gstreamer/docs/manual/plugins.xml

<chapter id="cha-plugins">
  <title>What are Plugins</title>
  <para> 
    A plugin is a shared library that contains at least one of the following items:
  </para>

  <itemizedlist>
    <listitem>
      <para>
        one or more elementfactories
      </para>
    </listitem>
    <listitem>
      <para>
        one or more typedefinitions
      </para>
    </listitem>
    <listitem>
      <para>
        one or more autopluggers
      </para>
    </listitem>
    <listitem>
      <para>
        exported symbols for use in other plugins
      </para>
    </listitem>
  </itemizedlist>
  <para> 
    The plugins have one simple method: plugin_init () where all the elementfactories are
    created and the typedefinitions are registered.
  </para> 
  <para> 
    the plugins are maintained in the plugin system. Optionally, the typedefinitions and 
    the elementfactories can be saved into an XML representation so that the plugin system
    does not have to load all available plugins in order to know their definition.
  </para> 
														  
  <para> 
    The basic plugin structure has the following fields:
  </para> 
  <programlisting>
struct _GstPlugin {
  gchar *name;                  /* name of the plugin */
  gchar *longname;              /* long name of plugin */
  gchar *filename;              /* filename it came from */

  GList *types;                 /* list of types provided */
  gint numtypes;
  GList *elements;              /* list of elements provided */
  gint numelements;
  GList *autopluggers;          /* list of autopluggers provided */
  gint numautopluggers;

  gboolean loaded;              /* if the plugin is in memory */
};
  </programlisting>

  <para> 
    You can query a GList of available plugins with:
  </para> 
  <programlisting>
    GList *plugins;
    
    plugins = gst_plugin_get_list ();

    while (plugins) {
      GstPlugin *plugin = (GstPlugin *)plugins-&gt;data;

      g_print ("plugin: %s\n", gst_plugin_get_name (plugin));

      plugins = g_list_next (plugins);
    }
  </programlisting>
</chapter>