| /* |
| * 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 libavcodec/ac3.h |
| * Common code between the AC-3 encoder and decoder. |
| */ |
| |
| #ifndef AVCODEC_AC3_H |
| #define AVCODEC_AC3_H |
| |
| #include "ac3tab.h" |
| |
| #define AC3_MAX_CODED_FRAME_SIZE 3840 /* in bytes */ |
| #define AC3_MAX_CHANNELS 6 /* including LFE channel */ |
| |
| #define NB_BLOCKS 6 /* number of PCM blocks inside an AC-3 frame */ |
| #define AC3_FRAME_SIZE (NB_BLOCKS * 256) |
| |
| /* 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 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; |
| /** @} */ |
| } AC3HeaderInfo; |
| |
| typedef enum { |
| EAC3_FRAME_TYPE_INDEPENDENT = 0, |
| EAC3_FRAME_TYPE_DEPENDENT, |
| EAC3_FRAME_TYPE_AC3_CONVERT, |
| EAC3_FRAME_TYPE_RESERVED |
| } EAC3FrameType; |
| |
| void ac3_common_init(void); |
| |
| /** |
| * Calculates 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); |
| |
| /** |
| * Calculates the masking curve. |
| * First, the excitation is calculated using parameters in \p 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); |
| |
| /** |
| * Calculates 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 \p 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); |
| |
| void ac3_parametric_bit_allocation(AC3BitAllocParameters *s, uint8_t *bap, |
| int8_t *exp, int start, int end, |
| int snr_offset, int fast_gain, int is_lfe, |
| int dba_mode, int dba_nsegs, |
| uint8_t *dba_offsets, uint8_t *dba_lengths, |
| uint8_t *dba_values); |
| |
| #endif /* AVCODEC_AC3_H */ |
