2 * Common code between AC3 encoder and decoder
3 * Copyright (c) 2000, 2001, 2002 Fabrice Bellard.
5 * This file is part of FFmpeg.
7 * FFmpeg is free software; you can redistribute it and/or
8 * modify it under the terms of the GNU Lesser General Public
9 * License as published by the Free Software Foundation; either
10 * version 2.1 of the License, or (at your option) any later version.
12 * FFmpeg is distributed in the hope that it will be useful,
13 * but WITHOUT ANY WARRANTY; without even the implied warranty of
14 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
15 * Lesser General Public License for more details.
17 * You should have received a copy of the GNU Lesser General Public
18 * License along with FFmpeg; if not, write to the Free Software
19 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
24 * Common code between AC3 encoder and decoder.
27 #define AC3_MAX_CODED_FRAME_SIZE 3840 /* in bytes */
28 #define AC3_MAX_CHANNELS 6 /* including LFE channel */
30 #define NB_BLOCKS 6 /* number of PCM blocks inside an AC3 frame */
31 #define AC3_FRAME_SIZE (NB_BLOCKS * 256)
33 /* exponent encoding strategy */
41 typedef struct AC3BitAllocParameters {
42 int fscod; /* frequency */
44 int sgain, sdecay, fdecay, dbknee, floor;
45 int cplfleak, cplsleak;
46 } AC3BitAllocParameters;
49 * @struct AC3HeaderInfo
50 * Coded AC-3 header values up to the lfeon element, plus derived values.
53 /** @defgroup coded Coded elements
69 /** @defgroup derived Derived values
81 * Parses AC-3 frame header.
82 * Parses the header up to the lfeon element, which is the first 52 or 54 bits
83 * depending on the audio coding mode.
84 * @param buf[in] Array containing the first 7 bytes of the frame.
85 * @param hdr[out] Pointer to struct where header info is written.
86 * @return Returns 0 on success, -1 if there is a sync word mismatch,
87 * -2 if the bsid (version) element is invalid, -3 if the fscod (sample rate)
88 * element is invalid, or -4 if the frmsizecod (bit rate) element is invalid.
90 int ff_ac3_parse_header(const uint8_t buf[7], AC3HeaderInfo *hdr);
92 extern const uint16_t ff_ac3_frame_sizes[38][3];
93 extern const uint8_t ff_ac3_channels[8];
94 extern const uint16_t ff_ac3_freqs[3];
95 extern const uint16_t ff_ac3_bitratetab[19];
96 extern const int16_t ff_ac3_window[256];
97 extern const uint8_t ff_sdecaytab[4];
98 extern const uint8_t ff_fdecaytab[4];
99 extern const uint16_t ff_sgaintab[4];
100 extern const uint16_t ff_dbkneetab[4];
101 extern const int16_t ff_floortab[8];
102 extern const uint16_t ff_fgaintab[8];
104 void ac3_common_init(void);
105 void ac3_parametric_bit_allocation(AC3BitAllocParameters *s, uint8_t *bap,
106 int8_t *exp, int start, int end,
107 int snroffset, int fgain, int is_lfe,
108 int deltbae,int deltnseg,
109 uint8_t *deltoffst, uint8_t *deltlen, uint8_t *deltba);