[gst-embedded] Any API to extract the parent element information?

[Edward Hervey]

On Thu, 2008-11-06 at 18:46 +0530, Gireesh Kumar M wrote:
> Hi All,
> 
> Is there any way to extract the parent element information from a
> gstreamer element?
> I tried it using the following code snippets but none of them worked. 
> 
> 
> GstElement *elem =
> GST_ELEMENT_CAST(gst_element_get_parent(GST_ELEMENT(pad)));

  Yay, casting a GstPad to a GstElement (!?!?!?).
  Yay, not checking for the return value of gst_element_get_parent().

> g_print("In element %s\n", gst_element_get_name(elem)); //-------this
> displays current element name properly
> 
> elem = GST_ELEMENT_CAST(gst_element_get_parent(elem));

  Yay, not checking for the return value of gst_element_get_parent().

> g_print("Parent element is %s\n",
> gst_element_get_name(elem)); //---this displays pipeline0
> 
> 
> elem = GST_ELEMENT_CAST(gst_element_get_parent(elem));  //--this

  Yay, not checking for the return value of gst_element_get_parent().

>  throws the following error
> g_print("Grand Parent element is %s\n", gst_element_get_name(elem));
> 
> /*(gst-launch-0.10:488): GStreamer-CRITICAL **: gst_object_get_name:
> assertion `GS
> T_IS_OBJECT (object)' failed
> Caught SIGSEGV accessing address (nil)
> Spinning.  Please run 'gdb gst-launch 488' to continue debugging,
> Ctrl-C to quit
> , or Ctrl-\ to dump core. */
> 
> 
> Then I tried,
> 
> GstElement *elem =
> GST_ELEMENT_CAST(gst_element_get_parent(GST_ELEMENT(pad)));

  Yay, not checking for the return value of gst_element_get_parent().
  YAY, casting a GstPad to a GstElement (!?!?!?!)

> elem = GST_ELEMENT_CAST(gst_element_get_parent(elem));
> 
  Yay, not checking for the return value of gst_element_get_parent().

> GstElementClass *kl = GST_ELEMENT_GET_CLASS(elem);

  Yay, not checking for the return value of GST_ELEMENT_GET_CLASS().

> g_print("In element %s\n",
> gst_object_get_name((GstObject*)(kl.details->longname));
> 
> This again gave pipeline0, where I'm expecting the actual name of the
> element. It would be great if anyone can guide me.

  So, to summarize: You're asking for the parent of the parent of the
pad.
  The parent of the pad : The element to which the pad (maybe) belongs.
  The parent of the element to which the pad belongs : a pipeline.

  There's nothing wrong in what it's returning, but please... if you
haven't noticed by now... always check the return values of
functions/methods. It'll avoid you from calling methods/functions with
invalid arguments.

    Edward

> 
> Many thanks in advance,
> Gireesh
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