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<a name="implementing-media-engines-full-example"></a>Implementing Media Engines: Full Example</h2></div></div></div>
<p>In addition, the external <a class="ulink" href="http://git.gnome.org/browse/rygel-gst-0-10-media-engine" target="_top">rygel-gst-0-10-media-engine</a> project provides a Rygel media engine that uses an older GStreamer version and is an example of an external Rygel media-engine implemented in C.</p>
<p>The media engine plugin provides a <code class="function">module_get_instance()</code> function, called by Rygel, which returns an instance of our derived <a class="link" href="RygelDataSource.html" title="RygelDataSource">RygelDataSource</a> class.</p>
<p>This <code class="classname">RygelGstMediaEngine</code> class implements the virtual functions from its <a class="link" href="RygelMediaEngine.html" title="RygelMediaEngine">RygelMediaEngine</a> base class, such as <code class="function">get_dlna_profiles()</code>, <code class="function">get_transcoders()</code> to report what DLNA profiles this media engine supports and what transcoding capabilities it offers.</p>
<p>It also implements the <code class="function">create_data_source()</code> virtual function, returning an instance of our <code class="classname">RygelGstDataSource</code> class, which implements the <a class="link" href="RygelDataSource.html" title="RygelDataSource">RygelDataSource</a> interface. This implements the virtual functions of the <a class="link" href="RygelDataSource.html" title="RygelDataSource">RygelDataSource</a> interface, such as <code class="function">start()</code>, <code class="function">freeze()</code>, <code class="function">thaw()</code>, and <code class="function">stop()</code> by setting the state of its GStreamer <code class="classname">GstPipeline</code>.</p>
<p>The list of transcoders returned by the <code class="classname">RygelGstMediaEngine</code> <code class="function">get_transcoders()</code> implementation provides instances of every transcoder provided by our media engine. These classes derive from RygelTranscoder, implementing its <code class="function">create_source()</code> virtual function, returning an instance of our <code class="classname">RygelGstDataSource</code> class which uses a GStreamer <code class="classname">GstBin</code> that uses a GStreamer decoder and encoder to transcode the original data into the desired format. These derived RygelTranscoder objects also have appropriate values for the <code class="literal">mime-type</code>, <code class="literal">dlna-profile</code>, and <code class="literal">extension</code> properties, allowing Rygel to decide which transcoder to use.</p>
<p>The derived RygelTranscoder classes also implement the <code class="function">add_resource</code> virtual function, to set transcoder-specific details on a <code class="classname">GUPnPDIDLLiteResource</code> that is first instantiated by calling the <code class="function">add_resource</code> implementation in the base class. For instance, by calling <code class="function">gupnp_didl_lite_resource_set_bitrate()</code>.</p>
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