重新排序破折号段列表中的段
Reordering segments in dash segment list
我有一个 live dash 清单，看起来像这样。
<MPD xmlns="urn:mpeg:dash:schema:mpd:2011" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" id="" maxSegmentDuration="PT4S" minimumUpdatePeriod="PT595H" minBufferTime="PT2S" type="dynamic" availabilityStartTime="2016-11-20T17:00:54Z" publishTime="2016-11-20T17:00:54Z" profiles="urn:hbbtv:dash:profile:isoff-live:2012,urn:mpeg:dash:profile:isoff-live:2011" xsi:schemaLocation="urn:mpeg:dash:schema:mpd:2011 DASH-MPD.xsd" timeShiftBufferDepth="PT120S">
<ProgramInformation>
<Title>Title</Title>
</ProgramInformation>
<Period start="PT0S" id="p1">
<AdaptationSet mimeType="audio/mp4" lang="en" startWithSAP="1" contentType="audio" segmentAlignment="true">
<Representation audioSamplingRate="48000" bandwidth="128000" id="128kb" codecs="mp4a.40.2">
<AudioChannelConfiguration value="2" schemeIdUri="urn:mpeg:dash:23003:3:audio_channel_configuration:2011"/>
<SegmentTemplate duration="4" media="audio/128kbps/segment_$Number$.m4s" initialization="audio/128kbps/init.mp4" startNumber="0"/>
</Representation>
</AdaptationSet>
<AdaptationSet mimeType="video/mp4" minWidth="426" contentType="video" maxWidth="1920" minHeight="240" segmentAlignment="true" startWithSAP="1" maxHeight="1080">
<Representation frameRate="60000/1000" height="480" width="858" bandwidth="1200000" codecs="avc1.42c00d" id="1200kb">
<SegmentTemplate duration="4" media="video/480p/segment_$Number$.m4s" initialization="video/480p/init.mp4" startNumber="0"/>
</Representation>
<!-- Some more representations -->
</AdaptationSet>
</Period>
流式传输时，所有片段都会保存到磁盘，以用于流式传输会话中的 VOD 和精彩片段。我通过将实时清单重新制作成静态清单来完成 VOD 解决方案。
我的问题是当我想要创建精彩片段时，我想重新排序片段并准确指定应该下载和播放哪些片段。我尝试使用 SegmentationList 执行此操作。我的新清单
我创建的看起来像这样：
<?xml version="1.0" encoding="UTF-8" standalone="no"?>
高亮测试
<Period start="PT0S" duration="PT0H2M24.000S">
<AdaptationSet mimeType="video/mp4" minWidth="426" contentType="video" maxWidth="1920" minHeight="240" segmentAlignment="true" startWithSAP="1" maxHeight="1080">
<Representation frameRate="60000/1000" height="480" width="858" bandwidth="1200000" codecs="avc1.42c00d" id="1200kb">
<SegmentList duration="61440" timescale="15360">
<Initialization sourceURL="video/480p/init.mp4"/>
<!--Highlight 1-->
<SegmentURL media="video/480p/segment_9399.m4s"/>
<SegmentURL media="video/480p/segment_9400.m4s"/>
<!--Highlight 2-->
<SegmentURL media="video/480p/segment_9351.m4s"/>
<SegmentURL media="video/480p/segment_9352.m4s"/>
<!--Highlight 3-->
<SegmentURL media="video/480p/segment_9449.m4s"/>
<SegmentURL media="video/480p/segment_9450.m4s"/>
</SegmentList>
</Representation>
</AdaptationSet>
<AdaptationSet mimeType="audio/mp4" lang="en" startWithSAP="1" contentType="audio" segmentAlignment="true">
<Representation audioSamplingRate="48000" bandwidth="128000" id="128kb" codecs="mp4a.40.2">
<AudioChannelConfiguration value="2" schemeIdUri="urn:mpeg:dash:23003:3:audio_channel_configuration:2011"/>
<SegmentList duration="192000" timescale="48000">
<Initialization sourceURL="audio/128kbps/init.mp4"/>
<!--Highlight 1-->
<SegmentURL media="audio/128kbps/segment_9399.m4s"/>
<SegmentURL media="audio/128kbps/segment_9400.m4s"/>
<!--Highlight 2-->
<SegmentURL media="audio/128kbps/segment_9351.m4s"/>
<SegmentURL media="audio/128kbps/segment_9352.m4s"/>
<SegmentURL media="audio/128kbps/segment_9357.m4s"/>
<!--Highlight 3-->
<SegmentURL media="audio/128kbps/segment_9449.m4s"/>
<SegmentURL media="audio/128kbps/segment_9450.m4s"/>
</SegmentList>
</Representation>
</AdaptationSet>
</Period>
我 运行 这个解决方案的问题首先是计时器不是从 0 开始，而是从 37596 (9399*4) 开始。我的第二个问题是当亮点 1 结束时它不播放亮点 2。相反，如果停止，就好像已经到达视频的结尾。
我猜初始化文件中有一些内容指定了如何播放片段。
有没有办法通过只创建一个新的清单而不创建一个新的初始化文件来做到这一点？
您不需要新的初始化文件。主要问题是媒体片段的时间戳。要解决初始时间的问题，您应该在 Manifest 中添加 presentationTimeOffset 属性，其中包含您要播放的第一个片段的开始时间。
第二个问题是不连续性（在您的情况下是两个亮点之间的时间变化）应该按照 MPEG-DASH 标准的建议将它们分成新的周期来处理：
In case of discontinuities it is recommended to add a new Period to reset the value of @presentationTimeOffset.
这两个东西可以组合如下所示（为了简单起见，我跳过了音频 AdaptationSets）。我在这种情况下使用了 SegmentTimeline。
<MPD type="static" mediaPresentationDuration="PT0H2M24.000S" minBufferTime="PT4S" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="urn:mpeg:dash:schema:mpd:2011" xsi:schemaLocation="urn:mpeg:dash:schema:mpd:2011 http://standards.iso.org/ittf/PubliclyAvailableStandards/MPEG-DASH_schema_files/DASH-MPD.xsd" profiles="urn:mpeg:dash:profile:isoff-live:2011,urn:com:dashif:dash264">
<Period start="PT0S" duration="PT8S">
<!--Highlight 1-->
<AdaptationSet mimeType="video/mp4" minWidth="426" contentType="video" maxWidth="1920" minHeight="240" segmentAlignment="true" startWithSAP="1" maxHeight="1080">
<SegmentTemplate timescale="1" presentationTimeOffset="37596" startNumber="9399" initialization="video/480p/init.mp4" media="video/$RepresentationID$/segment_$Number$.m4s">
<SegmentTimeline>
<S t="37596" d="4" r="1"/>
</SegmentTimeline>
</SegmentTemplate>
<Representation frameRate="60000/1000" height="480" width="858" bandwidth="1200000" codecs="avc1.42c00d" id="480p" />
</AdaptationSet>
</Period>
<Period duration="PT8S">
<!--Highlight 2-->
<AdaptationSet mimeType="video/mp4" minWidth="426" contentType="video" maxWidth="1920" minHeight="240" segmentAlignment="true" startWithSAP="1" maxHeight="1080">
<SegmentTemplate timescale="1" presentationTimeOffset="37404" startNumber="9351" initialization="video/480p/init.mp4" media="video/$RepresentationID$/segment_$Number$.m4s">
<SegmentTimeline>
<S t="37404" d="61440" r="1"/>
</SegmentTimeline>
</SegmentTemplate>
<Representation frameRate="60000/1000" height="480" width="858" bandwidth="1200000" codecs="avc1.42c00d" id="480p" />
</AdaptationSet>
</Period>
<Period duration="PT8S">
<!--Highlight 3-->
<AdaptationSet mimeType="video/mp4" minWidth="426" contentType="video" maxWidth="1920" minHeight="240" segmentAlignment="true" startWithSAP="1" maxHeight="1080">
<SegmentTemplate timescale="1" presentationTimeOffset="37796" startNumber="9449" initialization="video/480p/init.mp4" media="video/$RepresentationID$/segment_$Number$.m4s">
<SegmentTimeline>
<S t="37796" d="61440" r="1"/>
</SegmentTimeline>
</SegmentTemplate>
<Representation frameRate="60000/1000" height="480" width="858" bandwidth="1200000" codecs="avc1.42c00d" id="480p" />
</AdaptationSet>
</Period>
</MPD>
当然，播放器需要同时支持presentationTimeOffset和多期。我认为 Bitmovin Player should work, not sure about others like dash.js.
我有一个 live dash 清单，看起来像这样。
<MPD xmlns="urn:mpeg:dash:schema:mpd:2011" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" id="" maxSegmentDuration="PT4S" minimumUpdatePeriod="PT595H" minBufferTime="PT2S" type="dynamic" availabilityStartTime="2016-11-20T17:00:54Z" publishTime="2016-11-20T17:00:54Z" profiles="urn:hbbtv:dash:profile:isoff-live:2012,urn:mpeg:dash:profile:isoff-live:2011" xsi:schemaLocation="urn:mpeg:dash:schema:mpd:2011 DASH-MPD.xsd" timeShiftBufferDepth="PT120S">
<ProgramInformation>
<Title>Title</Title>
</ProgramInformation>
<Period start="PT0S" id="p1">
<AdaptationSet mimeType="audio/mp4" lang="en" startWithSAP="1" contentType="audio" segmentAlignment="true">
<Representation audioSamplingRate="48000" bandwidth="128000" id="128kb" codecs="mp4a.40.2">
<AudioChannelConfiguration value="2" schemeIdUri="urn:mpeg:dash:23003:3:audio_channel_configuration:2011"/>
<SegmentTemplate duration="4" media="audio/128kbps/segment_$Number$.m4s" initialization="audio/128kbps/init.mp4" startNumber="0"/>
</Representation>
</AdaptationSet>
<AdaptationSet mimeType="video/mp4" minWidth="426" contentType="video" maxWidth="1920" minHeight="240" segmentAlignment="true" startWithSAP="1" maxHeight="1080">
<Representation frameRate="60000/1000" height="480" width="858" bandwidth="1200000" codecs="avc1.42c00d" id="1200kb">
<SegmentTemplate duration="4" media="video/480p/segment_$Number$.m4s" initialization="video/480p/init.mp4" startNumber="0"/>
</Representation>
<!-- Some more representations -->
</AdaptationSet>
</Period>
流式传输时，所有片段都会保存到磁盘，以用于流式传输会话中的 VOD 和精彩片段。我通过将实时清单重新制作成静态清单来完成 VOD 解决方案。
我的问题是当我想要创建精彩片段时，我想重新排序片段并准确指定应该下载和播放哪些片段。我尝试使用 SegmentationList 执行此操作。我的新清单 我创建的看起来像这样：
<?xml version="1.0" encoding="UTF-8" standalone="no"?>
高亮测试
<Period start="PT0S" duration="PT0H2M24.000S">
<AdaptationSet mimeType="video/mp4" minWidth="426" contentType="video" maxWidth="1920" minHeight="240" segmentAlignment="true" startWithSAP="1" maxHeight="1080">
<Representation frameRate="60000/1000" height="480" width="858" bandwidth="1200000" codecs="avc1.42c00d" id="1200kb">
<SegmentList duration="61440" timescale="15360">
<Initialization sourceURL="video/480p/init.mp4"/>
<!--Highlight 1-->
<SegmentURL media="video/480p/segment_9399.m4s"/>
<SegmentURL media="video/480p/segment_9400.m4s"/>
<!--Highlight 2-->
<SegmentURL media="video/480p/segment_9351.m4s"/>
<SegmentURL media="video/480p/segment_9352.m4s"/>
<!--Highlight 3-->
<SegmentURL media="video/480p/segment_9449.m4s"/>
<SegmentURL media="video/480p/segment_9450.m4s"/>
</SegmentList>
</Representation>
</AdaptationSet>
<AdaptationSet mimeType="audio/mp4" lang="en" startWithSAP="1" contentType="audio" segmentAlignment="true">
<Representation audioSamplingRate="48000" bandwidth="128000" id="128kb" codecs="mp4a.40.2">
<AudioChannelConfiguration value="2" schemeIdUri="urn:mpeg:dash:23003:3:audio_channel_configuration:2011"/>
<SegmentList duration="192000" timescale="48000">
<Initialization sourceURL="audio/128kbps/init.mp4"/>
<!--Highlight 1-->
<SegmentURL media="audio/128kbps/segment_9399.m4s"/>
<SegmentURL media="audio/128kbps/segment_9400.m4s"/>
<!--Highlight 2-->
<SegmentURL media="audio/128kbps/segment_9351.m4s"/>
<SegmentURL media="audio/128kbps/segment_9352.m4s"/>
<SegmentURL media="audio/128kbps/segment_9357.m4s"/>
<!--Highlight 3-->
<SegmentURL media="audio/128kbps/segment_9449.m4s"/>
<SegmentURL media="audio/128kbps/segment_9450.m4s"/>
</SegmentList>
</Representation>
</AdaptationSet>
</Period>
我 运行 这个解决方案的问题首先是计时器不是从 0 开始，而是从 37596 (9399*4) 开始。我的第二个问题是当亮点 1 结束时它不播放亮点 2。相反，如果停止，就好像已经到达视频的结尾。
我猜初始化文件中有一些内容指定了如何播放片段。
有没有办法通过只创建一个新的清单而不创建一个新的初始化文件来做到这一点？
您不需要新的初始化文件。主要问题是媒体片段的时间戳。要解决初始时间的问题，您应该在 Manifest 中添加 presentationTimeOffset 属性，其中包含您要播放的第一个片段的开始时间。
第二个问题是不连续性（在您的情况下是两个亮点之间的时间变化）应该按照 MPEG-DASH 标准的建议将它们分成新的周期来处理：
In case of discontinuities it is recommended to add a new Period to reset the value of @presentationTimeOffset.
这两个东西可以组合如下所示（为了简单起见，我跳过了音频 AdaptationSets）。我在这种情况下使用了 SegmentTimeline。
<MPD type="static" mediaPresentationDuration="PT0H2M24.000S" minBufferTime="PT4S" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="urn:mpeg:dash:schema:mpd:2011" xsi:schemaLocation="urn:mpeg:dash:schema:mpd:2011 http://standards.iso.org/ittf/PubliclyAvailableStandards/MPEG-DASH_schema_files/DASH-MPD.xsd" profiles="urn:mpeg:dash:profile:isoff-live:2011,urn:com:dashif:dash264">
<Period start="PT0S" duration="PT8S">
<!--Highlight 1-->
<AdaptationSet mimeType="video/mp4" minWidth="426" contentType="video" maxWidth="1920" minHeight="240" segmentAlignment="true" startWithSAP="1" maxHeight="1080">
<SegmentTemplate timescale="1" presentationTimeOffset="37596" startNumber="9399" initialization="video/480p/init.mp4" media="video/$RepresentationID$/segment_$Number$.m4s">
<SegmentTimeline>
<S t="37596" d="4" r="1"/>
</SegmentTimeline>
</SegmentTemplate>
<Representation frameRate="60000/1000" height="480" width="858" bandwidth="1200000" codecs="avc1.42c00d" id="480p" />
</AdaptationSet>
</Period>
<Period duration="PT8S">
<!--Highlight 2-->
<AdaptationSet mimeType="video/mp4" minWidth="426" contentType="video" maxWidth="1920" minHeight="240" segmentAlignment="true" startWithSAP="1" maxHeight="1080">
<SegmentTemplate timescale="1" presentationTimeOffset="37404" startNumber="9351" initialization="video/480p/init.mp4" media="video/$RepresentationID$/segment_$Number$.m4s">
<SegmentTimeline>
<S t="37404" d="61440" r="1"/>
</SegmentTimeline>
</SegmentTemplate>
<Representation frameRate="60000/1000" height="480" width="858" bandwidth="1200000" codecs="avc1.42c00d" id="480p" />
</AdaptationSet>
</Period>
<Period duration="PT8S">
<!--Highlight 3-->
<AdaptationSet mimeType="video/mp4" minWidth="426" contentType="video" maxWidth="1920" minHeight="240" segmentAlignment="true" startWithSAP="1" maxHeight="1080">
<SegmentTemplate timescale="1" presentationTimeOffset="37796" startNumber="9449" initialization="video/480p/init.mp4" media="video/$RepresentationID$/segment_$Number$.m4s">
<SegmentTimeline>
<S t="37796" d="61440" r="1"/>
</SegmentTimeline>
</SegmentTemplate>
<Representation frameRate="60000/1000" height="480" width="858" bandwidth="1200000" codecs="avc1.42c00d" id="480p" />
</AdaptationSet>
</Period>
</MPD>
当然，播放器需要同时支持presentationTimeOffset和多期。我认为 Bitmovin Player should work, not sure about others like dash.js.