1/*
2 * MLP codec common header file
3 * Copyright (c) 2007-2008 Ian Caulfield
4 *
5 * This file is part of FFmpeg.
6 *
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.
11 *
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.
16 *
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
20 */
21
22#ifndef AVCODEC_MLP_H
23#define AVCODEC_MLP_H
24
25#include <stdint.h>
26
27#include "avcodec.h"
28
29/** Maximum number of channels that can be decoded. */
30#define MAX_CHANNELS        16
31
32/** Maximum number of matrices used in decoding; most streams have one matrix
33 *  per output channel, but some rematrix a channel (usually 0) more than once.
34 */
35#define MAX_MATRICES        15
36
37/** Maximum number of substreams that can be decoded. This could also be set
38 *  higher, but I haven't seen any examples with more than two.
39 */
40#define MAX_SUBSTREAMS      2
41
42/** maximum sample frequency seen in files */
43#define MAX_SAMPLERATE      192000
44
45/** maximum number of audio samples within one access unit */
46#define MAX_BLOCKSIZE       (40 * (MAX_SAMPLERATE / 48000))
47/** next power of two greater than MAX_BLOCKSIZE */
48#define MAX_BLOCKSIZE_POW2  (64 * (MAX_SAMPLERATE / 48000))
49
50/** number of allowed filters */
51#define NUM_FILTERS         2
52
53/** The maximum number of taps in either the IIR or FIR filter;
54 *  I believe MLP actually specifies the maximum order for IIR filters as four,
55 *  and that the sum of the orders of both filters must be <= 8.
56*/
57#define MAX_FILTER_ORDER    8
58
59/** Code that signals end of a stream. */
60#define END_OF_STREAM       0xd234d234
61
62#define FIR 0
63#define IIR 1
64
65/** filter data */
66typedef struct {
67    uint8_t     order; ///< number of taps in filter
68    uint8_t     shift; ///< Right shift to apply to output of filter.
69
70    int32_t     coeff[MAX_FILTER_ORDER];
71    int32_t     state[MAX_FILTER_ORDER];
72} FilterParams;
73
74/** sample data coding information */
75typedef struct {
76    FilterParams filter_params[NUM_FILTERS];
77
78    int16_t     huff_offset;      ///< Offset to apply to residual values.
79    int32_t     sign_huff_offset; ///< sign/rounding-corrected version of huff_offset
80    uint8_t     codebook;         ///< Which VLC codebook to use to read residuals.
81    uint8_t     huff_lsbs;        ///< Size of residual suffix not encoded using VLC.
82} ChannelParams;
83
84/** Tables defining the Huffman codes.
85 *  There are three entropy coding methods used in MLP (four if you count
86 *  "none" as a method). These use the same sequences for codes starting with
87 *  00 or 01, but have different codes starting with 1.
88 */
89extern const uint8_t ff_mlp_huffman_tables[3][18][2];
90
91/** MLP uses checksums that seem to be based on the standard CRC algorithm, but
92 *  are not (in implementation terms, the table lookup and XOR are reversed).
93 *  We can implement this behavior using a standard av_crc on all but the
94 *  last element, then XOR that with the last element.
95 */
96uint8_t  ff_mlp_checksum8 (const uint8_t *buf, unsigned int buf_size);
97uint16_t ff_mlp_checksum16(const uint8_t *buf, unsigned int buf_size);
98
99/** Calculate an 8-bit checksum over a restart header -- a non-multiple-of-8
100 *  number of bits, starting two bits into the first byte of buf.
101 */
102uint8_t ff_mlp_restart_checksum(const uint8_t *buf, unsigned int bit_size);
103
104/** XOR together all the bytes of a buffer.
105 *  Does this belong in dspcontext?
106 */
107uint8_t ff_mlp_calculate_parity(const uint8_t *buf, unsigned int buf_size);
108
109void ff_mlp_init_crc(void);
110
111/** XOR four bytes into one. */
112static inline uint8_t xor_32_to_8(uint32_t value)
113{
114    value ^= value >> 16;
115    value ^= value >>  8;
116    return value;
117}
118
119#endif /* AVCODEC_MLP_H */
120