gstreamer/docs/gst/tmpl/gstpadtemplate.sgml

<!-- ##### SECTION Title ##### -->
GstPadTemplate

<!-- ##### SECTION Short_Description ##### -->
Describe the media type of a pad.

<!-- ##### SECTION Long_Description ##### -->
<para>
Padtemplates describe the possible media types a pad or an elementfactory can
handle. 
</para>
<para>
Pad and PadTemplates have #GstCaps attached to it to describe the media type they
are capable of dealing with.  gst_pad_template_get_caps() is used to get the
caps of a padtemplate. It's not possible to modify the caps of a padtemplate after
creation. 
</para>
<para>
Padtemplates can be created with gst_pad_template_new() or with the convenient
GST_PAD_TEMPLATE_FACTORY() macro. A padtemplate can be used to create a pad or 
to add to an elementfactory.
</para>
<para>
The following code example shows the code to create a pad from a padtemplate.
<programlisting>
  GST_PAD_TEMPLATE_FACTORY (my_template_factory,
    "sink",		/* the name of the pad */
    GST_PAD_SINK,	/* the direction of the pad */
    GST_PAD_ALWAYS, 	/* when this pad will be present */
    GST_CAPS_NEW (	/* the capabilities of the padtemplate */
      "my_caps",
      "audio/raw",
        "format",	GST_PROPS_STRING ("int"),
        "channels",	GST_PROPS_INT_RANGE (1, 6)
    )
  )

  void
  my_method (void) 
  {
    GstPad *pad;
  
    pad = gst_pad_new_from_template (GST_PAD_TEMPLATE_GET (my_template_factory), "sink");
    ...
  }
</programlisting>
</para>
<para>
The following example shows you how to add the padtemplate to an elementfactory:
<programlisting>
  gboolean
  my_factory_init (GstPlugin *plugin)
  {
    GstElementFactory *factory;

    factory = gst_element_factory_new ("my_factory", GST_TYPE_MYFACTORY, &amp;gst_myfactory_details);
    g_return_val_if_fail (factory != NULL, FALSE);

    gst_element_factory_add_pad_template (factory, GST_PAD_TEMPLATE_GET (my_template_factory));

    gst_plugin_add_feature (plugin, GST_PLUGIN_FEATURE (factory));

    return TRUE;
  }

</programlisting>
</para>

<!-- ##### SECTION See_Also ##### -->
<para>
#GstPad, #GstElementFactory
</para>

<!-- ##### ENUM GstPadPresence ##### -->
<para>
Indicates when this pad will become available.
</para>

@GST_PAD_ALWAYS: the pad is always available
@GST_PAD_SOMETIMES: the pad will become available depending on the media stream
@GST_PAD_REQUEST: th pad is only available on request with 
gst_element_request_pad_by_name() or gst_element_request_compatible_pad().

<!-- ##### STRUCT GstPadTemplate ##### -->
<para>
The padtemplate object.
</para>


<!-- ##### ENUM GstPadTemplateFlags ##### -->
<para>
Flags for the padtemplate
</para>

@GST_PAD_TEMPLATE_FIXED: The padtemplate has no variable properties
@GST_PAD_TEMPLATE_FLAG_LAST: first flag that can be used by subclasses.

<!-- ##### MACRO GST_PAD_TEMPLATE_CAPS ##### -->
<para>
Get a handle to the padtemplate #GstCaps
</para>

@templ: the template to query


<!-- ##### MACRO GST_PAD_TEMPLATE_DIRECTION ##### -->
<para>
Get the direction of the padtemplate.
</para>

@templ: the template to query


<!-- ##### MACRO GST_PAD_TEMPLATE_NAME_TEMPLATE ##### -->
<para>
Get the nametemplate of the padtemplate.
</para>

@templ: the template to query


<!-- ##### MACRO GST_PAD_TEMPLATE_PRESENCE ##### -->
<para>
Get the presence of the padtemplate.
</para>

@templ: the template to query


<!-- ##### MACRO GST_PAD_TEMPLATE_NEW ##### -->
<para>
Create a new padtemplate.
</para>

@padname: the nametemplate for the pads that will be created with this template
@dir: the direction of the pads.
@pres: the presence of the pads.
@...: the capabilities of this padtemplate usually created with GST_CAPS_NEW()


<!-- ##### MACRO GST_PAD_TEMPLATE_FACTORY ##### -->
<para>
Create a factory for a padtemplate. This can be used if you only want one instance
of the padtemplate. Use GST_PAD_TEMPLATE_GET() to get the unique padtemplate.
</para>

@name: th name of the factory
@padname: the nametemplate of the pads
@dir: the direction of the pads.
@pres: the presence of the pads.
@...: the capabilities of this padtemplate, usually created with GST_CAPS_NEW()


<!-- ##### MACRO GST_PAD_TEMPLATE_GET ##### -->
<para>
Get the padtemplate of the factory created with GST_PAD_TEMPLATE_FACTORY()
</para>

@fact: the factory name to get the padtemplate from.


<!-- ##### MACRO GST_PAD_TEMPLATE_IS_FIXED ##### -->
<para>
Check if the properties of the padtemplate are fixed
</para>

@templ: the template to query


<!-- ##### FUNCTION gst_pad_template_new ##### -->
<para>

</para>

@name_template: 
@direction: 
@presence: 
@caps: 
@Varargs: 
@Returns: 


<!-- ##### FUNCTION gst_pad_template_get_caps ##### -->
<para>

</para>

@templ: 
@Returns: 


<!-- ##### FUNCTION gst_pad_template_get_caps_by_name ##### -->
<para>

</para>

@templ: 
@name: 
@Returns: 


<!-- ##### SIGNAL GstPadTemplate::pad-created ##### -->
<para>
This signal is fired when an element creates a pad from this 
template.
</para>

@gstpadtemplate: the object which received the signal.
@arg1: The pad that was created.