2 * Copyright (C) 1999,2000 Erik Walthinsen <omega@cse.ogi.edu>
3 * 2004 Wim Taymans <wim@fluendo.com>
5 * gstelement.c: The base element, all elements derive from this
7 * This library is free software; you can redistribute it and/or
8 * modify it under the terms of the GNU Library General Public
9 * License as published by the Free Software Foundation; either
10 * version 2 of the License, or (at your option) any later version.
12 * This library is distributed in the hope that it will be useful,
13 * but WITHOUT ANY WARRANTY; without even the implied warranty of
14 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
15 * Library General Public License for more details.
17 * You should have received a copy of the GNU Library General Public
18 * License along with this library; if not, write to the
19 * Free Software Foundation, Inc., 51 Franklin St, Fifth Floor,
20 * Boston, MA 02110-1301, USA.
25 * @short_description: Abstract base class for all pipeline elements
26 * @see_also: #GstElementFactory, #GstPad
28 * GstElement is the abstract base class needed to construct an element that
29 * can be used in a GStreamer pipeline. Please refer to the plugin writers
30 * guide for more information on creating #GstElement subclasses.
32 * The name of a #GstElement can be get with gst_element_get_name() and set with
33 * gst_element_set_name(). For speed, GST_ELEMENT_NAME() can be used in the
34 * core when using the appropriate locking. Do not use this in plug-ins or
35 * applications in order to retain ABI compatibility.
37 * Elements can have pads (of the type #GstPad). These pads link to pads on
38 * other elements. #GstBuffer flow between these linked pads.
39 * A #GstElement has a #GList of #GstPad structures for all their input (or sink)
40 * and output (or source) pads.
41 * Core and plug-in writers can add and remove pads with gst_element_add_pad()
42 * and gst_element_remove_pad().
44 * An existing pad of an element can be retrieved by name with
45 * gst_element_get_static_pad(). A new dynamic pad can be created using
46 * gst_element_request_pad() with a #GstPadTemplate.
47 * An iterator of all pads can be retrieved with gst_element_iterate_pads().
49 * Elements can be linked through their pads.
50 * If the link is straightforward, use the gst_element_link()
51 * convenience function to link two elements, or gst_element_link_many()
52 * for more elements in a row.
53 * Use gst_element_link_filtered() to link two elements constrained by
54 * a specified set of #GstCaps.
55 * For finer control, use gst_element_link_pads() and
56 * gst_element_link_pads_filtered() to specify the pads to link on
57 * each element by name.
59 * Each element has a state (see #GstState). You can get and set the state
60 * of an element with gst_element_get_state() and gst_element_set_state().
61 * Setting a state triggers a #GstStateChange. To get a string representation
62 * of a #GstState, use gst_element_state_get_name().
64 * You can get and set a #GstClock on an element using gst_element_get_clock()
65 * and gst_element_set_clock().
66 * Some elements can provide a clock for the pipeline if
67 * the #GST_ELEMENT_FLAG_PROVIDE_CLOCK flag is set. With the
68 * gst_element_provide_clock() method one can retrieve the clock provided by
70 * Not all elements require a clock to operate correctly. If the
71 * #GST_ELEMENT_FLAG_REQUIRE_CLOCK() flag is set, a clock should be set on the
72 * element with gst_element_set_clock().
74 * Note that clock selection and distribution is normally handled by the
75 * toplevel #GstPipeline so the clock functions are only to be used in very
76 * specific situations.
79 #include "gst_private.h"
82 #include <gobject/gvaluecollector.h>
84 #include "gstelement.h"
85 #include "gstelementmetadata.h"
86 #include "gstenumtypes.h"
93 #include "gsttracerutils.h"
95 #include "gst-i18n-lib.h"
96 #include "glib-compat-private.h"
98 #ifndef GST_DISABLE_GST_DEBUG
99 #include "printf/printf.h"
102 /* Element signals and args */
118 static void gst_element_class_init (GstElementClass * klass);
119 static void gst_element_init (GstElement * element);
120 static void gst_element_base_class_init (gpointer g_class);
121 static void gst_element_base_class_finalize (gpointer g_class);
123 static void gst_element_constructed (GObject * object);
124 static void gst_element_dispose (GObject * object);
125 static void gst_element_finalize (GObject * object);
127 static GstStateChangeReturn gst_element_change_state_func (GstElement * element,
128 GstStateChange transition);
129 static GstStateChangeReturn gst_element_get_state_func (GstElement * element,
130 GstState * state, GstState * pending, GstClockTime timeout);
131 static GstStateChangeReturn gst_element_set_state_func (GstElement * element,
133 static gboolean gst_element_set_clock_func (GstElement * element,
135 static void gst_element_set_bus_func (GstElement * element, GstBus * bus);
136 static gboolean gst_element_post_message_default (GstElement * element,
137 GstMessage * message);
138 static void gst_element_set_context_default (GstElement * element,
139 GstContext * context);
141 static gboolean gst_element_default_send_event (GstElement * element,
143 static gboolean gst_element_default_query (GstElement * element,
146 static GstPadTemplate
147 * gst_element_class_get_request_pad_template (GstElementClass *
148 element_class, const gchar * name);
150 static GstObjectClass *parent_class = NULL;
151 static guint gst_element_signals[LAST_SIGNAL] = { 0 };
153 /* this is used in gstelementfactory.c:gst_element_register() */
154 GQuark __gst_elementclass_factory = 0;
157 gst_element_get_type (void)
159 static volatile gsize gst_element_type = 0;
161 if (g_once_init_enter (&gst_element_type)) {
163 static const GTypeInfo element_info = {
164 sizeof (GstElementClass),
165 gst_element_base_class_init,
166 gst_element_base_class_finalize,
167 (GClassInitFunc) gst_element_class_init,
172 (GInstanceInitFunc) gst_element_init,
176 _type = g_type_register_static (GST_TYPE_OBJECT, "GstElement",
177 &element_info, G_TYPE_FLAG_ABSTRACT);
179 __gst_elementclass_factory =
180 g_quark_from_static_string ("GST_ELEMENTCLASS_FACTORY");
181 g_once_init_leave (&gst_element_type, _type);
183 return gst_element_type;
187 gst_element_class_init (GstElementClass * klass)
189 GObjectClass *gobject_class;
191 gobject_class = (GObjectClass *) klass;
193 parent_class = g_type_class_peek_parent (klass);
196 * GstElement::pad-added:
197 * @gstelement: the object which received the signal
198 * @new_pad: the pad that has been added
200 * a new #GstPad has been added to the element. Note that this signal will
201 * usually be emitted from the context of the streaming thread. Also keep in
202 * mind that if you add new elements to the pipeline in the signal handler
203 * you will need to set them to the desired target state with
204 * gst_element_set_state() or gst_element_sync_state_with_parent().
206 gst_element_signals[PAD_ADDED] =
207 g_signal_new ("pad-added", G_TYPE_FROM_CLASS (klass), G_SIGNAL_RUN_LAST,
208 G_STRUCT_OFFSET (GstElementClass, pad_added), NULL, NULL,
209 g_cclosure_marshal_generic, G_TYPE_NONE, 1, GST_TYPE_PAD);
211 * GstElement::pad-removed:
212 * @gstelement: the object which received the signal
213 * @old_pad: the pad that has been removed
215 * a #GstPad has been removed from the element
217 gst_element_signals[PAD_REMOVED] =
218 g_signal_new ("pad-removed", G_TYPE_FROM_CLASS (klass), G_SIGNAL_RUN_LAST,
219 G_STRUCT_OFFSET (GstElementClass, pad_removed), NULL, NULL,
220 g_cclosure_marshal_generic, G_TYPE_NONE, 1, GST_TYPE_PAD);
222 * GstElement::no-more-pads:
223 * @gstelement: the object which received the signal
225 * This signals that the element will not generate more dynamic pads.
226 * Note that this signal will usually be emitted from the context of
227 * the streaming thread.
229 gst_element_signals[NO_MORE_PADS] =
230 g_signal_new ("no-more-pads", G_TYPE_FROM_CLASS (klass),
231 G_SIGNAL_RUN_LAST, G_STRUCT_OFFSET (GstElementClass, no_more_pads), NULL,
232 NULL, g_cclosure_marshal_generic, G_TYPE_NONE, 0);
234 gobject_class->dispose = gst_element_dispose;
235 gobject_class->finalize = gst_element_finalize;
236 gobject_class->constructed = gst_element_constructed;
238 klass->change_state = GST_DEBUG_FUNCPTR (gst_element_change_state_func);
239 klass->set_state = GST_DEBUG_FUNCPTR (gst_element_set_state_func);
240 klass->get_state = GST_DEBUG_FUNCPTR (gst_element_get_state_func);
241 klass->set_clock = GST_DEBUG_FUNCPTR (gst_element_set_clock_func);
242 klass->set_bus = GST_DEBUG_FUNCPTR (gst_element_set_bus_func);
243 klass->query = GST_DEBUG_FUNCPTR (gst_element_default_query);
244 klass->send_event = GST_DEBUG_FUNCPTR (gst_element_default_send_event);
245 klass->numpadtemplates = 0;
246 klass->post_message = GST_DEBUG_FUNCPTR (gst_element_post_message_default);
247 klass->set_context = GST_DEBUG_FUNCPTR (gst_element_set_context_default);
249 klass->elementfactory = NULL;
253 gst_element_base_class_init (gpointer g_class)
255 GstElementClass *element_class = GST_ELEMENT_CLASS (g_class);
256 GList *node, *padtemplates;
258 /* Copy the element details here so elements can inherit the
259 * details from their base class and classes only need to set
260 * the details in class_init instead of base_init */
261 element_class->metadata =
262 element_class->metadata ? gst_structure_copy (element_class->metadata) :
263 gst_structure_new_empty ("metadata");
265 /* Copy the pad templates so elements inherit them
266 * from their base class but elements can add pad templates in class_init
267 * instead of base_init.
269 padtemplates = g_list_copy (element_class->padtemplates);
270 for (node = padtemplates; node != NULL; node = node->next) {
271 GstPadTemplate *tmpl = (GstPadTemplate *) node->data;
272 gst_object_ref (tmpl);
274 element_class->padtemplates = padtemplates;
276 /* set the factory, see gst_element_register() */
277 element_class->elementfactory =
278 g_type_get_qdata (G_TYPE_FROM_CLASS (element_class),
279 __gst_elementclass_factory);
280 GST_CAT_DEBUG (GST_CAT_ELEMENT_PADS, "type %s : factory %p",
281 G_OBJECT_CLASS_NAME (element_class), element_class->elementfactory);
285 gst_element_base_class_finalize (gpointer g_class)
287 GstElementClass *klass = GST_ELEMENT_CLASS (g_class);
289 g_list_foreach (klass->padtemplates, (GFunc) gst_object_unref, NULL);
290 g_list_free (klass->padtemplates);
292 gst_structure_free (klass->metadata);
296 gst_element_init (GstElement * element)
298 GST_STATE (element) = GST_STATE_NULL;
299 GST_STATE_TARGET (element) = GST_STATE_NULL;
300 GST_STATE_NEXT (element) = GST_STATE_VOID_PENDING;
301 GST_STATE_PENDING (element) = GST_STATE_VOID_PENDING;
302 GST_STATE_RETURN (element) = GST_STATE_CHANGE_SUCCESS;
304 g_rec_mutex_init (&element->state_lock);
305 g_cond_init (&element->state_cond);
309 gst_element_constructed (GObject * object)
311 GST_TRACER_ELEMENT_NEW (GST_ELEMENT_CAST (object));
312 G_OBJECT_CLASS (parent_class)->constructed (object);
316 * gst_element_release_request_pad:
317 * @element: a #GstElement to release the request pad of.
318 * @pad: the #GstPad to release.
320 * Makes the element free the previously requested pad as obtained
321 * with gst_element_request_pad().
323 * This does not unref the pad. If the pad was created by using
324 * gst_element_request_pad(), gst_element_release_request_pad() needs to be
325 * followed by gst_object_unref() to free the @pad.
330 gst_element_release_request_pad (GstElement * element, GstPad * pad)
332 GstElementClass *oclass;
334 g_return_if_fail (GST_IS_ELEMENT (element));
335 g_return_if_fail (GST_IS_PAD (pad));
336 g_return_if_fail (GST_PAD_PAD_TEMPLATE (pad) == NULL ||
337 GST_PAD_TEMPLATE_PRESENCE (GST_PAD_PAD_TEMPLATE (pad)) ==
340 oclass = GST_ELEMENT_GET_CLASS (element);
342 /* if the element implements a custom release function we call that, else we
343 * simply remove the pad from the element */
344 if (oclass->release_pad)
345 oclass->release_pad (element, pad);
347 gst_element_remove_pad (element, pad);
351 * gst_element_provide_clock:
352 * @element: a #GstElement to query
354 * Get the clock provided by the given element.
355 * <note>An element is only required to provide a clock in the PAUSED
356 * state. Some elements can provide a clock in other states.</note>
358 * Returns: (transfer full) (nullable): the GstClock provided by the
359 * element or %NULL if no clock could be provided. Unref after usage.
364 gst_element_provide_clock (GstElement * element)
366 GstClock *result = NULL;
367 GstElementClass *oclass;
369 g_return_val_if_fail (GST_IS_ELEMENT (element), NULL);
371 oclass = GST_ELEMENT_GET_CLASS (element);
373 if (oclass->provide_clock)
374 result = oclass->provide_clock (element);
380 gst_element_set_clock_func (GstElement * element, GstClock * clock)
384 GST_OBJECT_LOCK (element);
385 clock_p = &element->clock;
386 gst_object_replace ((GstObject **) clock_p, (GstObject *) clock);
387 GST_OBJECT_UNLOCK (element);
393 * gst_element_set_clock:
394 * @element: a #GstElement to set the clock for.
395 * @clock: the #GstClock to set for the element.
397 * Sets the clock for the element. This function increases the
398 * refcount on the clock. Any previously set clock on the object
401 * Returns: %TRUE if the element accepted the clock. An element can refuse a
402 * clock when it, for example, is not able to slave its internal clock to the
403 * @clock or when it requires a specific clock to operate.
408 gst_element_set_clock (GstElement * element, GstClock * clock)
410 GstElementClass *oclass;
411 gboolean res = FALSE;
413 g_return_val_if_fail (GST_IS_ELEMENT (element), FALSE);
414 g_return_val_if_fail (clock == NULL || GST_IS_CLOCK (clock), FALSE);
416 oclass = GST_ELEMENT_GET_CLASS (element);
418 GST_CAT_DEBUG_OBJECT (GST_CAT_CLOCK, element, "setting clock %p", clock);
420 if (oclass->set_clock)
421 res = oclass->set_clock (element, clock);
427 * gst_element_get_clock:
428 * @element: a #GstElement to get the clock of.
430 * Gets the currently configured clock of the element. This is the clock as was
431 * last set with gst_element_set_clock().
433 * Elements in a pipeline will only have their clock set when the
434 * pipeline is in the PLAYING state.
436 * Returns: (transfer full): the #GstClock of the element. unref after usage.
441 gst_element_get_clock (GstElement * element)
445 g_return_val_if_fail (GST_IS_ELEMENT (element), NULL);
447 GST_OBJECT_LOCK (element);
448 if ((result = element->clock))
449 gst_object_ref (result);
450 GST_OBJECT_UNLOCK (element);
456 * gst_element_set_base_time:
457 * @element: a #GstElement.
458 * @time: the base time to set.
460 * Set the base time of an element. See gst_element_get_base_time().
465 gst_element_set_base_time (GstElement * element, GstClockTime time)
469 g_return_if_fail (GST_IS_ELEMENT (element));
471 GST_OBJECT_LOCK (element);
472 old = element->base_time;
473 element->base_time = time;
474 GST_OBJECT_UNLOCK (element);
476 GST_CAT_DEBUG_OBJECT (GST_CAT_CLOCK, element,
477 "set base_time=%" GST_TIME_FORMAT ", old %" GST_TIME_FORMAT,
478 GST_TIME_ARGS (time), GST_TIME_ARGS (old));
482 * gst_element_get_base_time:
483 * @element: a #GstElement.
485 * Returns the base time of the element. The base time is the
486 * absolute time of the clock when this element was last put to
487 * PLAYING. Subtracting the base time from the clock time gives
488 * the running time of the element.
490 * Returns: the base time of the element.
495 gst_element_get_base_time (GstElement * element)
499 g_return_val_if_fail (GST_IS_ELEMENT (element), GST_CLOCK_TIME_NONE);
501 GST_OBJECT_LOCK (element);
502 result = element->base_time;
503 GST_OBJECT_UNLOCK (element);
509 * gst_element_set_start_time:
510 * @element: a #GstElement.
511 * @time: the base time to set.
513 * Set the start time of an element. The start time of the element is the
514 * running time of the element when it last went to the PAUSED state. In READY
515 * or after a flushing seek, it is set to 0.
517 * Toplevel elements like #GstPipeline will manage the start_time and
518 * base_time on its children. Setting the start_time to #GST_CLOCK_TIME_NONE
519 * on such a toplevel element will disable the distribution of the base_time to
520 * the children and can be useful if the application manages the base_time
521 * itself, for example if you want to synchronize capture from multiple
522 * pipelines, and you can also ensure that the pipelines have the same clock.
527 gst_element_set_start_time (GstElement * element, GstClockTime time)
531 g_return_if_fail (GST_IS_ELEMENT (element));
533 GST_OBJECT_LOCK (element);
534 old = GST_ELEMENT_START_TIME (element);
535 GST_ELEMENT_START_TIME (element) = time;
536 GST_OBJECT_UNLOCK (element);
538 GST_CAT_DEBUG_OBJECT (GST_CAT_CLOCK, element,
539 "set start_time=%" GST_TIME_FORMAT ", old %" GST_TIME_FORMAT,
540 GST_TIME_ARGS (time), GST_TIME_ARGS (old));
544 * gst_element_get_start_time:
545 * @element: a #GstElement.
547 * Returns the start time of the element. The start time is the
548 * running time of the clock when this element was last put to PAUSED.
550 * Usually the start_time is managed by a toplevel element such as
555 * Returns: the start time of the element.
558 gst_element_get_start_time (GstElement * element)
562 g_return_val_if_fail (GST_IS_ELEMENT (element), GST_CLOCK_TIME_NONE);
564 GST_OBJECT_LOCK (element);
565 result = GST_ELEMENT_START_TIME (element);
566 GST_OBJECT_UNLOCK (element);
573 * gst_element_set_index:
574 * @element: a #GstElement.
575 * @index: (transfer none): a #GstIndex.
577 * Set @index on the element. The refcount of the index
578 * will be increased, any previously set index is unreffed.
583 gst_element_set_index (GstElement * element, GstIndex * index)
585 GstElementClass *oclass;
587 g_return_if_fail (GST_IS_ELEMENT (element));
588 g_return_if_fail (index == NULL || GST_IS_INDEX (index));
590 oclass = GST_ELEMENT_GET_CLASS (element);
592 if (oclass->set_index)
593 oclass->set_index (element, index);
597 * gst_element_get_index:
598 * @element: a #GstElement.
600 * Gets the index from the element.
602 * Returns: (transfer full) (nullable): a #GstIndex or %NULL when no
603 * index was set on the element. unref after usage.
608 gst_element_get_index (GstElement * element)
610 GstElementClass *oclass;
611 GstIndex *result = NULL;
613 g_return_val_if_fail (GST_IS_ELEMENT (element), NULL);
615 oclass = GST_ELEMENT_GET_CLASS (element);
617 if (oclass->get_index)
618 result = oclass->get_index (element);
625 * gst_element_add_pad:
626 * @element: a #GstElement to add the pad to.
627 * @pad: (transfer full): the #GstPad to add to the element.
629 * Adds a pad (link point) to @element. @pad's parent will be set to @element;
630 * see gst_object_set_parent() for refcounting information.
632 * Pads are not automatically activated so elements should perform the needed
633 * steps to activate the pad in case this pad is added in the PAUSED or PLAYING
634 * state. See gst_pad_set_active() for more information about activating pads.
636 * The pad and the element should be unlocked when calling this function.
638 * This function will emit the #GstElement::pad-added signal on the element.
640 * Returns: %TRUE if the pad could be added. This function can fail when
641 * a pad with the same name already existed or the pad already had another
647 gst_element_add_pad (GstElement * element, GstPad * pad)
652 g_return_val_if_fail (GST_IS_ELEMENT (element), FALSE);
653 g_return_val_if_fail (GST_IS_PAD (pad), FALSE);
655 /* locking pad to look at the name */
656 GST_OBJECT_LOCK (pad);
657 pad_name = g_strdup (GST_PAD_NAME (pad));
658 GST_CAT_INFO_OBJECT (GST_CAT_ELEMENT_PADS, element, "adding pad '%s'",
659 GST_STR_NULL (pad_name));
660 active = GST_PAD_IS_ACTIVE (pad);
661 GST_OBJECT_FLAG_SET (pad, GST_PAD_FLAG_NEED_PARENT);
662 GST_OBJECT_UNLOCK (pad);
664 /* then check to see if there's already a pad by that name here */
665 GST_OBJECT_LOCK (element);
666 if (G_UNLIKELY (!gst_object_check_uniqueness (element->pads, pad_name)))
669 /* try to set the pad's parent */
670 if (G_UNLIKELY (!gst_object_set_parent (GST_OBJECT_CAST (pad),
671 GST_OBJECT_CAST (element))))
674 /* check for active pads */
675 if (!active && (GST_STATE (element) > GST_STATE_READY ||
676 GST_STATE_NEXT (element) == GST_STATE_PAUSED)) {
677 g_warning ("adding inactive pad '%s' to running element '%s', you need to "
678 "use gst_pad_set_active(pad,TRUE) before adding it.",
679 GST_STR_NULL (pad_name), GST_ELEMENT_NAME (element));
680 gst_pad_set_active (pad, TRUE);
685 /* add it to the list */
686 switch (gst_pad_get_direction (pad)) {
688 element->srcpads = g_list_append (element->srcpads, pad);
689 element->numsrcpads++;
692 element->sinkpads = g_list_append (element->sinkpads, pad);
693 element->numsinkpads++;
698 element->pads = g_list_append (element->pads, pad);
700 element->pads_cookie++;
701 GST_OBJECT_UNLOCK (element);
703 /* emit the PAD_ADDED signal */
704 g_signal_emit (element, gst_element_signals[PAD_ADDED], 0, pad);
705 GST_TRACER_ELEMENT_ADD_PAD (element, pad);
711 g_critical ("Padname %s is not unique in element %s, not adding",
712 pad_name, GST_ELEMENT_NAME (element));
713 GST_OBJECT_UNLOCK (element);
720 ("Pad %s already has parent when trying to add to element %s",
721 pad_name, GST_ELEMENT_NAME (element));
722 GST_OBJECT_UNLOCK (element);
728 GST_OBJECT_LOCK (pad);
730 ("Trying to add pad %s to element %s, but it has no direction",
731 GST_OBJECT_NAME (pad), GST_ELEMENT_NAME (element));
732 GST_OBJECT_UNLOCK (pad);
733 GST_OBJECT_UNLOCK (element);
739 * gst_element_remove_pad:
740 * @element: a #GstElement to remove pad from.
741 * @pad: (transfer full): the #GstPad to remove from the element.
743 * Removes @pad from @element. @pad will be destroyed if it has not been
744 * referenced elsewhere using gst_object_unparent().
746 * This function is used by plugin developers and should not be used
747 * by applications. Pads that were dynamically requested from elements
748 * with gst_element_request_pad() should be released with the
749 * gst_element_release_request_pad() function instead.
751 * Pads are not automatically deactivated so elements should perform the needed
752 * steps to deactivate the pad in case this pad is removed in the PAUSED or
753 * PLAYING state. See gst_pad_set_active() for more information about
756 * The pad and the element should be unlocked when calling this function.
758 * This function will emit the #GstElement::pad-removed signal on the element.
760 * Returns: %TRUE if the pad could be removed. Can return %FALSE if the
761 * pad does not belong to the provided element.
766 gst_element_remove_pad (GstElement * element, GstPad * pad)
770 g_return_val_if_fail (GST_IS_ELEMENT (element), FALSE);
771 g_return_val_if_fail (GST_IS_PAD (pad), FALSE);
773 /* locking pad to look at the name and parent */
774 GST_OBJECT_LOCK (pad);
775 GST_CAT_INFO_OBJECT (GST_CAT_ELEMENT_PADS, element, "removing pad '%s'",
776 GST_STR_NULL (GST_PAD_NAME (pad)));
778 if (G_UNLIKELY (GST_PAD_PARENT (pad) != element))
780 GST_OBJECT_UNLOCK (pad);
783 if ((peer = gst_pad_get_peer (pad))) {
784 /* window for MT unsafeness, someone else could unlink here
785 * and then we call unlink with wrong pads. The unlink
786 * function would catch this and safely return failed. */
787 if (GST_PAD_IS_SRC (pad))
788 gst_pad_unlink (pad, peer);
790 gst_pad_unlink (peer, pad);
792 gst_object_unref (peer);
795 GST_OBJECT_LOCK (element);
796 /* remove it from the list */
797 switch (gst_pad_get_direction (pad)) {
799 element->srcpads = g_list_remove (element->srcpads, pad);
800 element->numsrcpads--;
803 element->sinkpads = g_list_remove (element->sinkpads, pad);
804 element->numsinkpads--;
807 g_critical ("Removing pad without direction???");
810 element->pads = g_list_remove (element->pads, pad);
812 element->pads_cookie++;
813 GST_OBJECT_UNLOCK (element);
815 /* emit the PAD_REMOVED signal before unparenting and losing the last ref. */
816 g_signal_emit (element, gst_element_signals[PAD_REMOVED], 0, pad);
817 GST_TRACER_ELEMENT_REMOVE_PAD (element, pad);
818 gst_object_unparent (GST_OBJECT_CAST (pad));
825 /* locking order is element > pad */
826 GST_OBJECT_UNLOCK (pad);
828 GST_OBJECT_LOCK (element);
829 GST_OBJECT_LOCK (pad);
830 g_critical ("Padname %s:%s does not belong to element %s when removing",
831 GST_DEBUG_PAD_NAME (pad), GST_ELEMENT_NAME (element));
832 GST_OBJECT_UNLOCK (pad);
833 GST_OBJECT_UNLOCK (element);
839 * gst_element_no_more_pads:
840 * @element: a #GstElement
842 * Use this function to signal that the element does not expect any more pads
843 * to show up in the current pipeline. This function should be called whenever
844 * pads have been added by the element itself. Elements with #GST_PAD_SOMETIMES
845 * pad templates use this in combination with autopluggers to figure out that
846 * the element is done initializing its pads.
848 * This function emits the #GstElement::no-more-pads signal.
853 gst_element_no_more_pads (GstElement * element)
855 g_return_if_fail (GST_IS_ELEMENT (element));
857 g_signal_emit (element, gst_element_signals[NO_MORE_PADS], 0);
861 pad_compare_name (GstPad * pad1, const gchar * name)
865 GST_OBJECT_LOCK (pad1);
866 result = strcmp (GST_PAD_NAME (pad1), name);
867 GST_OBJECT_UNLOCK (pad1);
873 * gst_element_get_static_pad:
874 * @element: a #GstElement to find a static pad of.
875 * @name: the name of the static #GstPad to retrieve.
877 * Retrieves a pad from @element by name. This version only retrieves
878 * already-existing (i.e. 'static') pads.
880 * Returns: (transfer full) (nullable): the requested #GstPad if
881 * found, otherwise %NULL. unref after usage.
886 gst_element_get_static_pad (GstElement * element, const gchar * name)
889 GstPad *result = NULL;
891 g_return_val_if_fail (GST_IS_ELEMENT (element), NULL);
892 g_return_val_if_fail (name != NULL, NULL);
894 GST_OBJECT_LOCK (element);
896 g_list_find_custom (element->pads, name, (GCompareFunc) pad_compare_name);
898 result = GST_PAD_CAST (find->data);
899 gst_object_ref (result);
902 if (result == NULL) {
903 GST_CAT_INFO (GST_CAT_ELEMENT_PADS, "no such pad '%s' in element \"%s\"",
904 name, GST_ELEMENT_NAME (element));
906 GST_CAT_INFO (GST_CAT_ELEMENT_PADS, "found pad %s:%s",
907 GST_ELEMENT_NAME (element), name);
909 GST_OBJECT_UNLOCK (element);
915 _gst_element_request_pad (GstElement * element, GstPadTemplate * templ,
916 const gchar * name, const GstCaps * caps)
918 GstPad *newpad = NULL;
919 GstElementClass *oclass;
921 oclass = GST_ELEMENT_GET_CLASS (element);
923 #ifndef G_DISABLE_CHECKS
924 /* Some sanity checking here */
928 /* Is this the template name? */
929 if (strstr (name, "%") || !strchr (templ->name_template, '%')) {
930 g_return_val_if_fail (strcmp (name, templ->name_template) == 0, NULL);
932 const gchar *str, *data;
935 /* Otherwise check if it's a valid name for the name template */
936 str = strchr (templ->name_template, '%');
937 g_return_val_if_fail (str != NULL, NULL);
938 g_return_val_if_fail (strncmp (templ->name_template, name,
939 str - templ->name_template) == 0, NULL);
940 g_return_val_if_fail (strlen (name) > str - templ->name_template, NULL);
942 data = name + (str - templ->name_template);
944 /* Can either be %s or %d or %u, do sanity checking for %d */
945 if (*(str + 1) == 'd') {
949 tmp = g_ascii_strtoll (data, &endptr, 10);
950 g_return_val_if_fail (tmp >= G_MININT && tmp <= G_MAXINT
951 && *endptr == '\0', NULL);
952 } else if (*(str + 1) == 'u') {
956 tmp = g_ascii_strtoull (data, &endptr, 10);
957 g_return_val_if_fail (tmp <= G_MAXUINT && *endptr == '\0', NULL);
961 pad = gst_element_get_static_pad (element, name);
963 gst_object_unref (pad);
964 /* FIXME 2.0: Change this to g_return_val_if_fail() */
965 g_critical ("Element %s already has a pad named %s, the behaviour of "
966 " gst_element_get_request_pad() for existing pads is undefined!",
967 GST_ELEMENT_NAME (element), name);
972 if (oclass->request_new_pad)
973 newpad = (oclass->request_new_pad) (element, templ, name, caps);
976 gst_object_ref (newpad);
982 * gst_element_get_request_pad:
983 * @element: a #GstElement to find a request pad of.
984 * @name: the name of the request #GstPad to retrieve.
986 * Retrieves a pad from the element by name (e.g. "src_\%d"). This version only
987 * retrieves request pads. The pad should be released with
988 * gst_element_release_request_pad().
990 * This method is slower than manually getting the pad template and calling
991 * gst_element_request_pad() if the pads should have a specific name (e.g.
992 * @name is "src_1" instead of "src_\%u").
994 * Returns: (transfer full) (nullable): requested #GstPad if found,
995 * otherwise %NULL. Release after usage.
998 gst_element_get_request_pad (GstElement * element, const gchar * name)
1000 GstPadTemplate *templ = NULL;
1002 const gchar *req_name = NULL;
1003 gboolean templ_found = FALSE;
1006 gchar *str, *endptr = NULL;
1007 GstElementClass *class;
1009 g_return_val_if_fail (GST_IS_ELEMENT (element), NULL);
1010 g_return_val_if_fail (name != NULL, NULL);
1012 class = GST_ELEMENT_GET_CLASS (element);
1014 /* if the name contains a %, we assume it's the complete template name. Get
1015 * the template and try to get a pad */
1016 if (strstr (name, "%")) {
1017 templ = gst_element_class_get_request_pad_template (class, name);
1022 /* there is no % in the name, try to find a matching template */
1023 list = class->padtemplates;
1024 while (!templ_found && list) {
1025 templ = (GstPadTemplate *) list->data;
1026 if (templ->presence == GST_PAD_REQUEST) {
1027 GST_CAT_DEBUG (GST_CAT_PADS, "comparing %s to %s", name,
1028 templ->name_template);
1029 /* see if we find an exact match */
1030 if (strcmp (name, templ->name_template) == 0) {
1035 /* Because of sanity checks in gst_pad_template_new(), we know that %s
1036 and %d and %u, occurring at the end of the name_template, are the only
1038 else if ((str = strchr (templ->name_template, '%'))
1039 && strncmp (templ->name_template, name,
1040 str - templ->name_template) == 0
1041 && strlen (name) > str - templ->name_template) {
1042 data = name + (str - templ->name_template);
1043 if (*(str + 1) == 'd') {
1047 tmp = strtol (data, &endptr, 10);
1048 if (tmp != G_MINLONG && tmp != G_MAXLONG && endptr &&
1054 } else if (*(str + 1) == 'u') {
1058 tmp = strtoul (data, &endptr, 10);
1059 if (tmp != G_MAXULONG && endptr && *endptr == '\0') {
1079 pad = _gst_element_request_pad (element, templ, req_name, NULL);
1085 * gst_element_request_pad: (virtual request_new_pad)
1086 * @element: a #GstElement to find a request pad of.
1087 * @templ: a #GstPadTemplate of which we want a pad of.
1088 * @name: (transfer none) (allow-none): the name of the request #GstPad
1089 * to retrieve. Can be %NULL.
1090 * @caps: (transfer none) (allow-none): the caps of the pad we want to
1091 * request. Can be %NULL.
1093 * Retrieves a request pad from the element according to the provided template.
1094 * Pad templates can be looked up using
1095 * gst_element_factory_get_static_pad_templates().
1097 * The pad should be released with gst_element_release_request_pad().
1099 * Returns: (transfer full) (nullable): requested #GstPad if found,
1100 * otherwise %NULL. Release after usage.
1103 gst_element_request_pad (GstElement * element,
1104 GstPadTemplate * templ, const gchar * name, const GstCaps * caps)
1106 g_return_val_if_fail (GST_IS_ELEMENT (element), NULL);
1107 g_return_val_if_fail (templ != NULL, NULL);
1108 g_return_val_if_fail (templ->presence == GST_PAD_REQUEST, NULL);
1110 return _gst_element_request_pad (element, templ, name, caps);
1113 static GstIterator *
1114 gst_element_iterate_pad_list (GstElement * element, GList ** padlist)
1116 GstIterator *result;
1118 GST_OBJECT_LOCK (element);
1119 result = gst_iterator_new_list (GST_TYPE_PAD,
1120 GST_OBJECT_GET_LOCK (element),
1121 &element->pads_cookie, padlist, (GObject *) element, NULL);
1122 GST_OBJECT_UNLOCK (element);
1128 * gst_element_iterate_pads:
1129 * @element: a #GstElement to iterate pads of.
1131 * Retrieves an iterator of @element's pads. The iterator should
1132 * be freed after usage. Also more specialized iterators exists such as
1133 * gst_element_iterate_src_pads() or gst_element_iterate_sink_pads().
1135 * The order of pads returned by the iterator will be the order in which
1136 * the pads were added to the element.
1138 * Returns: (transfer full): the #GstIterator of #GstPad.
1143 gst_element_iterate_pads (GstElement * element)
1145 g_return_val_if_fail (GST_IS_ELEMENT (element), NULL);
1147 return gst_element_iterate_pad_list (element, &element->pads);
1151 * gst_element_iterate_src_pads:
1152 * @element: a #GstElement.
1154 * Retrieves an iterator of @element's source pads.
1156 * The order of pads returned by the iterator will be the order in which
1157 * the pads were added to the element.
1159 * Returns: (transfer full): the #GstIterator of #GstPad.
1164 gst_element_iterate_src_pads (GstElement * element)
1166 g_return_val_if_fail (GST_IS_ELEMENT (element), NULL);
1168 return gst_element_iterate_pad_list (element, &element->srcpads);
1172 * gst_element_iterate_sink_pads:
1173 * @element: a #GstElement.
1175 * Retrieves an iterator of @element's sink pads.
1177 * The order of pads returned by the iterator will be the order in which
1178 * the pads were added to the element.
1180 * Returns: (transfer full): the #GstIterator of #GstPad.
1185 gst_element_iterate_sink_pads (GstElement * element)
1187 g_return_val_if_fail (GST_IS_ELEMENT (element), NULL);
1189 return gst_element_iterate_pad_list (element, &element->sinkpads);
1193 * gst_element_class_add_pad_template:
1194 * @klass: the #GstElementClass to add the pad template to.
1195 * @templ: (transfer full): a #GstPadTemplate to add to the element class.
1197 * Adds a padtemplate to an element class. This is mainly used in the _class_init
1198 * functions of classes. If a pad template with the same name as an already
1199 * existing one is added the old one is replaced by the new one.
1203 gst_element_class_add_pad_template (GstElementClass * klass,
1204 GstPadTemplate * templ)
1206 GList *template_list = klass->padtemplates;
1208 g_return_if_fail (GST_IS_ELEMENT_CLASS (klass));
1209 g_return_if_fail (GST_IS_PAD_TEMPLATE (templ));
1211 /* If we already have a pad template with the same name replace the
1213 while (template_list) {
1214 GstPadTemplate *padtempl = (GstPadTemplate *) template_list->data;
1216 /* Found pad with the same name, replace and return */
1217 if (strcmp (templ->name_template, padtempl->name_template) == 0) {
1218 gst_object_unref (padtempl);
1219 template_list->data = templ;
1222 template_list = g_list_next (template_list);
1225 /* Take ownership of the floating ref */
1226 gst_object_ref_sink (templ);
1228 klass->padtemplates = g_list_append (klass->padtemplates, templ);
1229 klass->numpadtemplates++;
1233 * gst_element_class_add_metadata:
1234 * @klass: class to set metadata for
1235 * @key: the key to set
1236 * @value: the value to set
1238 * Set @key with @value as metadata in @klass.
1241 gst_element_class_add_metadata (GstElementClass * klass,
1242 const gchar * key, const gchar * value)
1244 g_return_if_fail (GST_IS_ELEMENT_CLASS (klass));
1245 g_return_if_fail (key != NULL);
1246 g_return_if_fail (value != NULL);
1248 gst_structure_set ((GstStructure *) klass->metadata,
1249 key, G_TYPE_STRING, value, NULL);
1253 * gst_element_class_add_static_metadata:
1254 * @klass: class to set metadata for
1255 * @key: the key to set
1256 * @value: the value to set
1258 * Set @key with @value as metadata in @klass.
1260 * Same as gst_element_class_add_metadata(), but @value must be a static string
1261 * or an inlined string, as it will not be copied. (GStreamer plugins will
1262 * be made resident once loaded, so this function can be used even from
1263 * dynamically loaded plugins.)
1266 gst_element_class_add_static_metadata (GstElementClass * klass,
1267 const gchar * key, const gchar * value)
1269 GValue val = G_VALUE_INIT;
1271 g_return_if_fail (GST_IS_ELEMENT_CLASS (klass));
1272 g_return_if_fail (key != NULL);
1273 g_return_if_fail (value != NULL);
1275 g_value_init (&val, G_TYPE_STRING);
1276 g_value_set_static_string (&val, value);
1277 gst_structure_take_value ((GstStructure *) klass->metadata, key, &val);
1281 * gst_element_class_set_metadata:
1282 * @klass: class to set metadata for
1283 * @longname: The long English name of the element. E.g. "File Sink"
1284 * @classification: String describing the type of element, as an unordered list
1285 * separated with slashes ('/'). See draft-klass.txt of the design docs
1286 * for more details and common types. E.g: "Sink/File"
1287 * @description: Sentence describing the purpose of the element.
1288 * E.g: "Write stream to a file"
1289 * @author: Name and contact details of the author(s). Use \n to separate
1290 * multiple author metadata. E.g: "Joe Bloggs <joe.blogs at foo.com>"
1292 * Sets the detailed information for a #GstElementClass.
1293 * <note>This function is for use in _class_init functions only.</note>
1296 gst_element_class_set_metadata (GstElementClass * klass,
1297 const gchar * longname, const gchar * classification,
1298 const gchar * description, const gchar * author)
1300 g_return_if_fail (GST_IS_ELEMENT_CLASS (klass));
1301 g_return_if_fail (longname != NULL && *longname != '\0');
1302 g_return_if_fail (classification != NULL && *classification != '\0');
1303 g_return_if_fail (description != NULL && *description != '\0');
1304 g_return_if_fail (author != NULL && *author != '\0');
1306 gst_structure_id_set ((GstStructure *) klass->metadata,
1307 GST_QUARK (ELEMENT_METADATA_LONGNAME), G_TYPE_STRING, longname,
1308 GST_QUARK (ELEMENT_METADATA_KLASS), G_TYPE_STRING, classification,
1309 GST_QUARK (ELEMENT_METADATA_DESCRIPTION), G_TYPE_STRING, description,
1310 GST_QUARK (ELEMENT_METADATA_AUTHOR), G_TYPE_STRING, author, NULL);
1314 * gst_element_class_set_static_metadata:
1315 * @klass: class to set metadata for
1316 * @longname: The long English name of the element. E.g. "File Sink"
1317 * @classification: String describing the type of element, as an unordered list
1318 * separated with slashes ('/'). See draft-klass.txt of the design docs
1319 * for more details and common types. E.g: "Sink/File"
1320 * @description: Sentence describing the purpose of the element.
1321 * E.g: "Write stream to a file"
1322 * @author: Name and contact details of the author(s). Use \n to separate
1323 * multiple author metadata. E.g: "Joe Bloggs <joe.blogs at foo.com>"
1325 * Sets the detailed information for a #GstElementClass.
1326 * <note>This function is for use in _class_init functions only.</note>
1328 * Same as gst_element_class_set_metadata(), but @longname, @classification,
1329 * @description, and @author must be static strings or inlined strings, as
1330 * they will not be copied. (GStreamer plugins will be made resident once
1331 * loaded, so this function can be used even from dynamically loaded plugins.)
1334 gst_element_class_set_static_metadata (GstElementClass * klass,
1335 const gchar * longname, const gchar * classification,
1336 const gchar * description, const gchar * author)
1338 GstStructure *s = (GstStructure *) klass->metadata;
1339 GValue val = G_VALUE_INIT;
1341 g_return_if_fail (GST_IS_ELEMENT_CLASS (klass));
1342 g_return_if_fail (longname != NULL && *longname != '\0');
1343 g_return_if_fail (classification != NULL && *classification != '\0');
1344 g_return_if_fail (description != NULL && *description != '\0');
1345 g_return_if_fail (author != NULL && *author != '\0');
1347 g_value_init (&val, G_TYPE_STRING);
1349 g_value_set_static_string (&val, longname);
1350 gst_structure_id_set_value (s, GST_QUARK (ELEMENT_METADATA_LONGNAME), &val);
1352 g_value_set_static_string (&val, classification);
1353 gst_structure_id_set_value (s, GST_QUARK (ELEMENT_METADATA_KLASS), &val);
1355 g_value_set_static_string (&val, description);
1356 gst_structure_id_set_value (s, GST_QUARK (ELEMENT_METADATA_DESCRIPTION),
1359 g_value_set_static_string (&val, author);
1360 gst_structure_id_take_value (s, GST_QUARK (ELEMENT_METADATA_AUTHOR), &val);
1364 * gst_element_class_get_metadata:
1365 * @klass: class to get metadata for
1366 * @key: the key to get
1368 * Get metadata with @key in @klass.
1370 * Returns: the metadata for @key.
1373 gst_element_class_get_metadata (GstElementClass * klass, const gchar * key)
1375 g_return_val_if_fail (GST_IS_ELEMENT_CLASS (klass), NULL);
1376 g_return_val_if_fail (key != NULL, NULL);
1378 return gst_structure_get_string ((GstStructure *) klass->metadata, key);
1382 * gst_element_class_get_pad_template_list:
1383 * @element_class: a #GstElementClass to get pad templates of.
1385 * Retrieves a list of the pad templates associated with @element_class. The
1386 * list must not be modified by the calling code.
1387 * <note>If you use this function in the #GInstanceInitFunc of an object class
1388 * that has subclasses, make sure to pass the g_class parameter of the
1389 * #GInstanceInitFunc here.</note>
1391 * Returns: (transfer none) (element-type Gst.PadTemplate): the #GList of
1395 gst_element_class_get_pad_template_list (GstElementClass * element_class)
1397 g_return_val_if_fail (GST_IS_ELEMENT_CLASS (element_class), NULL);
1399 return element_class->padtemplates;
1403 * gst_element_class_get_pad_template:
1404 * @element_class: a #GstElementClass to get the pad template of.
1405 * @name: the name of the #GstPadTemplate to get.
1407 * Retrieves a padtemplate from @element_class with the given name.
1408 * <note>If you use this function in the #GInstanceInitFunc of an object class
1409 * that has subclasses, make sure to pass the g_class parameter of the
1410 * #GInstanceInitFunc here.</note>
1412 * Returns: (transfer none) (nullable): the #GstPadTemplate with the
1413 * given name, or %NULL if none was found. No unreferencing is
1417 gst_element_class_get_pad_template (GstElementClass *
1418 element_class, const gchar * name)
1422 g_return_val_if_fail (GST_IS_ELEMENT_CLASS (element_class), NULL);
1423 g_return_val_if_fail (name != NULL, NULL);
1425 padlist = element_class->padtemplates;
1428 GstPadTemplate *padtempl = (GstPadTemplate *) padlist->data;
1430 if (strcmp (padtempl->name_template, name) == 0)
1433 padlist = g_list_next (padlist);
1439 static GstPadTemplate *
1440 gst_element_class_get_request_pad_template (GstElementClass *
1441 element_class, const gchar * name)
1443 GstPadTemplate *tmpl;
1445 tmpl = gst_element_class_get_pad_template (element_class, name);
1446 if (tmpl != NULL && tmpl->presence == GST_PAD_REQUEST)
1452 /* get a random pad on element of the given direction.
1453 * The pad is random in a sense that it is the first pad that is (optionaly) linked.
1456 gst_element_get_random_pad (GstElement * element,
1457 gboolean need_linked, GstPadDirection dir)
1459 GstPad *result = NULL;
1462 GST_CAT_DEBUG (GST_CAT_ELEMENT_PADS, "getting a random pad");
1466 GST_OBJECT_LOCK (element);
1467 pads = element->srcpads;
1470 GST_OBJECT_LOCK (element);
1471 pads = element->sinkpads;
1474 goto wrong_direction;
1476 for (; pads; pads = g_list_next (pads)) {
1477 GstPad *pad = GST_PAD_CAST (pads->data);
1479 GST_OBJECT_LOCK (pad);
1480 GST_CAT_DEBUG (GST_CAT_ELEMENT_PADS, "checking pad %s:%s",
1481 GST_DEBUG_PAD_NAME (pad));
1483 if (need_linked && !GST_PAD_IS_LINKED (pad)) {
1484 /* if we require a linked pad, and it is not linked, continue the
1486 GST_CAT_DEBUG (GST_CAT_ELEMENT_PADS, "pad %s:%s is not linked",
1487 GST_DEBUG_PAD_NAME (pad));
1488 GST_OBJECT_UNLOCK (pad);
1491 /* found a pad, stop search */
1492 GST_CAT_DEBUG (GST_CAT_ELEMENT_PADS, "found pad %s:%s",
1493 GST_DEBUG_PAD_NAME (pad));
1494 GST_OBJECT_UNLOCK (pad);
1500 gst_object_ref (result);
1502 GST_OBJECT_UNLOCK (element);
1506 /* ERROR handling */
1509 g_warning ("unknown pad direction %d", dir);
1515 gst_element_default_send_event (GstElement * element, GstEvent * event)
1517 gboolean result = FALSE;
1520 pad = GST_EVENT_IS_DOWNSTREAM (event) ?
1521 gst_element_get_random_pad (element, TRUE, GST_PAD_SINK) :
1522 gst_element_get_random_pad (element, TRUE, GST_PAD_SRC);
1525 GST_CAT_DEBUG (GST_CAT_ELEMENT_PADS,
1526 "pushing %s event to random %s pad %s:%s",
1527 GST_EVENT_TYPE_NAME (event),
1528 (GST_PAD_DIRECTION (pad) == GST_PAD_SRC ? "src" : "sink"),
1529 GST_DEBUG_PAD_NAME (pad));
1531 result = gst_pad_send_event (pad, event);
1532 gst_object_unref (pad);
1534 GST_CAT_INFO (GST_CAT_ELEMENT_PADS, "can't send %s event on element %s",
1535 GST_EVENT_TYPE_NAME (event), GST_ELEMENT_NAME (element));
1536 gst_event_unref (event);
1542 * gst_element_send_event:
1543 * @element: a #GstElement to send the event to.
1544 * @event: (transfer full): the #GstEvent to send to the element.
1546 * Sends an event to an element. If the element doesn't implement an
1547 * event handler, the event will be pushed on a random linked sink pad for
1548 * downstream events or a random linked source pad for upstream events.
1550 * This function takes ownership of the provided event so you should
1551 * gst_event_ref() it if you want to reuse the event after this call.
1555 * Returns: %TRUE if the event was handled. Events that trigger a preroll (such
1556 * as flushing seeks and steps) will emit %GST_MESSAGE_ASYNC_DONE.
1559 gst_element_send_event (GstElement * element, GstEvent * event)
1561 GstElementClass *oclass;
1562 gboolean result = FALSE;
1564 g_return_val_if_fail (GST_IS_ELEMENT (element), FALSE);
1565 g_return_val_if_fail (event != NULL, FALSE);
1567 oclass = GST_ELEMENT_GET_CLASS (element);
1569 GST_STATE_LOCK (element);
1570 if (oclass->send_event) {
1571 GST_CAT_DEBUG (GST_CAT_ELEMENT_PADS, "send %s event on element %s",
1572 GST_EVENT_TYPE_NAME (event), GST_ELEMENT_NAME (element));
1573 result = oclass->send_event (element, event);
1575 gst_event_unref (event);
1577 GST_STATE_UNLOCK (element);
1584 * @element: a #GstElement to send the event to.
1585 * @rate: The new playback rate
1586 * @format: The format of the seek values
1587 * @flags: The optional seek flags.
1588 * @start_type: The type and flags for the new start position
1589 * @start: The value of the new start position
1590 * @stop_type: The type and flags for the new stop position
1591 * @stop: The value of the new stop position
1593 * Sends a seek event to an element. See gst_event_new_seek() for the details of
1594 * the parameters. The seek event is sent to the element using
1595 * gst_element_send_event().
1599 * Returns: %TRUE if the event was handled. Flushing seeks will trigger a
1600 * preroll, which will emit %GST_MESSAGE_ASYNC_DONE.
1603 gst_element_seek (GstElement * element, gdouble rate, GstFormat format,
1604 GstSeekFlags flags, GstSeekType start_type, gint64 start,
1605 GstSeekType stop_type, gint64 stop)
1610 g_return_val_if_fail (GST_IS_ELEMENT (element), FALSE);
1613 gst_event_new_seek (rate, format, flags, start_type, start, stop_type,
1615 result = gst_element_send_event (element, event);
1621 gst_element_default_query (GstElement * element, GstQuery * query)
1623 gboolean result = FALSE;
1626 pad = gst_element_get_random_pad (element, FALSE, GST_PAD_SRC);
1628 result = gst_pad_query (pad, query);
1630 gst_object_unref (pad);
1632 pad = gst_element_get_random_pad (element, TRUE, GST_PAD_SINK);
1634 GstPad *peer = gst_pad_get_peer (pad);
1637 result = gst_pad_query (peer, query);
1639 gst_object_unref (peer);
1641 gst_object_unref (pad);
1648 * gst_element_query:
1649 * @element: a #GstElement to perform the query on.
1650 * @query: (transfer none): the #GstQuery.
1652 * Performs a query on the given element.
1654 * For elements that don't implement a query handler, this function
1655 * forwards the query to a random srcpad or to the peer of a
1656 * random linked sinkpad of this element.
1658 * Please note that some queries might need a running pipeline to work.
1660 * Returns: %TRUE if the query could be performed.
1665 gst_element_query (GstElement * element, GstQuery * query)
1667 GstElementClass *klass;
1668 gboolean res = FALSE;
1670 g_return_val_if_fail (GST_IS_ELEMENT (element), FALSE);
1671 g_return_val_if_fail (query != NULL, FALSE);
1673 GST_TRACER_ELEMENT_QUERY_PRE (element, query);
1675 klass = GST_ELEMENT_GET_CLASS (element);
1677 GST_CAT_DEBUG (GST_CAT_ELEMENT_PADS, "send query on element %s",
1678 GST_ELEMENT_NAME (element));
1679 res = klass->query (element, query);
1682 GST_TRACER_ELEMENT_QUERY_POST (element, query, res);
1687 gst_element_post_message_default (GstElement * element, GstMessage * message)
1690 gboolean result = FALSE;
1692 g_return_val_if_fail (GST_IS_ELEMENT (element), FALSE);
1693 g_return_val_if_fail (message != NULL, FALSE);
1695 GST_OBJECT_LOCK (element);
1698 if (G_UNLIKELY (bus == NULL))
1701 gst_object_ref (bus);
1702 GST_OBJECT_UNLOCK (element);
1704 /* we release the element lock when posting the message so that any
1705 * (synchronous) message handlers can operate on the element */
1706 result = gst_bus_post (bus, message);
1707 gst_object_unref (bus);
1714 GST_CAT_DEBUG_OBJECT (GST_CAT_MESSAGE, element,
1715 "not posting message %p: no bus", message);
1716 GST_OBJECT_UNLOCK (element);
1717 gst_message_unref (message);
1723 * gst_element_post_message:
1724 * @element: a #GstElement posting the message
1725 * @message: (transfer full): a #GstMessage to post
1727 * Post a message on the element's #GstBus. This function takes ownership of the
1728 * message; if you want to access the message after this call, you should add an
1729 * additional reference before calling.
1731 * Returns: %TRUE if the message was successfully posted. The function returns
1732 * %FALSE if the element did not have a bus.
1737 gst_element_post_message (GstElement * element, GstMessage * message)
1739 GstElementClass *klass;
1740 gboolean res = FALSE;
1742 g_return_val_if_fail (GST_IS_ELEMENT (element), FALSE);
1743 g_return_val_if_fail (message != NULL, FALSE);
1745 GST_TRACER_ELEMENT_POST_MESSAGE_PRE (element, message);
1747 klass = GST_ELEMENT_GET_CLASS (element);
1748 if (klass->post_message)
1749 res = klass->post_message (element, message);
1751 gst_message_unref (message);
1753 GST_TRACER_ELEMENT_POST_MESSAGE_POST (element, res);
1758 * _gst_element_error_printf:
1759 * @format: (allow-none): the printf-like format to use, or %NULL
1761 * This function is only used internally by the gst_element_error() macro.
1763 * Returns: (transfer full) (nullable): a newly allocated string, or
1764 * %NULL if the format was %NULL or ""
1769 _gst_element_error_printf (const gchar * format, ...)
1780 va_start (args, format);
1782 len = __gst_vasprintf (&buffer, format, args);
1793 * gst_element_message_full:
1794 * @element: a #GstElement to send message from
1795 * @type: the #GstMessageType
1796 * @domain: the GStreamer GError domain this message belongs to
1797 * @code: the GError code belonging to the domain
1798 * @text: (allow-none) (transfer full): an allocated text string to be used
1799 * as a replacement for the default message connected to code,
1801 * @debug: (allow-none) (transfer full): an allocated debug message to be
1802 * used as a replacement for the default debugging information,
1804 * @file: the source code file where the error was generated
1805 * @function: the source code function where the error was generated
1806 * @line: the source code line where the error was generated
1808 * Post an error, warning or info message on the bus from inside an element.
1810 * @type must be of #GST_MESSAGE_ERROR, #GST_MESSAGE_WARNING or
1811 * #GST_MESSAGE_INFO.
1815 void gst_element_message_full
1816 (GstElement * element, GstMessageType type,
1817 GQuark domain, gint code, gchar * text,
1818 gchar * debug, const gchar * file, const gchar * function, gint line)
1820 GError *gerror = NULL;
1824 gboolean has_debug = TRUE;
1825 GstMessage *message = NULL;
1828 GST_CAT_DEBUG_OBJECT (GST_CAT_MESSAGE, element, "start");
1829 g_return_if_fail (GST_IS_ELEMENT (element));
1830 g_return_if_fail ((type == GST_MESSAGE_ERROR) ||
1831 (type == GST_MESSAGE_WARNING) || (type == GST_MESSAGE_INFO));
1833 /* check if we send the given text or the default error text */
1834 if ((text == NULL) || (text[0] == 0)) {
1835 /* text could have come from g_strdup_printf (""); */
1837 sent_text = gst_error_get_message (domain, code);
1841 /* construct a sent_debug with extra information from source */
1842 if ((debug == NULL) || (debug[0] == 0)) {
1843 /* debug could have come from g_strdup_printf (""); */
1847 name = gst_object_get_path_string (GST_OBJECT_CAST (element));
1849 sent_debug = g_strdup_printf ("%s(%d): %s (): %s:\n%s",
1850 file, line, function, name, debug);
1852 sent_debug = g_strdup_printf ("%s(%d): %s (): %s",
1853 file, line, function, name);
1857 /* create gerror and post message */
1858 GST_CAT_INFO_OBJECT (GST_CAT_ERROR_SYSTEM, element, "posting message: %s",
1860 gerror = g_error_new_literal (domain, code, sent_text);
1863 case GST_MESSAGE_ERROR:
1865 gst_message_new_error (GST_OBJECT_CAST (element), gerror, sent_debug);
1867 case GST_MESSAGE_WARNING:
1868 message = gst_message_new_warning (GST_OBJECT_CAST (element), gerror,
1871 case GST_MESSAGE_INFO:
1872 message = gst_message_new_info (GST_OBJECT_CAST (element), gerror,
1876 g_assert_not_reached ();
1879 gst_element_post_message (element, message);
1881 GST_CAT_INFO_OBJECT (GST_CAT_ERROR_SYSTEM, element, "posted %s message: %s",
1882 (type == GST_MESSAGE_ERROR ? "error" : "warning"), sent_text);
1885 g_error_free (gerror);
1886 g_free (sent_debug);
1891 * gst_element_is_locked_state:
1892 * @element: a #GstElement.
1894 * Checks if the state of an element is locked.
1895 * If the state of an element is locked, state changes of the parent don't
1896 * affect the element.
1897 * This way you can leave currently unused elements inside bins. Just lock their
1898 * state before changing the state from #GST_STATE_NULL.
1902 * Returns: %TRUE, if the element's state is locked.
1905 gst_element_is_locked_state (GstElement * element)
1909 g_return_val_if_fail (GST_IS_ELEMENT (element), FALSE);
1911 GST_OBJECT_LOCK (element);
1912 result = GST_ELEMENT_IS_LOCKED_STATE (element);
1913 GST_OBJECT_UNLOCK (element);
1919 * gst_element_set_locked_state:
1920 * @element: a #GstElement
1921 * @locked_state: %TRUE to lock the element's state
1923 * Locks the state of an element, so state changes of the parent don't affect
1924 * this element anymore.
1928 * Returns: %TRUE if the state was changed, %FALSE if bad parameters were given
1929 * or the elements state-locking needed no change.
1932 gst_element_set_locked_state (GstElement * element, gboolean locked_state)
1936 g_return_val_if_fail (GST_IS_ELEMENT (element), FALSE);
1938 GST_OBJECT_LOCK (element);
1939 old = GST_ELEMENT_IS_LOCKED_STATE (element);
1941 if (G_UNLIKELY (old == locked_state))
1945 GST_CAT_DEBUG (GST_CAT_STATES, "locking state of element %s",
1946 GST_ELEMENT_NAME (element));
1947 GST_OBJECT_FLAG_SET (element, GST_ELEMENT_FLAG_LOCKED_STATE);
1949 GST_CAT_DEBUG (GST_CAT_STATES, "unlocking state of element %s",
1950 GST_ELEMENT_NAME (element));
1951 GST_OBJECT_FLAG_UNSET (element, GST_ELEMENT_FLAG_LOCKED_STATE);
1953 GST_OBJECT_UNLOCK (element);
1959 GST_CAT_DEBUG (GST_CAT_STATES,
1960 "elements %s was already in locked state %d",
1961 GST_ELEMENT_NAME (element), old);
1962 GST_OBJECT_UNLOCK (element);
1969 * gst_element_sync_state_with_parent:
1970 * @element: a #GstElement.
1972 * Tries to change the state of the element to the same as its parent.
1973 * If this function returns %FALSE, the state of element is undefined.
1975 * Returns: %TRUE, if the element's state could be synced to the parent's state.
1980 gst_element_sync_state_with_parent (GstElement * element)
1984 GstStateChangeReturn ret;
1986 g_return_val_if_fail (GST_IS_ELEMENT (element), FALSE);
1988 if ((parent = GST_ELEMENT_CAST (gst_element_get_parent (element)))) {
1989 GstState parent_current, parent_pending;
1991 GST_OBJECT_LOCK (parent);
1992 parent_current = GST_STATE (parent);
1993 parent_pending = GST_STATE_PENDING (parent);
1994 GST_OBJECT_UNLOCK (parent);
1996 /* set to pending if there is one, else we set it to the current state of
1998 if (parent_pending != GST_STATE_VOID_PENDING)
1999 target = parent_pending;
2001 target = parent_current;
2003 GST_CAT_DEBUG_OBJECT (GST_CAT_STATES, element,
2004 "syncing state (%s) to parent %s %s (%s, %s)",
2005 gst_element_state_get_name (GST_STATE (element)),
2006 GST_ELEMENT_NAME (parent), gst_element_state_get_name (target),
2007 gst_element_state_get_name (parent_current),
2008 gst_element_state_get_name (parent_pending));
2010 ret = gst_element_set_state (element, target);
2011 if (ret == GST_STATE_CHANGE_FAILURE)
2014 gst_object_unref (parent);
2018 GST_CAT_DEBUG_OBJECT (GST_CAT_STATES, element, "element has no parent");
2025 GST_CAT_DEBUG_OBJECT (GST_CAT_STATES, element,
2026 "syncing state failed (%s)",
2027 gst_element_state_change_return_get_name (ret));
2028 gst_object_unref (parent);
2034 static GstStateChangeReturn
2035 gst_element_get_state_func (GstElement * element,
2036 GstState * state, GstState * pending, GstClockTime timeout)
2038 GstStateChangeReturn ret = GST_STATE_CHANGE_FAILURE;
2039 GstState old_pending;
2041 GST_CAT_DEBUG_OBJECT (GST_CAT_STATES, element, "getting state, timeout %"
2042 GST_TIME_FORMAT, GST_TIME_ARGS (timeout));
2044 GST_OBJECT_LOCK (element);
2045 ret = GST_STATE_RETURN (element);
2046 GST_CAT_DEBUG_OBJECT (GST_CAT_STATES, element, "RETURN is %s",
2047 gst_element_state_change_return_get_name (ret));
2049 /* we got an error, report immediately */
2050 if (ret == GST_STATE_CHANGE_FAILURE)
2053 /* we got no_preroll, report immediately */
2054 if (ret == GST_STATE_CHANGE_NO_PREROLL)
2057 /* no need to wait async if we are not async */
2058 if (ret != GST_STATE_CHANGE_ASYNC)
2061 old_pending = GST_STATE_PENDING (element);
2062 if (old_pending != GST_STATE_VOID_PENDING) {
2066 /* get cookie to detect state changes during waiting */
2067 cookie = element->state_cookie;
2069 GST_CAT_INFO_OBJECT (GST_CAT_STATES, element,
2070 "waiting for element to commit state");
2072 /* we have a pending state change, wait for it to complete */
2073 if (timeout != GST_CLOCK_TIME_NONE) {
2075 /* make timeout absolute */
2076 end_time = g_get_monotonic_time () + (timeout / 1000);
2077 signaled = GST_STATE_WAIT_UNTIL (element, end_time);
2079 GST_STATE_WAIT (element);
2084 GST_CAT_INFO_OBJECT (GST_CAT_STATES, element, "timed out");
2085 /* timeout triggered */
2086 ret = GST_STATE_CHANGE_ASYNC;
2088 if (cookie != element->state_cookie)
2091 /* could be success or failure */
2092 if (old_pending == GST_STATE (element)) {
2093 GST_CAT_DEBUG_OBJECT (GST_CAT_STATES, element, "got success");
2094 ret = GST_STATE_CHANGE_SUCCESS;
2096 GST_CAT_DEBUG_OBJECT (GST_CAT_STATES, element, "got failure");
2097 ret = GST_STATE_CHANGE_FAILURE;
2100 /* if nothing is pending anymore we can return SUCCESS */
2101 if (GST_STATE_PENDING (element) == GST_STATE_VOID_PENDING) {
2102 GST_CAT_LOG_OBJECT (GST_CAT_STATES, element, "nothing pending");
2103 ret = GST_STATE_CHANGE_SUCCESS;
2109 *state = GST_STATE (element);
2111 *pending = GST_STATE_PENDING (element);
2113 GST_CAT_DEBUG_OBJECT (GST_CAT_STATES, element,
2114 "state current: %s, pending: %s, result: %s",
2115 gst_element_state_get_name (GST_STATE (element)),
2116 gst_element_state_get_name (GST_STATE_PENDING (element)),
2117 gst_element_state_change_return_get_name (ret));
2118 GST_OBJECT_UNLOCK (element);
2125 *state = GST_STATE_VOID_PENDING;
2127 *pending = GST_STATE_VOID_PENDING;
2129 GST_CAT_INFO_OBJECT (GST_CAT_STATES, element, "interruped");
2131 GST_OBJECT_UNLOCK (element);
2133 return GST_STATE_CHANGE_FAILURE;
2138 * gst_element_get_state:
2139 * @element: a #GstElement to get the state of.
2140 * @state: (out) (allow-none): a pointer to #GstState to hold the state.
2142 * @pending: (out) (allow-none): a pointer to #GstState to hold the pending
2143 * state. Can be %NULL.
2144 * @timeout: a #GstClockTime to specify the timeout for an async
2145 * state change or %GST_CLOCK_TIME_NONE for infinite timeout.
2147 * Gets the state of the element.
2149 * For elements that performed an ASYNC state change, as reported by
2150 * gst_element_set_state(), this function will block up to the
2151 * specified timeout value for the state change to complete.
2152 * If the element completes the state change or goes into
2153 * an error, this function returns immediately with a return value of
2154 * %GST_STATE_CHANGE_SUCCESS or %GST_STATE_CHANGE_FAILURE respectively.
2156 * For elements that did not return %GST_STATE_CHANGE_ASYNC, this function
2157 * returns the current and pending state immediately.
2159 * This function returns %GST_STATE_CHANGE_NO_PREROLL if the element
2160 * successfully changed its state but is not able to provide data yet.
2161 * This mostly happens for live sources that only produce data in
2162 * %GST_STATE_PLAYING. While the state change return is equivalent to
2163 * %GST_STATE_CHANGE_SUCCESS, it is returned to the application to signal that
2164 * some sink elements might not be able to complete their state change because
2165 * an element is not producing data to complete the preroll. When setting the
2166 * element to playing, the preroll will complete and playback will start.
2168 * Returns: %GST_STATE_CHANGE_SUCCESS if the element has no more pending state
2169 * and the last state change succeeded, %GST_STATE_CHANGE_ASYNC if the
2170 * element is still performing a state change or
2171 * %GST_STATE_CHANGE_FAILURE if the last state change failed.
2175 GstStateChangeReturn
2176 gst_element_get_state (GstElement * element,
2177 GstState * state, GstState * pending, GstClockTime timeout)
2179 GstElementClass *oclass;
2180 GstStateChangeReturn result = GST_STATE_CHANGE_FAILURE;
2182 g_return_val_if_fail (GST_IS_ELEMENT (element), GST_STATE_CHANGE_FAILURE);
2184 oclass = GST_ELEMENT_GET_CLASS (element);
2186 if (oclass->get_state)
2187 result = (oclass->get_state) (element, state, pending, timeout);
2193 * gst_element_abort_state:
2194 * @element: a #GstElement to abort the state of.
2196 * Abort the state change of the element. This function is used
2197 * by elements that do asynchronous state changes and find out
2198 * something is wrong.
2200 * This function should be called with the STATE_LOCK held.
2205 gst_element_abort_state (GstElement * element)
2209 #ifndef GST_DISABLE_GST_DEBUG
2213 g_return_if_fail (GST_IS_ELEMENT (element));
2215 GST_OBJECT_LOCK (element);
2216 pending = GST_STATE_PENDING (element);
2218 if (pending == GST_STATE_VOID_PENDING ||
2219 GST_STATE_RETURN (element) == GST_STATE_CHANGE_FAILURE)
2220 goto nothing_aborted;
2222 #ifndef GST_DISABLE_GST_DEBUG
2223 old_state = GST_STATE (element);
2225 GST_CAT_INFO_OBJECT (GST_CAT_STATES, element,
2226 "aborting state from %s to %s", gst_element_state_get_name (old_state),
2227 gst_element_state_get_name (pending));
2231 GST_STATE_RETURN (element) = GST_STATE_CHANGE_FAILURE;
2233 GST_STATE_BROADCAST (element);
2234 GST_OBJECT_UNLOCK (element);
2240 GST_OBJECT_UNLOCK (element);
2245 /* Not static because GstBin has manual state handling too */
2247 _priv_gst_element_state_changed (GstElement * element, GstState oldstate,
2248 GstState newstate, GstState pending)
2250 GstElementClass *klass = GST_ELEMENT_GET_CLASS (element);
2251 GstMessage *message;
2253 GST_CAT_INFO_OBJECT (GST_CAT_STATES, element,
2254 "notifying about state-changed %s to %s (%s pending)",
2255 gst_element_state_get_name (oldstate),
2256 gst_element_state_get_name (newstate),
2257 gst_element_state_get_name (pending));
2259 if (klass->state_changed)
2260 klass->state_changed (element, oldstate, newstate, pending);
2262 message = gst_message_new_state_changed (GST_OBJECT_CAST (element),
2263 oldstate, newstate, pending);
2264 gst_element_post_message (element, message);
2268 * gst_element_continue_state:
2269 * @element: a #GstElement to continue the state change of.
2270 * @ret: The previous state return value
2272 * Commit the state change of the element and proceed to the next
2273 * pending state if any. This function is used
2274 * by elements that do asynchronous state changes.
2275 * The core will normally call this method automatically when an
2276 * element returned %GST_STATE_CHANGE_SUCCESS from the state change function.
2278 * If after calling this method the element still has not reached
2279 * the pending state, the next state change is performed.
2281 * This method is used internally and should normally not be called by plugins
2284 * Returns: The result of the commit state change.
2288 GstStateChangeReturn
2289 gst_element_continue_state (GstElement * element, GstStateChangeReturn ret)
2291 GstStateChangeReturn old_ret;
2292 GstState old_state, old_next;
2293 GstState current, next, pending;
2294 GstStateChange transition;
2296 GST_OBJECT_LOCK (element);
2297 old_ret = GST_STATE_RETURN (element);
2298 GST_STATE_RETURN (element) = ret;
2299 pending = GST_STATE_PENDING (element);
2301 /* check if there is something to commit */
2302 if (pending == GST_STATE_VOID_PENDING)
2303 goto nothing_pending;
2305 old_state = GST_STATE (element);
2306 /* this is the state we should go to next */
2307 old_next = GST_STATE_NEXT (element);
2308 /* update current state */
2309 current = GST_STATE (element) = old_next;
2311 /* see if we reached the final state */
2312 if (pending == current)
2315 next = GST_STATE_GET_NEXT (current, pending);
2316 transition = (GstStateChange) GST_STATE_TRANSITION (current, next);
2318 GST_STATE_NEXT (element) = next;
2320 GST_STATE_RETURN (element) = GST_STATE_CHANGE_ASYNC;
2321 GST_OBJECT_UNLOCK (element);
2323 GST_CAT_INFO_OBJECT (GST_CAT_STATES, element,
2324 "committing state from %s to %s, pending %s, next %s",
2325 gst_element_state_get_name (old_state),
2326 gst_element_state_get_name (old_next),
2327 gst_element_state_get_name (pending), gst_element_state_get_name (next));
2329 _priv_gst_element_state_changed (element, old_state, old_next, pending);
2331 GST_CAT_INFO_OBJECT (GST_CAT_STATES, element,
2332 "continue state change %s to %s, final %s",
2333 gst_element_state_get_name (current),
2334 gst_element_state_get_name (next), gst_element_state_get_name (pending));
2336 ret = gst_element_change_state (element, transition);
2342 GST_CAT_INFO_OBJECT (GST_CAT_STATES, element, "nothing pending");
2343 GST_OBJECT_UNLOCK (element);
2348 GST_STATE_PENDING (element) = GST_STATE_VOID_PENDING;
2349 GST_STATE_NEXT (element) = GST_STATE_VOID_PENDING;
2351 GST_CAT_INFO_OBJECT (GST_CAT_STATES, element,
2352 "completed state change to %s", gst_element_state_get_name (pending));
2353 GST_OBJECT_UNLOCK (element);
2355 /* don't post silly messages with the same state. This can happen
2356 * when an element state is changed to what it already was. For bins
2357 * this can be the result of a lost state, which we check with the
2358 * previous return value.
2359 * We do signal the cond though as a _get_state() might be blocking
2361 if (old_state != old_next || old_ret == GST_STATE_CHANGE_ASYNC)
2362 _priv_gst_element_state_changed (element, old_state, old_next,
2363 GST_STATE_VOID_PENDING);
2365 GST_STATE_BROADCAST (element);
2372 * gst_element_lost_state:
2373 * @element: a #GstElement the state is lost of
2375 * Brings the element to the lost state. The current state of the
2376 * element is copied to the pending state so that any call to
2377 * gst_element_get_state() will return %GST_STATE_CHANGE_ASYNC.
2379 * An ASYNC_START message is posted. If the element was PLAYING, it will
2380 * go to PAUSED. The element will be restored to its PLAYING state by
2381 * the parent pipeline when it prerolls again.
2383 * This is mostly used for elements that lost their preroll buffer
2384 * in the %GST_STATE_PAUSED or %GST_STATE_PLAYING state after a flush,
2385 * they will go to their pending state again when a new preroll buffer is
2386 * queued. This function can only be called when the element is currently
2387 * not in error or an async state change.
2389 * This function is used internally and should normally not be called from
2390 * plugins or applications.
2393 gst_element_lost_state (GstElement * element)
2395 GstState old_state, new_state;
2396 GstMessage *message;
2398 g_return_if_fail (GST_IS_ELEMENT (element));
2400 GST_OBJECT_LOCK (element);
2401 if (GST_STATE_RETURN (element) == GST_STATE_CHANGE_FAILURE)
2404 if (GST_STATE_PENDING (element) != GST_STATE_VOID_PENDING)
2405 goto only_async_start;
2407 old_state = GST_STATE (element);
2409 /* when we were PLAYING, the new state is PAUSED. We will also not
2410 * automatically go to PLAYING but let the parent bin(s) set us to PLAYING
2411 * when we preroll. */
2412 if (old_state > GST_STATE_PAUSED)
2413 new_state = GST_STATE_PAUSED;
2415 new_state = old_state;
2417 GST_CAT_DEBUG_OBJECT (GST_CAT_STATES, element,
2418 "lost state of %s to %s", gst_element_state_get_name (old_state),
2419 gst_element_state_get_name (new_state));
2421 GST_STATE (element) = new_state;
2422 GST_STATE_NEXT (element) = new_state;
2423 GST_STATE_PENDING (element) = new_state;
2424 GST_STATE_RETURN (element) = GST_STATE_CHANGE_ASYNC;
2425 GST_OBJECT_UNLOCK (element);
2427 _priv_gst_element_state_changed (element, new_state, new_state, new_state);
2429 message = gst_message_new_async_start (GST_OBJECT_CAST (element));
2430 gst_element_post_message (element, message);
2436 GST_OBJECT_UNLOCK (element);
2441 GST_OBJECT_UNLOCK (element);
2443 message = gst_message_new_async_start (GST_OBJECT_CAST (element));
2444 gst_element_post_message (element, message);
2450 * gst_element_set_state:
2451 * @element: a #GstElement to change state of.
2452 * @state: the element's new #GstState.
2454 * Sets the state of the element. This function will try to set the
2455 * requested state by going through all the intermediary states and calling
2456 * the class's state change function for each.
2458 * This function can return #GST_STATE_CHANGE_ASYNC, in which case the
2459 * element will perform the remainder of the state change asynchronously in
2461 * An application can use gst_element_get_state() to wait for the completion
2462 * of the state change or it can wait for a %GST_MESSAGE_ASYNC_DONE or
2463 * %GST_MESSAGE_STATE_CHANGED on the bus.
2465 * State changes to %GST_STATE_READY or %GST_STATE_NULL never return
2466 * #GST_STATE_CHANGE_ASYNC.
2468 * Returns: Result of the state change using #GstStateChangeReturn.
2472 GstStateChangeReturn
2473 gst_element_set_state (GstElement * element, GstState state)
2475 GstElementClass *oclass;
2476 GstStateChangeReturn result = GST_STATE_CHANGE_FAILURE;
2478 g_return_val_if_fail (GST_IS_ELEMENT (element), GST_STATE_CHANGE_FAILURE);
2480 oclass = GST_ELEMENT_GET_CLASS (element);
2482 if (oclass->set_state)
2483 result = (oclass->set_state) (element, state);
2489 * default set state function, calculates the next state based
2490 * on current state and calls the change_state function
2492 static GstStateChangeReturn
2493 gst_element_set_state_func (GstElement * element, GstState state)
2495 GstState current, next, old_pending;
2496 GstStateChangeReturn ret;
2497 GstStateChange transition;
2498 GstStateChangeReturn old_ret;
2500 g_return_val_if_fail (GST_IS_ELEMENT (element), GST_STATE_CHANGE_FAILURE);
2502 GST_CAT_DEBUG_OBJECT (GST_CAT_STATES, element, "set_state to %s",
2503 gst_element_state_get_name (state));
2505 /* state lock is taken to protect the set_state() and get_state()
2506 * procedures, it does not lock any variables. */
2507 GST_STATE_LOCK (element);
2509 /* now calculate how to get to the new state */
2510 GST_OBJECT_LOCK (element);
2511 old_ret = GST_STATE_RETURN (element);
2512 /* previous state change returned an error, remove all pending
2513 * and next states */
2514 if (old_ret == GST_STATE_CHANGE_FAILURE) {
2515 GST_STATE_NEXT (element) = GST_STATE_VOID_PENDING;
2516 GST_STATE_PENDING (element) = GST_STATE_VOID_PENDING;
2517 GST_STATE_RETURN (element) = GST_STATE_CHANGE_SUCCESS;
2520 current = GST_STATE (element);
2521 next = GST_STATE_NEXT (element);
2522 old_pending = GST_STATE_PENDING (element);
2524 /* this is the (new) state we should go to. TARGET is the last state we set on
2526 if (state != GST_STATE_TARGET (element)) {
2527 GST_CAT_DEBUG_OBJECT (GST_CAT_STATES, element,
2528 "setting target state to %s", gst_element_state_get_name (state));
2529 GST_STATE_TARGET (element) = state;
2530 /* increment state cookie so that we can track each state change. We only do
2531 * this if this is actually a new state change. */
2532 element->state_cookie++;
2534 GST_STATE_PENDING (element) = state;
2536 GST_CAT_DEBUG_OBJECT (GST_CAT_STATES, element,
2537 "current %s, old_pending %s, next %s, old return %s",
2538 gst_element_state_get_name (current),
2539 gst_element_state_get_name (old_pending),
2540 gst_element_state_get_name (next),
2541 gst_element_state_change_return_get_name (old_ret));
2543 /* if the element was busy doing a state change, we just update the
2544 * target state, it'll get to it async then. */
2545 if (old_pending != GST_STATE_VOID_PENDING) {
2546 /* upwards state change will happen ASYNC */
2547 if (old_pending <= state)
2549 /* element is going to this state already */
2550 else if (next == state)
2552 /* element was performing an ASYNC upward state change and
2553 * we request to go downward again. Start from the next pending
2555 else if (next > state
2556 && GST_STATE_RETURN (element) == GST_STATE_CHANGE_ASYNC) {
2560 next = GST_STATE_GET_NEXT (current, state);
2561 /* now we store the next state */
2562 GST_STATE_NEXT (element) = next;
2563 /* mark busy, we need to check that there is actually a state change
2564 * to be done else we could accidentally override SUCCESS/NO_PREROLL and
2565 * the default element change_state function has no way to know what the
2566 * old value was... could consider this a FIXME...*/
2567 if (current != next)
2568 GST_STATE_RETURN (element) = GST_STATE_CHANGE_ASYNC;
2570 transition = (GstStateChange) GST_STATE_TRANSITION (current, next);
2572 GST_CAT_DEBUG_OBJECT (GST_CAT_STATES, element,
2573 "%s: setting state from %s to %s",
2574 (next != state ? "intermediate" : "final"),
2575 gst_element_state_get_name (current), gst_element_state_get_name (next));
2577 /* now signal any waiters, they will error since the cookie was incremented */
2578 GST_STATE_BROADCAST (element);
2580 GST_OBJECT_UNLOCK (element);
2582 ret = gst_element_change_state (element, transition);
2584 GST_STATE_UNLOCK (element);
2586 GST_CAT_DEBUG_OBJECT (GST_CAT_STATES, element, "returned %s",
2587 gst_element_state_change_return_get_name (ret));
2593 GST_STATE_RETURN (element) = GST_STATE_CHANGE_ASYNC;
2594 GST_CAT_DEBUG_OBJECT (GST_CAT_STATES, element,
2595 "element was busy with async state change");
2596 GST_OBJECT_UNLOCK (element);
2598 GST_STATE_UNLOCK (element);
2600 return GST_STATE_CHANGE_ASYNC;
2605 * gst_element_change_state:
2606 * @element: a #GstElement
2607 * @transition: the requested transition
2609 * Perform @transition on @element.
2611 * This function must be called with STATE_LOCK held and is mainly used
2614 * Returns: the #GstStateChangeReturn of the state transition.
2616 GstStateChangeReturn
2617 gst_element_change_state (GstElement * element, GstStateChange transition)
2619 GstElementClass *oclass;
2620 GstStateChangeReturn ret = GST_STATE_CHANGE_SUCCESS;
2622 oclass = GST_ELEMENT_GET_CLASS (element);
2624 GST_TRACER_ELEMENT_CHANGE_STATE_PRE (element, transition);
2626 /* call the state change function so it can set the state */
2627 if (oclass->change_state)
2628 ret = (oclass->change_state) (element, transition);
2630 ret = GST_STATE_CHANGE_FAILURE;
2632 GST_TRACER_ELEMENT_CHANGE_STATE_POST (element, transition, ret);
2635 case GST_STATE_CHANGE_FAILURE:
2636 GST_CAT_INFO_OBJECT (GST_CAT_STATES, element,
2637 "have FAILURE change_state return");
2638 /* state change failure */
2639 gst_element_abort_state (element);
2641 case GST_STATE_CHANGE_ASYNC:
2645 GST_CAT_DEBUG_OBJECT (GST_CAT_STATES, element,
2646 "element will change state ASYNC");
2648 target = GST_STATE_TARGET (element);
2650 if (target > GST_STATE_READY)
2653 /* else we just continue the state change downwards */
2654 GST_CAT_INFO_OBJECT (GST_CAT_STATES, element,
2655 "forcing commit state %s <= %s",
2656 gst_element_state_get_name (target),
2657 gst_element_state_get_name (GST_STATE_READY));
2659 ret = gst_element_continue_state (element, GST_STATE_CHANGE_SUCCESS);
2662 case GST_STATE_CHANGE_SUCCESS:
2663 GST_CAT_DEBUG_OBJECT (GST_CAT_STATES, element,
2664 "element changed state SUCCESS");
2665 /* we can commit the state now which will proceeed to
2667 ret = gst_element_continue_state (element, ret);
2669 case GST_STATE_CHANGE_NO_PREROLL:
2670 GST_CAT_DEBUG_OBJECT (GST_CAT_STATES, element,
2671 "element changed state NO_PREROLL");
2672 /* we can commit the state now which will proceeed to
2674 ret = gst_element_continue_state (element, ret);
2677 goto invalid_return;
2680 GST_CAT_LOG_OBJECT (GST_CAT_STATES, element, "exit state change %d", ret);
2685 GST_CAT_LOG_OBJECT (GST_CAT_STATES, element, "exit async state change %d",
2693 GST_OBJECT_LOCK (element);
2694 /* somebody added a GST_STATE_ and forgot to do stuff here ! */
2695 g_critical ("%s: unknown return value %d from a state change function",
2696 GST_ELEMENT_NAME (element), ret);
2698 /* we are in error now */
2699 ret = GST_STATE_CHANGE_FAILURE;
2700 GST_STATE_RETURN (element) = ret;
2701 GST_OBJECT_UNLOCK (element);
2707 /* gst_iterator_fold functions for pads_activate
2708 * Stop the iterator if activating one pad failed, but only if that pad
2709 * has not been removed from the element. */
2711 activate_pads (const GValue * vpad, GValue * ret, gboolean * active)
2713 GstPad *pad = g_value_get_object (vpad);
2714 gboolean cont = TRUE;
2716 if (!gst_pad_set_active (pad, *active)) {
2717 if (GST_PAD_PARENT (pad) != NULL) {
2719 g_value_set_boolean (ret, FALSE);
2726 /* returns false on error or early cutout of the fold, true if all
2727 * pads in @iter were (de)activated successfully. */
2729 iterator_activate_fold_with_resync (GstIterator * iter,
2730 GstIteratorFoldFunction func, gpointer user_data)
2732 GstIteratorResult ires;
2735 /* no need to unset this later, it's just a boolean */
2736 g_value_init (&ret, G_TYPE_BOOLEAN);
2737 g_value_set_boolean (&ret, TRUE);
2740 ires = gst_iterator_fold (iter, func, &ret, user_data);
2742 case GST_ITERATOR_RESYNC:
2743 /* need to reset the result again */
2744 g_value_set_boolean (&ret, TRUE);
2745 gst_iterator_resync (iter);
2747 case GST_ITERATOR_DONE:
2748 /* all pads iterated, return collected value */
2751 /* iterator returned _ERROR or premature end with _OK,
2752 * mark an error and exit */
2753 g_value_set_boolean (&ret, FALSE);
2758 /* return collected value */
2759 return g_value_get_boolean (&ret);
2762 /* is called with STATE_LOCK
2764 * Pads are activated from source pads to sinkpads.
2767 gst_element_pads_activate (GstElement * element, gboolean active)
2772 GST_CAT_DEBUG_OBJECT (GST_CAT_ELEMENT_PADS, element,
2773 "%s pads", active ? "activate" : "deactivate");
2775 iter = gst_element_iterate_src_pads (element);
2777 iterator_activate_fold_with_resync (iter,
2778 (GstIteratorFoldFunction) activate_pads, &active);
2779 gst_iterator_free (iter);
2780 if (G_UNLIKELY (!res))
2783 iter = gst_element_iterate_sink_pads (element);
2785 iterator_activate_fold_with_resync (iter,
2786 (GstIteratorFoldFunction) activate_pads, &active);
2787 gst_iterator_free (iter);
2788 if (G_UNLIKELY (!res))
2791 GST_CAT_DEBUG_OBJECT (GST_CAT_ELEMENT_PADS, element,
2792 "pad %sactivation successful", active ? "" : "de");
2799 GST_CAT_DEBUG_OBJECT (GST_CAT_ELEMENT_PADS, element,
2800 "pad %sactivation failed", active ? "" : "de");
2805 GST_CAT_DEBUG_OBJECT (GST_CAT_ELEMENT_PADS, element,
2806 "sink pads_activate failed");
2811 /* is called with STATE_LOCK */
2812 static GstStateChangeReturn
2813 gst_element_change_state_func (GstElement * element, GstStateChange transition)
2815 GstState state, next;
2816 GstStateChangeReturn result = GST_STATE_CHANGE_SUCCESS;
2818 g_return_val_if_fail (GST_IS_ELEMENT (element), GST_STATE_CHANGE_FAILURE);
2820 state = (GstState) GST_STATE_TRANSITION_CURRENT (transition);
2821 next = GST_STATE_TRANSITION_NEXT (transition);
2823 /* if the element already is in the given state, we just return success */
2824 if (next == GST_STATE_VOID_PENDING || state == next)
2827 GST_CAT_LOG_OBJECT (GST_CAT_STATES, element,
2828 "default handler tries setting state from %s to %s (%04x)",
2829 gst_element_state_get_name (state),
2830 gst_element_state_get_name (next), transition);
2832 switch (transition) {
2833 case GST_STATE_CHANGE_NULL_TO_READY:
2835 case GST_STATE_CHANGE_READY_TO_PAUSED:
2836 if (!gst_element_pads_activate (element, TRUE)) {
2837 result = GST_STATE_CHANGE_FAILURE;
2840 case GST_STATE_CHANGE_PAUSED_TO_PLAYING:
2842 case GST_STATE_CHANGE_PLAYING_TO_PAUSED:
2844 case GST_STATE_CHANGE_PAUSED_TO_READY:
2845 case GST_STATE_CHANGE_READY_TO_NULL:{
2848 /* deactivate pads in both cases, since they are activated on
2849 ready->paused but the element might not have made it to paused */
2850 if (!gst_element_pads_activate (element, FALSE)) {
2851 result = GST_STATE_CHANGE_FAILURE;
2854 /* Remove all non-persistent contexts */
2855 GST_OBJECT_LOCK (element);
2856 for (l = element->contexts; l;) {
2857 GstContext *context = l->data;
2859 if (!gst_context_is_persistent (context)) {
2862 gst_context_unref (context);
2864 element->contexts = g_list_delete_link (element->contexts, l);
2870 GST_OBJECT_UNLOCK (element);
2874 /* this will catch real but unhandled state changes;
2875 * can only be caused by:
2876 * - a new state was added
2877 * - somehow the element was asked to jump across an intermediate state
2879 g_warning ("Unhandled state change from %s to %s",
2880 gst_element_state_get_name (state),
2881 gst_element_state_get_name (next));
2888 GST_OBJECT_LOCK (element);
2889 result = GST_STATE_RETURN (element);
2890 GST_CAT_DEBUG_OBJECT (GST_CAT_STATES, element,
2891 "element is already in the %s state",
2892 gst_element_state_get_name (state));
2893 GST_OBJECT_UNLOCK (element);
2900 * gst_element_get_factory:
2901 * @element: a #GstElement to request the element factory of.
2903 * Retrieves the factory that was used to create this element.
2905 * Returns: (transfer none): the #GstElementFactory used for creating this
2906 * element. no refcounting is needed.
2909 gst_element_get_factory (GstElement * element)
2911 g_return_val_if_fail (GST_IS_ELEMENT (element), NULL);
2913 return GST_ELEMENT_GET_CLASS (element)->elementfactory;
2917 gst_element_dispose (GObject * object)
2919 GstElement *element = GST_ELEMENT_CAST (object);
2922 GstElementClass *oclass;
2925 oclass = GST_ELEMENT_GET_CLASS (element);
2927 GST_CAT_INFO_OBJECT (GST_CAT_REFCOUNTING, element, "dispose");
2929 if (GST_STATE (element) != GST_STATE_NULL)
2932 /* start by releasing all request pads, this might also remove some dynamic
2934 walk = element->pads;
2936 GstPad *pad = GST_PAD_CAST (walk->data);
2940 if (oclass->release_pad && GST_PAD_PAD_TEMPLATE (pad) &&
2941 GST_PAD_TEMPLATE_PRESENCE (GST_PAD_PAD_TEMPLATE (pad))
2942 == GST_PAD_REQUEST) {
2943 GST_CAT_DEBUG_OBJECT (GST_CAT_ELEMENT_PADS, element,
2944 "removing request pad %s:%s", GST_DEBUG_PAD_NAME (pad));
2945 oclass->release_pad (element, pad);
2947 /* in case the release_pad function removed the next pad too */
2948 if (walk && g_list_position (element->pads, walk) == -1)
2949 walk = element->pads;
2952 /* remove the remaining pads */
2953 while (element->pads) {
2954 GstPad *pad = GST_PAD_CAST (element->pads->data);
2955 GST_CAT_DEBUG_OBJECT (GST_CAT_ELEMENT_PADS, element,
2956 "removing pad %s:%s", GST_DEBUG_PAD_NAME (pad));
2957 if (!gst_element_remove_pad (element, pad)) {
2958 /* only happens when someone unparented our pad.. */
2959 g_critical ("failed to remove pad %s:%s", GST_DEBUG_PAD_NAME (pad));
2964 GST_OBJECT_LOCK (element);
2965 clock_p = &element->clock;
2966 bus_p = &element->bus;
2967 gst_object_replace ((GstObject **) clock_p, NULL);
2968 gst_object_replace ((GstObject **) bus_p, NULL);
2969 g_list_free_full (element->contexts, (GDestroyNotify) gst_context_unref);
2970 GST_OBJECT_UNLOCK (element);
2972 GST_CAT_INFO_OBJECT (GST_CAT_REFCOUNTING, element, "parent class dispose");
2974 G_OBJECT_CLASS (parent_class)->dispose (object);
2983 is_locked = GST_ELEMENT_IS_LOCKED_STATE (element);
2985 ("\nTrying to dispose element %s, but it is in %s%s instead of the NULL"
2987 "You need to explicitly set elements to the NULL state before\n"
2988 "dropping the final reference, to allow them to clean up.\n"
2989 "This problem may also be caused by a refcounting bug in the\n"
2990 "application or some element.\n",
2991 GST_OBJECT_NAME (element),
2992 gst_element_state_get_name (GST_STATE (element)),
2993 is_locked ? " (locked)" : "");
2999 gst_element_finalize (GObject * object)
3001 GstElement *element = GST_ELEMENT_CAST (object);
3003 GST_CAT_INFO_OBJECT (GST_CAT_REFCOUNTING, element, "finalize");
3005 g_cond_clear (&element->state_cond);
3006 g_rec_mutex_clear (&element->state_lock);
3008 GST_CAT_INFO_OBJECT (GST_CAT_REFCOUNTING, element, "finalize parent");
3010 G_OBJECT_CLASS (parent_class)->finalize (object);
3014 gst_element_set_bus_func (GstElement * element, GstBus * bus)
3018 g_return_if_fail (GST_IS_ELEMENT (element));
3020 GST_CAT_DEBUG_OBJECT (GST_CAT_PARENTAGE, element, "setting bus to %p", bus);
3022 GST_OBJECT_LOCK (element);
3023 bus_p = &GST_ELEMENT_BUS (element);
3024 gst_object_replace ((GstObject **) bus_p, GST_OBJECT_CAST (bus));
3025 GST_OBJECT_UNLOCK (element);
3029 * gst_element_set_bus:
3030 * @element: a #GstElement to set the bus of.
3031 * @bus: (transfer none): the #GstBus to set.
3033 * Sets the bus of the element. Increases the refcount on the bus.
3034 * For internal use only, unless you're testing elements.
3039 gst_element_set_bus (GstElement * element, GstBus * bus)
3041 GstElementClass *oclass;
3043 g_return_if_fail (GST_IS_ELEMENT (element));
3045 oclass = GST_ELEMENT_GET_CLASS (element);
3047 if (oclass->set_bus)
3048 oclass->set_bus (element, bus);
3052 * gst_element_get_bus:
3053 * @element: a #GstElement to get the bus of.
3055 * Returns the bus of the element. Note that only a #GstPipeline will provide a
3056 * bus for the application.
3058 * Returns: (transfer full): the element's #GstBus. unref after usage.
3063 gst_element_get_bus (GstElement * element)
3065 GstBus *result = NULL;
3067 g_return_val_if_fail (GST_IS_ELEMENT (element), result);
3069 GST_OBJECT_LOCK (element);
3070 if ((result = GST_ELEMENT_BUS (element)))
3071 gst_object_ref (result);
3072 GST_OBJECT_UNLOCK (element);
3074 GST_CAT_DEBUG_OBJECT (GST_CAT_BUS, element, "got bus %" GST_PTR_FORMAT,
3081 gst_element_set_context_default (GstElement * element, GstContext * context)
3083 const gchar *context_type;
3086 GST_OBJECT_LOCK (element);
3087 context_type = gst_context_get_context_type (context);
3088 for (l = element->contexts; l; l = l->next) {
3089 GstContext *tmp = l->data;
3090 const gchar *tmp_type = gst_context_get_context_type (tmp);
3092 /* Always store newest context but never replace
3093 * a persistent one by a non-persistent one */
3094 if (strcmp (context_type, tmp_type) == 0 &&
3095 (gst_context_is_persistent (context) ||
3096 !gst_context_is_persistent (tmp))) {
3097 gst_context_replace ((GstContext **) & l->data, context);
3101 /* Not found? Add */
3104 g_list_prepend (element->contexts, gst_context_ref (context));
3106 GST_OBJECT_UNLOCK (element);
3110 * gst_element_set_context:
3111 * @element: a #GstElement to set the context of.
3112 * @context: (transfer none): the #GstContext to set.
3114 * Sets the context of the element. Increases the refcount of the context.
3119 gst_element_set_context (GstElement * element, GstContext * context)
3121 GstElementClass *oclass;
3123 g_return_if_fail (GST_IS_ELEMENT (element));
3125 oclass = GST_ELEMENT_GET_CLASS (element);
3127 GST_CAT_DEBUG_OBJECT (GST_CAT_CONTEXT, element,
3128 "set context %p %" GST_PTR_FORMAT, context,
3129 gst_context_get_structure (context));
3131 if (oclass->set_context)
3132 oclass->set_context (element, context);
3136 * gst_element_get_contexts:
3137 * @element: a #GstElement to set the context of.
3139 * Gets the contexts set on the element.
3143 * Returns: (element-type Gst.Context) (transfer full): List of #GstContext
3148 gst_element_get_contexts (GstElement * element)
3152 g_return_val_if_fail (GST_IS_ELEMENT (element), NULL);
3154 GST_OBJECT_LOCK (element);
3155 ret = g_list_copy_deep (element->contexts, (GCopyFunc) gst_context_ref, NULL);
3156 GST_OBJECT_UNLOCK (element);
3162 _match_context_type (GstContext * c1, const gchar * context_type)
3164 const gchar *c1_type;
3166 c1_type = gst_context_get_context_type (c1);
3168 return g_strcmp0 (c1_type, context_type);
3172 * gst_element_get_context_unlocked:
3173 * @element: a #GstElement to get the context of.
3174 * @context_type: a name of a context to retrieve
3176 * Gets the context with @context_type set on the element or NULL.
3178 * Returns: (transfer full): A #GstContext or NULL
3183 gst_element_get_context_unlocked (GstElement * element,
3184 const gchar * context_type)
3186 GstContext *ret = NULL;
3189 g_return_val_if_fail (GST_IS_ELEMENT (element), NULL);
3192 g_list_find_custom (element->contexts, context_type,
3193 (GCompareFunc) _match_context_type);
3194 if (node && node->data)
3195 ret = gst_context_ref (node->data);
3201 * gst_element_get_context:
3202 * @element: a #GstElement to get the context of.
3203 * @context_type: a name of a context to retrieve
3205 * Gets the context with @context_type set on the element or NULL.
3209 * Returns: (transfer full): A #GstContext or NULL
3214 gst_element_get_context (GstElement * element, const gchar * context_type)
3216 GstContext *ret = NULL;
3218 g_return_val_if_fail (GST_IS_ELEMENT (element), NULL);
3220 GST_OBJECT_LOCK (element);
3221 ret = gst_element_get_context_unlocked (element, context_type);
3222 GST_OBJECT_UNLOCK (element);