GstPadTemplate

Name

GstPadTemplate -- Describe the media type of a pad.

Synopsis


#include <gst/gst.h>


enum        GstPadPresence;
struct      GstPadTemplate;
#define     GST_PAD_TEMPLATE_CAPS           (templ)
#define     GST_PAD_TEMPLATE_DIRECTION      (templ)
#define     GST_PAD_TEMPLATE_NAME_TEMPLATE  (templ)
#define     GST_PAD_TEMPLATE_PRESENCE       (templ)
#define     GST_PAD_TEMPLATE_NEW            (padname, dir, pres, ...)
#define     GST_PAD_TEMPLATE_FACTORY        (name, padname, dir, pres, ...)
#define     GST_PAD_TEMPLATE_GET            (fact)
#define     GST_PAD_TEMPLATE_IS_FIXED       (templ)
GstPadTemplate* gst_pad_template_new        (const gchar *name_template,
                                             GstPadDirection direction,
                                             GstPadPresence presence,
                                             GstCaps *caps,
                                             ...);
GstCaps*    gst_pad_template_get_caps       (GstPadTemplate *templ);
GstCaps*    gst_pad_template_get_caps_by_name
                                            (GstPadTemplate *templ,
                                             const gchar *name);

Object Hierarchy


  GObject
   +----GstObject
         +----GstPadTemplate

Signal Prototypes


"pad-created"
            void        user_function      (GstPadTemplate *gstpadtemplate,
                                            gpointer arg1,
                                            gpointer user_data);

Description

Padtemplates describe the possible media types a pad or an elementfactory can handle.

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.

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.

The following code example shows the code to create a pad from a padtemplate.
  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");
    ...
  }

The following example shows you how to add the padtemplate to an elementfactory:
  gboolean
  my_factory_init (GstPlugin *plugin)
  {
    GstElementFactory *factory;

    factory = gst_element_factory_new ("my_factory", GST_TYPE_MYFACTORY, &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;
  }

Details

enum GstPadPresence

typedef enum {
  GST_PAD_ALWAYS,
  GST_PAD_SOMETIMES,
  GST_PAD_REQUEST
} GstPadPresence;

Indicates when this pad will become available.

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

struct GstPadTemplate;

The padtemplate object.


GST_PAD_TEMPLATE_CAPS()

#define GST_PAD_TEMPLATE_CAPS(templ)		(((GstPadTemplate *)(templ))->caps)

Get a handle to the padtemplate GstCaps

templ :

the template to query


GST_PAD_TEMPLATE_DIRECTION()

#define GST_PAD_TEMPLATE_DIRECTION(templ)	(((GstPadTemplate *)(templ))->direction)

Get the direction of the padtemplate.

templ :

the template to query


GST_PAD_TEMPLATE_NAME_TEMPLATE()

#define GST_PAD_TEMPLATE_NAME_TEMPLATE(templ)	(((GstPadTemplate *)(templ))->name_template)

Get the nametemplate of the padtemplate.

templ :

the template to query


GST_PAD_TEMPLATE_PRESENCE()

#define GST_PAD_TEMPLATE_PRESENCE(templ)	(((GstPadTemplate *)(templ))->presence)

Get the presence of the padtemplate.

templ :

the template to query


GST_PAD_TEMPLATE_NEW()

#define     GST_PAD_TEMPLATE_NEW(padname, dir, pres, ...)

Create a new padtemplate.

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()


GST_PAD_TEMPLATE_FACTORY()

#define     GST_PAD_TEMPLATE_FACTORY(name, padname, dir, pres, ...)

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.

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()


GST_PAD_TEMPLATE_GET()

#define GST_PAD_TEMPLATE_GET(fact) (fact)()

Get the padtemplate of the factory created with GST_PAD_TEMPLATE_FACTORY()

fact :

the factory name to get the padtemplate from.


GST_PAD_TEMPLATE_IS_FIXED()

#define GST_PAD_TEMPLATE_IS_FIXED(templ)        (GST_FLAG_IS_SET(templ), GST_PAD_TEMPLATE_FIXED)

Check if the properties of the padtemplate are fixed

templ :

the template to query


gst_pad_template_new ()

GstPadTemplate* gst_pad_template_new        (const gchar *name_template,
                                             GstPadDirection direction,
                                             GstPadPresence presence,
                                             GstCaps *caps,
                                             ...);

Creates a new pad template with a name according to the given template and with the given arguments.

name_template :

the name template.

direction :

the GstPadDirection of the template.

presence :

the GstPadPresence of the pad.

caps :

a GstCaps set for the template.

... :

a NULL-terminated list of GstCaps.

Returns :

a new GstPadTemplate.


gst_pad_template_get_caps ()

GstCaps*    gst_pad_template_get_caps       (GstPadTemplate *templ);

Gets the capabilities of the pad template.

templ :

a GstPadTemplate to get capabilities of.

Returns :

the GstCaps of the pad template.


gst_pad_template_get_caps_by_name ()

GstCaps*    gst_pad_template_get_caps_by_name
                                            (GstPadTemplate *templ,
                                             const gchar *name);

Gets the capability with the given name from this pad template.

templ :

a GstPadTemplate to get the capabilities of.

name :

the name of the capability to get.

Returns :

the GstCaps, or NULL if not found or in case of an error.

Signals

The "pad-created" signal

void        user_function                  (GstPadTemplate *gstpadtemplate,
                                            gpointer arg1,
                                            gpointer user_data);

This signal is fired when an element creates a pad from this template.

gstpadtemplate :

the object which received the signal.

arg1 :

The pad that was created.

user_data :

user data set when the signal handler was connected.

See Also

GstPad, GstElementFactory