GstPad

GstPad — Object contained by elements that allows links to other elements

Synopsis

#include <gst/gst.h>

struct              GstPad;
enum                GstPadDirection;
enum                GstPadFlags;
enum                GstPadLinkReturn;
#define             GST_PAD_LINK_FAILED                 (ret)
#define             GST_PAD_LINK_SUCCESSFUL             (ret)
enum                GstPadLinkCheck;
enum                GstFlowReturn;
const gchar *       gst_flow_get_name                   (GstFlowReturn ret);
GQuark              gst_flow_to_quark                   (GstFlowReturn ret);
enum                GstPadMode;
const gchar *       gst_pad_mode_get_name               (GstPadMode mode);

#define             gst_pad_get_name                    (pad)
GstPadDirection     gst_pad_get_direction               (GstPad *pad);
#define             gst_pad_get_parent                  (pad)
GstElement *        gst_pad_get_parent_element          (GstPad *pad);
GstPadTemplate *    gst_pad_get_pad_template            (GstPad *pad);
GstPadLinkReturn    gst_pad_link                        (GstPad *srcpad,
                                                         GstPad *sinkpad);
GstPadLinkReturn    gst_pad_link_full                   (GstPad *srcpad,
                                                         GstPad *sinkpad,
                                                         GstPadLinkCheck flags);
gboolean            gst_pad_unlink                      (GstPad *srcpad,
                                                         GstPad *sinkpad);
gboolean            gst_pad_is_linked                   (GstPad *pad);
gboolean            gst_pad_can_link                    (GstPad *srcpad,
                                                         GstPad *sinkpad);
GstCaps *           gst_pad_get_allowed_caps            (GstPad *pad);
GstCaps *           gst_pad_get_current_caps            (GstPad *pad);
GstCaps *           gst_pad_get_pad_template_caps       (GstPad *pad);
GstPad *            gst_pad_get_peer                    (GstPad *pad);
void                gst_pad_use_fixed_caps              (GstPad *pad);
gboolean            gst_pad_has_current_caps            (GstPad *pad);
GstEvent *          gst_pad_get_sticky_event            (GstPad *pad,
                                                         GstEventType event_type,
                                                         guint idx);
gboolean            (*GstPadStickyEventsForeachFunction)
                                                        (GstPad *pad,
                                                         GstEvent **event,
                                                         gpointer user_data);
void                gst_pad_sticky_events_foreach       (GstPad *pad,
                                                         GstPadStickyEventsForeachFunction foreach_func,
                                                         gpointer user_data);
gboolean            gst_pad_is_active                   (GstPad *pad);

enum                GstPadProbeReturn;
enum                GstPadProbeType;
struct              GstPadProbeInfo;
#define             GST_PAD_PROBE_INFO_TYPE             (d)
#define             GST_PAD_PROBE_INFO_ID               (d)
#define             GST_PAD_PROBE_INFO_DATA             (d)
#define             GST_PAD_PROBE_INFO_BUFFER           (d)
#define             GST_PAD_PROBE_INFO_BUFFER_LIST      (d)
#define             GST_PAD_PROBE_INFO_EVENT            (d)
#define             GST_PAD_PROBE_INFO_QUERY            (d)
GstBuffer *         gst_pad_probe_info_get_buffer       (GstPadProbeInfo *info);
GstBufferList *     gst_pad_probe_info_get_buffer_list  (GstPadProbeInfo *info);
GstEvent *          gst_pad_probe_info_get_event        (GstPadProbeInfo *info);
GstQuery *          gst_pad_probe_info_get_query        (GstPadProbeInfo *info);
#define             GST_PAD_PROBE_INFO_OFFSET           (d)
#define             GST_PAD_PROBE_INFO_SIZE             (d)
GstPadProbeReturn   (*GstPadProbeCallback)              (GstPad *pad,
                                                         GstPadProbeInfo *info,
                                                         gpointer user_data);
gulong              gst_pad_add_probe                   (GstPad *pad,
                                                         GstPadProbeType mask,
                                                         GstPadProbeCallback callback,
                                                         gpointer user_data,
                                                         GDestroyNotify destroy_data);
void                gst_pad_remove_probe                (GstPad *pad,
                                                         gulong id);
gboolean            gst_pad_is_blocked                  (GstPad *pad);
gboolean            gst_pad_is_blocking                 (GstPad *pad);

gint64              gst_pad_get_offset                  (GstPad *pad);
void                gst_pad_set_offset                  (GstPad *pad,
                                                         gint64 offset);

GstPad *            gst_pad_new                         (const gchar *name,
                                                         GstPadDirection direction);
GstPad *            gst_pad_new_from_template           (GstPadTemplate *templ,
                                                         const gchar *name);
GstPad *            gst_pad_new_from_static_template    (GstStaticPadTemplate *templ,
                                                         const gchar *name);
#define             gst_pad_set_chain_function          (p,
                                                         f)
void                gst_pad_set_chain_function_full     (GstPad *pad,
                                                         GstPadChainFunction chain,
                                                         gpointer user_data,
                                                         GDestroyNotify notify);
GstFlowReturn       (*GstPadChainFunction)              (GstPad *pad,
                                                         GstObject *parent,
                                                         GstBuffer *buffer);
#define             gst_pad_set_chain_list_function     (p,
                                                         f)
void                gst_pad_set_chain_list_function_full
                                                        (GstPad *pad,
                                                         GstPadChainListFunction chainlist,
                                                         gpointer user_data,
                                                         GDestroyNotify notify);
GstFlowReturn       (*GstPadChainListFunction)          (GstPad *pad,
                                                         GstObject *parent,
                                                         GstBufferList *list);
GstFlowReturn       gst_pad_get_range                   (GstPad *pad,
                                                         guint64 offset,
                                                         guint size,
                                                         GstBuffer **buffer);
#define             gst_pad_set_getrange_function       (p,
                                                         f)
void                gst_pad_set_getrange_function_full  (GstPad *pad,
                                                         GstPadGetRangeFunction get,
                                                         gpointer user_data,
                                                         GDestroyNotify notify);
GstFlowReturn       (*GstPadGetRangeFunction)           (GstPad *pad,
                                                         GstObject *parent,
                                                         guint64 offset,
                                                         guint length,
                                                         GstBuffer **buffer);
#define             gst_pad_set_event_function          (p,
                                                         f)
void                gst_pad_set_event_function_full     (GstPad *pad,
                                                         GstPadEventFunction event,
                                                         gpointer user_data,
                                                         GDestroyNotify notify);
gboolean            (*GstPadEventFunction)              (GstPad *pad,
                                                         GstObject *parent,
                                                         GstEvent *event);
#define             gst_pad_set_link_function           (p,
                                                         f)
void                gst_pad_set_link_function_full      (GstPad *pad,
                                                         GstPadLinkFunction link,
                                                         gpointer user_data,
                                                         GDestroyNotify notify);
GstPadLinkReturn    (*GstPadLinkFunction)               (GstPad *pad,
                                                         GstObject *parent,
                                                         GstPad *peer);
#define             gst_pad_set_unlink_function         (p,
                                                         f)
void                gst_pad_set_unlink_function_full    (GstPad *pad,
                                                         GstPadUnlinkFunction unlink,
                                                         gpointer user_data,
                                                         GDestroyNotify notify);
void                (*GstPadUnlinkFunction)             (GstPad *pad,
                                                         GstObject *parent);
gboolean            gst_pad_proxy_query_caps            (GstPad *pad,
                                                         GstQuery *query);
gboolean            gst_pad_proxy_query_accept_caps     (GstPad *pad,
                                                         GstQuery *query);
#define             gst_pad_set_activate_function       (p,
                                                         f)
void                gst_pad_set_activate_function_full  (GstPad *pad,
                                                         GstPadActivateFunction activate,
                                                         gpointer user_data,
                                                         GDestroyNotify notify);
gboolean            (*GstPadActivateFunction)           (GstPad *pad,
                                                         GstObject *parent);
#define             gst_pad_set_activatemode_function   (p,
                                                         f)
void                gst_pad_set_activatemode_function_full
                                                        (GstPad *pad,
                                                         GstPadActivateModeFunction activatemode,
                                                         gpointer user_data,
                                                         GDestroyNotify notify);
gboolean            (*GstPadActivateModeFunction)       (GstPad *pad,
                                                         GstObject *parent,
                                                         GstPadMode mode,
                                                         gboolean active);
gboolean            gst_pad_needs_reconfigure           (GstPad *pad);
gboolean            gst_pad_check_reconfigure           (GstPad *pad);
void                gst_pad_mark_reconfigure            (GstPad *pad);
GstFlowReturn       gst_pad_push                        (GstPad *pad,
                                                         GstBuffer *buffer);
gboolean            gst_pad_push_event                  (GstPad *pad,
                                                         GstEvent *event);
GstFlowReturn       gst_pad_push_list                   (GstPad *pad,
                                                         GstBufferList *list);
GstFlowReturn       gst_pad_pull_range                  (GstPad *pad,
                                                         guint64 offset,
                                                         guint size,
                                                         GstBuffer **buffer);
gboolean            gst_pad_activate_mode               (GstPad *pad,
                                                         GstPadMode mode,
                                                         gboolean active);
gboolean            gst_pad_send_event                  (GstPad *pad,
                                                         GstEvent *event);
gboolean            gst_pad_event_default               (GstPad *pad,
                                                         GstObject *parent,
                                                         GstEvent *event);
gboolean            gst_pad_query                       (GstPad *pad,
                                                         GstQuery *query);
gboolean            gst_pad_peer_query                  (GstPad *pad,
                                                         GstQuery *query);
gboolean            gst_pad_query_default               (GstPad *pad,
                                                         GstObject *parent,
                                                         GstQuery *query);
gboolean            gst_pad_query_position              (GstPad *pad,
                                                         GstFormat format,
                                                         gint64 *cur);
gboolean            gst_pad_query_duration              (GstPad *pad,
                                                         GstFormat format,
                                                         gint64 *duration);
gboolean            gst_pad_query_convert               (GstPad *pad,
                                                         GstFormat src_format,
                                                         gint64 src_val,
                                                         GstFormat dest_format,
                                                         gint64 *dest_val);
gboolean            gst_pad_query_accept_caps           (GstPad *pad,
                                                         GstCaps *caps);
GstCaps *           gst_pad_query_caps                  (GstPad *pad,
                                                         GstCaps *filter);
gboolean            gst_pad_peer_query_position         (GstPad *pad,
                                                         GstFormat format,
                                                         gint64 *cur);
gboolean            gst_pad_peer_query_duration         (GstPad *pad,
                                                         GstFormat format,
                                                         gint64 *duration);
gboolean            gst_pad_peer_query_convert          (GstPad *pad,
                                                         GstFormat src_format,
                                                         gint64 src_val,
                                                         GstFormat dest_format,
                                                         gint64 *dest_val);
gboolean            gst_pad_peer_query_accept_caps      (GstPad *pad,
                                                         GstCaps *caps);
GstCaps *           gst_pad_peer_query_caps             (GstPad *pad,
                                                         GstCaps *filter);
#define             gst_pad_set_query_function          (p,
                                                         f)
void                gst_pad_set_query_function_full     (GstPad *pad,
                                                         GstPadQueryFunction query,
                                                         gpointer user_data,
                                                         GDestroyNotify notify);
gboolean            (*GstPadQueryFunction)              (GstPad *pad,
                                                         GstObject *parent,
                                                         GstQuery *query);
#define             gst_pad_set_iterate_internal_links_function(p,
                                                         f)
void                gst_pad_set_iterate_internal_links_function_full
                                                        (GstPad *pad,
                                                         GstPadIterIntLinkFunction iterintlink,
                                                         gpointer user_data,
                                                         GDestroyNotify notify);
GstIterator *       (*GstPadIterIntLinkFunction)        (GstPad *pad,
                                                         GstObject *parent);
GstIterator *       gst_pad_iterate_internal_links      (GstPad *pad);
GstIterator *       gst_pad_iterate_internal_links_default
                                                        (GstPad *pad,
                                                         GstObject *parent);
void                gst_pad_set_element_private         (GstPad *pad,
                                                         gpointer priv);
gpointer            gst_pad_get_element_private         (GstPad *pad);
gchar *             gst_pad_create_stream_id            (GstPad *pad,
                                                         GstElement *parent,
                                                         const gchar *stream_id);
gchar *             gst_pad_create_stream_id_printf     (GstPad *pad,
                                                         GstElement *parent,
                                                         const gchar *stream_id,
                                                         ...);
gchar *             gst_pad_create_stream_id_printf_valist
                                                        (GstPad *pad,
                                                         GstElement *parent,
                                                         const gchar *stream_id,
                                                         va_list var_args);
gchar *             gst_pad_get_stream_id               (GstPad *pad);
gboolean            (*GstPadForwardFunction)            (GstPad *pad,
                                                         gpointer user_data);
gboolean            gst_pad_forward                     (GstPad *pad,
                                                         GstPadForwardFunction forward,
                                                         gpointer user_data);

GstFlowReturn       gst_pad_chain                       (GstPad *pad,
                                                         GstBuffer *buffer);
GstFlowReturn       gst_pad_chain_list                  (GstPad *pad,
                                                         GstBufferList *list);
gboolean            gst_pad_start_task                  (GstPad *pad,
                                                         GstTaskFunction func,
                                                         gpointer user_data,
                                                         GDestroyNotify notify);
gboolean            gst_pad_pause_task                  (GstPad *pad);
gboolean            gst_pad_stop_task                   (GstPad *pad);
gboolean            gst_pad_set_active                  (GstPad *pad,
                                                         gboolean active);
#define             GST_PAD_GET_STREAM_LOCK             (pad)
#define             GST_PAD_STREAM_LOCK                 (pad)
#define             GST_PAD_STREAM_TRYLOCK              (pad)
#define             GST_PAD_STREAM_UNLOCK               (pad)

Object Hierarchy

  GObject
   +----GInitiallyUnowned
         +----GstObject
               +----GstPad
                     +----GstProxyPad

Properties

  "caps"                     GstCaps*              : Read
  "direction"                GstPadDirection       : Read / Write / Construct Only
  "template"                 GstPadTemplate*       : Read / Write

Signals

  "linked"                                         : Run Last
  "unlinked"                                       : Run Last

Description

A GstElement is linked to other elements via "pads", which are extremely light-weight generic link points.

Pads have a GstPadDirection, source pads produce data, sink pads consume data.

Pads are typically created from a GstPadTemplate with gst_pad_new_from_template() and are then added to a GstElement. This usually happens when the element is created but it can also happen dynamically based on the data that the element is processing or based on the pads that the application requests.

Pads without pad templates can be created with gst_pad_new(), which takes a direction and a name as an argument. If the name is NULL, then a guaranteed unique name will be assigned to it.

A GstElement creating a pad will typically use the various gst_pad_set_*_function() calls to register callbacks for events, queries or dataflow on the pads.

gst_pad_get_parent() will retrieve the GstElement that owns the pad.

After two pads are retrieved from an element with gst_element_get_pad(), the pads can be linked with gst_pad_link(). (For quick links, you can also use gst_element_link(), which will make the obvious link for you if it's straightforward.). Pads can be unlinked again with gst_pad_unlink(). gst_pad_get_peer() can be used to check what the pad is linked to.

Before dataflow is possible on the pads, they need to be activated with gst_pad_set_active().

gst_pad_query() and gst_pad_peer_query() can be used to query various properties of the pad and the stream.

To send a GstEvent on a pad, use gst_pad_send_event() and gst_pad_push_event(). Some events will be sticky on the pad, meaning that after they pass on the pad they can be queried later with gst_pad_get_sticky_event() and gst_pad_sticky_events_foreach(). gst_pad_get_current_caps() and gst_pad_has_current_caps() are convenience functions to query the current sticky CAPS event on a pad.

GstElements will use gst_pad_push() and gst_pad_pull_range() to push out or pull in a buffer.

The dataflow, events and queries that happen on a pad can be monitored with probes that can be installed with gst_pad_add_probe(). gst_pad_is_blocked() can be used to check if a block probe is installed on the pad. gst_pad_is_blocking() checks if the blocking probe is currently blocking the pad. gst_pad_remove_probe() is used to remove a previously installed probe and unblock blocking probes if any.

Pad have an offset that can be retrieved with gst_pad_get_offset(). This offset will be applied to the running_time of all data passing over the pad. gst_pad_set_offset() can be used to change the offset.

Convenience functions exist to start, pause and stop the task on a pad with gst_pad_start_task(), gst_pad_pause_task() and gst_pad_stop_task() respectively.

Last reviewed on 2012-03-29 (0.11.3)

Details

struct GstPad

struct GstPad {
  gpointer                       element_private;

  GstPadTemplate                *padtemplate;

  GstPadDirection                direction;
};

The GstPad structure. Use the functions to update the variables.

gpointer element_private;

private data owned by the parent element

GstPadTemplate *padtemplate;

padtemplate for this pad

GstPadDirection direction;

the direction of the pad, cannot change after creating the pad.

enum GstPadDirection

typedef enum {
  GST_PAD_UNKNOWN,
  GST_PAD_SRC,
  GST_PAD_SINK
} GstPadDirection;

The direction of a pad.

GST_PAD_UNKNOWN

direction is unknown.

GST_PAD_SRC

the pad is a source pad.

GST_PAD_SINK

the pad is a sink pad.

enum GstPadFlags

typedef enum {
  GST_PAD_FLAG_BLOCKED          = (GST_OBJECT_FLAG_LAST << 0),
  GST_PAD_FLAG_FLUSHING         = (GST_OBJECT_FLAG_LAST << 1),
  GST_PAD_FLAG_EOS              = (GST_OBJECT_FLAG_LAST << 2),
  GST_PAD_FLAG_BLOCKING         = (GST_OBJECT_FLAG_LAST << 3),
  GST_PAD_FLAG_NEED_PARENT      = (GST_OBJECT_FLAG_LAST << 4),
  GST_PAD_FLAG_NEED_RECONFIGURE = (GST_OBJECT_FLAG_LAST << 5),
  GST_PAD_FLAG_PENDING_EVENTS   = (GST_OBJECT_FLAG_LAST << 6),
  GST_PAD_FLAG_FIXED_CAPS       = (GST_OBJECT_FLAG_LAST << 7),
  GST_PAD_FLAG_PROXY_CAPS       = (GST_OBJECT_FLAG_LAST << 8),
  GST_PAD_FLAG_PROXY_ALLOCATION = (GST_OBJECT_FLAG_LAST << 9),
  GST_PAD_FLAG_PROXY_SCHEDULING = (GST_OBJECT_FLAG_LAST << 10),
  /* padding */
  GST_PAD_FLAG_LAST        = (GST_OBJECT_FLAG_LAST << 16)
} GstPadFlags;

GST_PAD_FLAG_BLOCKED

is dataflow on a pad blocked

GST_PAD_FLAG_FLUSHING

is pad flushing

GST_PAD_FLAG_EOS

is pad in EOS state

GST_PAD_FLAG_BLOCKING

is pad currently blocking on a buffer or event

GST_PAD_FLAG_NEED_PARENT

ensure that there is a parent object before calling into the pad callbacks.

GST_PAD_FLAG_NEED_RECONFIGURE

the pad should be reconfigured/renegotiated. The flag has to be unset manually after reconfiguration happened.

GST_PAD_FLAG_PENDING_EVENTS

the pad has pending events

GST_PAD_FLAG_FIXED_CAPS

the pad is using fixed caps this means that once the caps are set on the pad, the caps query function only

GST_PAD_FLAG_PROXY_CAPS

GST_PAD_FLAG_PROXY_ALLOCATION

GST_PAD_FLAG_PROXY_SCHEDULING

GST_PAD_FLAG_LAST


enum GstPadLinkReturn

typedef enum {
  GST_PAD_LINK_OK               =  0,
  GST_PAD_LINK_WRONG_HIERARCHY  = -1,
  GST_PAD_LINK_WAS_LINKED       = -2,
  GST_PAD_LINK_WRONG_DIRECTION  = -3,
  GST_PAD_LINK_NOFORMAT         = -4,
  GST_PAD_LINK_NOSCHED          = -5,
  GST_PAD_LINK_REFUSED          = -6
} GstPadLinkReturn;

Result values from gst_pad_link and friends.

GST_PAD_LINK_OK

link succeeded

GST_PAD_LINK_WRONG_HIERARCHY

pads have no common grandparent

GST_PAD_LINK_WAS_LINKED

pad was already linked

GST_PAD_LINK_WRONG_DIRECTION

pads have wrong direction

GST_PAD_LINK_NOFORMAT

pads do not have common format

GST_PAD_LINK_NOSCHED

pads cannot cooperate in scheduling

GST_PAD_LINK_REFUSED

refused for some reason

GST_PAD_LINK_FAILED()

#define GST_PAD_LINK_FAILED(ret) ((ret) < GST_PAD_LINK_OK)

Macro to test if the given GstPadLinkReturn value indicates a failed link step.

ret :

the GstPadLinkReturn value

GST_PAD_LINK_SUCCESSFUL()

#define GST_PAD_LINK_SUCCESSFUL(ret) ((ret) >= GST_PAD_LINK_OK)

Macro to test if the given GstPadLinkReturn value indicates a successful link step.

ret :

the GstPadLinkReturn value

enum GstPadLinkCheck

typedef enum {
  GST_PAD_LINK_CHECK_NOTHING       = 0,
  GST_PAD_LINK_CHECK_HIERARCHY     = 1 << 0,
  GST_PAD_LINK_CHECK_TEMPLATE_CAPS = 1 << 1,
  GST_PAD_LINK_CHECK_CAPS          = 1 << 2,

  GST_PAD_LINK_CHECK_DEFAULT       = GST_PAD_LINK_CHECK_HIERARCHY | GST_PAD_LINK_CHECK_CAPS
} GstPadLinkCheck;

The amount of checking to be done when linking pads. GST_PAD_LINK_CHECK_CAPS and GST_PAD_LINK_CHECK_TEMPLATE_CAPS are mutually exclusive. If both are specified, expensive but safe GST_PAD_LINK_CHECK_CAPS are performed.

Warning

Only disable some of the checks if you are 100% certain you know the link will not fail because of hierarchy/caps compatibility failures. If uncertain, use the default checks (GST_PAD_LINK_CHECK_DEFAULT) or the regular methods for linking the pads.

GST_PAD_LINK_CHECK_NOTHING

Don't check hierarchy or caps compatibility.

GST_PAD_LINK_CHECK_HIERARCHY

Check the pads have same parents/grandparents. Could be omitted if it is already known that the two elements that own the pads are in the same bin.

GST_PAD_LINK_CHECK_TEMPLATE_CAPS

Check if the pads are compatible by using their template caps. This is much faster than GST_PAD_LINK_CHECK_CAPS, but would be unsafe e.g. if one pad has GST_CAPS_ANY.

GST_PAD_LINK_CHECK_CAPS

Check if the pads are compatible by comparing the caps returned by gst_pad_query_caps().

GST_PAD_LINK_CHECK_DEFAULT

The default checks done when linking pads (i.e. the ones used by gst_pad_link()).

enum GstFlowReturn

typedef enum {
  /* custom success starts here */
  GST_FLOW_CUSTOM_SUCCESS_2 = 102,
  GST_FLOW_CUSTOM_SUCCESS_1 = 101,
  GST_FLOW_CUSTOM_SUCCESS = 100,

  /* core predefined */
  GST_FLOW_OK		  =  0,
  /* expected failures */
  GST_FLOW_NOT_LINKED     = -1,
  GST_FLOW_FLUSHING       = -2,
  /* error cases */
  GST_FLOW_EOS            = -3,
  GST_FLOW_NOT_NEGOTIATED = -4,
  GST_FLOW_ERROR	  = -5,
  GST_FLOW_NOT_SUPPORTED  = -6,

  /* custom error starts here */
  GST_FLOW_CUSTOM_ERROR   = -100,
  GST_FLOW_CUSTOM_ERROR_1 = -101,
  GST_FLOW_CUSTOM_ERROR_2 = -102
} GstFlowReturn;

The result of passing data to a pad.

Note that the custom return values should not be exposed outside of the element scope.

GST_FLOW_CUSTOM_SUCCESS_2

Pre-defined custom success code.

GST_FLOW_CUSTOM_SUCCESS_1

Pre-defined custom success code (define your custom success code to this to avoid compiler warnings).

GST_FLOW_CUSTOM_SUCCESS

Elements can use values starting from this (and higher) to define custom success codes.

GST_FLOW_OK

Data passing was ok.

GST_FLOW_NOT_LINKED

Pad is not linked.

GST_FLOW_FLUSHING

Pad is flushing.

GST_FLOW_EOS

Pad is EOS.

GST_FLOW_NOT_NEGOTIATED

Pad is not negotiated.

GST_FLOW_ERROR

Some (fatal) error occured. Element generating this error should post an error message with more details.

GST_FLOW_NOT_SUPPORTED

This operation is not supported.

GST_FLOW_CUSTOM_ERROR

Elements can use values starting from this (and lower) to define custom error codes.

GST_FLOW_CUSTOM_ERROR_1

Pre-defined custom error code (define your custom error code to this to avoid compiler warnings).

GST_FLOW_CUSTOM_ERROR_2

Pre-defined custom error code.

gst_flow_get_name ()

const gchar *       gst_flow_get_name                   (GstFlowReturn ret);

Gets a string representing the given flow return.

ret :

a GstFlowReturn to get the name of.

Returns :

a static string with the name of the flow return.

gst_flow_to_quark ()

GQuark              gst_flow_to_quark                   (GstFlowReturn ret);

Get the unique quark for the given GstFlowReturn.

ret :

a GstFlowReturn to get the quark of.

Returns :

the quark associated with the flow return or 0 if an invalid return was specified.

enum GstPadMode

typedef enum {
  GST_PAD_MODE_NONE,
  GST_PAD_MODE_PUSH,
  GST_PAD_MODE_PULL
} GstPadMode;

The status of a GstPad. After activating a pad, which usually happens when the parent element goes from READY to PAUSED, the GstPadMode defines if the pad operates in push or pull mode.

GST_PAD_MODE_NONE

Pad will not handle dataflow

GST_PAD_MODE_PUSH

Pad handles dataflow in downstream push mode

GST_PAD_MODE_PULL

Pad handles dataflow in upstream pull mode

gst_pad_mode_get_name ()

const gchar *       gst_pad_mode_get_name               (GstPadMode mode);

Return the name of a pad mode, for use in debug messages mostly.

mode :

the pad mode

Returns :

short mnemonic for pad mode mode

gst_pad_get_name()

#define gst_pad_get_name(pad) gst_object_get_name (GST_OBJECT_CAST (pad))

Get a copy of the name of the pad. g_free() after usage.

MT safe.

pad :

the pad to get the name from

gst_pad_get_direction ()

GstPadDirection     gst_pad_get_direction               (GstPad *pad);

Gets the direction of the pad. The direction of the pad is decided at construction time so this function does not take the LOCK.

pad :

a GstPad to get the direction of.

Returns :

the GstPadDirection of the pad. MT safe.

gst_pad_get_parent()

#define gst_pad_get_parent(pad) gst_object_get_parent (GST_OBJECT_CAST (pad))

Get the parent of pad. This function increases the refcount of the parent object so you should gst_object_unref() it after usage. Can return NULL if the pad did not have a parent.

MT safe.

pad :

the pad to get the parent of

gst_pad_get_parent_element ()

GstElement *        gst_pad_get_parent_element          (GstPad *pad);

Gets the parent of pad, cast to a GstElement. If a pad has no parent or its parent is not an element, return NULL.

pad :

a pad

Returns :

the parent of the pad. The caller has a reference on the parent, so unref when you're finished with it. MT safe. [transfer full]

gst_pad_get_pad_template ()

GstPadTemplate *    gst_pad_get_pad_template            (GstPad *pad);

Gets the template for pad.

pad :

a GstPad.

Returns :

the GstPadTemplate from which this pad was instantiated, or NULL if this pad has no template. Unref after usage. [transfer full]

gst_pad_link ()

GstPadLinkReturn    gst_pad_link                        (GstPad *srcpad,
                                                         GstPad *sinkpad);

Links the source pad and the sink pad.

srcpad :

the source GstPad to link.

sinkpad :

the sink GstPad to link.

Returns :

A result code indicating if the connection worked or what went wrong. MT Safe.

gst_pad_link_full ()

GstPadLinkReturn    gst_pad_link_full                   (GstPad *srcpad,
                                                         GstPad *sinkpad,
                                                         GstPadLinkCheck flags);

Links the source pad and the sink pad.

This variant of gst_pad_link provides a more granular control on the checks being done when linking. While providing some considerable speedups the caller of this method must be aware that wrong usage of those flags can cause severe issues. Refer to the documentation of GstPadLinkCheck for more information.

MT Safe.

srcpad :

the source GstPad to link.

sinkpad :

the sink GstPad to link.

flags :

the checks to validate when linking

Returns :

A result code indicating if the connection worked or what went wrong.

gst_pad_unlink ()

gboolean            gst_pad_unlink                      (GstPad *srcpad,
                                                         GstPad *sinkpad);

Unlinks the source pad from the sink pad. Will emit the "unlinked" signal on both pads.

srcpad :

the source GstPad to unlink.

sinkpad :

the sink GstPad to unlink.

Returns :

TRUE if the pads were unlinked. This function returns FALSE if the pads were not linked together. MT safe.

gst_pad_is_linked ()

gboolean            gst_pad_is_linked                   (GstPad *pad);

Checks if a pad is linked to another pad or not.

pad :

pad to check

Returns :

TRUE if the pad is linked, FALSE otherwise. MT safe.

gst_pad_can_link ()

gboolean            gst_pad_can_link                    (GstPad *srcpad,
                                                         GstPad *sinkpad);

Checks if the source pad and the sink pad are compatible so they can be linked.

srcpad :

the source GstPad.

sinkpad :

the sink GstPad.

Returns :

TRUE if the pads can be linked.

gst_pad_get_allowed_caps ()

GstCaps *           gst_pad_get_allowed_caps            (GstPad *pad);

Gets the capabilities of the allowed media types that can flow through pad and its peer.

The allowed capabilities is calculated as the intersection of the results of calling gst_pad_query_caps() on pad and its peer. The caller owns a reference on the resulting caps.

pad :

a GstPad.

Returns :

the allowed GstCaps of the pad link. Unref the caps when you no longer need it. This function returns NULL when pad has no peer. MT safe. [transfer full]

gst_pad_get_current_caps ()

GstCaps *           gst_pad_get_current_caps            (GstPad *pad);

Gets the capabilities currently configured on pad with the last GST_EVENT_CAPS event.

pad :

a GstPad to get the current capabilities of.

Returns :

the current caps of the pad with incremented ref-count.

gst_pad_get_pad_template_caps ()

GstCaps *           gst_pad_get_pad_template_caps       (GstPad *pad);

Gets the capabilities for pad's template.

pad :

a GstPad to get the template capabilities from.

Returns :

the GstCaps of this pad template. Unref after usage. [transfer full]

gst_pad_get_peer ()

GstPad *            gst_pad_get_peer                    (GstPad *pad);

Gets the peer of pad. This function refs the peer pad so you need to unref it after use.

pad :

a GstPad to get the peer of.

Returns :

the peer GstPad. Unref after usage. MT safe. [transfer full]

gst_pad_use_fixed_caps ()

void                gst_pad_use_fixed_caps              (GstPad *pad);

A helper function you can use that sets the FIXED_CAPS flag This way the default CAPS query will always return the negotiated caps or in case the pad is not negotiated, the padtemplate caps.

The negotiated caps are the caps of the last CAPS event that passed on the pad. Use this function on a pad that, once it negotiated to a CAPS, cannot be renegotiated to something else.

pad :

the pad to use

gst_pad_has_current_caps ()

gboolean            gst_pad_has_current_caps            (GstPad *pad);

Check if pad has caps set on it with a GST_EVENT_CAPS event.

pad :

a GstPad to check

Returns :

TRUE when pad has caps associated with it.

gst_pad_get_sticky_event ()

GstEvent *          gst_pad_get_sticky_event            (GstPad *pad,
                                                         GstEventType event_type,
                                                         guint idx);

Returns a new reference of the sticky event of type event_type from the event.

pad :

the GstPad to get the event from.

event_type :

the GstEventType that should be retrieved.

idx :

the index of the event

Returns :

a GstEvent of type event_type or NULL when no event of event_type was on pad. Unref after usage. [transfer full]

GstPadStickyEventsForeachFunction ()

gboolean            (*GstPadStickyEventsForeachFunction)
                                                        (GstPad *pad,
                                                         GstEvent **event,
                                                         gpointer user_data);

Callback used by gst_pad_sticky_events_foreach().

When this function returns TRUE, the next event will be returned. When FALSE is returned, gst_pad_sticky_events_foreach() will return.

When event is set to NULL, the item will be removed from the list of sticky events. event can be replaced by assigning a new reference to it. This function is responsible for unreffing the old event when removing or modifying.

pad :

the GstPad.

event :

a sticky GstEvent.

user_data :

the gpointer to optional user data.

Returns :

TRUE if the iteration should continue

gst_pad_sticky_events_foreach ()

void                gst_pad_sticky_events_foreach       (GstPad *pad,
                                                         GstPadStickyEventsForeachFunction foreach_func,
                                                         gpointer user_data);

Iterates all sticky events on pad and calls foreach_func for every event. If foreach_func returns FALSE the iteration is immediately stopped.

pad :

the GstPad that should be used for iteration.

foreach_func :

the GstPadStickyEventsForeachFunction that should be called for every event. [scope call]

user_data :

the optional user data. [closure]

gst_pad_is_active ()

gboolean            gst_pad_is_active                   (GstPad *pad);

Query if a pad is active

pad :

the GstPad to query

Returns :

TRUE if the pad is active. MT safe.

enum GstPadProbeReturn

typedef enum {
  GST_PAD_PROBE_DROP,
  GST_PAD_PROBE_OK,
  GST_PAD_PROBE_REMOVE,
  GST_PAD_PROBE_PASS,
} GstPadProbeReturn;

GST_PAD_PROBE_DROP

drop data in data probes. For push mode this means that the data item is not sent downstream. For pull mode, it means that the data item is not passed upstream. In both cases, this result code

GST_PAD_PROBE_OK

normal probe return value

GST_PAD_PROBE_REMOVE

GST_PAD_PROBE_PASS


enum GstPadProbeType

typedef enum {
  GST_PAD_PROBE_TYPE_INVALID          = 0,
  /* flags to control blocking */
  GST_PAD_PROBE_TYPE_IDLE             = (1 << 0),
  GST_PAD_PROBE_TYPE_BLOCK            = (1 << 1),
  /* flags to select datatypes */
  GST_PAD_PROBE_TYPE_BUFFER           = (1 << 4),
  GST_PAD_PROBE_TYPE_BUFFER_LIST      = (1 << 5),
  GST_PAD_PROBE_TYPE_EVENT_DOWNSTREAM = (1 << 6),
  GST_PAD_PROBE_TYPE_EVENT_UPSTREAM   = (1 << 7),
  GST_PAD_PROBE_TYPE_EVENT_FLUSH      = (1 << 8),
  GST_PAD_PROBE_TYPE_QUERY_DOWNSTREAM = (1 << 9),
  GST_PAD_PROBE_TYPE_QUERY_UPSTREAM   = (1 << 10),
  /* flags to select scheduling mode */
  GST_PAD_PROBE_TYPE_PUSH             = (1 << 12),
  GST_PAD_PROBE_TYPE_PULL             = (1 << 13),

  /* flag combinations */
  GST_PAD_PROBE_TYPE_BLOCKING         = GST_PAD_PROBE_TYPE_IDLE | GST_PAD_PROBE_TYPE_BLOCK,
  GST_PAD_PROBE_TYPE_DATA_DOWNSTREAM  = GST_PAD_PROBE_TYPE_BUFFER | GST_PAD_PROBE_TYPE_BUFFER_LIST | GST_PAD_PROBE_TYPE_EVENT_DOWNSTREAM,
  GST_PAD_PROBE_TYPE_DATA_UPSTREAM    = GST_PAD_PROBE_TYPE_EVENT_UPSTREAM,
  GST_PAD_PROBE_TYPE_DATA_BOTH        = GST_PAD_PROBE_TYPE_DATA_DOWNSTREAM | GST_PAD_PROBE_TYPE_DATA_UPSTREAM,
  GST_PAD_PROBE_TYPE_BLOCK_DOWNSTREAM = GST_PAD_PROBE_TYPE_BLOCK | GST_PAD_PROBE_TYPE_DATA_DOWNSTREAM,
  GST_PAD_PROBE_TYPE_BLOCK_UPSTREAM   = GST_PAD_PROBE_TYPE_BLOCK | GST_PAD_PROBE_TYPE_DATA_UPSTREAM,
  GST_PAD_PROBE_TYPE_EVENT_BOTH       = GST_PAD_PROBE_TYPE_EVENT_DOWNSTREAM | GST_PAD_PROBE_TYPE_EVENT_UPSTREAM,
  GST_PAD_PROBE_TYPE_QUERY_BOTH       = GST_PAD_PROBE_TYPE_QUERY_DOWNSTREAM | GST_PAD_PROBE_TYPE_QUERY_UPSTREAM,
  GST_PAD_PROBE_TYPE_ALL_BOTH         = GST_PAD_PROBE_TYPE_DATA_BOTH | GST_PAD_PROBE_TYPE_QUERY_BOTH,
  GST_PAD_PROBE_TYPE_SCHEDULING       = GST_PAD_PROBE_TYPE_PUSH | GST_PAD_PROBE_TYPE_PULL
} GstPadProbeType;

The different probing types that can occur. When either one of GST_PAD_PROBE_TYPE_IDLE or GST_PAD_PROBE_TYPE_BLOCK is used, the probe will be a blocking probe.

GST_PAD_PROBE_TYPE_INVALID

invalid probe type

GST_PAD_PROBE_TYPE_IDLE

probe idle pads and block

GST_PAD_PROBE_TYPE_BLOCK

probe and block pads

GST_PAD_PROBE_TYPE_BUFFER

probe buffers

GST_PAD_PROBE_TYPE_BUFFER_LIST

probe buffer lists

GST_PAD_PROBE_TYPE_EVENT_DOWNSTREAM

probe downstream events

GST_PAD_PROBE_TYPE_EVENT_UPSTREAM

probe upstream events

GST_PAD_PROBE_TYPE_EVENT_FLUSH

probe flush events. This probe has to be explicitly enabled and is not included in the @GST_PAD_PROBE_TYPE_EVENT_DOWNSTREAM or @GST_PAD_PROBE_TYPE_EVENT_UPSTREAM probe types.

GST_PAD_PROBE_TYPE_QUERY_DOWNSTREAM

probe downstream queries

GST_PAD_PROBE_TYPE_QUERY_UPSTREAM

probe upstream queries

GST_PAD_PROBE_TYPE_PUSH

probe push

GST_PAD_PROBE_TYPE_PULL

probe pull

GST_PAD_PROBE_TYPE_BLOCKING

probe and block at the next opportunity, at data flow or when idle

GST_PAD_PROBE_TYPE_DATA_DOWNSTREAM

probe downstream data (buffers, buffer lists, and events)

GST_PAD_PROBE_TYPE_DATA_UPSTREAM

probe upstream data (events)

GST_PAD_PROBE_TYPE_DATA_BOTH

probe upstream and downstream data (buffers, buffer lists, and events)

GST_PAD_PROBE_TYPE_BLOCK_DOWNSTREAM

probe and block downstream data (buffers, buffer lists, and events)

GST_PAD_PROBE_TYPE_BLOCK_UPSTREAM

probe and block upstream data (events)

GST_PAD_PROBE_TYPE_EVENT_BOTH

probe upstream and downstream events

GST_PAD_PROBE_TYPE_QUERY_BOTH

probe upstream and downstream queries

GST_PAD_PROBE_TYPE_ALL_BOTH

probe upstream events and queries and downstream buffers, buffer lists, events and queries

GST_PAD_PROBE_TYPE_SCHEDULING

probe push and pull

struct GstPadProbeInfo

struct GstPadProbeInfo {
  GstPadProbeType type;
  gulong id;
  gpointer data;
  guint64 offset;
  guint size;
};

Info passed in the GstPadProbeCallback.

GstPadProbeType type;

the current probe type

gulong id;

the id of the probe

gpointer data;

type specific data, check the type field to know the datatype. This field can be NULL.

guint64 offset;

offset of pull probe, this field is valid when type contains GST_PAD_PROBE_TYPE_PULL

guint size;

size of pull probe, this field is valid when type contains GST_PAD_PROBE_TYPE_PULL

GST_PAD_PROBE_INFO_TYPE()

#define GST_PAD_PROBE_INFO_TYPE(d)         ((d)->type)

GST_PAD_PROBE_INFO_ID()

#define GST_PAD_PROBE_INFO_ID(d)           ((d)->id)

GST_PAD_PROBE_INFO_DATA()

#define GST_PAD_PROBE_INFO_DATA(d)         ((d)->data)

GST_PAD_PROBE_INFO_BUFFER()

#define GST_PAD_PROBE_INFO_BUFFER(d)       GST_BUFFER_CAST(GST_PAD_PROBE_INFO_DATA(d))

GST_PAD_PROBE_INFO_BUFFER_LIST()

#define GST_PAD_PROBE_INFO_BUFFER_LIST(d)  GST_BUFFER_LIST_CAST(GST_PAD_PROBE_INFO_DATA(d))

GST_PAD_PROBE_INFO_EVENT()

#define GST_PAD_PROBE_INFO_EVENT(d)        GST_EVENT_CAST(GST_PAD_PROBE_INFO_DATA(d))

GST_PAD_PROBE_INFO_QUERY()

#define GST_PAD_PROBE_INFO_QUERY(d)        GST_QUERY_CAST(GST_PAD_PROBE_INFO_DATA(d))

gst_pad_probe_info_get_buffer ()

GstBuffer *         gst_pad_probe_info_get_buffer       (GstPadProbeInfo *info);

info :

a GstPadProbeInfo

Returns :

The GstBuffer from the probe. [transfer none]

gst_pad_probe_info_get_buffer_list ()

GstBufferList *     gst_pad_probe_info_get_buffer_list  (GstPadProbeInfo *info);

gst_pad_probe_info_get_event ()

GstEvent *          gst_pad_probe_info_get_event        (GstPadProbeInfo *info);

info :

a GstPadProbeInfo

Returns :

The GstEvent from the probe. [transfer none]

gst_pad_probe_info_get_query ()

GstQuery *          gst_pad_probe_info_get_query        (GstPadProbeInfo *info);

info :

a GstPadProbeInfo

Returns :

The GstQuery from the probe. [transfer none]

GST_PAD_PROBE_INFO_OFFSET()

#define GST_PAD_PROBE_INFO_OFFSET(d)       ((d)->offset)

GST_PAD_PROBE_INFO_SIZE()

#define GST_PAD_PROBE_INFO_SIZE(d)         ((d)->size)

GstPadProbeCallback ()

GstPadProbeReturn   (*GstPadProbeCallback)              (GstPad *pad,
                                                         GstPadProbeInfo *info,
                                                         gpointer user_data);

Callback used by gst_pad_add_probe(). Gets called to notify about the current blocking type.

The callback is allowed to modify the data pointer in info.

pad :

the GstPad that is blocked

info :

GstPadProbeInfo

user_data :

the gpointer to optional user data.

Returns :

a GstPadProbeReturn

gst_pad_add_probe ()

gulong              gst_pad_add_probe                   (GstPad *pad,
                                                         GstPadProbeType mask,
                                                         GstPadProbeCallback callback,
                                                         gpointer user_data,
                                                         GDestroyNotify destroy_data);

Be notified of different states of pads. The provided callback is called for every state that matches mask.

pad :

the GstPad to add the probe to

mask :

the probe mask

callback :

GstPadProbeCallback that will be called with notifications of the pad state

user_data :

user data passed to the callback. [closure]

destroy_data :

GDestroyNotify for user_data

Returns :

an id or 0 on error. The id can be used to remove the probe with gst_pad_remove_probe(). MT safe.

gst_pad_remove_probe ()

void                gst_pad_remove_probe                (GstPad *pad,
                                                         gulong id);

Remove the probe with id from pad.

MT safe.

pad :

the GstPad with the probe

id :

the probe id to remove

gst_pad_is_blocked ()

gboolean            gst_pad_is_blocked                  (GstPad *pad);

Checks if the pad is blocked or not. This function returns the last requested state of the pad. It is not certain that the pad is actually blocking at this point (see gst_pad_is_blocking()).

pad :

the GstPad to query

Returns :

TRUE if the pad is blocked. MT safe.

gst_pad_is_blocking ()

gboolean            gst_pad_is_blocking                 (GstPad *pad);

Checks if the pad is blocking or not. This is a guaranteed state of whether the pad is actually blocking on a GstBuffer or a GstEvent.

pad :

the GstPad to query

Returns :

TRUE if the pad is blocking. MT safe.

gst_pad_get_offset ()

gint64              gst_pad_get_offset                  (GstPad *pad);

Get the offset applied to the running time of pad. pad has to be a source pad.

pad :

a GstPad

Returns :

the offset.

gst_pad_set_offset ()

void                gst_pad_set_offset                  (GstPad *pad,
                                                         gint64 offset);

Set the offset that will be applied to the running time of pad.

pad :

a GstPad

offset :

the offset

gst_pad_new ()

GstPad *            gst_pad_new                         (const gchar *name,
                                                         GstPadDirection direction);

Creates a new pad with the given name in the given direction. If name is NULL, a guaranteed unique name (across all pads) will be assigned. This function makes a copy of the name so you can safely free the name.

name :

the name of the new pad.

direction :

the GstPadDirection of the pad.

Returns :

a new GstPad, or NULL in case of an error. MT safe. [transfer floating]

gst_pad_new_from_template ()

GstPad *            gst_pad_new_from_template           (GstPadTemplate *templ,
                                                         const gchar *name);

Creates a new pad with the given name from the given template. If name is NULL, a guaranteed unique name (across all pads) will be assigned. This function makes a copy of the name so you can safely free the name.

templ :

the pad template to use

name :

the name of the element

Returns :

a new GstPad, or NULL in case of an error. [transfer full]

gst_pad_new_from_static_template ()

GstPad *            gst_pad_new_from_static_template    (GstStaticPadTemplate *templ,
                                                         const gchar *name);

Creates a new pad with the given name from the given static template. If name is NULL, a guaranteed unique name (across all pads) will be assigned. This function makes a copy of the name so you can safely free the name.

templ :

the GstStaticPadTemplate to use

name :

the name of the element

Returns :

a new GstPad, or NULL in case of an error. [transfer full]

gst_pad_set_chain_function()

#define gst_pad_set_chain_function(p,f)         gst_pad_set_chain_function_full((p),(f),NULL,NULL)

Calls gst_pad_set_chain_function_full() with NULL for the user_data and notify.

p :

a sink GstPad.

f :

the GstPadChainFunction to set.

gst_pad_set_chain_function_full ()

void                gst_pad_set_chain_function_full     (GstPad *pad,
                                                         GstPadChainFunction chain,
                                                         gpointer user_data,
                                                         GDestroyNotify notify);

Sets the given chain function for the pad. The chain function is called to process a GstBuffer input buffer. see GstPadChainFunction for more details.

pad :

a sink GstPad.

chain :

the GstPadChainFunction to set.

user_data :

user_data passed to notify

notify :

notify called when chain will not be used anymore.

GstPadChainFunction ()

GstFlowReturn       (*GstPadChainFunction)              (GstPad *pad,
                                                         GstObject *parent,
                                                         GstBuffer *buffer);

A function that will be called on sinkpads when chaining buffers. The function typically processes the data contained in the buffer and either consumes the data or passes it on to the internally linked pad(s).

The implementer of this function receives a refcount to buffer and should gst_buffer_unref() when the buffer is no longer needed.

When a chain function detects an error in the data stream, it must post an error on the bus and return an appropriate GstFlowReturn value.

pad :

the sink GstPad that performed the chain.

parent :

the parent of pad. If the GST_PAD_FLAG_NEED_PARENT flag is set, parent is guaranteed to be not-NULL and remain valid during the execution of this function.

buffer :

the GstBuffer that is chained, not NULL.

Returns :

GST_FLOW_OK for success

gst_pad_set_chain_list_function()

#define gst_pad_set_chain_list_function(p,f)    gst_pad_set_chain_list_function_full((p),(f),NULL,NULL)

Calls gst_pad_set_chain_list_function_full() with NULL for the user_data and notify.

p :

a sink GstPad.

f :

the GstPadChainListFunction to set.

gst_pad_set_chain_list_function_full ()

void                gst_pad_set_chain_list_function_full
                                                        (GstPad *pad,
                                                         GstPadChainListFunction chainlist,
                                                         gpointer user_data,
                                                         GDestroyNotify notify);

Sets the given chain list function for the pad. The chainlist function is called to process a GstBufferList input buffer list. See GstPadChainListFunction for more details.

pad :

a sink GstPad.

chainlist :

the GstPadChainListFunction to set.

user_data :

user_data passed to notify

notify :

notify called when chainlist will not be used anymore.

GstPadChainListFunction ()

GstFlowReturn       (*GstPadChainListFunction)          (GstPad *pad,
                                                         GstObject *parent,
                                                         GstBufferList *list);

A function that will be called on sinkpads when chaining buffer lists. The function typically processes the data contained in the buffer list and either consumes the data or passes it on to the internally linked pad(s).

The implementer of this function receives a refcount to list and should gst_buffer_list_unref() when the list is no longer needed.

When a chainlist function detects an error in the data stream, it must post an error on the bus and return an appropriate GstFlowReturn value.

pad :

the sink GstPad that performed the chain.

parent :

the parent of pad. If the GST_PAD_FLAG_NEED_PARENT flag is set, parent is guaranteed to be not-NULL and remain valid during the execution of this function.

list :

the GstBufferList that is chained, not NULL.

Returns :

GST_FLOW_OK for success

gst_pad_get_range ()

GstFlowReturn       gst_pad_get_range                   (GstPad *pad,
                                                         guint64 offset,
                                                         guint size,
                                                         GstBuffer **buffer);

returns GST_FLOW_ERROR if NULL.

When pad is flushing this function returns GST_FLOW_FLUSHING immediately and buffer is NULL.

Calls the getrange function of pad, see GstPadGetRangeFunction for a description of a getrange function. If pad has no getrange function installed (see gst_pad_set_getrange_function()) this function returns GST_FLOW_NOT_SUPPORTED.

If buffer points to a variable holding NULL, a valid new GstBuffer will be placed in buffer when this function returns GST_FLOW_OK. The new buffer must be freed with gst_buffer_unref() after usage.

When buffer points to a variable that points to a valid GstBuffer, the buffer will be filled with the result data when this function returns GST_FLOW_OK. If the provided buffer is larger than size, only size bytes will be filled in the result buffer and its size will be updated accordingly.

Note that less than size bytes can be returned in buffer when, for example, an EOS condition is near or when buffer is not large enough to hold size bytes. The caller should check the result buffer size to get the result size.

When this function returns any other result value than GST_FLOW_OK, buffer will be unchanged.

This is a lowlevel function. Usualy gst_pad_pull_range() is used.

pad :

a src GstPad, returns GST_FLOW_ERROR if not.

offset :

The start offset of the buffer

size :

The length of the buffer

buffer :

a pointer to hold the GstBuffer,. [out callee-allocates]

Returns :

a GstFlowReturn from the pad. MT safe.

gst_pad_set_getrange_function()

#define gst_pad_set_getrange_function(p,f)      gst_pad_set_getrange_function_full((p),(f),NULL,NULL)

Calls gst_pad_set_getrange_function_full() with NULL for the user_data and notify.

p :

a source GstPad.

f :

the GstPadGetRangeFunction to set.

gst_pad_set_getrange_function_full ()

void                gst_pad_set_getrange_function_full  (GstPad *pad,
                                                         GstPadGetRangeFunction get,
                                                         gpointer user_data,
                                                         GDestroyNotify notify);

Sets the given getrange function for the pad. The getrange function is called to produce a new GstBuffer to start the processing pipeline. see GstPadGetRangeFunction for a description of the getrange function.

pad :

a source GstPad.

get :

the GstPadGetRangeFunction to set.

user_data :

user_data passed to notify

notify :

notify called when get will not be used anymore.

GstPadGetRangeFunction ()

GstFlowReturn       (*GstPadGetRangeFunction)           (GstPad *pad,
                                                         GstObject *parent,
                                                         guint64 offset,
                                                         guint length,
                                                         GstBuffer **buffer);

This function will be called on source pads when a peer element request a buffer at the specified offset and length. If this function returns GST_FLOW_OK, the result buffer will be stored in buffer. The contents of buffer is invalid for any other return value.

This function is installed on a source pad with gst_pad_set_getrange_function() and can only be called on source pads after they are successfully activated with gst_pad_activate_mode() with the GST_PAD_MODE_PULL.

offset and length are always given in byte units. offset must normally be a value between 0 and the length in bytes of the data available on pad. The length (duration in bytes) can be retrieved with a GST_QUERY_DURATION or with a GST_QUERY_SEEKING.

Any offset larger or equal than the length will make the function return GST_FLOW_EOS, which corresponds to EOS. In this case buffer does not contain a valid buffer.

The buffer size of buffer will only be smaller than length when offset is near the end of the stream. In all other cases, the size of buffer must be exactly the requested size.

It is allowed to call this function with a 0 length and valid offset, in which case buffer will contain a 0-sized buffer and the function returns GST_FLOW_OK.

When this function is called with a -1 offset, the sequentially next buffer of length length in the stream is returned.

When this function is called with a -1 length, a buffer with a default optimal length is returned in buffer. The length might depend on the value of offset.

pad :

the src GstPad to perform the getrange on.

parent :

the parent of pad. If the GST_PAD_FLAG_NEED_PARENT flag is set, parent is guaranteed to be not-NULL and remain valid during the execution of this function.

offset :

the offset of the range

length :

the length of the range

buffer :

a memory location to hold the result buffer, cannot be NULL.

Returns :

GST_FLOW_OK for success and a valid buffer in buffer. Any other return value leaves buffer undefined.

gst_pad_set_event_function()

#define gst_pad_set_event_function(p,f)         gst_pad_set_event_function_full((p),(f),NULL,NULL)

Calls gst_pad_set_event_function_full() with NULL for the user_data and notify.

p :

a GstPad of either direction.

f :

the GstPadEventFunction to set.

gst_pad_set_event_function_full ()

void                gst_pad_set_event_function_full     (GstPad *pad,
                                                         GstPadEventFunction event,
                                                         gpointer user_data,
                                                         GDestroyNotify notify);

Sets the given event handler for the pad.

pad :

a GstPad of either direction.

event :

the GstPadEventFunction to set.

user_data :

user_data passed to notify

notify :

notify called when event will not be used anymore.

GstPadEventFunction ()

gboolean            (*GstPadEventFunction)              (GstPad *pad,
                                                         GstObject *parent,
                                                         GstEvent *event);

Function signature to handle an event for the pad.

pad :

the GstPad to handle the event.

parent :

the parent of pad. If the GST_PAD_FLAG_NEED_PARENT flag is set, parent is guaranteed to be not-NULL and remain valid during the execution of this function.

event :

the GstEvent to handle.

Returns :

TRUE if the pad could handle the event.

gst_pad_set_link_function()

#define gst_pad_set_link_function(p,f)          gst_pad_set_link_function_full((p),(f),NULL,NULL)

Calls gst_pad_set_link_function_full() with NULL for the user_data and notify.

p :

a GstPad.

f :

the GstPadLinkFunction to set.

gst_pad_set_link_function_full ()

void                gst_pad_set_link_function_full      (GstPad *pad,
                                                         GstPadLinkFunction link,
                                                         gpointer user_data,
                                                         GDestroyNotify notify);

Sets the given link function for the pad. It will be called when the pad is linked with another pad.

The return value GST_PAD_LINK_OK should be used when the connection can be made.

The return value GST_PAD_LINK_REFUSED should be used when the connection cannot be made for some reason.

If link is installed on a source pad, it should call the GstPadLinkFunction of the peer sink pad, if present.

pad :

a GstPad.

link :

the GstPadLinkFunction to set.

user_data :

user_data passed to notify

notify :

notify called when link will not be used anymore.

GstPadLinkFunction ()

GstPadLinkReturn    (*GstPadLinkFunction)               (GstPad *pad,
                                                         GstObject *parent,
                                                         GstPad *peer);

Function signature to handle a new link on the pad.

pad :

the GstPad that is linked.

parent :

the parent of pad. If the GST_PAD_FLAG_NEED_PARENT flag is set, parent is guaranteed to be not-NULL and remain valid during the execution of this function.

peer :

the peer GstPad of the link

Returns :

the result of the link with the specified peer.

gst_pad_set_unlink_function()

#define gst_pad_set_unlink_function(p,f)        gst_pad_set_unlink_function_full((p),(f),NULL,NULL)

Calls gst_pad_set_unlink_function_full() with NULL for the user_data and notify.

p :

a GstPad.

f :

the GstPadUnlinkFunction to set.

gst_pad_set_unlink_function_full ()

void                gst_pad_set_unlink_function_full    (GstPad *pad,
                                                         GstPadUnlinkFunction unlink,
                                                         gpointer user_data,
                                                         GDestroyNotify notify);

Sets the given unlink function for the pad. It will be called when the pad is unlinked.

pad :

a GstPad.

unlink :

the GstPadUnlinkFunction to set.

user_data :

user_data passed to notify

notify :

notify called when unlink will not be used anymore.

GstPadUnlinkFunction ()

void                (*GstPadUnlinkFunction)             (GstPad *pad,
                                                         GstObject *parent);

Function signature to handle a unlinking the pad prom its peer.

pad :

the GstPad that is linked.

parent :

the parent of pad. If the GST_PAD_FLAG_NEED_PARENT flag is set, parent is guaranteed to be not-NULL and remain valid during the execution of this function.

gst_pad_proxy_query_caps ()

gboolean            gst_pad_proxy_query_caps            (GstPad *pad,
                                                         GstQuery *query);

Calls gst_pad_query_caps() for all internally linked pads fof pad and returns the intersection of the results.

This function is useful as a default caps query function for an element that can handle any stream format, but requires all its pads to have the same caps. Two such elements are tee and adder.

pad :

a GstPad to proxy.

query :

a CAPS GstQuery.

Returns :

TRUE if query could be executed

gst_pad_proxy_query_accept_caps ()

gboolean            gst_pad_proxy_query_accept_caps     (GstPad *pad,
                                                         GstQuery *query);

Calls gst_pad_accept_caps() for all internally linked pads of pad and returns the intersection of the results.

This function is useful as a default accept caps query function for an element that can handle any stream format, but requires caps that are acceptable for all oposite pads.

pad :

a GstPad to proxy.

query :

an ACCEPT_CAPS GstQuery.

Returns :

TRUE if query could be executed

gst_pad_set_activate_function()

#define gst_pad_set_activate_function(p,f)      gst_pad_set_activate_function_full((p),(f),NULL,NULL)

Calls gst_pad_set_activate_function_full() with NULL for the user_data and notify.

p :

a GstPad.

f :

the GstPadActivateFunction to set.

gst_pad_set_activate_function_full ()

void                gst_pad_set_activate_function_full  (GstPad *pad,
                                                         GstPadActivateFunction activate,
                                                         gpointer user_data,
                                                         GDestroyNotify notify);

Sets the given activate function for pad. The activate function will dispatch to gst_pad_activate_mode() to perform the actual activation. Only makes sense to set on sink pads.

Call this function if your sink pad can start a pull-based task.

pad :

a GstPad.

activate :

the GstPadActivateFunction to set.

user_data :

user_data passed to notify

notify :

notify called when activate will not be used anymore.

GstPadActivateFunction ()

gboolean            (*GstPadActivateFunction)           (GstPad *pad,
                                                         GstObject *parent);

This function is called when the pad is activated during the element READY to PAUSED state change. By default this function will call the activate function that puts the pad in push mode but elements can override this function to activate the pad in pull mode if they wish.

pad :

a GstPad

parent :

the parent of pad

Returns :

TRUE if the pad could be activated.

gst_pad_set_activatemode_function()

#define gst_pad_set_activatemode_function(p,f)  gst_pad_set_activatemode_function_full((p),(f),NULL,NULL)

Calls gst_pad_set_activatemode_function_full() with NULL for the user_data and notify.

p :

a GstPad.

f :

the GstPadActivateModeFunction to set.

gst_pad_set_activatemode_function_full ()

void                gst_pad_set_activatemode_function_full
                                                        (GstPad *pad,
                                                         GstPadActivateModeFunction activatemode,
                                                         gpointer user_data,
                                                         GDestroyNotify notify);

Sets the given activate_mode function for the pad. An activate_mode function prepares the element for data passing.

pad :

a GstPad.

activatemode :

the GstPadActivateModeFunction to set.

user_data :

user_data passed to notify

notify :

notify called when activatemode will not be used anymore.

GstPadActivateModeFunction ()

gboolean            (*GstPadActivateModeFunction)       (GstPad *pad,
                                                         GstObject *parent,
                                                         GstPadMode mode,
                                                         gboolean active);

The prototype of the push and pull activate functions.

pad :

a GstPad

parent :

the parent of pad

mode :

the requested activation mode of pad

active :

activate or deactivate the pad.

Returns :

TRUE if the pad could be activated or deactivated.

gst_pad_needs_reconfigure ()

gboolean            gst_pad_needs_reconfigure           (GstPad *pad);

Check the GST_PAD_FLAG_NEED_RECONFIGURE flag on pad and return TRUE if the flag was set.

pad :

the GstPad to check

Returns :

TRUE is the GST_PAD_FLAG_NEED_RECONFIGURE flag is set on pad.

gst_pad_check_reconfigure ()

gboolean            gst_pad_check_reconfigure           (GstPad *pad);

Check and clear the GST_PAD_FLAG_NEED_RECONFIGURE flag on pad and return TRUE if the flag was set.

pad :

the GstPad to check

Returns :

TRUE is the GST_PAD_FLAG_NEED_RECONFIGURE flag was set on pad.

gst_pad_mark_reconfigure ()

void                gst_pad_mark_reconfigure            (GstPad *pad);

Mark a pad for needing reconfiguration. The next call to gst_pad_check_reconfigure() will return TRUE after this call.

pad :

the GstPad to mark

gst_pad_push ()

GstFlowReturn       gst_pad_push                        (GstPad *pad,
                                                         GstBuffer *buffer);

Pushes a buffer to the peer of pad.

This function will call installed block probes before triggering any installed data probes.

The function proceeds calling gst_pad_chain() on the peer pad and returns the value from that function. If pad has no peer, GST_FLOW_NOT_LINKED will be returned.

In all cases, success or failure, the caller loses its reference to buffer after calling this function.

pad :

a source GstPad, returns GST_FLOW_ERROR if not.

buffer :

the GstBuffer to push returns GST_FLOW_ERROR if not. [transfer full]

Returns :

a GstFlowReturn from the peer pad. MT safe.

gst_pad_push_event ()

gboolean            gst_pad_push_event                  (GstPad *pad,
                                                         GstEvent *event);

Sends the event to the peer of the given pad. This function is mainly used by elements to send events to their peer elements.

This function takes owership of the provided event so you should gst_event_ref() it if you want to reuse the event after this call.

pad :

a GstPad to push the event to.

event :

the GstEvent to send to the pad. [transfer full]

Returns :

TRUE if the event was handled. MT safe.

gst_pad_push_list ()

GstFlowReturn       gst_pad_push_list                   (GstPad *pad,
                                                         GstBufferList *list);

Pushes a buffer list to the peer of pad.

This function will call installed block probes before triggering any installed data probes.

The function proceeds calling the chain function on the peer pad and returns the value from that function. If pad has no peer, GST_FLOW_NOT_LINKED will be returned. If the peer pad does not have any installed chainlist function every group buffer of the list will be merged into a normal GstBuffer and chained via gst_pad_chain().

In all cases, success or failure, the caller loses its reference to list after calling this function.

pad :

a source GstPad, returns GST_FLOW_ERROR if not.

list :

the GstBufferList to push returns GST_FLOW_ERROR if not. [transfer full]

Returns :

a GstFlowReturn from the peer pad. MT safe.

gst_pad_pull_range ()

GstFlowReturn       gst_pad_pull_range                  (GstPad *pad,
                                                         guint64 offset,
                                                         guint size,
                                                         GstBuffer **buffer);

Pulls a buffer from the peer pad or fills up a provided buffer.

This function will first trigger the pad block signal if it was installed.

When pad is not linked GST_FLOW_NOT_LINKED is returned else this function returns the result of gst_pad_get_range() on the peer pad. See gst_pad_get_range() for a list of return values and for the semantics of the arguments of this function.

If buffer points to a variable holding NULL, a valid new GstBuffer will be placed in buffer when this function returns GST_FLOW_OK. The new buffer must be freed with gst_buffer_unref() after usage. When this function returns any other result value, buffer will still point to NULL.

When buffer points to a variable that points to a valid GstBuffer, the buffer will be filled with the result data when this function returns GST_FLOW_OK. When this function returns any other result value, buffer will be unchanged. If the provided buffer is larger than size, only size bytes will be filled in the result buffer and its size will be updated accordingly.

Note that less than size bytes can be returned in buffer when, for example, an EOS condition is near or when buffer is not large enough to hold size bytes. The caller should check the result buffer size to get the result size.

pad :

a sink GstPad, returns GST_FLOW_ERROR if not.

offset :

The start offset of the buffer

size :

The length of the buffer

buffer :

a pointer to hold the GstBuffer, returns GST_FLOW_ERROR if NULL. [out callee-allocates]

Returns :

a GstFlowReturn from the peer pad. MT safe.

gst_pad_activate_mode ()

gboolean            gst_pad_activate_mode               (GstPad *pad,
                                                         GstPadMode mode,
                                                         gboolean active);

Activates or deactivates the given pad in mode via dispatching to the pad's activatemodefunc. For use from within pad activation functions only.

If you don't know what this is, you probably don't want to call it.

pad :

the GstPad to activate or deactivate.

mode :

the requested activation mode

active :

whether or not the pad should be active.

Returns :

TRUE if the operation was successful. MT safe.

gst_pad_send_event ()

gboolean            gst_pad_send_event                  (GstPad *pad,
                                                         GstEvent *event);

Sends the event to the pad. This function can be used by applications to send events in the pipeline.

If pad is a source pad, event should be an upstream event. If pad is a sink pad, event should be a downstream event. For example, you would not send a GST_EVENT_EOS on a src pad; EOS events only propagate downstream. Furthermore, some downstream events have to be serialized with data flow, like EOS, while some can travel out-of-band, like GST_EVENT_FLUSH_START. If the event needs to be serialized with data flow, this function will take the pad's stream lock while calling its event function.

To find out whether an event type is upstream, downstream, or downstream and serialized, see GstEventTypeFlags, gst_event_type_get_flags(), GST_EVENT_IS_UPSTREAM, GST_EVENT_IS_DOWNSTREAM, and GST_EVENT_IS_SERIALIZED. Note that in practice that an application or plugin doesn't need to bother itself with this information; the core handles all necessary locks and checks.

This function takes owership of the provided event so you should gst_event_ref() it if you want to reuse the event after this call.

pad :

a GstPad to send the event to.

event :

the GstEvent to send to the pad. [transfer full]

Returns :

TRUE if the event was handled.

gst_pad_event_default ()

gboolean            gst_pad_event_default               (GstPad *pad,
                                                         GstObject *parent,
                                                         GstEvent *event);

Invokes the default event handler for the given pad.

The EOS event will pause the task associated with pad before it is forwarded to all internally linked pads,

The the event is sent to all pads internally linked to pad. This function takes ownership of event.

pad :

a GstPad to call the default event handler on.

parent :

the parent of pad or NULL. [allow-none]

event :

the GstEvent to handle. [transfer full]

Returns :

TRUE if the event was sent successfully.

gst_pad_query ()

gboolean            gst_pad_query                       (GstPad *pad,
                                                         GstQuery *query);

Dispatches a query to a pad. The query should have been allocated by the caller via one of the type-specific allocation functions. The element that the pad belongs to is responsible for filling the query with an appropriate response, which should then be parsed with a type-specific query parsing function.

Again, the caller is responsible for both the allocation and deallocation of the query structure.

Please also note that some queries might need a running pipeline to work.

pad :

a GstPad to invoke the default query on.

query :

the GstQuery to perform. [transfer none]

Returns :

TRUE if the query could be performed.

gst_pad_peer_query ()

gboolean            gst_pad_peer_query                  (GstPad *pad,
                                                         GstQuery *query);

Performs gst_pad_query() on the peer of pad.

The caller is responsible for both the allocation and deallocation of the query structure.

pad :

a GstPad to invoke the peer query on.

query :

the GstQuery to perform. [transfer none]

Returns :

TRUE if the query could be performed. This function returns FALSE if pad has no peer.

gst_pad_query_default ()

gboolean            gst_pad_query_default               (GstPad *pad,
                                                         GstObject *parent,
                                                         GstQuery *query);

Invokes the default query handler for the given pad. The query is sent to all pads internally linked to pad. Note that if there are many possible sink pads that are internally linked to pad, only one will be sent the query. Multi-sinkpad elements should implement custom query handlers.

pad :

a GstPad to call the default query handler on.

parent :

the parent of pad or NULL. [allow-none]

query :

the GstQuery to handle. [transfer none]

Returns :

TRUE if the query was performed successfully.

gst_pad_query_position ()

gboolean            gst_pad_query_position              (GstPad *pad,
                                                         GstFormat format,
                                                         gint64 *cur);

Queries a pad for the stream position.

pad :

a GstPad to invoke the position query on.

format :

the GstFormat requested

cur :

A location in which to store the current position, or NULL. [out][allow-none]

Returns :

TRUE if the query could be performed.

gst_pad_query_duration ()

gboolean            gst_pad_query_duration              (GstPad *pad,
                                                         GstFormat format,
                                                         gint64 *duration);

Queries a pad for the total stream duration.

pad :

a GstPad to invoke the duration query on.

format :

the GstFormat requested

duration :

a location in which to store the total duration, or NULL. [out][allow-none]

Returns :

TRUE if the query could be performed.

gst_pad_query_convert ()

gboolean            gst_pad_query_convert               (GstPad *pad,
                                                         GstFormat src_format,
                                                         gint64 src_val,
                                                         GstFormat dest_format,
                                                         gint64 *dest_val);

Queries a pad to convert src_val in src_format to dest_format.

pad :

a GstPad to invoke the convert query on.

src_format :

a GstFormat to convert from.

src_val :

a value to convert.

dest_format :

the GstFormat to convert to.

dest_val :

a pointer to the result. [out]

Returns :

TRUE if the query could be performed.

gst_pad_query_accept_caps ()

gboolean            gst_pad_query_accept_caps           (GstPad *pad,
                                                         GstCaps *caps);

Check if the given pad accepts the caps.

pad :

a GstPad to check

caps :

a GstCaps to check on the pad

Returns :

TRUE if the pad can accept the caps.

gst_pad_query_caps ()

GstCaps *           gst_pad_query_caps                  (GstPad *pad,
                                                         GstCaps *filter);

Gets the capabilities this pad can produce or consume. Note that this method doesn't necessarily return the caps set by sending a gst_event_new_caps() - use gst_pad_get_current_caps() for that instead. gst_pad_query_caps returns all possible caps a pad can operate with, using the pad's CAPS query function, If the query fails, this function will return filter, if not NULL, otherwise ANY.

When called on sinkpads filter contains the caps that upstream could produce in the order preferred by upstream. When called on srcpads filter contains the caps accepted by downstream in the preffered order. filter might be NULL but if it is not NULL the returned caps will be a subset of filter.

Note that this function does not return writable GstCaps, use gst_caps_make_writable() before modifying the caps.

pad :

a GstPad to get the capabilities of.

filter :

suggested GstCaps, or NULL. [allow-none]

Returns :

the caps of the pad with incremented ref-count. [transfer full]

gst_pad_peer_query_position ()

gboolean            gst_pad_peer_query_position         (GstPad *pad,
                                                         GstFormat format,
                                                         gint64 *cur);

Queries the peer of a given sink pad for the stream position.

pad :

a GstPad on whose peer to invoke the position query on. Must be a sink pad.

format :

the GstFormat requested

cur :

a location in which to store the current position, or NULL. [out][allow-none]

Returns :

TRUE if the query could be performed.

gst_pad_peer_query_duration ()

gboolean            gst_pad_peer_query_duration         (GstPad *pad,
                                                         GstFormat format,
                                                         gint64 *duration);

Queries the peer pad of a given sink pad for the total stream duration.

pad :

a GstPad on whose peer pad to invoke the duration query on. Must be a sink pad.

format :

the GstFormat requested

duration :

a location in which to store the total duration, or NULL. [out][allow-none]

Returns :

TRUE if the query could be performed.

gst_pad_peer_query_convert ()

gboolean            gst_pad_peer_query_convert          (GstPad *pad,
                                                         GstFormat src_format,
                                                         gint64 src_val,
                                                         GstFormat dest_format,
                                                         gint64 *dest_val);

Queries the peer pad of a given sink pad to convert src_val in src_format to dest_format.

pad :

a GstPad, on whose peer pad to invoke the convert query on. Must be a sink pad.

src_format :

a GstFormat to convert from.

src_val :

a value to convert.

dest_format :

the GstFormat to convert to.

dest_val :

a pointer to the result. [out]

Returns :

TRUE if the query could be performed.

gst_pad_peer_query_accept_caps ()

gboolean            gst_pad_peer_query_accept_caps      (GstPad *pad,
                                                         GstCaps *caps);

Check if the peer of pad accepts caps. If pad has no peer, this function returns TRUE.

pad :

a GstPad to check the peer of

caps :

a GstCaps to check on the pad

Returns :

TRUE if the peer of pad can accept the caps or pad has no peer.

gst_pad_peer_query_caps ()

GstCaps *           gst_pad_peer_query_caps             (GstPad *pad,
                                                         GstCaps *filter);

Gets the capabilities of the peer connected to this pad. Similar to gst_pad_query_caps().

When called on srcpads filter contains the caps that upstream could produce in the order preferred by upstream. When called on sinkpads filter contains the caps accepted by downstream in the preffered order. filter might be NULL but if it is not NULL the returned caps will be a subset of filter.

pad :

a GstPad to get the capabilities of.

filter :

a GstCaps filter, or NULL. [allow-none]

Returns :

the caps of the peer pad with incremented ref-count. When there is no peer pad, this function returns filter or, when filter is NULL, ANY caps.

gst_pad_set_query_function()

#define gst_pad_set_query_function(p,f)   gst_pad_set_query_function_full((p),(f),NULL,NULL)

Calls gst_pad_set_query_function_full() with NULL for the user_data and notify.

p :

a GstPad of either direction.

f :

the GstPadQueryFunction to set.

gst_pad_set_query_function_full ()

void                gst_pad_set_query_function_full     (GstPad *pad,
                                                         GstPadQueryFunction query,
                                                         gpointer user_data,
                                                         GDestroyNotify notify);

Set the given query function for the pad.

pad :

a GstPad of either direction.

query :

the GstPadQueryFunction to set.

user_data :

user_data passed to notify

notify :

notify called when query will not be used anymore.

GstPadQueryFunction ()

gboolean            (*GstPadQueryFunction)              (GstPad *pad,
                                                         GstObject *parent,
                                                         GstQuery *query);

The signature of the query function.

pad :

the GstPad to query.

parent :

the parent of pad. If the GST_PAD_FLAG_NEED_PARENT flag is set, parent is guaranteed to be not-NULL and remain valid during the execution of this function.

query :

the GstQuery object to execute

Returns :

TRUE if the query could be performed.

gst_pad_set_iterate_internal_links_function()

#define gst_pad_set_iterate_internal_links_function(p,f) gst_pad_set_iterate_internal_links_function_full((p),(f),NULL,NULL)

Calls gst_pad_set_iterate_internal_links_function_full() with NULL for the user_data and notify.

p :

a GstPad of either direction.

f :

the GstPadIterIntLinkFunction to set.

gst_pad_set_iterate_internal_links_function_full ()

void                gst_pad_set_iterate_internal_links_function_full
                                                        (GstPad *pad,
                                                         GstPadIterIntLinkFunction iterintlink,
                                                         gpointer user_data,
                                                         GDestroyNotify notify);

Sets the given internal link iterator function for the pad.

pad :

a GstPad of either direction.

iterintlink :

the GstPadIterIntLinkFunction to set.

user_data :

user_data passed to notify

notify :

notify called when iterintlink will not be used anymore.

GstPadIterIntLinkFunction ()

GstIterator *       (*GstPadIterIntLinkFunction)        (GstPad *pad,
                                                         GstObject *parent);

The signature of the internal pad link iterator function.

pad :

The GstPad to query.

parent :

the parent of pad. If the GST_PAD_FLAG_NEED_PARENT flag is set, parent is guaranteed to be not-NULL and remain valid during the execution of this function.

Returns :

a new GstIterator that will iterate over all pads that are linked to the given pad on the inside of the parent element. the caller must call gst_iterator_free() after usage.

gst_pad_iterate_internal_links ()

GstIterator *       gst_pad_iterate_internal_links      (GstPad *pad);

Gets an iterator for the pads to which the given pad is linked to inside of the parent element.

Each GstPad element yielded by the iterator will have its refcount increased, so unref after use.

Free-function: gst_iterator_free

pad :

the GstPad to get the internal links of.

Returns :

a new GstIterator of GstPad or NULL when the pad does not have an iterator function configured. Use gst_iterator_free() after usage. [transfer full]

gst_pad_iterate_internal_links_default ()

GstIterator *       gst_pad_iterate_internal_links_default
                                                        (GstPad *pad,
                                                         GstObject *parent);

Iterate the list of pads to which the given pad is linked to inside of the parent element. This is the default handler, and thus returns an iterator of all of the pads inside the parent element with opposite direction.

The caller must free this iterator after use with gst_iterator_free().

pad :

the GstPad to get the internal links of.

parent :

the parent of pad or NULL. [allow-none]

Returns :

a GstIterator of GstPad, or NULL if pad has no parent. Unref each returned pad with gst_object_unref().

gst_pad_set_element_private ()

void                gst_pad_set_element_private         (GstPad *pad,
                                                         gpointer priv);

Set the given private data gpointer on the pad. This function can only be used by the element that owns the pad. No locking is performed in this function.

pad :

the GstPad to set the private data of.

priv :

The private data to attach to the pad.

gst_pad_get_element_private ()

gpointer            gst_pad_get_element_private         (GstPad *pad);

Gets the private data of a pad. No locking is performed in this function.

pad :

the GstPad to get the private data of.

Returns :

a gpointer to the private data. [transfer none]

gst_pad_create_stream_id ()

gchar *             gst_pad_create_stream_id            (GstPad *pad,
                                                         GstElement *parent,
                                                         const gchar *stream_id);

Creates a stream-id for the source GstPad pad by combining the upstream information with the optional stream_id of the stream of pad. pad must have a parent GstElement and which must have zero or one sinkpad. stream_id can only be NULL if the parent element of pad has only a single source pad.

This function generates an unique stream-id by getting the upstream stream-start event stream ID and appending stream_id to it. If the element has no sinkpad it will generate an upstream stream-id by doing an URI query on the element and in the worst case just uses a random number. Source elements that don't implement the URI handler interface should ideally generate a unique, deterministic stream-id manually instead.

Since stream IDs are sorted alphabetically, any numbers in the stream ID should be printed with a fixed number of characters, preceded by 0's, such as by using the format %03u instead of %u.

pad :

A source GstPad

parent :

Parent GstElement of pad

stream_id :

The stream-id. [allow-none]

Returns :

A stream-id for pad. g_free() after usage.

gst_pad_create_stream_id_printf ()

gchar *             gst_pad_create_stream_id_printf     (GstPad *pad,
                                                         GstElement *parent,
                                                         const gchar *stream_id,
                                                         ...);

Creates a stream-id for the source GstPad pad by combining the upstream information with the optional stream_id of the stream of pad. pad must have a parent GstElement and which must have zero or one sinkpad. stream_id can only be NULL if the parent element of pad has only a single source pad.

This function generates an unique stream-id by getting the upstream stream-start event stream ID and appending stream_id to it. If the element has no sinkpad it will generate an upstream stream-id by doing an URI query on the element and in the worst case just uses a random number. Source elements that don't implement the URI handler interface should ideally generate a unique, deterministic stream-id manually instead.

pad :

A source GstPad

parent :

Parent GstElement of pad

stream_id :

The stream-id. [allow-none]

... :

parameters for the stream_id format string

Returns :

A stream-id for pad. g_free() after usage.

gst_pad_create_stream_id_printf_valist ()

gchar *             gst_pad_create_stream_id_printf_valist
                                                        (GstPad *pad,
                                                         GstElement *parent,
                                                         const gchar *stream_id,
                                                         va_list var_args);

Creates a stream-id for the source GstPad pad by combining the upstream information with the optional stream_id of the stream of pad. pad must have a parent GstElement and which must have zero or one sinkpad. stream_id can only be NULL if the parent element of pad has only a single source pad.

This function generates an unique stream-id by getting the upstream stream-start event stream ID and appending stream_id to it. If the element has no sinkpad it will generate an upstream stream-id by doing an URI query on the element and in the worst case just uses a random number. Source elements that don't implement the URI handler interface should ideally generate a unique, deterministic stream-id manually instead.

pad :

A source GstPad

parent :

Parent GstElement of pad

stream_id :

The stream-id. [allow-none]

var_args :

parameters for the stream_id format string

Returns :

A stream-id for pad. g_free() after usage.

gst_pad_get_stream_id ()

gchar *             gst_pad_get_stream_id               (GstPad *pad);

Returns the current stream-id for the pad, or NULL if none has been set yet, i.e. the pad has not received a stream-start event yet.

This is a convenience wrapper around gst_pad_get_sticky_event() and gst_event_parse_stream_start().

The returned stream-id string should be treated as an opaque string, its contents should not be interpreted.

pad :

A source GstPad

Returns :

a newly-allocated copy of the stream-idfor pad, or NULL. g_free() the returned string when no longer needed.

Since 1.2


GstPadForwardFunction ()

gboolean            (*GstPadForwardFunction)            (GstPad *pad,
                                                         gpointer user_data);

A forward function is called for all internally linked pads, see gst_pad_forward().

pad :

the GstPad that is forwarded.

user_data :

the gpointer to optional user data.

Returns :

TRUE if the dispatching procedure has to be stopped.

gst_pad_forward ()

gboolean            gst_pad_forward                     (GstPad *pad,
                                                         GstPadForwardFunction forward,
                                                         gpointer user_data);

Calls forward for all internally linked pads of pad. This function deals with dynamically changing internal pads and will make sure that the forward function is only called once for each pad.

When forward returns TRUE, no further pads will be processed.

pad :

a GstPad

forward :

a GstPadForwardFunction. [scope call]

user_data :

user data passed to forward

Returns :

TRUE if one of the dispatcher functions returned TRUE.

gst_pad_chain ()

GstFlowReturn       gst_pad_chain                       (GstPad *pad,
                                                         GstBuffer *buffer);

Chain a buffer to pad.

The function returns GST_FLOW_FLUSHING if the pad was flushing.

If the buffer type is not acceptable for pad (as negotiated with a preceeding GST_EVENT_CAPS event), this function returns GST_FLOW_NOT_NEGOTIATED.

The function proceeds calling the chain function installed on pad (see gst_pad_set_chain_function()) and the return value of that function is returned to the caller. GST_FLOW_NOT_SUPPORTED is returned if pad has no chain function.

In all cases, success or failure, the caller loses its reference to buffer after calling this function.

pad :

a sink GstPad, returns GST_FLOW_ERROR if not.

buffer :

the GstBuffer to send, return GST_FLOW_ERROR if not. [transfer full]

Returns :

a GstFlowReturn from the pad. MT safe.

gst_pad_chain_list ()

GstFlowReturn       gst_pad_chain_list                  (GstPad *pad,
                                                         GstBufferList *list);

Chain a bufferlist to pad.

The function returns GST_FLOW_FLUSHING if the pad was flushing.

If pad was not negotiated properly with a CAPS event, this function returns GST_FLOW_NOT_NEGOTIATED.

The function proceeds calling the chainlist function installed on pad (see gst_pad_set_chain_list_function()) and the return value of that function is returned to the caller. GST_FLOW_NOT_SUPPORTED is returned if pad has no chainlist function.

In all cases, success or failure, the caller loses its reference to list after calling this function.

MT safe.

pad :

a sink GstPad, returns GST_FLOW_ERROR if not.

list :

the GstBufferList to send, return GST_FLOW_ERROR if not. [transfer full]

Returns :

a GstFlowReturn from the pad.

gst_pad_start_task ()

gboolean            gst_pad_start_task                  (GstPad *pad,
                                                         GstTaskFunction func,
                                                         gpointer user_data,
                                                         GDestroyNotify notify);

Starts a task that repeatedly calls func with user_data. This function is mostly used in pad activation functions to start the dataflow. The GST_PAD_STREAM_LOCK of pad will automatically be acquired before func is called.

pad :

the GstPad to start the task of

func :

the task function to call

user_data :

user data passed to the task function

notify :

called when user_data is no longer referenced

Returns :

a TRUE if the task could be started.

gst_pad_pause_task ()

gboolean            gst_pad_pause_task                  (GstPad *pad);

Pause the task of pad. This function will also wait until the function executed by the task is finished if this function is not called from the task function.

pad :

the GstPad to pause the task of

Returns :

a TRUE if the task could be paused or FALSE when the pad has no task.

gst_pad_stop_task ()

gboolean            gst_pad_stop_task                   (GstPad *pad);

Stop the task of pad. This function will also make sure that the function executed by the task will effectively stop if not called from the GstTaskFunction.

This function will deadlock if called from the GstTaskFunction of the task. Use gst_task_pause() instead.

Regardless of whether the pad has a task, the stream lock is acquired and released so as to ensure that streaming through this pad has finished.

pad :

the GstPad to stop the task of

Returns :

a TRUE if the task could be stopped or FALSE on error.

gst_pad_set_active ()

gboolean            gst_pad_set_active                  (GstPad *pad,
                                                         gboolean active);

Activates or deactivates the given pad. Normally called from within core state change functions.

If active, makes sure the pad is active. If it is already active, either in push or pull mode, just return. Otherwise dispatches to the pad's activate function to perform the actual activation.

If not active, calls gst_pad_activate_mode() with the pad's current mode and a FALSE argument.

pad :

the GstPad to activate or deactivate.

active :

whether or not the pad should be active.

Returns :

TRUE if the operation was successful. MT safe.

GST_PAD_GET_STREAM_LOCK()

#define GST_PAD_GET_STREAM_LOCK(pad)    (&(GST_PAD_CAST(pad)->stream_rec_lock))

Get the stream lock of pad. The stream lock is protecting the resources used in the data processing functions of pad.

pad :

a GstPad

GST_PAD_STREAM_LOCK()

#define GST_PAD_STREAM_LOCK(pad)        g_rec_mutex_lock(GST_PAD_GET_STREAM_LOCK(pad))

Lock the stream lock of pad.

pad :

a GstPad

GST_PAD_STREAM_TRYLOCK()

#define GST_PAD_STREAM_TRYLOCK(pad)     g_rec_mutex_trylock(GST_PAD_GET_STREAM_LOCK(pad))

Try to Lock the stream lock of the pad, return TRUE if the lock could be taken.

pad :

a GstPad

GST_PAD_STREAM_UNLOCK()

#define GST_PAD_STREAM_UNLOCK(pad)      g_rec_mutex_unlock(GST_PAD_GET_STREAM_LOCK(pad))

Unlock the stream lock of pad.

pad :

a GstPad

Property Details

The "caps" property

  "caps"                     GstCaps*              : Read

The capabilities of the pad.


The "direction" property

  "direction"                GstPadDirection       : Read / Write / Construct Only

The direction of the pad.

Default value: GST_PAD_UNKNOWN


The "template" property

  "template"                 GstPadTemplate*       : Read / Write

The GstPadTemplate of this pad.

Signal Details

The "linked" signal

void                user_function                      (GstPad  *pad,
                                                        GstPad  *peer,
                                                        gpointer user_data)      : Run Last

Signals that a pad has been linked to the peer pad.

pad :

the pad that emitted the signal

peer :

the peer pad that has been connected

user_data :

user data set when the signal handler was connected.

The "unlinked" signal

void                user_function                      (GstPad  *pad,
                                                        GstPad  *peer,
                                                        gpointer user_data)      : Run Last

Signals that a pad has been unlinked from the peer pad.

pad :

the pad that emitted the signal

peer :

the peer pad that has been disconnected

user_data :

user data set when the signal handler was connected.

See Also

GstPadTemplate, GstElement, GstEvent, GstQuery, GstBuffer