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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.  
  30. static int adts_aac_probe(AVProbeData *p)
  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)
  70.         return AVPROBE_SCORE_EXTENSION;
  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.  
  79. static int adts_aac_read_header(AVFormatContext *s)
  80. {
  81.     AVStream *st;
  82.  
  83.     st = avformat_new_stream(s, NULL);
  84.     if (!st)
  85.         return AVERROR(ENOMEM);
  86.  
  87.     st->codec->codec_type = AVMEDIA_TYPE_AUDIO;
  88.     st->codec->codec_id   = s->iformat->raw_codec_id;
  89.     st->need_parsing      = AVSTREAM_PARSE_FULL_RAW;
  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);
  95.         ff_ape_parse_tag(s);
  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.  
  105. AVInputFormat ff_aac_demuxer = {
  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.     .mime_type    = "audio/aac,audio/aacp,audio/x-aac",
  114.     .raw_codec_id = AV_CODEC_ID_AAC,
  115. };
  116.