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 FFmpeg. 6 * 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. 11 * 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. 16 * 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 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#include "ac3tab.h" 31 32#define AC3_MAX_CODED_FRAME_SIZE 3840 /* in bytes */ 33#define AC3_MAX_CHANNELS 6 /* including LFE channel */ 34 35#define NB_BLOCKS 6 /* number of PCM blocks inside an AC-3 frame */ 36#define AC3_FRAME_SIZE (NB_BLOCKS * 256) 37 38/* exponent encoding strategy */ 39#define EXP_REUSE 0 40#define EXP_NEW 1 41 42#define EXP_D15 1 43#define EXP_D25 2 44#define EXP_D45 3 45 46/** Delta bit allocation strategy */ 47typedef enum { 48 DBA_REUSE = 0, 49 DBA_NEW, 50 DBA_NONE, 51 DBA_RESERVED 52} AC3DeltaStrategy; 53 54/** Channel mode (audio coding mode) */ 55typedef enum { 56 AC3_CHMODE_DUALMONO = 0, 57 AC3_CHMODE_MONO, 58 AC3_CHMODE_STEREO, 59 AC3_CHMODE_3F, 60 AC3_CHMODE_2F1R, 61 AC3_CHMODE_3F1R, 62 AC3_CHMODE_2F2R, 63 AC3_CHMODE_3F2R 64} AC3ChannelMode; 65 66typedef struct AC3BitAllocParameters { 67 int sr_code; 68 int sr_shift; 69 int slow_gain, slow_decay, fast_decay, db_per_bit, floor; 70 int cpl_fast_leak, cpl_slow_leak; 71} AC3BitAllocParameters; 72 73/** 74 * @struct AC3HeaderInfo 75 * Coded AC-3 header values up to the lfeon element, plus derived values. 76 */ 77typedef struct { 78 /** @defgroup coded Coded elements 79 * @{ 80 */ 81 uint16_t sync_word; 82 uint16_t crc1; 83 uint8_t sr_code; 84 uint8_t bitstream_id; 85 uint8_t channel_mode; 86 uint8_t lfe_on; 87 uint8_t frame_type; 88 int substreamid; ///< substream identification 89 int center_mix_level; ///< Center mix level index 90 int surround_mix_level; ///< Surround mix level index 91 uint16_t channel_map; 92 int num_blocks; ///< number of audio blocks 93 /** @} */ 94 95 /** @defgroup derived Derived values 96 * @{ 97 */ 98 uint8_t sr_shift; 99 uint16_t sample_rate; 100 uint32_t bit_rate; 101 uint8_t channels; 102 uint16_t frame_size; 103 int64_t channel_layout; 104 /** @} */ 105} AC3HeaderInfo; 106 107typedef enum { 108 EAC3_FRAME_TYPE_INDEPENDENT = 0, 109 EAC3_FRAME_TYPE_DEPENDENT, 110 EAC3_FRAME_TYPE_AC3_CONVERT, 111 EAC3_FRAME_TYPE_RESERVED 112} EAC3FrameType; 113 114void ac3_common_init(void); 115 116/** 117 * Calculates the log power-spectral density of the input signal. 118 * This gives a rough estimate of signal power in the frequency domain by using 119 * the spectral envelope (exponents). The psd is also separately grouped 120 * into critical bands for use in the calculating the masking curve. 121 * 128 units in psd = -6 dB. The dbknee parameter in AC3BitAllocParameters 122 * determines the reference level. 123 * 124 * @param[in] exp frequency coefficient exponents 125 * @param[in] start starting bin location 126 * @param[in] end ending bin location 127 * @param[out] psd signal power for each frequency bin 128 * @param[out] band_psd signal power for each critical band 129 */ 130void ff_ac3_bit_alloc_calc_psd(int8_t *exp, int start, int end, int16_t *psd, 131 int16_t *band_psd); 132 133/** 134 * Calculates the masking curve. 135 * First, the excitation is calculated using parameters in s and the signal 136 * power in each critical band. The excitation is compared with a predefined 137 * hearing threshold table to produce the masking curve. If delta bit 138 * allocation information is provided, it is used for adjusting the masking 139 * curve, usually to give a closer match to a better psychoacoustic model. 140 * 141 * @param[in] s adjustable bit allocation parameters 142 * @param[in] band_psd signal power for each critical band 143 * @param[in] start starting bin location 144 * @param[in] end ending bin location 145 * @param[in] fast_gain fast gain (estimated signal-to-mask ratio) 146 * @param[in] is_lfe whether or not the channel being processed is the LFE 147 * @param[in] dba_mode delta bit allocation mode (none, reuse, or new) 148 * @param[in] dba_nsegs number of delta segments 149 * @param[in] dba_offsets location offsets for each segment 150 * @param[in] dba_lengths length of each segment 151 * @param[in] dba_values delta bit allocation for each segment 152 * @param[out] mask calculated masking curve 153 * @return returns 0 for success, non-zero for error 154 */ 155int ff_ac3_bit_alloc_calc_mask(AC3BitAllocParameters *s, int16_t *band_psd, 156 int start, int end, int fast_gain, int is_lfe, 157 int dba_mode, int dba_nsegs, uint8_t *dba_offsets, 158 uint8_t *dba_lengths, uint8_t *dba_values, 159 int16_t *mask); 160 161/** 162 * Calculates bit allocation pointers. 163 * The SNR is the difference between the masking curve and the signal. AC-3 164 * uses this value for each frequency bin to allocate bits. The snroffset 165 * parameter is a global adjustment to the SNR for all bins. 166 * 167 * @param[in] mask masking curve 168 * @param[in] psd signal power for each frequency bin 169 * @param[in] start starting bin location 170 * @param[in] end ending bin location 171 * @param[in] snr_offset SNR adjustment 172 * @param[in] floor noise floor 173 * @param[in] bap_tab look-up table for bit allocation pointers 174 * @param[out] bap bit allocation pointers 175 */ 176void ff_ac3_bit_alloc_calc_bap(int16_t *mask, int16_t *psd, int start, int end, 177 int snr_offset, int floor, 178 const uint8_t *bap_tab, uint8_t *bap); 179 180void ac3_parametric_bit_allocation(AC3BitAllocParameters *s, uint8_t *bap, 181 int8_t *exp, int start, int end, 182 int snr_offset, int fast_gain, int is_lfe, 183 int dba_mode, int dba_nsegs, 184 uint8_t *dba_offsets, uint8_t *dba_lengths, 185 uint8_t *dba_values); 186 187#endif /* AVCODEC_AC3_H */ 188