MediaSource

MediaSource是Media Source Extensions API 表示媒体资源HTMLMediaElement对象的接口。MediaSource 对象可以附着在HTMLMediaElement在客户端进行播放。

构造函数

MediaSource()

构造并且返回一个新的MediaSource的空对象（with no associated source buffers）。

属性

从父接口EventTarget上继承而来。

MediaSource.sourceBuffers 只读

返回一个SourceBufferList 对象，包含了这个MediaSource的SourceBuffer的对象列表。

MediaSource.activeSourceBuffers 只读

Returns a SourceBufferList object containing a subset of the SourceBuffer objects contained within SourceBuffers — the list of objects providing the selected video track,  enabled audio tracks, and shown/hidden text tracks.

MediaSource.readyState 只读

返回一个包含当前MediaSource状态的集合，即使它当前没有附着到一个media元素(closed)，或者已附着并准备接收SourceBuffer 对象 (open)，亦或者已附着但这个流已被MediaSource.endOfStream()关闭(ended.)

MediaSource.duration

Gets and sets the duration of the current media being presented.

方法

Inherits properties from its parent interface, EventTarget.

MediaSource.addSourceBuffer()

创建一个带有给定MIME类型的新的 SourceBuffer 并添加到 MediaSource 的 SourceBuffers 列表。

MediaSource.removeSourceBuffer()

删除指定的SourceBuffer 从这个MediaSource对象中的 SourceBuffers列表。

MediaSource.endOfStream()

Signals the end of the stream.

静态方法

MediaSource.isTypeSupported()

返回一个 Boolean 值表明给定的MIME类型是否被当前的浏览器——这意味着可以成功的创建这个MIME类型的SourceBuffer 对象。

Examples

这个例子尽可能快地逐块加载视频，并在加载好后立刻播放。 This example was written by Nick Desaulniers and can be viewed live here (you can also download the source for further investigation.)

var video = document.querySelector('video');

var assetURL = 'frag_bunny.mp4';
// Need to be specific for Blink regarding codecs
// ./mp4info frag_bunny.mp4 | grep Codec
var mimeCodec = 'video/mp4; codecs="avc1.42E01E, mp4a.40.2"';

if ('MediaSource' in window && MediaSource.isTypeSupported(mimeCodec)) {
  var mediaSource = new MediaSource();
  //console.log(mediaSource.readyState); // closed
  video.src = URL.createObjectURL(mediaSource);
  mediaSource.addEventListener('sourceopen', sourceOpen);
} else {
  console.error('Unsupported MIME type or codec: ', mimeCodec);
}

function sourceOpen (_) {
  //console.log(this.readyState); // open
  var mediaSource = this;
  var sourceBuffer = mediaSource.addSourceBuffer(mimeCodec);
  fetchAB(assetURL, function (buf) {
    sourceBuffer.addEventListener('updateend', function (_) {
      mediaSource.endOfStream();
      video.play();
      //console.log(mediaSource.readyState); // ended
    });
    sourceBuffer.appendBuffer(buf);
  });
};

function fetchAB (url, cb) {
  console.log(url);
  var xhr = new XMLHttpRequest;
  xhr.open('get', url);
  xhr.responseType = 'arraybuffer';
  xhr.onload = function () {
    cb(xhr.response);
  };
  xhr.send();
};

说明

浏览器支持情况

[1] Available after switching the about:config preference media.mediasource.enabled to true. In addition, support was limited to a whitelist of sites, for example YouTube, Netflix, and other popular streaming sites. The whitelist was removed and Media Source Extensions was enabled by default in 42+ for all sites.

[2] Only works on Windows 8+.

See also

• SourceBuffer
• SourceBufferList