1 /*
2 * Audio and Video frame extraction
3 * Copyright (c) 2003 Fabrice Bellard
4 * Copyright (c) 2003 Michael Niedermayer
5 * Copyright (c) 2009 Alex Converse
6 *
7 * This file is part of FFmpeg.
8 *
9 * FFmpeg is free software; you can redistribute it and/or
10 * modify it under the terms of the GNU Lesser General Public
11 * License as published by the Free Software Foundation; either
12 * version 2.1 of the License, or (at your option) any later version.
13 *
14 * FFmpeg is distributed in the hope that it will be useful,
15 * but WITHOUT ANY WARRANTY; without even the implied warranty of
16 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
17 * Lesser General Public License for more details.
18 *
19 * You should have received a copy of the GNU Lesser General Public
20 * License along with FFmpeg; if not, write to the Free Software
21 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
22 */
23
24 #include "aac_ac3_parser.h"
25 #include "adts_header.h"
26 #include "adts_parser.h"
27 #include "get_bits.h"
28 #include "mpeg4audio.h"
29
ff_adts_header_parse(GetBitContext * gbc,AACADTSHeaderInfo * hdr)30 int ff_adts_header_parse(GetBitContext *gbc, AACADTSHeaderInfo *hdr)
31 {
32 int size, rdb, ch, sr;
33 int aot, crc_abs;
34
35 if (get_bits(gbc, 12) != 0xfff)
36 return AAC_AC3_PARSE_ERROR_SYNC;
37
38 skip_bits1(gbc); /* id */
39 skip_bits(gbc, 2); /* layer */
40 crc_abs = get_bits1(gbc); /* protection_absent */
41 aot = get_bits(gbc, 2); /* profile_objecttype */
42 sr = get_bits(gbc, 4); /* sample_frequency_index */
43 if (!avpriv_mpeg4audio_sample_rates[sr])
44 return AAC_AC3_PARSE_ERROR_SAMPLE_RATE;
45 skip_bits1(gbc); /* private_bit */
46 ch = get_bits(gbc, 3); /* channel_configuration */
47
48 skip_bits1(gbc); /* original/copy */
49 skip_bits1(gbc); /* home */
50
51 /* adts_variable_header */
52 skip_bits1(gbc); /* copyright_identification_bit */
53 skip_bits1(gbc); /* copyright_identification_start */
54 size = get_bits(gbc, 13); /* aac_frame_length */
55 if (size < AV_AAC_ADTS_HEADER_SIZE)
56 return AAC_AC3_PARSE_ERROR_FRAME_SIZE;
57
58 skip_bits(gbc, 11); /* adts_buffer_fullness */
59 rdb = get_bits(gbc, 2); /* number_of_raw_data_blocks_in_frame */
60
61 hdr->object_type = aot + 1;
62 hdr->chan_config = ch;
63 hdr->crc_absent = crc_abs;
64 hdr->num_aac_frames = rdb + 1;
65 hdr->sampling_index = sr;
66 hdr->sample_rate = avpriv_mpeg4audio_sample_rates[sr];
67 hdr->samples = (rdb + 1) * 1024;
68 hdr->bit_rate = size * 8 * hdr->sample_rate / hdr->samples;
69
70 return size;
71 }
72