FFmpeg
adts_header.c
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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 
31 {
32  int size, rdb, ch, sr;
33  int aot, crc_abs;
34 
35  if (get_bits(gbc, 12) != 0xfff)
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 */
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)
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;
67  hdr->samples = (rdb + 1) * 1024;
68  hdr->bit_rate = size * 8 * hdr->sample_rate / hdr->samples;
69 
70  return size;
71 }
uint8_t object_type
Definition: adts_header.h:33
static unsigned int get_bits(GetBitContext *s, int n)
Read 1-25 bits.
Definition: get_bits.h:379
bitstream reader API header.
ptrdiff_t size
Definition: opengl_enc.c:100
uint8_t sampling_index
Definition: adts_header.h:34
#define AV_AAC_ADTS_HEADER_SIZE
Definition: adts_parser.h:25
uint8_t chan_config
Definition: adts_header.h:35
uint8_t num_aac_frames
Definition: adts_header.h:36
uint32_t samples
Definition: adts_header.h:30
int ff_adts_header_parse(GetBitContext *gbc, AACADTSHeaderInfo *hdr)
Parse the ADTS frame header to the end of the variable header, which is the first 54 bits...
Definition: adts_header.c:30
static unsigned int get_bits1(GetBitContext *s)
Definition: get_bits.h:498
static void skip_bits1(GetBitContext *s)
Definition: get_bits.h:538
static void skip_bits(GetBitContext *s, int n)
Definition: get_bits.h:467
uint32_t bit_rate
Definition: adts_header.h:31
const int avpriv_mpeg4audio_sample_rates[16]
Definition: mpeg4audio.c:62
uint8_t crc_absent
Definition: adts_header.h:32
uint32_t sample_rate
Definition: adts_header.h:29