libavformat/loasdec.c

   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 "demux.h"
  26 #include "internal.h"
  27 #include "rawdec.h"
  28
  29 #define LOAS_SYNC_WORD 0x2b7
  30
  31 static int loas_probe(const AVProbeData *p)
  32 {
  33     int max_frames = 0, first_frames = 0;
  34     int fsize, frames;
  35     const uint8_t *buf0 = p->buf;
  36     const uint8_t *buf2;
  37     const uint8_t *buf;
  38     const uint8_t *end = buf0 + p->buf_size - 3;
  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_RB24(buf2);
  46             if ((header >> 13) != LOAS_SYNC_WORD)
  47                 break;
  48             fsize = (header & 0x1FFF) + 3;
  49             if (fsize < 7)
  50                 break;
  51             fsize = FFMIN(fsize, end - buf2);
  52             buf2 += fsize;
  53         }
  54         max_frames = FFMAX(max_frames, frames);
  55         if (buf == buf0)
  56             first_frames = frames;
  57     }
  58
  59     if (first_frames >= 3)
  60         return AVPROBE_SCORE_EXTENSION + 1;
  61     else if (max_frames > 100)
  62         return AVPROBE_SCORE_EXTENSION;
  63     else if (max_frames >= 3)
  64         return AVPROBE_SCORE_EXTENSION / 2;
  65     else
  66         return 0;
  67 }
  68
  69 static int loas_read_header(AVFormatContext *s)
  70 {
  71     AVStream *st;
  72
  73     st = avformat_new_stream(s, NULL);
  74     if (!st)
  75         return AVERROR(ENOMEM);
  76
  77     st->codecpar->codec_type = AVMEDIA_TYPE_AUDIO;
  78     st->codecpar->codec_id   = AV_CODEC_ID_AAC_LATM;
  79     ffstream(st)->need_parsing = AVSTREAM_PARSE_FULL_RAW;
  80
  81     //LCM of all possible AAC sample rates
  82     avpriv_set_pts_info(st, 64, 1, 28224000);
  83
  84     return 0;
  85 }
  86
  87 const FFInputFormat ff_loas_demuxer = {
  88     .p.name         = "loas",
  89     .p.long_name    = NULL_IF_CONFIG_SMALL("LOAS AudioSyncStream"),
  90     .p.flags        = AVFMT_GENERIC_INDEX,
  91     .p.priv_class   = &ff_raw_demuxer_class,
  92     .read_probe     = loas_probe,
  93     .read_header    = loas_read_header,
  94     .read_packet    = ff_raw_read_partial_packet,
  95     .raw_codec_id = AV_CODEC_ID_AAC_LATM,
  96     .priv_data_size = sizeof(FFRawDemuxerContext),
  97 };