DASH MPD中的段数

Question

如果MPD文件没有任何段URL列表,如何确定DASH介质的段数？它只有一个段模板,因此我不知道与该MPD关联的媒体有多少段.这是我正在谈论的MPD:

<MPD type="static" xmlns="urn:mpeg:DASH:schema:MPD:2011" profiles="urn:mpeg:dash:profile:full:2011" minBufferTime="PT1.5S" mediaPresentationDuration="PT0H1M59.89S">
 <ProgramInformation moreInformationURL="http://gpac.sourceforge.net">
  <Title>Media Presentation Description for file hdworld_0696kbps_ffmpeg_track1.mp4 generated with GPAC </Title>
 </ProgramInformation>
 <Period start="PT0S" duration="PT0H1M59.89S">
  <AdaptationSet>
   <ContentComponent id="1" contentType="video"/>
   <SegmentTemplate initialization="/$Bandwidth$/hdworld_ffmpeg_track1_dash.mp4" timescale="1000" duration="4920" media="/$Bandwidth$/hdworld_ffmpeg_track1_$Number$.m4s" startNumber="1"/>
   <Representation id="1" mimeType="video/mp4" codecs="avc1.64001f" width="1280" height="720" startWithSAP="1" bandwidth="534343"/>   
   <Representation id="2" mimeType="video/mp4" codecs="avc1.64001f" width="1280" height="720" startWithSAP="1" bandwidth="812553"/>
   <Representation id="3" mimeType="video/mp4" codecs="avc1.64001f" width="1280" height="720" startWithSAP="1" bandwidth="1607692"/>
  </AdaptationSet>
   <AdaptationSet>
   <ContentComponent id="2" contentType="audio" lang="und"/>
   <SegmentTemplate initialization="/audio/HDWorld_audio_init.mp4"/>
   <Representation id="6" mimeType="audio/mp4" codecs="mp4a.40.02" sampleRate="44100" numChannels="2" lang="und" startWithSAP="1" bandwidth="257141">
    <SegmentTemplate timescale="1000" duration="9980" media="/audio/hdworld_seg_audio$Number$.m4s" startNumber="1"/>
   </Representation>
  </AdaptationSet>
 </Period>
</MPD>

我的目标是检索所有现有段的URI.

Answer 1

在此示例中,您可以看到音频片段的长度均为9.98秒(持续时间= 9980,时间刻度= 1000).由于演示的持续时间是1m 59.89s,(持续时间="PT0H1M59.89S"),这大约是13段(最后一段更短).使用URL模板(/audio/hdworld_seg_audio$Number$.m4s)检索每个段(将$ Number $替换为您想要的段号(第一个为1).这同样适用于视频段(除了它们是4.92)每个秒,所以你将有25个段)