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 */ 64typedef enum { 65 DBA_REUSE = 0, 66 DBA_NEW, 67 DBA_NONE, 68 DBA_RESERVED 69} AC3DeltaStrategy; 70 71/** Channel mode (audio coding mode) */ 72typedef 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 83typedef struct AC3BitAllocParameters { 84 int sr_code; 85 int sr_shift; 86 int slow_gain, slow_decay, fast_decay, db_per_bit, floor; 87 int cpl_fast_leak, cpl_slow_leak; 88} AC3BitAllocParameters; 89 90/** 91 * @struct AC3HeaderInfo 92 * Coded AC-3 header values up to the lfeon element, plus derived values. 93 */ 94typedef struct { 95 /** @name Coded elements 96 * @{ 97 */ 98 uint16_t sync_word; 99 uint16_t crc1; 100 uint8_t sr_code; 101 uint8_t bitstream_id; 102 uint8_t bitstream_mode; 103 uint8_t channel_mode; 104 uint8_t lfe_on; 105 uint8_t frame_type; 106 int substreamid; ///< substream identification 107 int center_mix_level; ///< Center mix level index 108 int surround_mix_level; ///< Surround mix level index 109 uint16_t channel_map; 110 int num_blocks; ///< number of audio blocks 111 /** @} */ 112 113 /** @name Derived values 114 * @{ 115 */ 116 uint8_t sr_shift; 117 uint16_t sample_rate; 118 uint32_t bit_rate; 119 uint8_t channels; 120 uint16_t frame_size; 121 uint64_t channel_layout; 122 /** @} */ 123} AC3HeaderInfo; 124 125typedef enum { 126 EAC3_FRAME_TYPE_INDEPENDENT = 0, 127 EAC3_FRAME_TYPE_DEPENDENT, 128 EAC3_FRAME_TYPE_AC3_CONVERT, 129 EAC3_FRAME_TYPE_RESERVED 130} EAC3FrameType; 131 132void ff_ac3_common_init(void); 133 134/** 135 * Calculate the log power-spectral density of the input signal. 136 * This gives a rough estimate of signal power in the frequency domain by using 137 * the spectral envelope (exponents). The psd is also separately grouped 138 * into critical bands for use in the calculating the masking curve. 139 * 128 units in psd = -6 dB. The dbknee parameter in AC3BitAllocParameters 140 * determines the reference level. 141 * 142 * @param[in] exp frequency coefficient exponents 143 * @param[in] start starting bin location 144 * @param[in] end ending bin location 145 * @param[out] psd signal power for each frequency bin 146 * @param[out] band_psd signal power for each critical band 147 */ 148void ff_ac3_bit_alloc_calc_psd(int8_t *exp, int start, int end, int16_t *psd, 149 int16_t *band_psd); 150 151/** 152 * Calculate the masking curve. 153 * First, the excitation is calculated using parameters in s and the signal 154 * power in each critical band. The excitation is compared with a predefined 155 * hearing threshold table to produce the masking curve. If delta bit 156 * allocation information is provided, it is used for adjusting the masking 157 * curve, usually to give a closer match to a better psychoacoustic model. 158 * 159 * @param[in] s adjustable bit allocation parameters 160 * @param[in] band_psd signal power for each critical band 161 * @param[in] start starting bin location 162 * @param[in] end ending bin location 163 * @param[in] fast_gain fast gain (estimated signal-to-mask ratio) 164 * @param[in] is_lfe whether or not the channel being processed is the LFE 165 * @param[in] dba_mode delta bit allocation mode (none, reuse, or new) 166 * @param[in] dba_nsegs number of delta segments 167 * @param[in] dba_offsets location offsets for each segment 168 * @param[in] dba_lengths length of each segment 169 * @param[in] dba_values delta bit allocation for each segment 170 * @param[out] mask calculated masking curve 171 * @return returns 0 for success, non-zero for error 172 */ 173int ff_ac3_bit_alloc_calc_mask(AC3BitAllocParameters *s, int16_t *band_psd, 174 int start, int end, int fast_gain, int is_lfe, 175 int dba_mode, int dba_nsegs, uint8_t *dba_offsets, 176 uint8_t *dba_lengths, uint8_t *dba_values, 177 int16_t *mask); 178 179#endif /* AVCODEC_AC3_H */ 180