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 extern const uint16_t ac3_freqs[3];
50 extern const uint16_t ac3_bitratetab[19];
51 extern const int16_t ac3_window[256];
52 extern const uint8_t sdecaytab[4];
53 extern const uint8_t fdecaytab[4];
54 extern const uint16_t sgaintab[4];
55 extern const uint16_t dbkneetab[4];
56 extern const uint16_t floortab[8];
57 extern const uint16_t fgaintab[8];
60 void ac3_common_init(void);
61 void ac3_parametric_bit_allocation(AC3BitAllocParameters *s, uint8_t *bap,
62 int8_t *exp, int start, int end,
63 int snroffset, int fgain, int is_lfe,
64 int deltbae,int deltnseg,
65 uint8_t *deltoffst, uint8_t *deltlen, uint8_t *deltba);