关于<playlist>标签以及用例说明

Since video play a more important role in web, HTML should try best to make it convenient，not only publish but also republish. Web authors need a powerful Tag to integrate abundant media resources as well as benefit other authors. And think about many people improve or fork a same video, We can easily maintain video version with little expense like Git, especially in modern network education and media wiki.
<playlist> could have many <video> <img> <map><audio><p> <track><canvas>,and <playlist> too, but have "time" attribute which indicate duration, value can be -1 meant last to end 
and  "start" attribute which indicate start time in the playlist, value can be id of others meant synchronization.
and "level" attribute which indicate which level the picture is based on background
and "top", "left" attribute to position the content in percent
and  "mixed" attribute which indicate modes to insert into video, value is “auto” as default, “on” to mix as default, “alt” to replace and “cut” to insert. 
<playlist> uses "href" attribute to indicate the export and import video URL looking like “href=playlist1” and “href=http://www.example.org/index.html#playlist1”.

When a <playlist> embed, player should find the HTML codes in reference page. 
<a> used in <playlist> to define anchor in player’s controls.
<video>should also implement “Media Fragments URI” described at http://www.w3.org/TR/media-frags/ looking like
“http://www.example.org/video.ogv#t=60,100”, but time should best in milliseconds or  decimal mode.
Player should calculate the total time and play the right pieces in sequence, and realize standard video effects.
 
<effect> is used to add standard video effects, especially transitions. 
"vid" attribute tells which pictures dose the effect apply to, value maybe like "id1:id2".
"type" attribute tells which transition effect will be used,
value maybe like "dissolve", "slide". 
"during" attribute tells duration of the effect, it doesn’t count in the total time of <playlist>.
<effect> can also utilize player’s powerful decoding ability, using attribute such as "contrast", "balance" and "color".
 
Code Example:
<playlist>
<!—视频左上角放置logo，通过设置占播放窗口的百分比指定显示大小-->
<img src="images/logo.png" width="10%" height="5%" top="1%" left="5%" alt="Tip" mixed="on" time="-1" level="99"/>
<!—设置片头-->
<img src="images/title.png" width="100%" height="100%" start="0"
 time="4.00" mixed="cut"/>
<p start="0" time="4.00" level="10">
<h1>This is a representation of the playlist Tag</h1>
<p>
<video id="v1" mute="true"
src="http://www.example.org/video.ogv#t=60.00,100.50"/>
<!—替换上段视频的音频-->
<audio src="bg.mp3" start="v1"/>
<!—上段视频中插入另一段视频，之前的audio和track也接受判定 -->
<video id="v3" src="v.ogv" mixed="cut" start="v1+10.0"/>
 
<track kind=subtitles src=brave.en.vtt label="English" 
start="v1"/>
<playlist id="v2" href=http://www.example.org/index.html#playlist1/>
 
<!—在进度条添加一个说明链接-->
<a start="v2" title="play playlist at example.org"/>
<!—添加溶解渐变的转场特效-->
<effect vid="v1:v2" type="dissolve" during="2">
</playlist>



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