/* * Common code between the AC-3 encoder and decoder * Copyright (c) 2000, 2001, 2002 Fabrice Bellard * * This file is part of FFmpeg. * * FFmpeg is free software; you can redistribute it and/or * modify it under the terms of the GNU Lesser General Public * License as published by the Free Software Foundation; either * version 2.1 of the License, or (at your option) any later version. * * FFmpeg is distributed in the hope that it will be useful, * but WITHOUT ANY WARRANTY; without even the implied warranty of * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU * Lesser General Public License for more details. * * You should have received a copy of the GNU Lesser General Public * License along with FFmpeg; if not, write to the Free Software * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA */ /** * @file * Common code between the AC-3 encoder and decoder. */ #ifndef AVCODEC_AC3_H #define AVCODEC_AC3_H #define AC3_MAX_CODED_FRAME_SIZE 3840 /* in bytes */ #define AC3_MAX_CHANNELS 6 /* including LFE channel */ #define AC3_MAX_COEFS 256 #define AC3_BLOCK_SIZE 256 #define AC3_MAX_BLOCKS 6 #define AC3_FRAME_SIZE (AC3_MAX_BLOCKS * 256) #define AC3_WINDOW_SIZE (AC3_BLOCK_SIZE * 2) #define AC3_CRITICAL_BANDS 50 #define AC3_MAX_CPL_BANDS 18 #include "ac3tab.h" /* exponent encoding strategy */ #define EXP_REUSE 0 #define EXP_NEW 1 #define EXP_D15 1 #define EXP_D25 2 #define EXP_D45 3 /** Delta bit allocation strategy */ typedef enum { DBA_REUSE = 0, DBA_NEW, DBA_NONE, DBA_RESERVED } AC3DeltaStrategy; /** Channel mode (audio coding mode) */ typedef enum { AC3_CHMODE_DUALMONO = 0, AC3_CHMODE_MONO, AC3_CHMODE_STEREO, AC3_CHMODE_3F, AC3_CHMODE_2F1R, AC3_CHMODE_3F1R, AC3_CHMODE_2F2R, AC3_CHMODE_3F2R } AC3ChannelMode; typedef struct AC3BitAllocParameters { int sr_code; int sr_shift; int slow_gain, slow_decay, fast_decay, db_per_bit, floor; int cpl_fast_leak, cpl_slow_leak; } AC3BitAllocParameters; /** * @struct AC3HeaderInfo * Coded AC-3 header values up to the lfeon element, plus derived values. */ typedef struct { /** @defgroup coded Coded elements * @{ */ uint16_t sync_word; uint16_t crc1; uint8_t sr_code; uint8_t bitstream_id; uint8_t bitstream_mode; uint8_t channel_mode; uint8_t lfe_on; uint8_t frame_type; int substreamid; ///< substream identification int center_mix_level; ///< Center mix level index int surround_mix_level; ///< Surround mix level index uint16_t channel_map; int num_blocks; ///< number of audio blocks /** @} */ /** @defgroup derived Derived values * @{ */ uint8_t sr_shift; uint16_t sample_rate; uint32_t bit_rate; uint8_t channels; uint16_t frame_size; int64_t channel_layout; /** @} */ } AC3HeaderInfo; typedef enum { EAC3_FRAME_TYPE_INDEPENDENT = 0, EAC3_FRAME_TYPE_DEPENDENT, EAC3_FRAME_TYPE_AC3_CONVERT, EAC3_FRAME_TYPE_RESERVED } EAC3FrameType; void ff_ac3_common_init(void); /** * Calculate the log power-spectral density of the input signal. * This gives a rough estimate of signal power in the frequency domain by using * the spectral envelope (exponents). The psd is also separately grouped * into critical bands for use in the calculating the masking curve. * 128 units in psd = -6 dB. The dbknee parameter in AC3BitAllocParameters * determines the reference level. * * @param[in] exp frequency coefficient exponents * @param[in] start starting bin location * @param[in] end ending bin location * @param[out] psd signal power for each frequency bin * @param[out] band_psd signal power for each critical band */ void ff_ac3_bit_alloc_calc_psd(int8_t *exp, int start, int end, int16_t *psd, int16_t *band_psd); /** * Calculate the masking curve. * First, the excitation is calculated using parameters in s and the signal * power in each critical band. The excitation is compared with a predefined * hearing threshold table to produce the masking curve. If delta bit * allocation information is provided, it is used for adjusting the masking * curve, usually to give a closer match to a better psychoacoustic model. * * @param[in] s adjustable bit allocation parameters * @param[in] band_psd signal power for each critical band * @param[in] start starting bin location * @param[in] end ending bin location * @param[in] fast_gain fast gain (estimated signal-to-mask ratio) * @param[in] is_lfe whether or not the channel being processed is the LFE * @param[in] dba_mode delta bit allocation mode (none, reuse, or new) * @param[in] dba_nsegs number of delta segments * @param[in] dba_offsets location offsets for each segment * @param[in] dba_lengths length of each segment * @param[in] dba_values delta bit allocation for each segment * @param[out] mask calculated masking curve * @return returns 0 for success, non-zero for error */ int ff_ac3_bit_alloc_calc_mask(AC3BitAllocParameters *s, int16_t *band_psd, int start, int end, int fast_gain, int is_lfe, int dba_mode, int dba_nsegs, uint8_t *dba_offsets, uint8_t *dba_lengths, uint8_t *dba_values, int16_t *mask); /** * Calculate bit allocation pointers. * The SNR is the difference between the masking curve and the signal. AC-3 * uses this value for each frequency bin to allocate bits. The snroffset * parameter is a global adjustment to the SNR for all bins. * * @param[in] mask masking curve * @param[in] psd signal power for each frequency bin * @param[in] start starting bin location * @param[in] end ending bin location * @param[in] snr_offset SNR adjustment * @param[in] floor noise floor * @param[in] bap_tab look-up table for bit allocation pointers * @param[out] bap bit allocation pointers */ void ff_ac3_bit_alloc_calc_bap(int16_t *mask, int16_t *psd, int start, int end, int snr_offset, int floor, const uint8_t *bap_tab, uint8_t *bap); #endif /* AVCODEC_AC3_H */