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
153
154
155
156
157
158
159
160
161
162
163
|
/*
* AC3 parser
* Copyright (c) 2003 Fabrice Bellard.
* Copyright (c) 2003 Michael Niedermayer.
*
* This file is part of FFmpeg.
*
* FFmpeg 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.
*
* FFmpeg 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 FFmpeg; if not, write to the Free Software
* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
*/
#include "parser.h"
#include "ac3_parser.h"
#include "aac_ac3_parser.h"
#include "bitstream.h"
#define AC3_HEADER_SIZE 7
static const uint8_t eac3_blocks[4] = {
1, 2, 3, 6
};
int ff_ac3_parse_header(const uint8_t buf[7], AC3HeaderInfo *hdr)
{
GetBitContext gbc;
int frame_size_code;
int num_blocks;
memset(hdr, 0, sizeof(*hdr));
init_get_bits(&gbc, buf, 54);
hdr->sync_word = get_bits(&gbc, 16);
if(hdr->sync_word != 0x0B77)
return AC3_PARSE_ERROR_SYNC;
/* read ahead to bsid to distinguish between AC-3 and E-AC-3 */
hdr->bitstream_id = show_bits_long(&gbc, 29) & 0x1F;
if(hdr->bitstream_id > 16)
return AC3_PARSE_ERROR_BSID;
if(hdr->bitstream_id <= 10) {
/* Normal AC-3 */
hdr->crc1 = get_bits(&gbc, 16);
hdr->sr_code = get_bits(&gbc, 2);
if(hdr->sr_code == 3)
return AC3_PARSE_ERROR_SAMPLE_RATE;
frame_size_code = get_bits(&gbc, 6);
if(frame_size_code > 37)
return AC3_PARSE_ERROR_FRAME_SIZE;
skip_bits(&gbc, 5); // skip bsid, already got it
skip_bits(&gbc, 3); // skip bitstream mode
hdr->channel_mode = get_bits(&gbc, 3);
if((hdr->channel_mode & 1) && hdr->channel_mode != AC3_CHMODE_MONO) {
skip_bits(&gbc, 2); // skip center mix level
}
if(hdr->channel_mode & 4) {
skip_bits(&gbc, 2); // skip surround mix level
}
if(hdr->channel_mode == AC3_CHMODE_STEREO) {
skip_bits(&gbc, 2); // skip dolby surround mode
}
hdr->lfe_on = get_bits1(&gbc);
hdr->sr_shift = FFMAX(hdr->bitstream_id, 8) - 8;
hdr->sample_rate = ff_ac3_sample_rate_tab[hdr->sr_code] >> hdr->sr_shift;
hdr->bit_rate = (ff_ac3_bitrate_tab[frame_size_code>>1] * 1000) >> hdr->sr_shift;
hdr->channels = ff_ac3_channels_tab[hdr->channel_mode] + hdr->lfe_on;
hdr->frame_size = ff_ac3_frame_size_tab[frame_size_code][hdr->sr_code] * 2;
hdr->frame_type = EAC3_FRAME_TYPE_INDEPENDENT;
} else {
/* Enhanced AC-3 */
hdr->crc1 = 0;
hdr->frame_type = get_bits(&gbc, 2);
if(hdr->frame_type == EAC3_FRAME_TYPE_RESERVED)
return AC3_PARSE_ERROR_FRAME_TYPE;
skip_bits(&gbc, 3); // skip substream id
hdr->frame_size = (get_bits(&gbc, 11) + 1) << 1;
if(hdr->frame_size < AC3_HEADER_SIZE)
return AC3_PARSE_ERROR_FRAME_SIZE;
hdr->sr_code = get_bits(&gbc, 2);
if (hdr->sr_code == 3) {
int sr_code2 = get_bits(&gbc, 2);
if(sr_code2 == 3)
return AC3_PARSE_ERROR_SAMPLE_RATE;
hdr->sample_rate = ff_ac3_sample_rate_tab[sr_code2] / 2;
hdr->sr_shift = 1;
num_blocks = 6;
} else {
num_blocks = eac3_blocks[get_bits(&gbc, 2)];
hdr->sample_rate = ff_ac3_sample_rate_tab[hdr->sr_code];
hdr->sr_shift = 0;
}
hdr->channel_mode = get_bits(&gbc, 3);
hdr->lfe_on = get_bits1(&gbc);
hdr->bit_rate = (uint32_t)(8.0 * hdr->frame_size * hdr->sample_rate /
(num_blocks * 256.0));
hdr->channels = ff_ac3_channels_tab[hdr->channel_mode] + hdr->lfe_on;
}
return 0;
}
static int ac3_sync(uint64_t state, AACAC3ParseContext *hdr_info,
int *need_next_header, int *new_frame_start)
{
int err;
uint64_t tmp = be2me_64(state);
AC3HeaderInfo hdr;
err = ff_ac3_parse_header(((uint8_t *)&tmp)+8-AC3_HEADER_SIZE, &hdr);
if(err < 0)
return 0;
hdr_info->sample_rate = hdr.sample_rate;
hdr_info->bit_rate = hdr.bit_rate;
hdr_info->channels = hdr.channels;
hdr_info->samples = AC3_FRAME_SIZE;
*need_next_header = 0;//(hdr.frame_type != EAC3_FRAME_TYPE_AC3_CONVERT);
*new_frame_start = 1;//(hdr.frame_type != EAC3_FRAME_TYPE_DEPENDENT);
return hdr.frame_size;
}
static av_cold int ac3_parse_init(AVCodecParserContext *s1)
{
AACAC3ParseContext *s = s1->priv_data;
s->header_size = AC3_HEADER_SIZE;
s->sync = ac3_sync;
return 0;
}
AVCodecParser ac3_parser = {
{ CODEC_ID_AC3 },
sizeof(AACAC3ParseContext),
ac3_parse_init,
ff_aac_ac3_parse,
NULL,
};
|
