GstPadTemplate

GstPadTemplate — Describe the media type of a pad.

Synopsis


#include <gst/gst.h>


            GstPadTemplate;
            GstStaticPadTemplate;
#define     GST_PAD_TEMPLATE_NAME_TEMPLATE  (templ)
#define     GST_PAD_TEMPLATE_DIRECTION      (templ)
#define     GST_PAD_TEMPLATE_PRESENCE       (templ)
#define     GST_PAD_TEMPLATE_CAPS           (templ)
#define     GST_PAD_TEMPLATE_IS_FIXED       (templ)
enum        GstPadTemplateFlags;
enum        GstPadPresence;
GstPadTemplate* gst_pad_template_new        (const gchar *name_template,
                                             GstPadDirection direction,
                                             GstPadPresence presence,
                                             GstCaps *caps);
GstPadTemplate* gst_static_pad_template_get (GstStaticPadTemplate *pad_template);
GstCaps*    gst_static_pad_template_get_caps
                                            (GstStaticPadTemplate *templ);
GstCaps*    gst_pad_template_get_caps       (GstPadTemplate *templ);


Object Hierarchy


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

Signal Prototypes


"pad-created"
            void        user_function      (GstPadTemplate *pad_template,
                                            GstPad *pad,
                                            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.

Example 12. Create a pad from a padtemplate

  GstStaticPadTemplate my_template =
  GST_STATIC_PAD_TEMPLATE (
    "sink",          // the name of the pad
    GST_PAD_SINK,    // the direction of the pad
    GST_PAD_ALWAYS,  // when this pad will be present
    GST_STATIC_CAPS (        // the capabilities of the padtemplate
      "audio/x-raw-int, "
        "channels = (int) [ 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

GstPadTemplate

typedef struct _GstPadTemplate GstPadTemplate;

The padtemplate object.


GstStaticPadTemplate

typedef struct {
  gchar           *name_template;
  GstPadDirection  direction;
  GstPadPresence   presence;
  GstStaticCaps   static_caps;
} GstStaticPadTemplate;

Structure describing the GstStaticPadTemplate.

gchar *name_template; the name of the template
GstPadDirection direction; the direction of the template
GstPadPresence presence; the presence of the template
GstStaticCaps static_caps; the caps of the template.

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_DIRECTION()

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

Get the direction 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_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_IS_FIXED()

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

Check if the properties of the padtemplate are fixed

templ : the template to query

enum GstPadTemplateFlags

typedef enum {
  GST_PAD_TEMPLATE_FIXED        = (GST_OBJECT_FLAG_LAST << 0),
  /* padding */
  GST_PAD_TEMPLATE_FLAG_LAST    = (GST_OBJECT_FLAG_LAST << 4)
} GstPadTemplateFlags;

Flags for the padtemplate

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

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 the pad is only available on request with gst_element_request_pad_by_name() or gst_element_request_compatible_pad().

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. This functions takes ownership of the provided caps, so be sure to not use them afterwards.

name_template : the name template.
direction : the GstPadDirection of the template.
presence : the GstPadPresence of the pad.
caps : a GstCaps set for the template. The caps are taken ownership of.
Returns : a new GstPadTemplate.

gst_static_pad_template_get ()

GstPadTemplate* gst_static_pad_template_get (GstStaticPadTemplate *pad_template);

Converts a GstStaticPadTemplate into a GstPadTemplate.

pad_template : the static pad template
Returns : a new GstPadTemplate.

gst_static_pad_template_get_caps ()

GstCaps*    gst_static_pad_template_get_caps
                                            (GstStaticPadTemplate *templ);

Gets the capabilities of the static pad template.

templ : a GstStaticPadTemplate to get capabilities of.
Returns : the GstCaps of the static pad template. If you need to keep a reference to the caps, take a ref (see gst_caps_ref()).

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. If you need to keep a reference to the caps, take a ref (see gst_caps_ref()).

Signals

The "pad-created" signal

void        user_function                  (GstPadTemplate *pad_template,
                                            GstPad *pad,
                                            gpointer user_data);

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

pad_template : the object which received the signal.
pad : the pad that was created.
user_data : user data set when the signal handler was connected.

See Also

GstPad, GstElementFactory