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---
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>
{{Compat("api.MediaSource.activeSourceBuffers")}}
<h2 id="相關資料">相關資料</h2>
<ul>
<li>{{domxref("SourceBuffer")}}</li>
<li>{{domxref("SourceBufferList")}}</li>
</ul>
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