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‎VideoDevelopment/流媒体协议/DASH.md‎

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![image-20200406164238038](https://raw.githubusercontent.com/CharonChui/Pictures/master/mpd_hierarchical_data.png)
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```xml
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<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
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<MPD id="0564e940-122b-42bb-9d56-98f3def67247" profiles="urn:mpeg:dash:profile:isoff-main:2011" type="static" availabilityStartTime="2016-01-14T09:30:35.000Z" publishTime="2016-01-14T09:31:33.000Z" mediaPresentationDuration="P0Y0M0DT0H2M17.000S" minBufferTime="P0Y0M0DT0H0M1.000S" bitmovin:version="1.6.0" xmlns:ns2="http://www.w3.org/1999/xlink" xmlns="urn:mpeg:dash:schema:mpd:2011" xmlns:bitmovin="http://www.bitmovin.net/mpd/2015">
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<Period>
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<AdaptationSet mimeType="video/mp4" codecs="avc1.42c00d">
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<SegmentTemplate media="../video/$RepresentationID$/dash/segment_$Number$.m4s" initialization="../video/$RepresentationID$/dash/init.mp4" duration="120119" startNumber="0" timescale="30000"/>
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<Representation id="1920_9000000" bandwidth="9000000" width="3840" height="1920" frameRate="30"/>
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<Representation id="1080_5000000" bandwidth="5000000" width="2160" height="1080" frameRate="30"/>
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<Representation id="720_3000000" bandwidth="3000000" width="1440" height="720" frameRate="30"/>
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<Representation id="540_1500000" bandwidth="1500000" width="1080" height="540" frameRate="30"/>
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<Representation id="360_1000000" bandwidth="1000000" width="720" height="360" frameRate="30"/>
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</AdaptationSet>
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<AdaptationSet lang="en" mimeType="audio/mp4" codecs="mp4a.40.2" bitmovin:label="english stereo">
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<AudioChannelConfiguration schemeIdUri="urn:mpeg:dash:23003:3:audio_channel_configuration:2011" value="2"/>
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<SegmentTemplate media="../audio/$RepresentationID$/dash/segment_$Number$.m4s" initialization="../audio/$RepresentationID$/dash/init.mp4" duration="191472" startNumber="0" timescale="48000"/>
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<Representation id="1_stereo_128000" bandwidth="128000" audioSamplingRate="48000"/>
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</AdaptationSet>
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</Period>
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</MPD>
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```
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### MPD
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DASH采用3GPP AHS中定义的MPD(Media Presentation Description)作为媒体文件的描述文件（manifest），作用类似HLS的m3u8文件。MPD文件以XML格式组织，用于描述segment的信息，比如时间、url、视频分辨率、码率等。
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## DASH地址
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http://ftp.itec.aau.at/datasets/mmsys12/BigBuckBunny/MPDs/BigBuckBunnyNonSeg_2s_isoffmain_DIS_23009_1_v_2_1c2_2011_08_30.mpd
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http://www-itec.uni-klu.ac.at/ftp/datasets/mmsys12/BigBuckBunny/bunny_2s/bunny_2s_50kbit/bunny_50kbit_dashNonSeg.mp4
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## fMP4
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fMP4（fragmented MP4），可以简单理解为分片化的MP4，是DASH采用的媒体文件格式，文件扩展名通常为（.m4s或直接用.mp4）。
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### 测试流
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- HEVC HLS with fMP4: [http://bitmovin-a.akamaihd.net/content/dataset/multi-codec/hevc/stream_fmp4.m3u8](https://bitmovin-a.akamaihd.net/content/dataset/multi-codec/hevc/stream_fmp4.m3u8)
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- HEVC HLS with TS (not supported by Apple): [http://bitmovin-a.akamaihd.net/content/dataset/multi-codec/hevc/stream_ts.m3u8](https://bitmovin-a.akamaihd.net/content/dataset/multi-codec/hevc/stream_ts.m3u8)
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[https://bitmovin-a.akamaihd.net/content/playhouse-vr/m3u8s/105560.m3u8](https://bitmovin-a.akamaihd.net/content/playhouse-vr/m3u8s/105560.m3u8)
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- HEVC MPEG-DASH: [http://bitmovin-a.akamaihd.net/content/dataset/multi-codec/hevc/stream.mpd](https://bitmovin-a.akamaihd.net/content/dataset/multi-codec/hevc/stream.mpd)
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- Multi-Codec MPEG-DASH (AVC/H.264, HEVC/H.265, VP9): http://bitmovin-a.akamaihd.net/content/dataset/multi-codec/stream.mpd
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https://bitmovin-a.akamaihd.net/content/playhouse-vr/mpds/105560.mpd
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- VP9 MPEG-DASH: http://bitmovin-a.akamaihd.net/content/dataset/multi-codec/stream_vp9.mpd
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在线测试播放器:
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http://demo.theoplayer.com/test-your-stream-with-statistics
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‎VideoDevelopment/流媒体协议/HLS.md‎

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HLS协议规定:
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- 视频的封装格式是TS
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- 视频的编码格式为H264，音频编码格式为MP3、AAC或者AC-3
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- 视频的封装格式是ts(16年发布也支持了fMP4)
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- 视频的编码格式为H264、H265、VP9(17年支持H265、VP9)，音频编码格式为MP3、AAC或者AC-3
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- 除了TS视频文件本身，还定义了用来控制播放的m3u8文件(文本文件)
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HLS协议由三部分组成:
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### 多码率适配流(Master Playlist)
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<img src="https://raw.githubusercontent.com/CharonChui/Pictures/master/indexing_2x.png" style="zoom:70%;" />
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<img src="https://raw.githubusercontent.com/CharonChui/Pictures/master/adaptive_bitratestreaming_HLS.jpg" style="zoom:70%;" />
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客户端播放HLS视频流的逻辑其实非常简单，先下载一级Index file，它里面记录了二级索引文件（Alternate-A、Alternate-B、Alternate-C）的地址，然后客户端再去下载二级索引文件，二级索引文件中又记录了TS文件的下载地址，这样客户端就可以按顺序下载TS视频文件并连续播放。
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