GstElement

GstElement — Abstract base class for all pipeline elements

Synopsis


#include <gst/gst.h>


                    GstElement;
                    GstElementClass;
enum                GstElementFlags;
enum                GstState;
enum                GstStateChange;
enum                GstStateChangeReturn;
#define             GST_STATE                           (elem)
#define             GST_STATE_GET_NEXT                  (cur,pending)
#define             GST_STATE_NEXT                      (elem)
#define             GST_STATE_PENDING                   (elem)
#define             GST_STATE_RETURN                    (elem)
#define             GST_STATE_TARGET                    (elem)
#define             GST_STATE_TRANSITION                (cur,next)
#define             GST_STATE_TRANSITION_CURRENT        (trans)
#define             GST_STATE_TRANSITION_NEXT           (trans)
#define             GST_STATE_GET_LOCK                  (elem)
#define             GST_STATE_GET_COND                  (elem)
#define             GST_ELEMENT_NAME                    (elem)
#define             GST_ELEMENT_PARENT                  (elem)
#define             GST_ELEMENT_BUS                     (elem)
#define             GST_ELEMENT_CLOCK                   (elem)
#define             GST_ELEMENT_PADS                    (elem)
#define             GST_ELEMENT_ERROR                   (el, domain, code, text, debug)
#define             GST_ELEMENT_WARNING                 (el, domain, code, text, debug)
#define             GST_ELEMENT_INFO                    (el, domain, code, text, debug)
#define             GST_ELEMENT_IS_LOCKED_STATE         (elem)

void                gst_element_class_add_pad_template  (GstElementClass *klass,
                                                         GstPadTemplate *templ);
GstPadTemplate*     gst_element_class_get_pad_template  (GstElementClass *element_class,
                                                         const gchar *name);
GList*              gst_element_class_get_pad_template_list
                                                        (GstElementClass *element_class);
void                gst_element_class_install_std_props (GstElementClass *klass,
                                                         const gchar *first_name,
                                                         ...);
void                gst_element_class_set_details       (GstElementClass *klass,
                                                         const GstElementDetails *details);
void                gst_element_class_set_details_simple
                                                        (GstElementClass *klass,
                                                         const gchar *longname,
                                                         const gchar *classification,
                                                         const gchar *description,
                                                         const gchar *author);

gboolean            gst_element_add_pad                 (GstElement *element,
                                                         GstPad *pad);
GstPad*             gst_element_get_pad                 (GstElement *element,
                                                         const gchar *name);
void                gst_element_create_all_pads         (GstElement *element);
GstPad*             gst_element_get_compatible_pad      (GstElement *element,
                                                         GstPad *pad,
                                                         const GstCaps *caps);
GstPadTemplate*     gst_element_get_compatible_pad_template
                                                        (GstElement *element,
                                                         GstPadTemplate *compattempl);
GstPad*             gst_element_get_request_pad         (GstElement *element,
                                                         const gchar *name);
GstPad*             gst_element_get_static_pad          (GstElement *element,
                                                         const gchar *name);
void                gst_element_no_more_pads            (GstElement *element);
void                gst_element_release_request_pad     (GstElement *element,
                                                         GstPad *pad);
gboolean            gst_element_remove_pad              (GstElement *element,
                                                         GstPad *pad);
GstIterator*        gst_element_iterate_pads            (GstElement *element);
GstIterator*        gst_element_iterate_sink_pads       (GstElement *element);
GstIterator*        gst_element_iterate_src_pads        (GstElement *element);

gboolean            gst_element_link                    (GstElement *src,
                                                         GstElement *dest);
void                gst_element_unlink                  (GstElement *src,
                                                         GstElement *dest);
gboolean            gst_element_link_many               (GstElement *element_1,
                                                         GstElement *element_2,
                                                         ...);
void                gst_element_unlink_many             (GstElement *element_1,
                                                         GstElement *element_2,
                                                         ...);
gboolean            gst_element_link_pads               (GstElement *src,
                                                         const gchar *srcpadname,
                                                         GstElement *dest,
                                                         const gchar *destpadname);
void                gst_element_unlink_pads             (GstElement *src,
                                                         const gchar *srcpadname,
                                                         GstElement *dest,
                                                         const gchar *destpadname);
gboolean            gst_element_link_pads_filtered      (GstElement *src,
                                                         const gchar *srcpadname,
                                                         GstElement *dest,
                                                         const gchar *destpadname,
                                                         GstCaps *filter);
gboolean            gst_element_link_filtered           (GstElement *src,
                                                         GstElement *dest,
                                                         GstCaps *filter);

void                gst_element_set_base_time           (GstElement *element,
                                                         GstClockTime time);
GstClockTime        gst_element_get_base_time           (GstElement *element);
void                gst_element_set_bus                 (GstElement *element,
                                                         GstBus *bus);
GstBus*             gst_element_get_bus                 (GstElement *element);
GstElementFactory*  gst_element_get_factory             (GstElement *element);
void                gst_element_set_index               (GstElement *element,
                                                         GstIndex *index);
GstIndex*           gst_element_get_index               (GstElement *element);
gboolean            gst_element_is_indexable            (GstElement *element);
#define             gst_element_set_name                (elem,name)
#define             gst_element_get_name                (elem)
#define             gst_element_set_parent              (elem,parent)
#define             gst_element_get_parent              (elem)

gboolean            gst_element_requires_clock          (GstElement *element);
gboolean            gst_element_set_clock               (GstElement *element,
                                                         GstClock *clock);
GstClock*           gst_element_get_clock               (GstElement *element);
gboolean            gst_element_provides_clock          (GstElement *element);
GstClock*           gst_element_provide_clock           (GstElement *element);

GstStateChangeReturn gst_element_set_state              (GstElement *element,
                                                         GstState state);
GstStateChangeReturn gst_element_get_state              (GstElement *element,
                                                         GstState *state,
                                                         GstState *pending,
                                                         GstClockTime timeout);
gboolean            gst_element_set_locked_state        (GstElement *element,
                                                         gboolean locked_state);
gboolean            gst_element_is_locked_state         (GstElement *element);
void                gst_element_abort_state             (GstElement *element);
GstStateChangeReturn gst_element_continue_state         (GstElement *element,
                                                         GstStateChangeReturn ret);
void                gst_element_lost_state              (GstElement *element);
const gchar*        gst_element_state_get_name          (GstState state);
const gchar*        gst_element_state_change_return_get_name
                                                        (GstStateChangeReturn state_ret);
gboolean            gst_element_sync_state_with_parent  (GstElement *element);
GstStateChangeReturn gst_element_change_state           (GstElement *element,
                                                         GstStateChange transition);

void                gst_element_found_tags              (GstElement *element,
                                                         GstTagList *list);
void                gst_element_found_tags_for_pad      (GstElement *element,
                                                         GstPad *pad,
                                                         GstTagList *list);

void                gst_element_message_full            (GstElement *element,
                                                         GstMessageType type,
                                                         GQuark domain,
                                                         gint code,
                                                         gchar *text,
                                                         gchar *debug,
                                                         const gchar *file,
                                                         const gchar *function,
                                                         gint line);
gboolean            gst_element_post_message            (GstElement *element,
                                                         GstMessage *message);

const GstQueryType* gst_element_get_query_types         (GstElement *element);
gboolean            gst_element_query                   (GstElement *element,
                                                         GstQuery *query);
gboolean            gst_element_query_convert           (GstElement *element,
                                                         GstFormat src_format,
                                                         gint64 src_val,
                                                         GstFormat *dest_format,
                                                         gint64 *dest_val);
gboolean            gst_element_query_position          (GstElement *element,
                                                         GstFormat *format,
                                                         gint64 *cur);
gboolean            gst_element_query_duration          (GstElement *element,
                                                         GstFormat *format,
                                                         gint64 *duration);

gboolean            gst_element_send_event              (GstElement *element,
                                                         GstEvent *event);
gboolean            gst_element_seek_simple             (GstElement *element,
                                                         GstFormat format,
                                                         GstSeekFlags seek_flags,
                                                         gint64 seek_pos);
gboolean            gst_element_seek                    (GstElement *element,
                                                         gdouble rate,
                                                         GstFormat format,
                                                         GstSeekFlags flags,
                                                         GstSeekType cur_type,
                                                         gint64 cur,
                                                         GstSeekType stop_type,
                                                         gint64 stop);


Object Hierarchy


  GObject
   +----GstObject
         +----GstElement
               +----GstBin

Known Derived Interfaces

GstElement is required by GstImplementsInterface and GstTagSetter.

Signals


  "no-more-pads"                                   : Run Last
  "pad-added"                                      : Run Last
  "pad-removed"                                    : Run Last

Description

GstElement is the abstract base class needed to construct an element that can be used in a GStreamer pipeline. Please refer to the plugin writers guide for more information on creating GstElement subclasses.

The name of a GstElement can be get with gst_element_get_name() and set with gst_element_set_name(). For speed, GST_ELEMENT_NAME() can be used in the core when using the appropriate locking. Do not use this in plug-ins or applications in order to retain ABI compatibility.

All elements have pads (of the type GstPad). These pads link to pads on other elements. GstBuffer flow between these linked pads. A GstElement has a GList of GstPad structures for all their input (or sink) and output (or source) pads. Core and plug-in writers can add and remove pads with gst_element_add_pad() and gst_element_remove_pad().

A pad of an element can be retrieved by name with gst_element_get_pad(). An iterator of all pads can be retrieved with gst_element_iterate_pads().

Elements can be linked through their pads. If the link is straightforward, use the gst_element_link() convenience function to link two elements, or gst_element_link_many() for more elements in a row. Use gst_element_link_filtered() to link two elements constrained by a specified set of GstCaps. For finer control, use gst_element_link_pads() and gst_element_link_pads_filtered() to specify the pads to link on each element by name.

Each element has a state (see GstState). You can get and set the state of an element with gst_element_get_state() and gst_element_set_state(). To get a string representation of a GstState, use gst_element_state_get_name().

You can get and set a GstClock on an element using gst_element_get_clock() and gst_element_set_clock(). Some elements can provide a clock for the pipeline if gst_element_provides_clock() returns TRUE. With the gst_element_provide_clock() method one can retrieve the clock provided by such an element. Not all elements require a clock to operate correctly. If gst_element_requires_clock() returns TRUE, a clock should be set on the element with gst_element_set_clock().

Note that clock slection and distribution is normally handled by the toplevel GstPipeline so the clock functions are only to be used in very specific situations.

Last reviewed on 2006-03-12 (0.10.5)

Details

GstElement

typedef struct {
  GStaticRecMutex      *state_lock;

  /* element state */
  GCond                *state_cond;
  guint32		state_cookie;
  GstState              current_state;
  GstState              next_state;
  GstState              pending_state;
  GstStateChangeReturn  last_return;

  GstBus	       *bus;

  /* allocated clock */
  GstClock	       *clock;
  GstClockTimeDiff	base_time; /* NULL/READY: 0 - PAUSED: current time - PLAYING: difference to clock */

  /* element pads, these lists can only be iterated while holding
   * the LOCK or checking the cookie after each LOCK. */
  guint16               numpads;
  GList                *pads;
  guint16               numsrcpads;
  GList                *srcpads;
  guint16               numsinkpads;
  GList                *sinkpads;
  guint32               pads_cookie;
} GstElement;

GStreamer element abstract base class.

GStaticRecMutex *state_lock; Used to serialize execution of gst_element_set_state()
GCond *state_cond; Used to signal completion of a state change
guint32 state_cookie; Used to detect concurrent execution of gst_element_set_state() and gst_element_get_state()
GstState current_state; the current state of an element
GstState next_state; the next state of an element, can be GST_STATE_VOID_PENDING if the element is in the correct state.
GstState pending_state; the final state the element should go to, can be GST_STATE_VOID_PENDING if the element is in the correct state
GstStateChangeReturn last_return; the last return value of an element state change
GstBus *bus; the bus of the element. This bus is provided to the element by the parent element or the application. A GstPipeline has a bus of its own.
GstClock *clock; the clock of the element. This clock is usually provided by to the element by the toplevel GstPipeline.
GstClockTimeDiff base_time; the time of the clock right before the element is set to PLAYING. Subtracting base_time from the current clock time in the PLAYING state will yield the stream time.
guint16 numpads; number of pads of the element, includes both source and sink pads.
GList *pads; list of pads
guint16 numsrcpads; number of source pads of the element.
GList *srcpads; list of source pads
guint16 numsinkpads; number of sink pads of the element.
GList *sinkpads; list of sink pads
guint32 pads_cookie; updated whenever the a pad is added or removed

GstElementClass

typedef struct {
  GstObjectClass         parent_class;

  /* the element details */
  GstElementDetails	 details;

  /* factory that the element was created from */
  GstElementFactory	*elementfactory;

  /* templates for our pads */
  GList                 *padtemplates;
  gint                   numpadtemplates;
  guint32                pad_templ_cookie;

  /* virtual methods for subclasses */

  /* request/release pads */
  GstPad*		(*request_new_pad)	(GstElement *element, GstPadTemplate *templ, const gchar* name);
  void			(*release_pad)		(GstElement *element, GstPad *pad);

  /* state changes */
  GstStateChangeReturn (*get_state)		(GstElement * element, GstState * state,
						 GstState * pending, GstClockTime timeout);
  GstStateChangeReturn (*set_state)		(GstElement *element, GstState state);
  GstStateChangeReturn (*change_state)		(GstElement *element, GstStateChange transition);

  /* bus */
  void			(*set_bus)		(GstElement * element, GstBus * bus);

  /* set/get clocks */
  GstClock*		(*provide_clock)	(GstElement *element);
  gboolean		(*set_clock)		(GstElement *element, GstClock *clock);

  /* index */
  GstIndex*		(*get_index)		(GstElement *element);
  void			(*set_index)		(GstElement *element, GstIndex *index);

  /* query functions */
  gboolean		(*send_event)		(GstElement *element, GstEvent *event);

  const GstQueryType*	(*get_query_types)	(GstElement *element);
  gboolean		(*query)		(GstElement *element, GstQuery *query);
} GstElementClass;

GStreamer element class. Override the vmethods to implement the element functionality.

GstObjectClass parent_class; the parent class structure
GstElementDetails details; GstElementDetails for elements of this class
GstElementFactory *elementfactory; the GstElementFactory that creates these elements
GList *padtemplates; a GList of GstPadTemplate
gint numpadtemplates; the number of padtemplates
guint32 pad_templ_cookie; changed whenever the padtemplates change
request_new_pad () called when a new pad is requested
release_pad () called when a request pad is to be released
get_state () get the state of the element
set_state () set a new state on the element
change_state () called by set_state to perform an incremental state change
set_bus () set a GstBus on the element
provide_clock () gets the GstClock provided by the element
set_clock () set the GstClock on the element
get_index () set a GstIndex on the element
set_index () get the GstIndex of an element
send_event () send a GstEvent to the element
get_query_types () get the supported GstQueryType of this element
query () perform a GstQuery on the element

enum GstElementFlags

typedef enum
{
  GST_ELEMENT_LOCKED_STATE      = (GST_OBJECT_FLAG_LAST << 0),
  GST_ELEMENT_IS_SINK           = (GST_OBJECT_FLAG_LAST << 1),
  GST_ELEMENT_UNPARENTING       = (GST_OBJECT_FLAG_LAST << 2),
  /* padding */
  GST_ELEMENT_FLAG_LAST         = (GST_OBJECT_FLAG_LAST << 16)
} GstElementFlags;

The standard flags that an element may have.

GST_ELEMENT_LOCKED_STATE ignore state changes from parent
GST_ELEMENT_IS_SINK the element is a sink
GST_ELEMENT_UNPARENTING Child is being removed from the parent bin. gst_bin_remove() on a child already being removed immediately returns FALSE
GST_ELEMENT_FLAG_LAST offset to define more flags

enum GstState

typedef enum {
  GST_STATE_VOID_PENDING        = 0,
  GST_STATE_NULL                = 1,
  GST_STATE_READY               = 2,
  GST_STATE_PAUSED              = 3,
  GST_STATE_PLAYING             = 4
} GstState;

The posible states an element can be in.

GST_STATE_VOID_PENDING no pending state.
GST_STATE_NULL the NULL state or initial state of an element
GST_STATE_READY the element is ready to go to PAUSED
GST_STATE_PAUSED the element is PAUSED
GST_STATE_PLAYING the element is PLAYING

enum GstStateChange

typedef enum /*< flags=0 >*/
{
  GST_STATE_CHANGE_NULL_TO_READY	= (GST_STATE_NULL<<3) | GST_STATE_READY,
  GST_STATE_CHANGE_READY_TO_PAUSED	= (GST_STATE_READY<<3) | GST_STATE_PAUSED,
  GST_STATE_CHANGE_PAUSED_TO_PLAYING	= (GST_STATE_PAUSED<<3) | GST_STATE_PLAYING,
  GST_STATE_CHANGE_PLAYING_TO_PAUSED	= (GST_STATE_PLAYING<<3) | GST_STATE_PAUSED,
  GST_STATE_CHANGE_PAUSED_TO_READY	= (GST_STATE_PAUSED<<3) | GST_STATE_READY,
  GST_STATE_CHANGE_READY_TO_NULL	= (GST_STATE_READY<<3) | GST_STATE_NULL
} GstStateChange;

The different (interesting) state changes that are passed to the state change functions of elements.

GST_STATE_CHANGE_NULL_TO_READY state change from NULL to READY
GST_STATE_CHANGE_READY_TO_PAUSED state change from READY to PAUSED
GST_STATE_CHANGE_PAUSED_TO_PLAYING state change from PAUSED to PLAYING
GST_STATE_CHANGE_PLAYING_TO_PAUSED state change from PLAYING to PAUSED
GST_STATE_CHANGE_PAUSED_TO_READY state change from PAUSED to READY
GST_STATE_CHANGE_READY_TO_NULL state change from READY to NULL

enum GstStateChangeReturn

typedef enum {
  GST_STATE_CHANGE_FAILURE             = 0,
  GST_STATE_CHANGE_SUCCESS             = 1,
  GST_STATE_CHANGE_ASYNC               = 2,
  GST_STATE_CHANGE_NO_PREROLL          = 3
} GstStateChangeReturn;

The possible return values from a state change function. Only GST_STATE_CHANGE_FAILURE is a real failure.

GST_STATE_CHANGE_FAILURE the state change failed
GST_STATE_CHANGE_SUCCESS the state change succeeded
GST_STATE_CHANGE_ASYNC the state change will happen asynchronously
GST_STATE_CHANGE_NO_PREROLL the state change succeeded but the element cannot produce data in PAUSED. This typically happens with live sources.

GST_STATE()

#define GST_STATE(elem)			(GST_ELEMENT_CAST(elem)->current_state)

This macro returns the current GstState of the element.

elem : a GstElement to return state for.

GST_STATE_GET_NEXT()

#define GST_STATE_GET_NEXT(cur,pending)		((cur) + __GST_SIGN ((gint)(pending) - (gint)(cur)))

Given a current state cur and a target state pending, calculate the next (intermediate) GstState.

cur : A starting GstState
pending : A target GstState

GST_STATE_NEXT()

#define GST_STATE_NEXT(elem)		(GST_ELEMENT_CAST(elem)->next_state)

This macro returns the next GstState of the element.

elem : a GstElement to return the next state for.

GST_STATE_PENDING()

#define GST_STATE_PENDING(elem)		(GST_ELEMENT_CAST(elem)->pending_state)

This macro returns the currently pending GstState of the element.

elem : a GstElement to return the pending state for.

GST_STATE_RETURN()

#define GST_STATE_RETURN(elem)		(GST_ELEMENT_CAST(elem)->last_return)

This macro returns the last GstStateChangeReturn value.

elem : a GstElement to return the last state result for.

GST_STATE_TARGET()

#define GST_STATE_TARGET(elem)		(GST_ELEMENT_CAST(elem)->abidata.ABI.target_state)

This macro returns the target GstState of the element.

elem : a GstElement to return the target state for.

Since 0.10.13


GST_STATE_TRANSITION()

#define GST_STATE_TRANSITION(cur,next)		((GstStateChange)(((cur)<<3)|(next)))

Given a current state cur and a next state next, calculate the associated GstStateChange transition.

cur : A current state
next : A next state

GST_STATE_TRANSITION_CURRENT()

#define GST_STATE_TRANSITION_CURRENT(trans)	((GstState)((trans)>>3))

Given a state transition trans, extract the current GstState.

trans : A GstStateChange

GST_STATE_TRANSITION_NEXT()

#define GST_STATE_TRANSITION_NEXT(trans)	((GstState)((trans)&0x7))

Given a state transition trans, extract the next GstState.

trans : A GstStateChange

GST_STATE_GET_LOCK()

#define GST_STATE_GET_LOCK(elem)               (GST_ELEMENT_CAST(elem)->state_lock)

Get a reference to the state lock of elem. This lock is used by the core. It is taken while getting or setting the state, during state changes, and while finalizing.

elem : a GstElement

GST_STATE_GET_COND()

#define GST_STATE_GET_COND(elem)               (GST_ELEMENT_CAST(elem)->state_cond)

Get the conditional used to signal the completion of a state change.

elem : a GstElement

GST_ELEMENT_NAME()

#define GST_ELEMENT_NAME(elem)			(GST_OBJECT_NAME(elem))

Gets the name of this element. Use only in core as this is not ABI-compatible. Others use gst_element_get_name()

elem : A GstElement to query

GST_ELEMENT_PARENT()

#define GST_ELEMENT_PARENT(elem)		(GST_ELEMENT_CAST(GST_OBJECT_PARENT(elem)))

Get the parent object of this element.

elem : A GstElement to query

GST_ELEMENT_BUS()

#define GST_ELEMENT_BUS(elem)			(GST_ELEMENT_CAST(elem)->bus)

Get the message bus of this element.

elem : A GstElement to query

GST_ELEMENT_CLOCK()

#define GST_ELEMENT_CLOCK(elem)			(GST_ELEMENT_CAST(elem)->clock)

Get the clock of this element

elem : A GstElement to query

GST_ELEMENT_PADS()

#define GST_ELEMENT_PADS(elem)			(GST_ELEMENT_CAST(elem)->pads)

Get the pads of this elements.

elem : A GstElement to query

GST_ELEMENT_ERROR()

#define             GST_ELEMENT_ERROR(el, domain, code, text, debug)

Utility function that elements can use in case they encountered a fatal data processing error. The pipeline will post an error message and the application will be requested to stop further media processing.

el : the element that generates the error
domain : like CORE, LIBRARY, RESOURCE or STREAM (see GstGError)
code : error code defined for that domain (see GstGError)
text : the message to display (format string and args enclosed in parentheses)
debug : debugging information for the message (format string and args enclosed in parentheses)

GST_ELEMENT_WARNING()

#define             GST_ELEMENT_WARNING(el, domain, code, text, debug)

Utility function that elements can use in case they encountered a non-fatal data processing problem. The pipeline will post a warning message and the application will be informed.

el : the element that generates the warning
domain : like CORE, LIBRARY, RESOURCE or STREAM (see gstreamer-GstGError)
code : error code defined for that domain (see gstreamer-GstGError)
text : the message to display (format string and args enclosed in parentheses)
debug : debugging information for the message (format string and args enclosed in parentheses)

GST_ELEMENT_INFO()

#define             GST_ELEMENT_INFO(el, domain, code, text, debug)

Utility function that elements can use in case they want to inform the application of something noteworthy that is not an error. The pipeline will post a warning message and the application will be informed.

el : the element that generates the information
domain : like CORE, LIBRARY, RESOURCE or STREAM (see gstreamer-GstGError)
code : error code defined for that domain (see gstreamer-GstGError)
text : the message to display (format string and args enclosed in parentheses)
debug : debugging information for the message (format string and args enclosed in parentheses)

Since 0.10.12


GST_ELEMENT_IS_LOCKED_STATE()

#define GST_ELEMENT_IS_LOCKED_STATE(elem)        (GST_OBJECT_FLAG_IS_SET(elem,GST_ELEMENT_LOCKED_STATE))

Check if the element is in the locked state and therefore will ignore state changes from its parent object.

elem : A GstElement to query

gst_element_class_add_pad_template ()

void                gst_element_class_add_pad_template  (GstElementClass *klass,
                                                         GstPadTemplate *templ);

Adds a padtemplate to an element class. This is mainly used in the _base_init functions of classes.

klass : the GstElementClass to add the pad template to.
templ : a GstPadTemplate to add to the element class.

gst_element_class_get_pad_template ()

GstPadTemplate*     gst_element_class_get_pad_template  (GstElementClass *element_class,
                                                         const gchar *name);

Retrieves a padtemplate from element_class with the given name.

Note

If you use this function in the GInstanceInitFunc of an object class that has subclasses, make sure to pass the g_class parameter of the GInstanceInitFunc here.

element_class : a GstElementClass to get the pad template of.
name : the name of the GstPadTemplate to get.
Returns : the GstPadTemplate with the given name, or NULL if none was found. No unreferencing is necessary.

gst_element_class_get_pad_template_list ()

GList*              gst_element_class_get_pad_template_list
                                                        (GstElementClass *element_class);

Retrieves a list of the pad templates associated with element_class. The list must not be modified by the calling code.

Note

If you use this function in the GInstanceInitFunc of an object class that has subclasses, make sure to pass the g_class parameter of the GInstanceInitFunc here.

element_class : a GstElementClass to get pad templates of.
Returns : the GList of padtemplates.

gst_element_class_install_std_props ()

void                gst_element_class_install_std_props (GstElementClass *klass,
                                                         const gchar *first_name,
                                                         ...);

Adds a list of standardized properties with types to the klass. the id is for the property switch in your get_prop method, and the flags determine readability / writeability.

klass : the GstElementClass to add the properties to.
first_name : the name of the first property. in a NULL terminated
... : the id and flags of the first property, followed by further 'name', 'id', 'flags' triplets and terminated by NULL.

gst_element_class_set_details ()

void                gst_element_class_set_details       (GstElementClass *klass,
                                                         const GstElementDetails *details);

Sets the detailed information for a GstElementClass.

Note

This function is for use in _base_init functions only.

The details are copied.

klass : class to set details for
details : details to set

gst_element_class_set_details_simple ()

void                gst_element_class_set_details_simple
                                                        (GstElementClass *klass,
                                                         const gchar *longname,
                                                         const gchar *classification,
                                                         const gchar *description,
                                                         const gchar *author);

Sets the detailed information for a GstElementClass. Simpler version of gst_element_class_set_details() that generates less linker overhead.

Note

This function is for use in _base_init functions only.

The detail parameter strings are copied into the GstElementDetails for the element class.

klass : class to set details for
longname : The long English name of the element. E.g. "File Sink"
classification : String describing the type of element, as an unordered list separated with slashes ('/'). See draft-klass.txt of the design docs for more details and common types. E.g: "Sink/File"
description : Sentence describing the purpose of the element. E.g: "Write stream to a file"
author : Name and contact details of the author(s). Use \n to separate multiple author details. E.g: "Joe Bloggs <joe.blogs at foo.com>"

Since 0.10.14


gst_element_add_pad ()

gboolean            gst_element_add_pad                 (GstElement *element,
                                                         GstPad *pad);

Adds a pad (link point) to element. pad's parent will be set to element; see gst_object_set_parent() for refcounting information.

Pads are not automatically activated so elements should perform the needed steps to activate the pad in case this pad is added in the PAUSED or PLAYING state. See gst_pad_set_active() for more information about activating pads.

The pad and the element should be unlocked when calling this function.

This function will emit the GstElement::pad-added signal on the element.

element : a GstElement to add the pad to.
pad : the GstPad to add to the element.
Returns : TRUE if the pad could be added. This function can fail when a pad with the same name already existed or the pad already had another parent. MT safe.

gst_element_get_pad ()

GstPad*             gst_element_get_pad                 (GstElement *element,
                                                         const gchar *name);

Retrieves a pad from element by name. Tries gst_element_get_static_pad() first, then gst_element_get_request_pad().

Note

Usage of this function is not recommended as it is unclear if the reference to the result pad should be released with gst_object_unref() in case of a static pad or gst_element_release_request_pad() in case of a request pad.

element : a GstElement.
name : the name of the pad to retrieve.
Returns : the GstPad if found, otherwise NULL. Unref or Release after usage, depending on the type of the pad.

gst_element_create_all_pads ()

void                gst_element_create_all_pads         (GstElement *element);

Creates a pad for each pad template that is always available. This function is only useful during object intialization of subclasses of GstElement.

element : a GstElement to create pads for

gst_element_get_compatible_pad ()

GstPad*             gst_element_get_compatible_pad      (GstElement *element,
                                                         GstPad *pad,
                                                         const GstCaps *caps);

Looks for an unlinked pad to which the given pad can link. It is not guaranteed that linking the pads will work, though it should work in most cases.

element : a GstElement in which the pad should be found.
pad : the GstPad to find a compatible one for.
caps : the GstCaps to use as a filter.
Returns : the GstPad to which a link can be made, or NULL if one cannot be found.

gst_element_get_compatible_pad_template ()

GstPadTemplate*     gst_element_get_compatible_pad_template
                                                        (GstElement *element,
                                                         GstPadTemplate *compattempl);

Retrieves a pad template from element that is compatible with compattempl. Pads from compatible templates can be linked together.

element : a GstElement to get a compatible pad template for.
compattempl : the GstPadTemplate to find a compatible template for.
Returns : a compatible GstPadTemplate, or NULL if none was found. No unreferencing is necessary.

gst_element_get_request_pad ()

GstPad*             gst_element_get_request_pad         (GstElement *element,
                                                         const gchar *name);

Retrieves a pad from the element by name. This version only retrieves request pads. The pad should be released with gst_element_release_request_pad().

element : a GstElement to find a request pad of.
name : the name of the request GstPad to retrieve.
Returns : requested GstPad if found, otherwise NULL. Release after usage.

gst_element_get_static_pad ()

GstPad*             gst_element_get_static_pad          (GstElement *element,
                                                         const gchar *name);

Retrieves a pad from element by name. This version only retrieves already-existing (i.e. 'static') pads.

element : a GstElement to find a static pad of.
name : the name of the static GstPad to retrieve.
Returns : the requested GstPad if found, otherwise NULL. unref after usage. MT safe.

gst_element_no_more_pads ()

void                gst_element_no_more_pads            (GstElement *element);

Use this function to signal that the element does not expect any more pads to show up in the current pipeline. This function should be called whenever pads have been added by the element itself. Elements with GST_PAD_SOMETIMES pad templates use this in combination with autopluggers to figure out that the element is done initializing its pads.

This function emits the GstElement::no-more-pads signal.

MT safe.

element : a GstElement

gst_element_release_request_pad ()

void                gst_element_release_request_pad     (GstElement *element,
                                                         GstPad *pad);

Makes the element free the previously requested pad as obtained with gst_element_get_request_pad().

MT safe.

element : a GstElement to release the request pad of.
pad : the GstPad to release.

gst_element_remove_pad ()

gboolean            gst_element_remove_pad              (GstElement *element,
                                                         GstPad *pad);

Removes pad from element. pad will be destroyed if it has not been referenced elsewhere using gst_object_unparent().

This function is used by plugin developers and should not be used by applications. Pads that were dynamically requested from elements with gst_element_get_request_pad() should be released with the gst_element_release_request_pad() function instead.

Pads are not automatically deactivated so elements should perform the needed steps to deactivate the pad in case this pad is removed in the PAUSED or PLAYING state. See gst_pad_set_active() for more information about deactivating pads.

The pad and the element should be unlocked when calling this function.

This function will emit the GstElement::pad-removed signal on the element.

element : a GstElement to remove pad from.
pad : the GstPad to remove from the element.
Returns : TRUE if the pad could be removed. Can return FALSE if the pad does not belong to the provided element. MT safe.

gst_element_iterate_pads ()

GstIterator*        gst_element_iterate_pads            (GstElement *element);

Retrieves an iterattor of element's pads. The iterator should be freed after usage.

element : a GstElement to iterate pads of.
Returns : the GstIterator of GstPad. Unref each pad after use. MT safe.

gst_element_iterate_sink_pads ()

GstIterator*        gst_element_iterate_sink_pads       (GstElement *element);

Retrieves an iterator of element's sink pads.

element : a GstElement.
Returns : the GstIterator of GstPad. Unref each pad after use. MT safe.

gst_element_iterate_src_pads ()

GstIterator*        gst_element_iterate_src_pads        (GstElement *element);

Retrieves an iterator of element's source pads.

element : a GstElement.
Returns : the GstIterator of GstPad. Unref each pad after use. MT safe.

gst_element_link ()

gboolean            gst_element_link                    (GstElement *src,
                                                         GstElement *dest);

Links src to dest. The link must be from source to destination; the other direction will not be tried. The function looks for existing pads that aren't linked yet. It will request new pads if necessary. Such pads need to be released manualy when unlinking. If multiple links are possible, only one is established.

Make sure you have added your elements to a bin or pipeline with gst_bin_add() before trying to link them.

src : a GstElement containing the source pad.
dest : the GstElement containing the destination pad.
Returns : TRUE if the elements could be linked, FALSE otherwise.

gst_element_unlink ()

void                gst_element_unlink                  (GstElement *src,
                                                         GstElement *dest);

Unlinks all source pads of the source element with all sink pads of the sink element to which they are linked.

If the link has been made using gst_element_link(), it could have created an requestpad, which has to be released using gst_element_release_request_pad().

src : the source GstElement to unlink.
dest : the sink GstElement to unlink.

gst_element_link_many ()

gboolean            gst_element_link_many               (GstElement *element_1,
                                                         GstElement *element_2,
                                                         ...);

Chain together a series of elements. Uses gst_element_link(). Make sure you have added your elements to a bin or pipeline with gst_bin_add() before trying to link them.

element_1 : the first GstElement in the link chain.
element_2 : the second GstElement in the link chain.
... : the NULL-terminated list of elements to link in order.
Returns : TRUE on success, FALSE otherwise.

gst_element_unlink_many ()

void                gst_element_unlink_many             (GstElement *element_1,
                                                         GstElement *element_2,
                                                         ...);

Unlinks a series of elements. Uses gst_element_unlink().

element_1 : the first GstElement in the link chain.
element_2 : the second GstElement in the link chain.
... : the NULL-terminated list of elements to unlink in order.

gst_element_link_pads ()

gboolean            gst_element_link_pads               (GstElement *src,
                                                         const gchar *srcpadname,
                                                         GstElement *dest,
                                                         const gchar *destpadname);

Links the two named pads of the source and destination elements. Side effect is that if one of the pads has no parent, it becomes a child of the parent of the other element. If they have different parents, the link fails.

src : a GstElement containing the source pad.
srcpadname : the name of the GstPad in source element or NULL for any pad.
dest : the GstElement containing the destination pad.
destpadname : the name of the GstPad in destination element, or NULL for any pad.
Returns : TRUE if the pads could be linked, FALSE otherwise.

gst_element_unlink_pads ()

void                gst_element_unlink_pads             (GstElement *src,
                                                         const gchar *srcpadname,
                                                         GstElement *dest,
                                                         const gchar *destpadname);

Unlinks the two named pads of the source and destination elements.

src : a GstElement containing the source pad.
srcpadname : the name of the GstPad in source element.
dest : a GstElement containing the destination pad.
destpadname : the name of the GstPad in destination element.

gst_element_link_pads_filtered ()

gboolean            gst_element_link_pads_filtered      (GstElement *src,
                                                         const gchar *srcpadname,
                                                         GstElement *dest,
                                                         const gchar *destpadname,
                                                         GstCaps *filter);

Links the two named pads of the source and destination elements. Side effect is that if one of the pads has no parent, it becomes a child of the parent of the other element. If they have different parents, the link fails. If caps is not NULL, makes sure that the caps of the link is a subset of caps.

src : a GstElement containing the source pad.
srcpadname : the name of the GstPad in source element or NULL for any pad.
dest : the GstElement containing the destination pad.
destpadname : the name of the GstPad in destination element or NULL for any pad.
filter : the GstCaps to filter the link, or NULL for no filter.
Returns : TRUE if the pads could be linked, FALSE otherwise.

gst_element_link_filtered ()

gboolean            gst_element_link_filtered           (GstElement *src,
                                                         GstElement *dest,
                                                         GstCaps *filter);

Links src to dest using the given caps as filtercaps. The link must be from source to destination; the other direction will not be tried. The function looks for existing pads that aren't linked yet. It will request new pads if necessary. If multiple links are possible, only one is established.

Make sure you have added your elements to a bin or pipeline with gst_bin_add() before trying to link them.

src : a GstElement containing the source pad.
dest : the GstElement containing the destination pad.
filter : the GstCaps to filter the link, or NULL for no filter.
Returns : TRUE if the pads could be linked, FALSE otherwise.

gst_element_set_base_time ()

void                gst_element_set_base_time           (GstElement *element,
                                                         GstClockTime time);

Set the base time of an element. See gst_element_get_base_time().

MT safe.

element : a GstElement.
time : the base time to set.

gst_element_get_base_time ()

GstClockTime        gst_element_get_base_time           (GstElement *element);

Returns the base time of the element. The base time is the absolute time of the clock when this element was last put to PLAYING. Subtracting the base time from the clock time gives the stream time of the element.

element : a GstElement.
Returns : the base time of the element. MT safe.

gst_element_set_bus ()

void                gst_element_set_bus                 (GstElement *element,
                                                         GstBus *bus);

Sets the bus of the element. Increases the refcount on the bus. For internal use only, unless you're testing elements.

MT safe.

element : a GstElement to set the bus of.
bus : the GstBus to set.

gst_element_get_bus ()

GstBus*             gst_element_get_bus                 (GstElement *element);

Returns the bus of the element. Note that only a GstPipeline will provide a bus for the application.

element : a GstElement to get the bus of.
Returns : the element's GstBus. unref after usage. MT safe.

gst_element_get_factory ()

GstElementFactory*  gst_element_get_factory             (GstElement *element);

Retrieves the factory that was used to create this element.

element : a GstElement to request the element factory of.
Returns : the GstElementFactory used for creating this element. no refcounting is needed.

gst_element_set_index ()

void                gst_element_set_index               (GstElement *element,
                                                         GstIndex *index);

Set index on the element. The refcount of the index will be increased, any previously set index is unreffed.

MT safe.

element : a GstElement.
index : a GstIndex.

gst_element_get_index ()

GstIndex*           gst_element_get_index               (GstElement *element);

Gets the index from the element.

element : a GstElement.
Returns : a GstIndex or NULL when no index was set on the element. unref after usage. MT safe.

gst_element_is_indexable ()

gboolean            gst_element_is_indexable            (GstElement *element);

Queries if the element can be indexed.

element : a GstElement.
Returns : TRUE if the element can be indexed. MT safe.

gst_element_set_name()

#define			gst_element_set_name(elem,name)	gst_object_set_name(GST_OBJECT_CAST(elem),name)

Sets the name of the element, getting rid of the old name if there was one.

elem : a GstElement to set the name of.
name : the new name

gst_element_get_name()

#define			gst_element_get_name(elem)	gst_object_get_name(GST_OBJECT_CAST(elem))

Gets the name of the element.

elem : a GstElement to set the name of.

gst_element_set_parent()

#define			gst_element_set_parent(elem,parent)	gst_object_set_parent(GST_OBJECT_CAST(elem),parent)

Sets the parent of an element.

elem : a GstElement to set the parent of.
parent : the new parent GstObject of the element.

gst_element_get_parent()

#define			gst_element_get_parent(elem)	gst_object_get_parent(GST_OBJECT_CAST(elem))

Gets the parent of an element.

elem : a GstElement to get the parent of.

gst_element_requires_clock ()

gboolean            gst_element_requires_clock          (GstElement *element);

Query if the element requires a clock.

element : a GstElement to query
Returns : TRUE if the element requires a clock MT safe.

gst_element_set_clock ()

gboolean            gst_element_set_clock               (GstElement *element,
                                                         GstClock *clock);

Sets the clock for the element. This function increases the refcount on the clock. Any previously set clock on the object is unreffed.

element : a GstElement to set the clock for.
clock : the GstClock to set for the element.
Returns : TRUE if the element accepted the clock. An element can refuse a clock when it, for example, is not able to slave its internal clock to the clock or when it requires a specific clock to operate. MT safe.

gst_element_get_clock ()

GstClock*           gst_element_get_clock               (GstElement *element);

Gets the currently configured clock of the element. This is the clock as was last set with gst_element_set_clock().

element : a GstElement to get the clock of.
Returns : the GstClock of the element. unref after usage. MT safe.

gst_element_provides_clock ()

gboolean            gst_element_provides_clock          (GstElement *element);

Query if the element provides a clock. A GstClock provided by an element can be used as the global GstClock for the pipeline. An element that can provide a clock is only required to do so in the PAUSED state, this means when it is fully negotiated and has allocated the resources to operate the clock.

element : a GstElement to query
Returns : TRUE if the element provides a clock MT safe.

gst_element_provide_clock ()

GstClock*           gst_element_provide_clock           (GstElement *element);

Get the clock provided by the given element.

Note

An element is only required to provide a clock in the PAUSED state. Some elements can provide a clock in other states.

element : a GstElement to query
Returns : the GstClock provided by the element or NULL if no clock could be provided. Unref after usage. MT safe.

gst_element_set_state ()

GstStateChangeReturn gst_element_set_state              (GstElement *element,
                                                         GstState state);

Sets the state of the element. This function will try to set the requested state by going through all the intermediary states and calling the class's state change function for each.

This function can return GST_STATE_CHANGE_ASYNC, in which case the element will perform the remainder of the state change asynchronously in another thread. An application can use gst_element_get_state() to wait for the completion of the state change or it can wait for a state change message on the bus.

element : a GstElement to change state of.
state : the element's new GstState.
Returns : Result of the state change using GstStateChangeReturn. MT safe.

gst_element_get_state ()

GstStateChangeReturn gst_element_get_state              (GstElement *element,
                                                         GstState *state,
                                                         GstState *pending,
                                                         GstClockTime timeout);

Gets the state of the element.

For elements that performed an ASYNC state change, as reported by gst_element_set_state(), this function will block up to the specified timeout value for the state change to complete. If the element completes the state change or goes into an error, this function returns immediately with a return value of GST_STATE_CHANGE_SUCCESS or GST_STATE_CHANGE_FAILURE respectively.

For elements that did not return GST_STATE_CHANGE_ASYNC, this function returns the current and pending state immediately.

This function returns GST_STATE_CHANGE_NO_PREROLL if the element successfully changed its state but is not able to provide data yet. This mostly happens for live sources that only produce data in the PLAYING state. While the state change return is equivalent to GST_STATE_CHANGE_SUCCESS, it is returned to the application to signal that some sink elements might not be able to complete their state change because an element is not producing data to complete the preroll. When setting the element to playing, the preroll will complete and playback will start.

element : a GstElement to get the state of.
state : a pointer to GstState to hold the state. Can be NULL.
pending : a pointer to GstState to hold the pending state. Can be NULL.
timeout : a GstClockTime to specify the timeout for an async state change or GST_CLOCK_TIME_NONE for infinite timeout.
Returns : GST_STATE_CHANGE_SUCCESS if the element has no more pending state and the last state change succeeded, GST_STATE_CHANGE_ASYNC if the element is still performing a state change or GST_STATE_CHANGE_FAILURE if the last state change failed. MT safe.

gst_element_set_locked_state ()

gboolean            gst_element_set_locked_state        (GstElement *element,
                                                         gboolean locked_state);

Locks the state of an element, so state changes of the parent don't affect this element anymore.

MT safe.

element : a GstElement
locked_state : TRUE to lock the element's state
Returns : TRUE if the state was changed, FALSE if bad parameters were given or the elements state-locking needed no change.

gst_element_is_locked_state ()

gboolean            gst_element_is_locked_state         (GstElement *element);

Checks if the state of an element is locked. If the state of an element is locked, state changes of the parent don't affect the element. This way you can leave currently unused elements inside bins. Just lock their state before changing the state from GST_STATE_NULL.

MT safe.

element : a GstElement.
Returns : TRUE, if the element's state is locked.

gst_element_abort_state ()

void                gst_element_abort_state             (GstElement *element);

Abort the state change of the element. This function is used by elements that do asynchronous state changes and find out something is wrong.

This function should be called with the STATE_LOCK held.

MT safe.

element : a GstElement to abort the state of.

gst_element_continue_state ()

GstStateChangeReturn gst_element_continue_state         (GstElement *element,
                                                         GstStateChangeReturn ret);

Commit the state change of the element and proceed to the next pending state if any. This function is used by elements that do asynchronous state changes. The core will normally call this method automatically when an element returned GST_STATE_CHANGE_SUCCESS from the state change function.

If after calling this method the element still has not reached the pending state, the next state change is performed.

This method is used internally and should normally not be called by plugins or applications.

element : a GstElement to continue the state change of.
ret : The previous state return value
Returns : The result of the commit state change. MT safe.

gst_element_lost_state ()

void                gst_element_lost_state              (GstElement *element);

Brings the element to the lost state. The current state of the element is copied to the pending state so that any call to gst_element_get_state() will return GST_STATE_CHANGE_ASYNC.

An ASYNC_START message is posted with an indication to distribute a new base_time to the element. If the element was PLAYING, it will go to PAUSED. The element will be restored to its PLAYING state by the parent pipeline when it prerolls again.

This is mostly used for elements that lost their preroll buffer in the GST_STATE_PAUSED or GST_STATE_PLAYING state after a flush, they will go to their pending state again when a new preroll buffer is queued. This function can only be called when the element is currently not in error or an async state change.

This function is used internally and should normally not be called from plugins or applications.

MT safe.

element : a GstElement the state is lost of

gst_element_state_get_name ()

const gchar*        gst_element_state_get_name          (GstState state);

Gets a string representing the given state.

state : a GstState to get the name of.
Returns : a string with the name of the state.

gst_element_state_change_return_get_name ()

const gchar*        gst_element_state_change_return_get_name
                                                        (GstStateChangeReturn state_ret);

Gets a string representing the given state change result.

state_ret : a GstStateChangeReturn to get the name of.
Returns : a string with the name of the state change result.

gst_element_sync_state_with_parent ()

gboolean            gst_element_sync_state_with_parent  (GstElement *element);

Tries to change the state of the element to the same as its parent. If this function returns FALSE, the state of element is undefined.

element : a GstElement.
Returns : TRUE, if the element's state could be synced to the parent's state. MT safe.

gst_element_change_state ()

GstStateChangeReturn gst_element_change_state           (GstElement *element,
                                                         GstStateChange transition);

Perform transition on element.

This function must be called with STATE_LOCK held and is mainly used internally.

element : a GstElement
transition : the requested transition
Returns : the GstStateChangeReturn of the state transition.

gst_element_found_tags ()

void                gst_element_found_tags              (GstElement *element,
                                                         GstTagList *list);

Posts a message to the bus that new tags were found, and pushes an event to all sourcepads. Takes ownership of the list.

This is a utility method for elements. Applications should use the GstTagSetter interface.

element : element for which we found the tags.
list : list of tags.

gst_element_found_tags_for_pad ()

void                gst_element_found_tags_for_pad      (GstElement *element,
                                                         GstPad *pad,
                                                         GstTagList *list);

Posts a message to the bus that new tags were found and pushes the tags as event. Takes ownership of the list.

This is a utility method for elements. Applications should use the GstTagSetter interface.

element : element for which to post taglist to bus.
pad : pad on which to push tag-event.
list : the taglist to post on the bus and create event from.

gst_element_message_full ()

void                gst_element_message_full            (GstElement *element,
                                                         GstMessageType type,
                                                         GQuark domain,
                                                         gint code,
                                                         gchar *text,
                                                         gchar *debug,
                                                         const gchar *file,
                                                         const gchar *function,
                                                         gint line);

Post an error, warning or info message on the bus from inside an element.

type must be of GST_MESSAGE_ERROR, GST_MESSAGE_WARNING or GST_MESSAGE_INFO.

MT safe.

element : a GstElement to send message from
type : the GstMessageType
domain : the GStreamer GError domain this message belongs to
code : the GError code belonging to the domain
text : an allocated text string to be used as a replacement for the default message connected to code, or NULL
debug : an allocated debug message to be used as a replacement for the default debugging information, or NULL
file : the source code file where the error was generated
function : the source code function where the error was generated
line : the source code line where the error was generated

gst_element_post_message ()

gboolean            gst_element_post_message            (GstElement *element,
                                                         GstMessage *message);

Post a message on the element's GstBus. This function takes ownership of the message; if you want to access the message after this call, you should add an additional reference before calling.

element : a GstElement posting the message
message : a GstMessage to post
Returns : TRUE if the message was successfully posted. The function returns FALSE if the element did not have a bus. MT safe.

gst_element_get_query_types ()

const GstQueryType* gst_element_get_query_types         (GstElement *element);

Get an array of query types from the element. If the element doesn't implement a query types function, the query will be forwarded to the peer of a random linked sink pad.

element : a GstElement to query
Returns : An array of GstQueryType elements that should not be freed or modified. MT safe.

gst_element_query ()

gboolean            gst_element_query                   (GstElement *element,
                                                         GstQuery *query);

Performs a query on the given element.

For elements that don't implement a query handler, this function forwards the query to a random srcpad or to the peer of a random linked sinkpad of this element.

element : a GstElement to perform the query on.
query : the GstQuery.
Returns : TRUE if the query could be performed. MT safe.

gst_element_query_convert ()

gboolean            gst_element_query_convert           (GstElement *element,
                                                         GstFormat src_format,
                                                         gint64 src_val,
                                                         GstFormat *dest_format,
                                                         gint64 *dest_val);

Queries an element to convert src_val in src_format to dest_format.

element : a GstElement to invoke the convert query on.
src_format : a GstFormat to convert from.
src_val : a value to convert.
dest_format : a pointer to the GstFormat to convert to.
dest_val : a pointer to the result.
Returns : TRUE if the query could be performed.

gst_element_query_position ()

gboolean            gst_element_query_position          (GstElement *element,
                                                         GstFormat *format,
                                                         gint64 *cur);

Queries an element for the stream position.

element : a GstElement to invoke the position query on.
format : a pointer to the GstFormat asked for. On return contains the GstFormat used.
cur : A location in which to store the current position, or NULL.
Returns : TRUE if the query could be performed.

gst_element_query_duration ()

gboolean            gst_element_query_duration          (GstElement *element,
                                                         GstFormat *format,
                                                         gint64 *duration);

Queries an element for the total stream duration.

element : a GstElement to invoke the duration query on.
format : a pointer to the GstFormat asked for. On return contains the GstFormat used.
duration : A location in which to store the total duration, or NULL.
Returns : TRUE if the query could be performed.

gst_element_send_event ()

gboolean            gst_element_send_event              (GstElement *element,
                                                         GstEvent *event);

Sends an event to an element. If the element doesn't implement an event handler, the event will be pushed on a random linked sink pad for upstream events or a random linked source pad for downstream events.

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.

element : a GstElement to send the event to.
event : the GstEvent to send to the element.
Returns : TRUE if the event was handled. MT safe.

gst_element_seek_simple ()

gboolean            gst_element_seek_simple             (GstElement *element,
                                                         GstFormat format,
                                                         GstSeekFlags seek_flags,
                                                         gint64 seek_pos);

Simple API to perform a seek on the given element, meaning it just seeks to the given position relative to the start of the stream. For more complex operations like segment seeks (e.g. for looping) or changing the playback rate or seeking relative to the last configured playback segment you should use gst_element_seek().

In a completely prerolled PAUSED or PLAYING pipeline, seeking is always guaranteed to return TRUE on a seekable media type or FALSE when the media type is certainly not seekable (such as a live stream).

Some elements allow for seeking in the READY state, in this case they will store the seek event and execute it when they are put to PAUSED. If the element supports seek in READY, it will always return TRUE when it receives the event in the READY state.

element : a GstElement to seek on
format : a GstFormat to execute the seek in, such as GST_FORMAT_TIME
seek_flags : seek options; playback applications will usually want to use GST_SEEK_FLAG_FLUSH | GST_SEEK_FLAG_KEY_UNIT here
seek_pos : position to seek to (relative to the start); if you are doing a seek in GST_FORMAT_TIME this value is in nanoseconds - multiply with GST_SECOND to convert seconds to nanoseconds or with GST_MSECOND to convert milliseconds to nanoseconds.
Returns : TRUE if the seek operation succeeded (the seek might not always be executed instantly though)

Since 0.10.7


gst_element_seek ()

gboolean            gst_element_seek                    (GstElement *element,
                                                         gdouble rate,
                                                         GstFormat format,
                                                         GstSeekFlags flags,
                                                         GstSeekType cur_type,
                                                         gint64 cur,
                                                         GstSeekType stop_type,
                                                         gint64 stop);

Sends a seek event to an element. See gst_event_new_seek() for the details of the parameters. The seek event is sent to the element using gst_element_send_event().

element : a GstElement to send the event to.
rate : The new playback rate
format : The format of the seek values
flags : The optional seek flags.
cur_type : The type and flags for the new current position
cur : The value of the new current position
stop_type : The type and flags for the new stop position
stop : The value of the new stop position
Returns : TRUE if the event was handled. MT safe.

Signal Details

The "no-more-pads" signal

void                user_function                      (GstElement *gstelement,
                                                        gpointer    user_data)       : Run Last

This signals that the element will not generate more dynamic pads.

gstelement : the object which received the signal
user_data : user data set when the signal handler was connected.

The "pad-added" signal

void                user_function                      (GstElement *gstelement,
                                                        GstPad     *new_pad,
                                                        gpointer    user_data)       : Run Last

a new GstPad has been added to the element.

gstelement : the object which received the signal
new_pad : the pad that has been added
user_data : user data set when the signal handler was connected.

The "pad-removed" signal

void                user_function                      (GstElement *gstelement,
                                                        GstPad     *old_pad,
                                                        gpointer    user_data)       : Run Last

a GstPad has been removed from the element

gstelement : the object which received the signal
old_pad : the pad that has been removed
user_data : user data set when the signal handler was connected.

See Also

GstElementFactory, GstPad