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  1. /*
  2.  * AST demuxer
  3.  * Copyright (c) 2012 Paul B Mahol
  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/channel_layout.h"
  23. #include "libavutil/intreadwrite.h"
  24. #include "avformat.h"
  25. #include "internal.h"
  26. #include "ast.h"
  27.  
  28. static int ast_probe(AVProbeData *p)
  29. {
  30.     if (AV_RL32(p->buf) == MKTAG('S','T','R','M') &&
  31.         AV_RB16(p->buf + 10) &&
  32.         AV_RB16(p->buf + 12) &&
  33.         AV_RB32(p->buf + 16))
  34.         return AVPROBE_SCORE_MAX / 3 * 2;
  35.     return 0;
  36. }
  37.  
  38. static int ast_read_header(AVFormatContext *s)
  39. {
  40.     int depth;
  41.     AVStream *st;
  42.  
  43.     st = avformat_new_stream(s, NULL);
  44.     if (!st)
  45.         return AVERROR(ENOMEM);
  46.  
  47.     avio_skip(s->pb, 8);
  48.     st->codec->codec_type = AVMEDIA_TYPE_AUDIO;
  49.     st->codec->codec_id   = ff_codec_get_id(ff_codec_ast_tags, avio_rb16(s->pb));
  50.  
  51.     depth = avio_rb16(s->pb);
  52.     if (depth != 16) {
  53.         avpriv_request_sample(s, "depth %d", depth);
  54.         return AVERROR_INVALIDDATA;
  55.     }
  56.  
  57.     st->codec->channels = avio_rb16(s->pb);
  58.     if (!st->codec->channels)
  59.         return AVERROR_INVALIDDATA;
  60.  
  61.     if (st->codec->channels == 2)
  62.         st->codec->channel_layout = AV_CH_LAYOUT_STEREO;
  63.     else if (st->codec->channels == 4)
  64.         st->codec->channel_layout = AV_CH_LAYOUT_4POINT0;
  65.  
  66.     avio_skip(s->pb, 2);
  67.     st->codec->sample_rate = avio_rb32(s->pb);
  68.     if (st->codec->sample_rate <= 0)
  69.         return AVERROR_INVALIDDATA;
  70.     st->start_time         = 0;
  71.     st->duration           = avio_rb32(s->pb);
  72.     avio_skip(s->pb, 40);
  73.     avpriv_set_pts_info(st, 64, 1, st->codec->sample_rate);
  74.  
  75.     return 0;
  76. }
  77.  
  78. static int ast_read_packet(AVFormatContext *s, AVPacket *pkt)
  79. {
  80.     uint32_t type, size;
  81.     int64_t pos;
  82.     int ret;
  83.  
  84.     if (url_feof(s->pb))
  85.         return AVERROR_EOF;
  86.  
  87.     pos  = avio_tell(s->pb);
  88.     type = avio_rl32(s->pb);
  89.     size = avio_rb32(s->pb);
  90.     if (size > INT_MAX / s->streams[0]->codec->channels)
  91.         return AVERROR_INVALIDDATA;
  92.  
  93.     size *= s->streams[0]->codec->channels;
  94.     if ((ret = avio_skip(s->pb, 24)) < 0) // padding
  95.         return ret;
  96.  
  97.     if (type == MKTAG('B','L','C','K')) {
  98.         ret = av_get_packet(s->pb, pkt, size);
  99.         pkt->stream_index = 0;
  100.         pkt->pos = pos;
  101.     } else {
  102.         av_log(s, AV_LOG_ERROR, "unknown chunk %x\n", type);
  103.         avio_skip(s->pb, size);
  104.         ret = AVERROR_INVALIDDATA;
  105.     }
  106.  
  107.     return ret;
  108. }
  109.  
  110. AVInputFormat ff_ast_demuxer = {
  111.     .name           = "ast",
  112.     .long_name      = NULL_IF_CONFIG_SMALL("AST (Audio Stream)"),
  113.     .read_probe     = ast_probe,
  114.     .read_header    = ast_read_header,
  115.     .read_packet    = ast_read_packet,
  116.     .extensions     = "ast",
  117.     .flags          = AVFMT_GENERIC_INDEX,
  118.     .codec_tag      = (const AVCodecTag* const []){ff_codec_ast_tags, 0},
  119. };
  120.