2 * Audio and Video frame extraction
3 * Copyright (c) 2003 Fabrice Bellard
4 * Copyright (c) 2003 Michael Niedermayer
5 * Copyright (c) 2009 Alex Converse
7 * This file is part of FFmpeg.
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.
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.
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
24 #include "aac_ac3_parser.h"
25 #include "aacadtsdec.h"
27 #include "mpeg4audio.h"
29 int avpriv_aac_parse_header(GetBitContext *gbc, AACADTSHeaderInfo *hdr)
31 int size, rdb, ch, sr;
34 if(get_bits(gbc, 12) != 0xfff)
35 return AAC_AC3_PARSE_ERROR_SYNC;
37 skip_bits1(gbc); /* id */
38 skip_bits(gbc, 2); /* layer */
39 crc_abs = get_bits1(gbc); /* protection_absent */
40 aot = get_bits(gbc, 2); /* profile_objecttype */
41 sr = get_bits(gbc, 4); /* sample_frequency_index */
42 if(!avpriv_mpeg4audio_sample_rates[sr])
43 return AAC_AC3_PARSE_ERROR_SAMPLE_RATE;
44 skip_bits1(gbc); /* private_bit */
45 ch = get_bits(gbc, 3); /* channel_configuration */
47 skip_bits1(gbc); /* original/copy */
48 skip_bits1(gbc); /* home */
50 /* adts_variable_header */
51 skip_bits1(gbc); /* copyright_identification_bit */
52 skip_bits1(gbc); /* copyright_identification_start */
53 size = get_bits(gbc, 13); /* aac_frame_length */
54 if(size < AAC_ADTS_HEADER_SIZE)
55 return AAC_AC3_PARSE_ERROR_FRAME_SIZE;
57 skip_bits(gbc, 11); /* adts_buffer_fullness */
58 rdb = get_bits(gbc, 2); /* number_of_raw_data_blocks_in_frame */
60 hdr->object_type = aot + 1;
61 hdr->chan_config = ch;
62 hdr->crc_absent = crc_abs;
63 hdr->num_aac_frames = rdb + 1;
64 hdr->sampling_index = sr;
65 hdr->sample_rate = avpriv_mpeg4audio_sample_rates[sr];
66 hdr->samples = (rdb + 1) * 1024;
67 hdr->bit_rate = size * 8 * hdr->sample_rate / hdr->samples;