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

<p>{{domxref("SourceBuffer")}} 接口的 <code><strong>mode</strong></code> 属性用来控制媒体片段添加到<code>SourceBuffer</code> 时的顺序是可以任意的还是有严格顺序的。</p>

<p>两个可用的值:</p>

<ul>
 <li><code>segments</code>: 媒体片段的时间戳决定段的播放顺序。这些片段可以按任意顺序添加到sourcebuffer。</li>
 <li><code>sequence</code>: 媒体片段添加到sourcebuffer的顺序决定了它们的播放顺序。片段上的时间戳为遵守此顺序自动生成。</li>
</ul>

<p>moder的值最初是在使用mediasource.addsourcebuffer（）创建sourcebuffer时设置的。如果媒体片段上已经存在时间戳，则该值将设置为<code>segments</code>；如果没有，则该值将设置为<code>sequence</code>.</p>

<p>如果mode初始值为sequence想要改为segments则会引发错误, 必须以<code>sequence</code>模式维护现有段顺序。但是，可以将值从<code>segments模式</code>改为<code>sequence模式</code>。它意味着播放顺序将被固定，并会生成新的时间戳。</p>

<p>当 sourceBuffer 正在处理时mode的值无法改变，如 {{domxref("SourceBuffer.appendBuffer","appendBuffer()")}} 或 {{domxref("SourceBuffer.remove","remove()")}} .</p>

<h2 id="Syntax">Syntax</h2>

<pre class="brush: js">var myMode = sourceBuffer.mode;

sourceBuffer.mode = 'sequence';
</pre>

<h3 id="Value">Value</h3>

<p>A {{domxref("DOMString")}}.</p>

<h3 id="Errors">Errors</h3>

<p>The following errors may be thrown when setting a new value for this property.</p>

<table class="standard-table">
 <thead>
  <tr>
   <th scope="col">Error</th>
   <th scope="col">Explanation</th>
  </tr>
 </thead>
 <tbody>
  <tr>
   <td><code>InvalidAccessError</code></td>
   <td>An attempt was made to set the value to <code>segments</code> when the initial value is <code>sequence</code>.</td>
  </tr>
  <tr>
   <td><code>InvalidStateError</code></td>
   <td>The {{domxref("SourceBuffer")}} object is being updated (i.e. its {{domxref("SourceBuffer.updating")}} property is currently <code>true</code>), the last media segment appended to <code>this </code>SourceBuffer is incomplete, or this <code>SourceBuffer</code> has been removed from the {{domxref("MediaSource")}}.</td>
  </tr>
 </tbody>
</table>

<h2 id="Example">Example</h2>

<p>此代码段是将sourcebuffer的模式设置为“sequence”（如果当前设置为“segments”），假如原先的播放顺序为segments.</p>

<pre class="brush: js">var curMode = sourceBuffer.mode;
if (curMode == 'segments') {
  sourceBuffer.mode = 'sequence';
}</pre>

<h2 id="Specifications">Specifications</h2>

<table class="standard-table">
 <tbody>
  <tr>
   <th scope="col">Specification</th>
   <th scope="col">Status</th>
   <th scope="col">Comment</th>
  </tr>
  <tr>
   <td>{{SpecName('Media Source Extensions', '#widl-SourceBuffer-mode', 'mode')}}</td>
   <td>{{Spec2('Media Source Extensions')}}</td>
   <td>Initial definition.</td>
  </tr>
 </tbody>
</table>

<h2 id="Browser_compatibility">Browser compatibility</h2>

<div>


<p>{{Compat("api.SourceBuffer.mode")}}</p>
</div>

<h2 id="See_also">See also</h2>

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