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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..ae53a80c3 --- /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. + */ + +#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 + +typedef struct AC3BitAllocParameters { + int fscod; /* frequency */ + int halfratecod; + int sgain, sdecay, fdecay, dbknee, floor; + int cplfleak, cplsleak; +} 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 fscod; + uint8_t frmsizecod; + uint8_t bsid; + uint8_t bsmod; + uint8_t acmod; + uint8_t cmixlev; + uint8_t surmixlev; + uint8_t dsurmod; + uint8_t lfeon; + /** @} */ + + /** @defgroup derived Derived values + * @{ + */ + uint8_t halfratecod; + uint16_t sample_rate; + uint32_t bit_rate; + uint8_t channels; + uint16_t frame_size; + /** @} */ +} AC3HeaderInfo; + +/** + * Parses AC-3 frame header. + * Parses the header up to the lfeon element, which is the first 52 or 54 bits + * depending on the audio coding mode. + * @param buf[in] Array containing the first 7 bytes of the frame. + * @param hdr[out] Pointer to struct where header info is written. + * @return Returns 0 on success, -1 if there is a sync word mismatch, + * -2 if the bsid (version) element is invalid, -3 if the fscod (sample rate) + * element is invalid, or -4 if the frmsizecod (bit rate) element is invalid. + */ +int ff_ac3_parse_header(const uint8_t buf[7], AC3HeaderInfo *hdr); + +extern const uint16_t ff_ac3_frame_sizes[38][3]; +extern const uint8_t ff_ac3_channels[8]; +extern const uint16_t ff_ac3_freqs[3]; +extern const uint16_t ff_ac3_bitratetab[19]; +extern const int16_t ff_ac3_window[256]; +extern const uint8_t ff_sdecaytab[4]; +extern const uint8_t ff_fdecaytab[4]; +extern const uint16_t ff_sgaintab[4]; +extern const uint16_t ff_dbkneetab[4]; +extern const int16_t ff_floortab[8]; +extern const uint16_t ff_fgaintab[8]; + +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] bndpsd 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 *bndpsd); + +/** + * 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] bndpsd signal power for each critical band + * @param[in] start starting bin location + * @param[in] end ending bin location + * @param[in] fgain fast gain (estimated signal-to-mask ratio) + * @param[in] is_lfe whether or not the channel being processed is the LFE + * @param[in] deltbae delta bit allocation exists (none, reuse, or new) + * @param[in] deltnseg number of delta segments + * @param[in] deltoffst location offsets for each segment + * @param[in] deltlen length of each segment + * @param[in] deltba delta bit allocation for each segment + * @param[out] mask calculated masking curve + */ +void ff_ac3_bit_alloc_calc_mask(AC3BitAllocParameters *s, int16_t *bndpsd, + int start, int end, int fgain, int is_lfe, + int deltbae, int deltnseg, uint8_t *deltoffst, + uint8_t *deltlen, uint8_t *deltba, + 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] snroffset 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 snroffset, int floor, uint8_t *bap); + +void ac3_parametric_bit_allocation(AC3BitAllocParameters *s, uint8_t *bap, + int8_t *exp, int start, int end, + int snroffset, int fgain, int is_lfe, + int deltbae,int deltnseg, + uint8_t *deltoffst, uint8_t *deltlen, uint8_t *deltba); |