1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
|
/*
* FLAC common code
* Copyright (c) 2009 Justin Ruggles
*
* This file is part of Libav.
*
* Libav 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.
*
* Libav 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 Libav; if not, write to the Free Software
* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
*/
#include "libavutil/crc.h"
#include "flac.h"
#include "flacdata.h"
static const int8_t sample_size_table[] = { 0, 8, 12, 0, 16, 20, 24, 0 };
static int64_t get_utf8(GetBitContext *gb)
{
int64_t val;
GET_UTF8(val, get_bits(gb, 8), return -1;)
return val;
}
int ff_flac_decode_frame_header(AVCodecContext *avctx, GetBitContext *gb,
FLACFrameInfo *fi, int log_level_offset)
{
int bs_code, sr_code, bps_code;
/* frame sync code */
if ((get_bits(gb, 15) & 0x7FFF) != 0x7FFC) {
av_log(avctx, AV_LOG_ERROR + log_level_offset, "invalid sync code\n");
return -1;
}
/* variable block size stream code */
fi->is_var_size = get_bits1(gb);
/* block size and sample rate codes */
bs_code = get_bits(gb, 4);
sr_code = get_bits(gb, 4);
/* channels and decorrelation */
fi->ch_mode = get_bits(gb, 4);
if (fi->ch_mode < FLAC_MAX_CHANNELS) {
fi->channels = fi->ch_mode + 1;
fi->ch_mode = FLAC_CHMODE_INDEPENDENT;
} else if (fi->ch_mode < FLAC_MAX_CHANNELS + FLAC_CHMODE_MID_SIDE) {
fi->channels = 2;
fi->ch_mode -= FLAC_MAX_CHANNELS - 1;
} else {
av_log(avctx, AV_LOG_ERROR + log_level_offset,
"invalid channel mode: %d\n", fi->ch_mode);
return -1;
}
/* bits per sample */
bps_code = get_bits(gb, 3);
if (bps_code == 3 || bps_code == 7) {
av_log(avctx, AV_LOG_ERROR + log_level_offset,
"invalid sample size code (%d)\n",
bps_code);
return -1;
}
fi->bps = sample_size_table[bps_code];
/* reserved bit */
if (get_bits1(gb)) {
av_log(avctx, AV_LOG_ERROR + log_level_offset,
"broken stream, invalid padding\n");
return -1;
}
/* sample or frame count */
fi->frame_or_sample_num = get_utf8(gb);
if (fi->frame_or_sample_num < 0) {
av_log(avctx, AV_LOG_ERROR + log_level_offset,
"sample/frame number invalid; utf8 fscked\n");
return -1;
}
/* blocksize */
if (bs_code == 0) {
av_log(avctx, AV_LOG_ERROR + log_level_offset,
"reserved blocksize code: 0\n");
return -1;
} else if (bs_code == 6) {
fi->blocksize = get_bits(gb, 8) + 1;
} else if (bs_code == 7) {
fi->blocksize = get_bits(gb, 16) + 1;
} else {
fi->blocksize = ff_flac_blocksize_table[bs_code];
}
/* sample rate */
if (sr_code < 12) {
fi->samplerate = ff_flac_sample_rate_table[sr_code];
} else if (sr_code == 12) {
fi->samplerate = get_bits(gb, 8) * 1000;
} else if (sr_code == 13) {
fi->samplerate = get_bits(gb, 16);
} else if (sr_code == 14) {
fi->samplerate = get_bits(gb, 16) * 10;
} else {
av_log(avctx, AV_LOG_ERROR + log_level_offset,
"illegal sample rate code %d\n",
sr_code);
return -1;
}
/* header CRC-8 check */
skip_bits(gb, 8);
if (av_crc(av_crc_get_table(AV_CRC_8_ATM), 0, gb->buffer,
get_bits_count(gb)/8)) {
av_log(avctx, AV_LOG_ERROR + log_level_offset,
"header crc mismatch\n");
return -1;
}
return 0;
}
int ff_flac_get_max_frame_size(int blocksize, int ch, int bps)
{
/* Technically, there is no limit to FLAC frame size, but an encoder
should not write a frame that is larger than if verbatim encoding mode
were to be used. */
int count;
count = 16; /* frame header */
count += ch * ((7+bps+7)/8); /* subframe headers */
if (ch == 2) {
/* for stereo, need to account for using decorrelation */
count += (( 2*bps+1) * blocksize + 7) / 8;
} else {
count += ( ch*bps * blocksize + 7) / 8;
}
count += 2; /* frame footer */
return count;
}
|
