---
title: MediaSource.activeSourceBuffers
slug: Web/API/MediaSource/activeSourceBuffers
translation_of: Web/API/MediaSource/activeSourceBuffers
---
<div>{{APIRef("Media Source Extensions")}}{{SeeCompatTable}}</div>

<p><code><strong>activeSourceBuffers</strong></code> 是 {{domxref("MediaSource")}} 介面的唯讀屬性，回傳一個 {{domxref("SourceBufferList")}} 物件，含有在 {{domxref("SourceBuffers")}} 之中的 {{domxref("SourceBuffer")}} 物件子集合—物件的串列提供被選擇的影片軌 (video track), 啟用的音軌 (audio tracks), 以及顯示或隱藏的字軌。</p>

<h2 id="語法">語法</h2>

<pre class="brush: js">var myActiveSourceBuffers = mediaSource.activeSourceBuffers;</pre>

<h3 id="回傳值">回傳值</h3>

<p>一個 {{domxref("SourceBufferList")}} 。</p>

<h2 id="範例">範例</h2>

<p>以下的片段基於 Nick Desaulniers 所編纂的簡單範例（<a href="http://nickdesaulniers.github.io/netfix/demo/bufferAll.html">觀看實際演示</a>，或者<a href="https://github.com/nickdesaulniers/netfix/blob/gh-pages/demo/bufferAll.html">下載原始碼</a> 以利更進一步研究。）</p>

<pre class="brush: js  language-js"><code class="language-js"><span class="keyword token">function</span> sourceOpen <span class="punctuation token">(</span>_<span class="punctuation token">)</span> <span class="punctuation token">{</span>
 <span class="comment token"> //console.log(this.readyState); // open
</span>  <span class="keyword token">var</span> mediaSource <span class="operator token">=</span> <span class="keyword token">this</span><span class="punctuation token">;</span>
  <span class="keyword token">var</span> sourceBuffer <span class="operator token">=</span> mediaSource<span class="punctuation token">.</span><span class="function token">addSourceBuffer<span class="punctuation token">(</span></span>mimeCodec<span class="punctuation token">)</span><span class="punctuation token">;</span>
  <span class="function token">fetchAB<span class="punctuation token">(</span></span>assetURL<span class="punctuation token">,</span> <span class="keyword token">function</span> <span class="punctuation token">(</span>buf<span class="punctuation token">)</span> <span class="punctuation token">{</span>
    sourceBuffer<span class="punctuation token">.</span><span class="function token">addEventListener<span class="punctuation token">(</span></span><span class="string token">'updateend'</span><span class="punctuation token">,</span> <span class="keyword token">function</span> <span class="punctuation token">(</span>_<span class="punctuation token">)</span> <span class="punctuation token">{</span>
      mediaSource<span class="punctuation token">.</span><span class="function token">endOfStream<span class="punctuation token">(</span></span><span class="punctuation token">)</span><span class="punctuation token">;
      console.log(mediaSource.activeSourceBuffers);
      // will contain the source buffer that was added above,
      // as it is selected for playing in the video player</span>
      video<span class="punctuation token">.</span><span class="function token">play<span class="punctuation token">(</span></span><span class="punctuation token">)</span><span class="punctuation token">;</span>
     <span class="comment token"> //console.log(mediaSource.readyState); // ended
</span>    <span class="punctuation token">}</span><span class="punctuation token">)</span><span class="punctuation token">;</span>
    sourceBuffer<span class="punctuation token">.</span><span class="function token">appendBuffer<span class="punctuation token">(</span></span>buf<span class="punctuation token">)</span><span class="punctuation token">;</span>
  <span class="punctuation token">}</span><span class="punctuation token">)</span><span class="punctuation token">;</span>
<span class="punctuation token">}</span><span class="punctuation token">;

...</span></code></pre>

<h2 id="規格">規格</h2>

<table class="standard-table">
 <tbody>
  <tr>
   <th scope="col">規格</th>
   <th scope="col">狀態</th>
   <th scope="col">注釋</th>
  </tr>
  <tr>
   <td>{{SpecName('Media Source Extensions', '#widl-MediaSource-activeSourceBuffers', 'activeSourceBuffers')}}</td>
   <td>{{Spec2('Media Source Extensions')}}</td>
   <td>Initial definition.</td>
  </tr>
 </tbody>
</table>

<h2 id="相容性表格">相容性表格</h2>

<div>{{CompatibilityTable}}</div>

<div id="compat-desktop">
<table class="compat-table">
 <tbody>
  <tr>
   <th>Feature</th>
   <th>Chrome</th>
   <th>Edge</th>
   <th>Firefox (Gecko)</th>
   <th>Internet Explorer</th>
   <th>Opera</th>
   <th>Safari (WebKit)</th>
  </tr>
  <tr>
   <td>Basic support</td>
   <td>23</td>
   <td>{{CompatVersionUnknown}}</td>
   <td>{{CompatGeckoDesktop("25.0")}}<sup>[1]</sup><br>
    {{CompatGeckoDesktop("42.0")}}</td>
   <td>11<sup>[2]</sup></td>
   <td>15</td>
   <td>8</td>
  </tr>
 </tbody>
</table>
</div>

<div id="compat-mobile">
<table class="compat-table">
 <tbody>
  <tr>
   <th>Feature</th>
   <th>Android</th>
   <th>Edge</th>
   <th>Firefox Mobile (Gecko)</th>
   <th>Firefox OS (Gecko)</th>
   <th>IE Phone</th>
   <th>Opera Mobile</th>
   <th>Safari Mobile</th>
  </tr>
  <tr>
   <td>Basic support</td>
   <td>4.4.4</td>
   <td>{{CompatVersionUnknown}}</td>
   <td>
    <p>{{CompatNo}}</p>
   </td>
   <td>{{CompatNo}}</td>
   <td>11</td>
   <td>30</td>
   <td>{{CompatNo}}</td>
  </tr>
 </tbody>
</table>
</div>

<p>[1] 在切換 about:config 偏好設定 media.mediasource.enabled 為 true 時可以使用。此外，支援只限於白名單內的網站，如：YouTube, Netflix, 以及其他熱門的串流網站。白名單已經被移除且 Media Source Extensions 在 42+ 對所有網站已預設為啟用。</p>

<p>[2] 只在 Windows 8+ 上有效。</p>

<h2 id="相關資料">相關資料</h2>

<ul>
 <li>{{domxref("SourceBuffer")}}</li>
 <li>{{domxref("SourceBufferList")}}</li>
</ul>