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
    chain. 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>

  <sect1 id="sec-conn-basic">
   <title>Making simple connections</title>
   <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_pads ()
     function:
   </para>
  <programlisting>

 // connect them
 gst_element_connect_pads (element1, "src", element2, "sink");
   ....
 // and disconnect them
 gst_element_disconnect_pads (element1, "src", element2, "sink");

  </programlisting>
   <para>
     An even more convenient shortcut for single-source, single-sink elements is the
     gst_element_connect () function:
   </para>
  <programlisting>

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

  </programlisting>
   <para>
     If you have more than one element to connection, the gst_element_connect_many () function takes
     a NULL-terminated list of elements:
   </para>
  <programlisting>

 // connect them
 gst_element_connect_many (element1, element2, element3, element4, NULL);
   ....
 // and disconnect them
 gst_element_disconnect_many (element1, element2, element3, element4, NULL);

  </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> a pad is connected to, use 
     gst_pad_get_peer (pad).
   </para>
  </sect1>

  <sect1 id="sec-conn-filtered">
   <title>Making filtered connections</title>
    <para>
      You can also force a specific media type on the connection by using gst_pad_connect_filtered ()
      and gst_element_connect_filtered (). FIXME link to caps documentation.
    </para>
  </sect1>

</chapter>