gstreamer/docs/manual/connections.xml

<chapter id="cha-connections">
  <title>Connecting elements</title>
  <para> 
    You can connect the different pads of elements together so that the elements
    form a chain.
  </para>

  <figure float="1" id="sec-connection">
    <title>Visualisation of three connected elements</title>
      <mediaobject>
        <imageobject>
          <imagedata fileref="images/connected-elements.&magic;" format="&magic;" />
        </imageobject>
      </mediaobject>
  </figure>
  <para> 
    By connecting these three elements, we have created a very simple pipeline. The effect
    of this will be that the output of the source element (element1) will be used as input 
    for the filter element (element2). The filter element will do something with the data and 
    send the result to the final sink element (element3).
  </para>
  <para> 
    Imagine the above graph as a simple mpeg audio decoder. The source element is a 
    disk source, the filter element is the mpeg decoder and the sink element is your
    audiocard. We will use this simple graph to construct an mpeg player later
    in this manual.
  </para>
  <para> 
    You can connect two pads with:
  </para>
  <programlisting>
 GstPad *srcpad, *sinkpad;

 srcpad = gst_element_get_pad (element1, "src");
 sinpad = gst_element_get_pad (element2, "sink");

 // connect them
 gst_pad_connect (srcpad, sinkpad);
   ....
 // and disconnect them
 gst_pad_disconnect (srcpad, sinkpad);

 </programlisting>
  <para> 
    A convenient shortcut for the above code is done with the gst_element_connect ()
    function:
  </para>
  <programlisting>

 // connect them
 gst_element_connect (element1, "src", element2, "sink");
   ....
 // and disconnect them
 gst_element_disconnect (element1, "src", element2, "sink");

 </programlisting>
  <para> 
    You can query if a pad is connected with GST_PAD_IS_CONNECTED (pad). 
  </para>
  <para> 
    To query for the <classname>GstPad</classname> this srcpad is connected to, use 
    gst_pad_get_peer (srcpad).
  </para>

</chapter>