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110 lines
3.4 KiB
C
110 lines
3.4 KiB
C
/*
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* Common code between AC3 encoder and decoder
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* Copyright (c) 2000, 2001, 2002 Fabrice Bellard.
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*
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* This file is part of FFmpeg.
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*
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* FFmpeg is free software; you can redistribute it and/or
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* modify it under the terms of the GNU Lesser General Public
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* License as published by the Free Software Foundation; either
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* version 2.1 of the License, or (at your option) any later version.
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*
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* FFmpeg is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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* Lesser General Public License for more details.
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*
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* You should have received a copy of the GNU Lesser General Public
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* License along with FFmpeg; if not, write to the Free Software
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* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
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*/
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/**
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* @file ac3.h
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* Common code between AC3 encoder and decoder.
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*/
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#define AC3_MAX_CODED_FRAME_SIZE 3840 /* in bytes */
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#define AC3_MAX_CHANNELS 6 /* including LFE channel */
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#define NB_BLOCKS 6 /* number of PCM blocks inside an AC3 frame */
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#define AC3_FRAME_SIZE (NB_BLOCKS * 256)
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/* exponent encoding strategy */
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#define EXP_REUSE 0
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#define EXP_NEW 1
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#define EXP_D15 1
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#define EXP_D25 2
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#define EXP_D45 3
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typedef struct AC3BitAllocParameters {
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int fscod; /* frequency */
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int halfratecod;
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int sgain, sdecay, fdecay, dbknee, floor;
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int cplfleak, cplsleak;
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} AC3BitAllocParameters;
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/**
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* @struct AC3HeaderInfo
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* Coded AC-3 header values up to the lfeon element, plus derived values.
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*/
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typedef struct {
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/** @defgroup coded Coded elements
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* @{
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*/
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uint16_t sync_word;
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uint16_t crc1;
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uint8_t fscod;
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uint8_t frmsizecod;
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uint8_t bsid;
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uint8_t bsmod;
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uint8_t acmod;
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uint8_t cmixlev;
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uint8_t surmixlev;
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uint8_t dsurmod;
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uint8_t lfeon;
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/** @} */
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/** @defgroup derived Derived values
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* @{
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*/
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uint8_t halfratecod;
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uint16_t sample_rate;
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uint32_t bit_rate;
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uint8_t channels;
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uint16_t frame_size;
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/** @} */
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} AC3HeaderInfo;
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/**
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* Parses AC-3 frame header.
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* Parses the header up to the lfeon element, which is the first 52 or 54 bits
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* depending on the audio coding mode.
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* @param buf[in] Array containing the first 7 bytes of the frame.
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* @param hdr[out] Pointer to struct where header info is written.
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* @return Returns 0 on success, -1 if there is a sync word mismatch,
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* -2 if the bsid (version) element is invalid, -3 if the fscod (sample rate)
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* element is invalid, or -4 if the frmsizecod (bit rate) element is invalid.
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*/
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int ff_ac3_parse_header(const uint8_t buf[7], AC3HeaderInfo *hdr);
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extern uint16_t ff_ac3_frame_sizes[38][3];
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extern const uint8_t ff_ac3_channels[8];
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extern const uint16_t ff_ac3_freqs[3];
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extern const uint16_t ff_ac3_bitratetab[19];
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extern const int16_t ff_ac3_window[256];
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extern const uint8_t ff_sdecaytab[4];
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extern const uint8_t ff_fdecaytab[4];
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extern const uint16_t ff_sgaintab[4];
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extern const uint16_t ff_dbkneetab[4];
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extern const int16_t ff_floortab[8];
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extern const uint16_t ff_fgaintab[8];
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void ac3_common_init(void);
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void ac3_parametric_bit_allocation(AC3BitAllocParameters *s, uint8_t *bap,
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int8_t *exp, int start, int end,
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int snroffset, int fgain, int is_lfe,
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int deltbae,int deltnseg,
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uint8_t *deltoffst, uint8_t *deltlen, uint8_t *deltba);
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