Corrections of errors in aac_ac3_parser
[libav.git] / libavcodec / ac3_parser.c
1 /*
2 * AC3 parser
3 * Copyright (c) 2003 Fabrice Bellard.
4 * Copyright (c) 2003 Michael Niedermayer.
5 *
6 * This file is part of FFmpeg.
7 *
8 * FFmpeg is free software; you can redistribute it and/or
9 * modify it under the terms of the GNU Lesser General Public
10 * License as published by the Free Software Foundation; either
11 * version 2.1 of the License, or (at your option) any later version.
12 *
13 * FFmpeg is distributed in the hope that it will be useful,
14 * but WITHOUT ANY WARRANTY; without even the implied warranty of
15 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
16 * Lesser General Public License for more details.
17 *
18 * You should have received a copy of the GNU Lesser General Public
19 * License along with FFmpeg; if not, write to the Free Software
20 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
21 */
22
23 #include "parser.h"
24 #include "ac3_parser.h"
25 #include "aac_ac3_parser.h"
26 #include "bitstream.h"
27
28
29 #define AC3_HEADER_SIZE 7
30
31
32 static const uint8_t eac3_blocks[4] = {
33 1, 2, 3, 6
34 };
35
36
37 int ff_ac3_parse_header(const uint8_t buf[7], AC3HeaderInfo *hdr)
38 {
39 GetBitContext gbc;
40 int frame_size_code;
41 int num_blocks;
42
43 memset(hdr, 0, sizeof(*hdr));
44
45 init_get_bits(&gbc, buf, 54);
46
47 hdr->sync_word = get_bits(&gbc, 16);
48 if(hdr->sync_word != 0x0B77)
49 return AC3_PARSE_ERROR_SYNC;
50
51 /* read ahead to bsid to distinguish between AC-3 and E-AC-3 */
52 hdr->bitstream_id = show_bits_long(&gbc, 29) & 0x1F;
53 if(hdr->bitstream_id > 16)
54 return AC3_PARSE_ERROR_BSID;
55
56 if(hdr->bitstream_id <= 10) {
57 /* Normal AC-3 */
58 hdr->crc1 = get_bits(&gbc, 16);
59 hdr->sr_code = get_bits(&gbc, 2);
60 if(hdr->sr_code == 3)
61 return AC3_PARSE_ERROR_SAMPLE_RATE;
62
63 frame_size_code = get_bits(&gbc, 6);
64 if(frame_size_code > 37)
65 return AC3_PARSE_ERROR_FRAME_SIZE;
66
67 skip_bits(&gbc, 5); // skip bsid, already got it
68
69 skip_bits(&gbc, 3); // skip bitstream mode
70 hdr->channel_mode = get_bits(&gbc, 3);
71 if((hdr->channel_mode & 1) && hdr->channel_mode != AC3_CHMODE_MONO) {
72 skip_bits(&gbc, 2); // skip center mix level
73 }
74 if(hdr->channel_mode & 4) {
75 skip_bits(&gbc, 2); // skip surround mix level
76 }
77 if(hdr->channel_mode == AC3_CHMODE_STEREO) {
78 skip_bits(&gbc, 2); // skip dolby surround mode
79 }
80 hdr->lfe_on = get_bits1(&gbc);
81
82 hdr->sr_shift = FFMAX(hdr->bitstream_id, 8) - 8;
83 hdr->sample_rate = ff_ac3_sample_rate_tab[hdr->sr_code] >> hdr->sr_shift;
84 hdr->bit_rate = (ff_ac3_bitrate_tab[frame_size_code>>1] * 1000) >> hdr->sr_shift;
85 hdr->channels = ff_ac3_channels_tab[hdr->channel_mode] + hdr->lfe_on;
86 hdr->frame_size = ff_ac3_frame_size_tab[frame_size_code][hdr->sr_code] * 2;
87 hdr->frame_type = EAC3_FRAME_TYPE_INDEPENDENT;
88 } else {
89 /* Enhanced AC-3 */
90 hdr->crc1 = 0;
91 hdr->frame_type = get_bits(&gbc, 2);
92 if(hdr->frame_type == EAC3_FRAME_TYPE_RESERVED)
93 return AC3_PARSE_ERROR_FRAME_TYPE;
94
95 skip_bits(&gbc, 3); // skip substream id
96
97 hdr->frame_size = (get_bits(&gbc, 11) + 1) << 1;
98 if(hdr->frame_size < AC3_HEADER_SIZE)
99 return AC3_PARSE_ERROR_FRAME_SIZE;
100
101 hdr->sr_code = get_bits(&gbc, 2);
102 if (hdr->sr_code == 3) {
103 int sr_code2 = get_bits(&gbc, 2);
104 if(sr_code2 == 3)
105 return AC3_PARSE_ERROR_SAMPLE_RATE;
106 hdr->sample_rate = ff_ac3_sample_rate_tab[sr_code2] / 2;
107 hdr->sr_shift = 1;
108 num_blocks = 6;
109 } else {
110 num_blocks = eac3_blocks[get_bits(&gbc, 2)];
111 hdr->sample_rate = ff_ac3_sample_rate_tab[hdr->sr_code];
112 hdr->sr_shift = 0;
113 }
114
115 hdr->channel_mode = get_bits(&gbc, 3);
116 hdr->lfe_on = get_bits1(&gbc);
117
118 hdr->bit_rate = (uint32_t)(8.0 * hdr->frame_size * hdr->sample_rate /
119 (num_blocks * 256.0));
120 hdr->channels = ff_ac3_channels_tab[hdr->channel_mode] + hdr->lfe_on;
121 }
122
123 return 0;
124 }
125
126 static int ac3_sync(uint64_t state, AACAC3ParseContext *hdr_info,
127 int *need_next_header, int *new_frame_start)
128 {
129 int err;
130 uint64_t tmp = be2me_64(state);
131 AC3HeaderInfo hdr;
132
133 err = ff_ac3_parse_header(((uint8_t *)&tmp)+8-AC3_HEADER_SIZE, &hdr);
134
135 if(err < 0)
136 return 0;
137
138 hdr_info->sample_rate = hdr.sample_rate;
139 hdr_info->bit_rate = hdr.bit_rate;
140 hdr_info->channels = hdr.channels;
141 hdr_info->samples = AC3_FRAME_SIZE;
142
143 *need_next_header = (hdr.frame_type != EAC3_FRAME_TYPE_AC3_CONVERT);
144 *new_frame_start = (hdr.frame_type != EAC3_FRAME_TYPE_DEPENDENT);
145 return hdr.frame_size;
146 }
147
148 static av_cold int ac3_parse_init(AVCodecParserContext *s1)
149 {
150 AACAC3ParseContext *s = s1->priv_data;
151 s->header_size = AC3_HEADER_SIZE;
152 s->sync = ac3_sync;
153 return 0;
154 }
155
156
157 AVCodecParser ac3_parser = {
158 { CODEC_ID_AC3 },
159 sizeof(AACAC3ParseContext),
160 ac3_parse_init,
161 ff_aac_ac3_parse,
162 NULL,
163 };