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

[Edward Hervey]

On Thu, 2008-11-06 at 21:33 +0530, Gireesh Kumar M wrote:
> Hi Edward, 
> 
> Thanks for your reply. 
> Yes, it's essential to check the return values, but this is just a
> sample code by which I wanted to demonstrate what I'm trying to do. 

  Fair enough, in that case don't mention the segfaults.

> What I'm keen to know are 
> 1. is there any api which will directly give me the parent element
> details (something like gst_get_factory_name())

  Those are two things:
  * Getting the parent element (of what ? a pad ? another element ?) =>
use the appropriate gst_*_get_parent().
  * Getting the GstElementFactory details of an instance. =>
gst_element_get_factory() => gst_element_factory_get_*().

> 2. Is it possible to extract the element information by any other
> means?
> 
> Thanks again,
> Gireesh
> 
> On Thu, Nov 6, 2008 at 7:54 PM, Edward Hervey
> <edward.hervey at collabora.co.uk> wrote:
>         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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