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Diffstat (limited to 'contrib/ffmpeg/libavcodec/ac3.h')
| -rw-r--r-- | contrib/ffmpeg/libavcodec/ac3.h | 171 |
1 files changed, 171 insertions, 0 deletions
diff --git a/contrib/ffmpeg/libavcodec/ac3.h b/contrib/ffmpeg/libavcodec/ac3.h new file mode 100644 index 000000000..b5fa789c4 --- /dev/null +++ b/contrib/ffmpeg/libavcodec/ac3.h @@ -0,0 +1,171 @@ +/* + * Common code between AC3 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 ac3.h + * Common code between AC3 encoder and decoder. + */ + +#ifndef FFMPEG_AC3_H +#define FFMPEG_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 AC3 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; + /** @} */ + + /** @defgroup derived Derived values + * @{ + */ + uint8_t sr_shift; + uint16_t sample_rate; + uint32_t bit_rate; + uint8_t channels; + uint16_t frame_size; + /** @} */ +} AC3HeaderInfo; + + +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 + */ +void 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[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, 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 /* FFMPEG_AC3_H */ |