Revision 1131803 of MediaTrackConstraints.groupId

<div>{{APIRef("Media Capture and Streams")}}</div>

<p>The {{domxref("MediaTrackConstraints")}} dictionary's <code><strong>groupId</strong></code> property is a {{domxref("ConstrainDOMString")}} describing the requested or mandatory constraints placed upon the value of the {{domxref("MediaTrackSettings.groupId", "groupId")}} constrainable property.</p>

<p>If needed, you can determine whether or not this constraint is supported by checking the value of {{domxref("MediaTrackSupportedConstraints.groupId")}} as returned by a call to {{domxref("MediaDevices.getSupportedConstraints()")}}. However, typically this is unnecessary since browsers will simply ignore any constraints they're unfamiliar with.</p>

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

<pre class="syntaxbox">
var <em>constraintsObject</em> = { groupId: <em>constraint</em> };

<em>constraintsObject</em>.groupId = <em>constraint</em>;
</pre>

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

<p>An object based on {{domxref("ConstrainDOMString")}} specifying one or more acceptable, ideal, and/or exact (mandatory) group IDs which are acceptable as the source of media content.</p>

<p>Group IDs are unique for a given origin for the duration of a single browsing session, and are shared by all media sources that come from the same physical device. For example, the microphone and speaker on the same headset would share a group ID. This makes it possible to use the group ID to ensure that the audio and input devices are on the same headset by retrieving the group ID of the input device and specifying it when asking for an output device, perhaps.</p>

<p>However, the value of the <code>groupId</code> is determined by the source of the track's content, and there's no particular format mandated by the specification (although some kind of GUID is recommended). That means that a given track will only return one value for the <code>groupId</code> when you call {{domxref("MediaStreamTrack.getCapabilities", "getCapabilities()")}}, and keep in mind that this value will change for each browsing session.</p>

<p>Because of this, there's no use for the group ID when calling {{domxref("MediaStreamTrack.applyConstraints()")}}, since there is only one possible value, and you can't use it to ensure the same group is used across multiple browsing sessions when calling <code>getUserMedia()</code>.</p>

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

<p>See {{SectionOnPage("/en-US/docs/Web/API/Media_Streams_API/Constraints", "Example: Constraint exerciser")}} for an example.</p>

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

<table class="standard-table">
 <thead>
  <tr>
   <th scope="col">Specification</th>
   <th scope="col">Status</th>
   <th scope="col">Comment</th>
  </tr>
 </thead>
 <tbody>
  <tr>
   <td>{{ SpecName('Media Capture', '#widl-MediaTrackConstraints-groupId', 'groupId') }}</td>
   <td>{{ Spec2('Media Capture') }}</td>
   <td>Initial specification.</td>
  </tr>
 </tbody>
</table>

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

<p>{{CompatibilityTable}}</p>

<div id="compat-desktop">
<table class="compat-table">
 <tbody>
  <tr>
   <th>Feature</th>
   <th>Chrome</th>
   <th>Firefox (Gecko)</th>
   <th>Internet Explorer</th>
   <th>Opera</th>
   <th>Safari</th>
  </tr>
  <tr>
   <td>Basic support</td>
   <td>{{CompatVersionUnknown}}</td>
   <td>{{ CompatGeckoDesktop(50) }}</td>
   <td>{{CompatNo}}</td>
   <td>{{CompatVersionUnknown}}</td>
   <td>{{CompatUnknown}}</td>
  </tr>
 </tbody>
</table>
</div>

<div id="compat-mobile">
<table class="compat-table">
 <tbody>
  <tr>
   <th>Feature</th>
   <th>Android</th>
   <th>Android Webview</th>
   <th>Firefox Mobile (Gecko)</th>
   <th>IE Mobile</th>
   <th>Opera Mobile</th>
   <th>Safari Mobile</th>
   <th>Chrome for Android</th>
  </tr>
  <tr>
   <td>Basic support</td>
   <td>{{CompatUnknown}}</td>
   <td>{{CompatVersionUnknown}}</td>
   <td>{{ CompatGeckoMobile(50) }}</td>
   <td>{{CompatNo}}</td>
   <td>{{CompatUnknown}}</td>
   <td>{{CompatUnknown}}</td>
   <td>{{CompatVersionUnknown}}</td>
  </tr>
 </tbody>
</table>
</div>

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

<ul>
 <li><a href="/en-US/docs/Web/API/Media_Streams_API">Media Capture and Streams API</a></li>
 <li><a href="/en-US/docs/Web/API/Media_Streams_API/Constraints">Capabilities, constraints, and settings</a></li>
 <li>{{domxref("MediaTrackConstraints")}}</li>
 <li>{{domxref("MediaDevices.getSupportedConstraints()")}}</li>
 <li>{{domxref("MediaTrackSupportedConstraints")}}</li>
 <li>{{domxref("MediaStreamTrack")}}</li>
</ul>