## GstPadTemplate

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. unref the caps if you no longer need it.

## 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