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aacdec.c
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1 /*
2  * raw ADTS AAC demuxer
3  * Copyright (c) 2008 Michael Niedermayer <michaelni@gmx.at>
4  * Copyright (c) 2009 Robert Swain ( rob opendot cl )
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 "libavutil/intreadwrite.h"
24 #include "avformat.h"
25 #include "internal.h"
26 #include "rawdec.h"
27 #include "id3v1.h"
28 #include "apetag.h"
29 
31 {
32  int max_frames = 0, first_frames = 0;
33  int fsize, frames;
34  const uint8_t *buf0 = p->buf;
35  const uint8_t *buf2;
36  const uint8_t *buf;
37  const uint8_t *end = buf0 + p->buf_size - 7;
38 
39  buf = buf0;
40 
41  for (; buf < end; buf = buf2 + 1) {
42  buf2 = buf;
43 
44  for (frames = 0; buf2 < end; frames++) {
45  uint32_t header = AV_RB16(buf2);
46  if ((header & 0xFFF6) != 0xFFF0) {
47  if (buf != buf0) {
48  // Found something that isn't an ADTS header, starting
49  // from a position other than the start of the buffer.
50  // Discard the count we've accumulated so far since it
51  // probably was a false positive.
52  frames = 0;
53  }
54  break;
55  }
56  fsize = (AV_RB32(buf2 + 3) >> 13) & 0x1FFF;
57  if (fsize < 7)
58  break;
59  fsize = FFMIN(fsize, end - buf2);
60  buf2 += fsize;
61  }
62  max_frames = FFMAX(max_frames, frames);
63  if (buf == buf0)
64  first_frames = frames;
65  }
66 
67  if (first_frames >= 3)
68  return AVPROBE_SCORE_EXTENSION + 1;
69  else if (max_frames > 100)
71  else if (max_frames >= 3)
72  return AVPROBE_SCORE_EXTENSION / 2;
73  else if (max_frames >= 1)
74  return 1;
75  else
76  return 0;
77 }
78 
80 {
81  AVStream *st;
82 
83  st = avformat_new_stream(s, NULL);
84  if (!st)
85  return AVERROR(ENOMEM);
86 
90 
91  ff_id3v1_read(s);
92  if (s->pb->seekable &&
93  !av_dict_get(s->metadata, "", NULL, AV_DICT_IGNORE_SUFFIX)) {
94  int64_t cur = avio_tell(s->pb);
96  avio_seek(s->pb, cur, SEEK_SET);
97  }
98 
99  // LCM of all possible ADTS sample rates
100  avpriv_set_pts_info(st, 64, 1, 28224000);
101 
102  return 0;
103 }
104 
106  .name = "aac",
107  .long_name = NULL_IF_CONFIG_SMALL("raw ADTS AAC (Advanced Audio Coding)"),
108  .read_probe = adts_aac_probe,
109  .read_header = adts_aac_read_header,
110  .read_packet = ff_raw_read_partial_packet,
111  .flags = AVFMT_GENERIC_INDEX,
112  .extensions = "aac",
113  .raw_codec_id = AV_CODEC_ID_AAC,
114 };