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  1. /*
  2.  * LOAS AudioSyncStream demuxer
  3.  * Copyright (c) 2008 Michael Niedermayer <michaelni@gmx.at>
  4.  *
  5.  * This file is part of FFmpeg.
  6.  *
  7.  * FFmpeg is free software; you can redistribute it and/or
  8.  * modify it under the terms of the GNU Lesser General Public
  9.  * License as published by the Free Software Foundation; either
  10.  * version 2.1 of the License, or (at your option) any later version.
  11.  *
  12.  * FFmpeg is distributed in the hope that it will be useful,
  13.  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  14.  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  15.  * Lesser General Public License for more details.
  16.  *
  17.  * You should have received a copy of the GNU Lesser General Public
  18.  * License along with FFmpeg; if not, write to the Free Software
  19.  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
  20.  */
  21.  
  22. #include "libavutil/intreadwrite.h"
  23. #include "libavutil/internal.h"
  24. #include "avformat.h"
  25. #include "internal.h"
  26. #include "rawdec.h"
  27.  
  28. #define LOAS_SYNC_WORD 0x2b7
  29.  
  30. static int loas_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 - 3;
  38.     buf = buf0;
  39.  
  40.     for (; buf < end; buf = buf2 + 1) {
  41.         buf2 = buf;
  42.  
  43.         for (frames = 0; buf2 < end; frames++) {
  44.             uint32_t header = AV_RB24(buf2);
  45.             if ((header >> 13) != LOAS_SYNC_WORD)
  46.                 break;
  47.             fsize = (header & 0x1FFF) + 3;
  48.             if (fsize < 7)
  49.                 break;
  50.             fsize = FFMIN(fsize, end - buf2);
  51.             buf2 += fsize;
  52.         }
  53.         max_frames = FFMAX(max_frames, frames);
  54.         if (buf == buf0)
  55.             first_frames = frames;
  56.     }
  57.  
  58.     if (first_frames >= 3)
  59.         return AVPROBE_SCORE_EXTENSION + 1;
  60.     else if (max_frames > 100)
  61.         return AVPROBE_SCORE_EXTENSION;
  62.     else if (max_frames >= 3)
  63.         return AVPROBE_SCORE_EXTENSION / 2;
  64.     else
  65.         return 0;
  66. }
  67.  
  68. static int loas_read_header(AVFormatContext *s)
  69. {
  70.     AVStream *st;
  71.  
  72.     st = avformat_new_stream(s, NULL);
  73.     if (!st)
  74.         return AVERROR(ENOMEM);
  75.  
  76.     st->codec->codec_type = AVMEDIA_TYPE_AUDIO;
  77.     st->codec->codec_id = s->iformat->raw_codec_id;
  78.     st->need_parsing = AVSTREAM_PARSE_FULL_RAW;
  79.  
  80.     //LCM of all possible AAC sample rates
  81.     avpriv_set_pts_info(st, 64, 1, 28224000);
  82.  
  83.     return 0;
  84. }
  85.  
  86. AVInputFormat ff_loas_demuxer = {
  87.     .name           = "loas",
  88.     .long_name      = NULL_IF_CONFIG_SMALL("LOAS AudioSyncStream"),
  89.     .read_probe     = loas_probe,
  90.     .read_header    = loas_read_header,
  91.     .read_packet    = ff_raw_read_partial_packet,
  92.     .flags= AVFMT_GENERIC_INDEX,
  93.     .raw_codec_id = AV_CODEC_ID_AAC_LATM,
  94. };
  95.