174  *
 175  * @param[in]  exp        frequency coefficient exponents
 176  * @param[in]  start      starting bin location
 177  * @param[in]  end        ending bin location
 178  * @param[out] psd        signal power for each frequency bin
 179  * @param[out] band_psd   signal power for each critical band
 180  */
 181 void ff_ac3_bit_alloc_calc_psd(int8_t *exp, int start, int end, int16_t *psd,
 182                                int16_t *band_psd);
 183
 184 /**
 185  * Calculate the masking curve.
 186  * First, the excitation is calculated using parameters in s and the signal
 187  * power in each critical band.  The excitation is compared with a predefined
 188  * hearing threshold table to produce the masking curve.  If delta bit
 189  * allocation information is provided, it is used for adjusting the masking
 190  * curve, usually to give a closer match to a better psychoacoustic model.
 191  *
 192  * @param[in]  s            adjustable bit allocation parameters
 193  * @param[in]  band_psd     signal power for each critical band
 194  * @param[in]  start        starting bin location
 195  * @param[in]  end          ending bin location
 196  * @param[in]  fast_gain    fast gain (estimated signal-to-mask ratio)
 197  * @param[in]  is_lfe       whether or not the channel being processed is the LFE
 198  * @param[in]  dba_mode     delta bit allocation mode (none, reuse, or new)
 199  * @param[in]  dba_nsegs    number of delta segments
 200  * @param[in]  dba_offsets  location offsets for each segment
 201  * @param[in]  dba_lengths  length of each segment
 202  * @param[in]  dba_values   delta bit allocation for each segment
 203  * @param[out] mask         calculated masking curve
 204  * @return returns 0 for success, non-zero for error
 205  */
 206 int ff_ac3_bit_alloc_calc_mask(AC3BitAllocParameters *s, int16_t *band_psd,
 207                                int start, int end, int fast_gain, int is_lfe,
 208                                int dba_mode, int dba_nsegs, uint8_t *dba_offsets,
 209                                uint8_t *dba_lengths, uint8_t *dba_values,
 210                                int16_t *mask);
 211
 212 #endif /* AVCODEC_AC3_H */