GstPadTemplate: GStreamer 1.0 Core Reference Manual

GstPadTemplate

GstPadTemplate — Describe the media type of a pad.

Functions

#define	GST_STATIC_PAD_TEMPLATE()
GstPadTemplate *	gst_static_pad_template_get ()
GstCaps *	gst_static_pad_template_get_caps ()
#define	GST_PAD_TEMPLATE_NAME_TEMPLATE()
#define	GST_PAD_TEMPLATE_DIRECTION()
#define	GST_PAD_TEMPLATE_PRESENCE()
#define	GST_PAD_TEMPLATE_CAPS()
#define	GST_PAD_TEMPLATE_IS_FIXED()
GstPadTemplate *	gst_pad_template_new ()
GstCaps *	gst_pad_template_get_caps ()

Properties

GstCaps *	caps	Read / Write / Construct Only
GstPadDirection	direction	Read / Write / Construct Only
gchar *	name-template	Read / Write / Construct Only
GstPadPresence	presence	Read / Write / Construct Only

Signals

void

pad-created

Run Last

Types and Values

struct	GstStaticPadTemplate
struct	GstPadTemplate
enum	GstPadTemplateFlags
enum	GstPadPresence

Object Hierarchy

    GObject
    ╰── GInitiallyUnowned
        ╰── GstObject
            ╰── GstPadTemplate

Includes

#include <gst/gst.h>

Description

Padtemplates describe the possible media types a pad or an elementfactory can handle. This allows for both inspection of handled types before loading the element plugin as well as identifying pads on elements that are not yet created (request or sometimes pads).

Pad and PadTemplates have GstCaps attached to it to describe the media type they are capable of dealing with. gst_pad_template_get_caps() or GST_PAD_TEMPLATE_CAPS() are used to get the caps of a padtemplate. It's not possible to modify the caps of a padtemplate after creation.

PadTemplates have a GstPadPresence property which identifies the lifetime of the pad and that can be retrieved with GST_PAD_TEMPLATE_PRESENCE(). Also the direction of the pad can be retrieved from the GstPadTemplate with GST_PAD_TEMPLATE_DIRECTION().

The GST_PAD_TEMPLATE_NAME_TEMPLATE() is important for GST_PAD_REQUEST pads because it has to be used as the name in the gst_element_get_request_pad() call to instantiate a pad from this template.

Padtemplates can be created with gst_pad_template_new() or with gst_static_pad_template_get(), which creates a GstPadTemplate from a GstStaticPadTemplate that can be filled with the convenient GST_STATIC_PAD_TEMPLATE() macro.

A padtemplate can be used to create a pad (see gst_pad_new_from_template() or gst_pad_new_from_static_template()) or to add to an element class (see gst_element_class_add_static_pad_template()).

The following code example shows the code to 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, "
      "channels = (int) [ 1, 6 ]"
  )
);
void
my_method (void)
{
  GstPad *pad;
  pad = gst_pad_new_from_static_template (&my_template, "sink");
  ...
}

The following example shows you how to add the padtemplate to an element class, this is usually done in the class_init of the class:

static void
my_element_class_init (GstMyElementClass *klass)
{
  GstElementClass *gstelement_class = GST_ELEMENT_CLASS (klass);

  gst_element_class_add_static_pad_template (gstelement_class, &my_template);
}

Functions

GST_STATIC_PAD_TEMPLATE()

#define             GST_STATIC_PAD_TEMPLATE(padname, dir, pres, caps)

Convenience macro to fill the values of a GstStaticPadTemplate structure.

Parameters

padname	the name template of the pad
dir	the GstPadDirection of the pad
pres	the GstPadPresence of the pad
caps	the GstStaticCaps of the pad

gst_static_pad_template_get ()

GstPadTemplate *
gst_static_pad_template_get (GstStaticPadTemplate *pad_template);

Converts a GstStaticPadTemplate into a GstPadTemplate.

Parameters

pad_template

the static pad template

Returns

a new GstPadTemplate.

[transfer full]

gst_static_pad_template_get_caps ()

GstCaps *
gst_static_pad_template_get_caps (GstStaticPadTemplate *templ);

Gets the capabilities of the static pad template.

Parameters

templ

a GstStaticPadTemplate to get capabilities of.

Returns

the GstCaps of the static pad template. Unref after usage. Since the core holds an additional ref to the returned caps, use gst_caps_make_writable() on the returned caps to modify it.

[transfer full]

GST_PAD_TEMPLATE_NAME_TEMPLATE()

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

Get the nametemplate of the padtemplate.

Parameters

templ

the template to query

GST_PAD_TEMPLATE_DIRECTION()

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

Get the GstPadDirection of the padtemplate.

Parameters

templ

the template to query

GST_PAD_TEMPLATE_PRESENCE()

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

Get the GstPadPresence of the padtemplate.

Parameters

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

Parameters

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

Parameters

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.

Parameters

name_template	the name template.
direction	the GstPadDirection of the template.
presence	the GstPadPresence of the pad.
caps	a GstCaps set for the template.	[transfer none]

Returns

a new GstPadTemplate.

[transfer floating]

gst_pad_template_get_caps ()

GstCaps *
gst_pad_template_get_caps (GstPadTemplate *templ);

Gets the capabilities of the pad template.

Parameters

templ

a GstPadTemplate to get capabilities of.

Returns

the GstCaps of the pad template. Unref after usage.

[transfer full]

Types and Values

struct GstStaticPadTemplate

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

Structure describing the GstStaticPadTemplate.

Members

const 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.

struct GstPadTemplate

struct GstPadTemplate;

The padtemplate object.

enum GstPadTemplateFlags

Flags for the padtemplate

Members

GST_PAD_TEMPLATE_FLAG_LAST

first flag that can be used by subclasses.

enum GstPadPresence

Indicates when this pad will become available.

Members

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()`.

Property Details

The `“caps”` property

  “caps”                     GstCaps *

The capabilities of the pad described by the pad template.

Flags: Read / Write / Construct Only

The `“direction”` property

  “direction”                GstPadDirection

The direction of the pad described by the pad template.

Flags: Read / Write / Construct Only

Default value: GST_PAD_UNKNOWN

The `“name-template”` property

  “name-template”            gchar *

The name template of the pad template.

Flags: Read / Write / Construct Only

Default value: NULL

The `“presence”` property

  “presence”                 GstPadPresence

When the pad described by the pad template will become available.

Flags: Read / Write / Construct Only

Default value: GST_PAD_ALWAYS

Signal Details

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.

Parameters

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.

Flags: Run Last

GstPadTemplate

Functions

Properties

Signals

Types and Values

Object Hierarchy

Includes

Description

Functions

GST_STATIC_PAD_TEMPLATE()

Parameters

gst_static_pad_template_get ()

Parameters

Returns

gst_static_pad_template_get_caps ()

Parameters

Returns

GST_PAD_TEMPLATE_NAME_TEMPLATE()

Parameters

GST_PAD_TEMPLATE_DIRECTION()

Parameters

GST_PAD_TEMPLATE_PRESENCE()

Parameters

GST_PAD_TEMPLATE_CAPS()

Parameters

GST_PAD_TEMPLATE_IS_FIXED()

Parameters

gst_pad_template_new ()

Parameters

Returns

gst_pad_template_get_caps ()

Parameters

Returns

Types and Values

struct GstStaticPadTemplate

Members

struct GstPadTemplate

enum GstPadTemplateFlags

Members

enum GstPadPresence

Members

Property Details

The “caps” property

The “direction” property

The “name-template” property

The “presence” property

Signal Details

The “pad-created” signal

Parameters

See Also

The `“caps”` property

The `“direction”` property

The `“name-template”` property

The `“presence”` property

The `“pad-created”` signal