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 flushing = GST_PAD_IS_FLUSHING (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 flushing pads */
675 if (flushing && (GST_STATE (element) > GST_STATE_READY ||
676 GST_STATE_NEXT (element) == GST_STATE_PAUSED)) {
677 g_warning ("adding flushing 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));
681 GST_OBJECT_LOCK (pad);
682 GST_PAD_UNSET_FLUSHING (pad);
683 GST_OBJECT_UNLOCK (pad);
688 /* add it to the list */
689 switch (gst_pad_get_direction (pad)) {
691 element->srcpads = g_list_append (element->srcpads, pad);
692 element->numsrcpads++;
695 element->sinkpads = g_list_append (element->sinkpads, pad);
696 element->numsinkpads++;
701 element->pads = g_list_append (element->pads, pad);
703 element->pads_cookie++;
704 GST_OBJECT_UNLOCK (element);
706 /* emit the PAD_ADDED signal */
707 g_signal_emit (element, gst_element_signals[PAD_ADDED], 0, pad);
708 GST_TRACER_ELEMENT_ADD_PAD (element, pad);
714 g_critical ("Padname %s is not unique in element %s, not adding",
715 pad_name, GST_ELEMENT_NAME (element));
716 GST_OBJECT_UNLOCK (element);
723 ("Pad %s already has parent when trying to add to element %s",
724 pad_name, GST_ELEMENT_NAME (element));
725 GST_OBJECT_UNLOCK (element);
731 GST_OBJECT_LOCK (pad);
733 ("Trying to add pad %s to element %s, but it has no direction",
734 GST_OBJECT_NAME (pad), GST_ELEMENT_NAME (element));
735 GST_OBJECT_UNLOCK (pad);
736 GST_OBJECT_UNLOCK (element);
742 * gst_element_remove_pad:
743 * @element: a #GstElement to remove pad from.
744 * @pad: (transfer full): the #GstPad to remove from the element.
746 * Removes @pad from @element. @pad will be destroyed if it has not been
747 * referenced elsewhere using gst_object_unparent().
749 * This function is used by plugin developers and should not be used
750 * by applications. Pads that were dynamically requested from elements
751 * with gst_element_request_pad() should be released with the
752 * gst_element_release_request_pad() function instead.
754 * Pads are not automatically deactivated so elements should perform the needed
755 * steps to deactivate the pad in case this pad is removed in the PAUSED or
756 * PLAYING state. See gst_pad_set_active() for more information about
759 * The pad and the element should be unlocked when calling this function.
761 * This function will emit the #GstElement::pad-removed signal on the element.
763 * Returns: %TRUE if the pad could be removed. Can return %FALSE if the
764 * pad does not belong to the provided element.
769 gst_element_remove_pad (GstElement * element, GstPad * pad)
773 g_return_val_if_fail (GST_IS_ELEMENT (element), FALSE);
774 g_return_val_if_fail (GST_IS_PAD (pad), FALSE);
776 /* locking pad to look at the name and parent */
777 GST_OBJECT_LOCK (pad);
778 GST_CAT_INFO_OBJECT (GST_CAT_ELEMENT_PADS, element, "removing pad '%s'",
779 GST_STR_NULL (GST_PAD_NAME (pad)));
781 if (G_UNLIKELY (GST_PAD_PARENT (pad) != element))
783 GST_OBJECT_UNLOCK (pad);
786 if ((peer = gst_pad_get_peer (pad))) {
787 /* window for MT unsafeness, someone else could unlink here
788 * and then we call unlink with wrong pads. The unlink
789 * function would catch this and safely return failed. */
790 if (GST_PAD_IS_SRC (pad))
791 gst_pad_unlink (pad, peer);
793 gst_pad_unlink (peer, pad);
795 gst_object_unref (peer);
798 GST_OBJECT_LOCK (element);
799 /* remove it from the list */
800 switch (gst_pad_get_direction (pad)) {
802 element->srcpads = g_list_remove (element->srcpads, pad);
803 element->numsrcpads--;
806 element->sinkpads = g_list_remove (element->sinkpads, pad);
807 element->numsinkpads--;
810 g_critical ("Removing pad without direction???");
813 element->pads = g_list_remove (element->pads, pad);
815 element->pads_cookie++;
816 GST_OBJECT_UNLOCK (element);
818 /* emit the PAD_REMOVED signal before unparenting and losing the last ref. */
819 g_signal_emit (element, gst_element_signals[PAD_REMOVED], 0, pad);
820 GST_TRACER_ELEMENT_REMOVE_PAD (element, pad);
821 gst_object_unparent (GST_OBJECT_CAST (pad));
828 /* locking order is element > pad */
829 GST_OBJECT_UNLOCK (pad);
831 GST_OBJECT_LOCK (element);
832 GST_OBJECT_LOCK (pad);
833 g_critical ("Padname %s:%s does not belong to element %s when removing",
834 GST_DEBUG_PAD_NAME (pad), GST_ELEMENT_NAME (element));
835 GST_OBJECT_UNLOCK (pad);
836 GST_OBJECT_UNLOCK (element);
842 * gst_element_no_more_pads:
843 * @element: a #GstElement
845 * Use this function to signal that the element does not expect any more pads
846 * to show up in the current pipeline. This function should be called whenever
847 * pads have been added by the element itself. Elements with #GST_PAD_SOMETIMES
848 * pad templates use this in combination with autopluggers to figure out that
849 * the element is done initializing its pads.
851 * This function emits the #GstElement::no-more-pads signal.
856 gst_element_no_more_pads (GstElement * element)
858 g_return_if_fail (GST_IS_ELEMENT (element));
860 g_signal_emit (element, gst_element_signals[NO_MORE_PADS], 0);
864 pad_compare_name (GstPad * pad1, const gchar * name)
868 GST_OBJECT_LOCK (pad1);
869 result = strcmp (GST_PAD_NAME (pad1), name);
870 GST_OBJECT_UNLOCK (pad1);
876 * gst_element_get_static_pad:
877 * @element: a #GstElement to find a static pad of.
878 * @name: the name of the static #GstPad to retrieve.
880 * Retrieves a pad from @element by name. This version only retrieves
881 * already-existing (i.e. 'static') pads.
883 * Returns: (transfer full) (nullable): the requested #GstPad if
884 * found, otherwise %NULL. unref after usage.
889 gst_element_get_static_pad (GstElement * element, const gchar * name)
892 GstPad *result = NULL;
894 g_return_val_if_fail (GST_IS_ELEMENT (element), NULL);
895 g_return_val_if_fail (name != NULL, NULL);
897 GST_OBJECT_LOCK (element);
899 g_list_find_custom (element->pads, name, (GCompareFunc) pad_compare_name);
901 result = GST_PAD_CAST (find->data);
902 gst_object_ref (result);
905 if (result == NULL) {
906 GST_CAT_INFO (GST_CAT_ELEMENT_PADS, "no such pad '%s' in element \"%s\"",
907 name, GST_ELEMENT_NAME (element));
909 GST_CAT_INFO (GST_CAT_ELEMENT_PADS, "found pad %s:%s",
910 GST_ELEMENT_NAME (element), name);
912 GST_OBJECT_UNLOCK (element);
918 _gst_element_request_pad (GstElement * element, GstPadTemplate * templ,
919 const gchar * name, const GstCaps * caps)
921 GstPad *newpad = NULL;
922 GstElementClass *oclass;
924 oclass = GST_ELEMENT_GET_CLASS (element);
926 #ifndef G_DISABLE_CHECKS
927 /* Some sanity checking here */
931 /* Is this the template name? */
932 if (strstr (name, "%") || !strchr (templ->name_template, '%')) {
933 g_return_val_if_fail (strcmp (name, templ->name_template) == 0, NULL);
935 const gchar *str, *data;
938 /* Otherwise check if it's a valid name for the name template */
939 str = strchr (templ->name_template, '%');
940 g_return_val_if_fail (str != NULL, NULL);
941 g_return_val_if_fail (strncmp (templ->name_template, name,
942 str - templ->name_template) == 0, NULL);
943 g_return_val_if_fail (strlen (name) > str - templ->name_template, NULL);
945 data = name + (str - templ->name_template);
947 /* Can either be %s or %d or %u, do sanity checking for %d */
948 if (*(str + 1) == 'd') {
952 tmp = g_ascii_strtoll (data, &endptr, 10);
953 g_return_val_if_fail (tmp >= G_MININT && tmp <= G_MAXINT
954 && *endptr == '\0', NULL);
955 } else if (*(str + 1) == 'u') {
959 tmp = g_ascii_strtoull (data, &endptr, 10);
960 g_return_val_if_fail (tmp <= G_MAXUINT && *endptr == '\0', NULL);
964 pad = gst_element_get_static_pad (element, name);
966 gst_object_unref (pad);
967 /* FIXME 2.0: Change this to g_return_val_if_fail() */
968 g_critical ("Element %s already has a pad named %s, the behaviour of "
969 " gst_element_get_request_pad() for existing pads is undefined!",
970 GST_ELEMENT_NAME (element), name);
975 if (oclass->request_new_pad)
976 newpad = (oclass->request_new_pad) (element, templ, name, caps);
979 gst_object_ref (newpad);
985 * gst_element_get_request_pad:
986 * @element: a #GstElement to find a request pad of.
987 * @name: the name of the request #GstPad to retrieve.
989 * Retrieves a pad from the element by name (e.g. "src_\%d"). This version only
990 * retrieves request pads. The pad should be released with
991 * gst_element_release_request_pad().
993 * This method is slower than manually getting the pad template and calling
994 * gst_element_request_pad() if the pads should have a specific name (e.g.
995 * @name is "src_1" instead of "src_\%u").
997 * Returns: (transfer full) (nullable): requested #GstPad if found,
998 * otherwise %NULL. Release after usage.
1001 gst_element_get_request_pad (GstElement * element, const gchar * name)
1003 GstPadTemplate *templ = NULL;
1005 const gchar *req_name = NULL;
1006 gboolean templ_found = FALSE;
1009 gchar *str, *endptr = NULL;
1010 GstElementClass *class;
1012 g_return_val_if_fail (GST_IS_ELEMENT (element), NULL);
1013 g_return_val_if_fail (name != NULL, NULL);
1015 class = GST_ELEMENT_GET_CLASS (element);
1017 /* if the name contains a %, we assume it's the complete template name. Get
1018 * the template and try to get a pad */
1019 if (strstr (name, "%")) {
1020 templ = gst_element_class_get_request_pad_template (class, name);
1025 /* there is no % in the name, try to find a matching template */
1026 list = class->padtemplates;
1027 while (!templ_found && list) {
1028 templ = (GstPadTemplate *) list->data;
1029 if (templ->presence == GST_PAD_REQUEST) {
1030 GST_CAT_DEBUG (GST_CAT_PADS, "comparing %s to %s", name,
1031 templ->name_template);
1032 /* see if we find an exact match */
1033 if (strcmp (name, templ->name_template) == 0) {
1038 /* Because of sanity checks in gst_pad_template_new(), we know that %s
1039 and %d and %u, occurring at the end of the name_template, are the only
1041 else if ((str = strchr (templ->name_template, '%'))
1042 && strncmp (templ->name_template, name,
1043 str - templ->name_template) == 0
1044 && strlen (name) > str - templ->name_template) {
1045 data = name + (str - templ->name_template);
1046 if (*(str + 1) == 'd') {
1050 tmp = strtol (data, &endptr, 10);
1051 if (tmp != G_MINLONG && tmp != G_MAXLONG && endptr &&
1057 } else if (*(str + 1) == 'u') {
1061 tmp = strtoul (data, &endptr, 10);
1062 if (tmp != G_MAXULONG && endptr && *endptr == '\0') {
1082 pad = _gst_element_request_pad (element, templ, req_name, NULL);
1088 * gst_element_request_pad: (virtual request_new_pad)
1089 * @element: a #GstElement to find a request pad of.
1090 * @templ: a #GstPadTemplate of which we want a pad of.
1091 * @name: (transfer none) (allow-none): the name of the request #GstPad
1092 * to retrieve. Can be %NULL.
1093 * @caps: (transfer none) (allow-none): the caps of the pad we want to
1094 * request. Can be %NULL.
1096 * Retrieves a request pad from the element according to the provided template.
1097 * Pad templates can be looked up using
1098 * gst_element_factory_get_static_pad_templates().
1100 * The pad should be released with gst_element_release_request_pad().
1102 * Returns: (transfer full) (nullable): requested #GstPad if found,
1103 * otherwise %NULL. Release after usage.
1106 gst_element_request_pad (GstElement * element,
1107 GstPadTemplate * templ, const gchar * name, const GstCaps * caps)
1109 g_return_val_if_fail (GST_IS_ELEMENT (element), NULL);
1110 g_return_val_if_fail (templ != NULL, NULL);
1111 g_return_val_if_fail (templ->presence == GST_PAD_REQUEST, NULL);
1113 return _gst_element_request_pad (element, templ, name, caps);
1116 static GstIterator *
1117 gst_element_iterate_pad_list (GstElement * element, GList ** padlist)
1119 GstIterator *result;
1121 GST_OBJECT_LOCK (element);
1122 result = gst_iterator_new_list (GST_TYPE_PAD,
1123 GST_OBJECT_GET_LOCK (element),
1124 &element->pads_cookie, padlist, (GObject *) element, NULL);
1125 GST_OBJECT_UNLOCK (element);
1131 * gst_element_iterate_pads:
1132 * @element: a #GstElement to iterate pads of.
1134 * Retrieves an iterator of @element's pads. The iterator should
1135 * be freed after usage. Also more specialized iterators exists such as
1136 * gst_element_iterate_src_pads() or gst_element_iterate_sink_pads().
1138 * The order of pads returned by the iterator will be the order in which
1139 * the pads were added to the element.
1141 * Returns: (transfer full): the #GstIterator of #GstPad.
1146 gst_element_iterate_pads (GstElement * element)
1148 g_return_val_if_fail (GST_IS_ELEMENT (element), NULL);
1150 return gst_element_iterate_pad_list (element, &element->pads);
1154 * gst_element_iterate_src_pads:
1155 * @element: a #GstElement.
1157 * Retrieves an iterator of @element's source pads.
1159 * The order of pads returned by the iterator will be the order in which
1160 * the pads were added to the element.
1162 * Returns: (transfer full): the #GstIterator of #GstPad.
1167 gst_element_iterate_src_pads (GstElement * element)
1169 g_return_val_if_fail (GST_IS_ELEMENT (element), NULL);
1171 return gst_element_iterate_pad_list (element, &element->srcpads);
1175 * gst_element_iterate_sink_pads:
1176 * @element: a #GstElement.
1178 * Retrieves an iterator of @element's sink pads.
1180 * The order of pads returned by the iterator will be the order in which
1181 * the pads were added to the element.
1183 * Returns: (transfer full): the #GstIterator of #GstPad.
1188 gst_element_iterate_sink_pads (GstElement * element)
1190 g_return_val_if_fail (GST_IS_ELEMENT (element), NULL);
1192 return gst_element_iterate_pad_list (element, &element->sinkpads);
1196 * gst_element_class_add_pad_template:
1197 * @klass: the #GstElementClass to add the pad template to.
1198 * @templ: (transfer full): a #GstPadTemplate to add to the element class.
1200 * Adds a padtemplate to an element class. This is mainly used in the _class_init
1201 * functions of classes. If a pad template with the same name as an already
1202 * existing one is added the old one is replaced by the new one.
1206 gst_element_class_add_pad_template (GstElementClass * klass,
1207 GstPadTemplate * templ)
1209 GList *template_list = klass->padtemplates;
1211 g_return_if_fail (GST_IS_ELEMENT_CLASS (klass));
1212 g_return_if_fail (GST_IS_PAD_TEMPLATE (templ));
1214 /* If we already have a pad template with the same name replace the
1216 while (template_list) {
1217 GstPadTemplate *padtempl = (GstPadTemplate *) template_list->data;
1219 /* Found pad with the same name, replace and return */
1220 if (strcmp (templ->name_template, padtempl->name_template) == 0) {
1221 gst_object_unref (padtempl);
1222 template_list->data = templ;
1225 template_list = g_list_next (template_list);
1228 /* Take ownership of the floating ref */
1229 gst_object_ref_sink (templ);
1231 klass->padtemplates = g_list_append (klass->padtemplates, templ);
1232 klass->numpadtemplates++;
1236 * gst_element_class_add_metadata:
1237 * @klass: class to set metadata for
1238 * @key: the key to set
1239 * @value: the value to set
1241 * Set @key with @value as metadata in @klass.
1244 gst_element_class_add_metadata (GstElementClass * klass,
1245 const gchar * key, const gchar * value)
1247 g_return_if_fail (GST_IS_ELEMENT_CLASS (klass));
1248 g_return_if_fail (key != NULL);
1249 g_return_if_fail (value != NULL);
1251 gst_structure_set ((GstStructure *) klass->metadata,
1252 key, G_TYPE_STRING, value, NULL);
1256 * gst_element_class_add_static_metadata:
1257 * @klass: class to set metadata for
1258 * @key: the key to set
1259 * @value: the value to set
1261 * Set @key with @value as metadata in @klass.
1263 * Same as gst_element_class_add_metadata(), but @value must be a static string
1264 * or an inlined string, as it will not be copied. (GStreamer plugins will
1265 * be made resident once loaded, so this function can be used even from
1266 * dynamically loaded plugins.)
1269 gst_element_class_add_static_metadata (GstElementClass * klass,
1270 const gchar * key, const gchar * value)
1272 GValue val = G_VALUE_INIT;
1274 g_return_if_fail (GST_IS_ELEMENT_CLASS (klass));
1275 g_return_if_fail (key != NULL);
1276 g_return_if_fail (value != NULL);
1278 g_value_init (&val, G_TYPE_STRING);
1279 g_value_set_static_string (&val, value);
1280 gst_structure_take_value ((GstStructure *) klass->metadata, key, &val);
1284 * gst_element_class_set_metadata:
1285 * @klass: class to set metadata for
1286 * @longname: The long English name of the element. E.g. "File Sink"
1287 * @classification: String describing the type of element, as an unordered list
1288 * separated with slashes ('/'). See draft-klass.txt of the design docs
1289 * for more details and common types. E.g: "Sink/File"
1290 * @description: Sentence describing the purpose of the element.
1291 * E.g: "Write stream to a file"
1292 * @author: Name and contact details of the author(s). Use \n to separate
1293 * multiple author metadata. E.g: "Joe Bloggs <joe.blogs at foo.com>"
1295 * Sets the detailed information for a #GstElementClass.
1296 * <note>This function is for use in _class_init functions only.</note>
1299 gst_element_class_set_metadata (GstElementClass * klass,
1300 const gchar * longname, const gchar * classification,
1301 const gchar * description, const gchar * author)
1303 g_return_if_fail (GST_IS_ELEMENT_CLASS (klass));
1304 g_return_if_fail (longname != NULL && *longname != '\0');
1305 g_return_if_fail (classification != NULL && *classification != '\0');
1306 g_return_if_fail (description != NULL && *description != '\0');
1307 g_return_if_fail (author != NULL && *author != '\0');
1309 gst_structure_id_set ((GstStructure *) klass->metadata,
1310 GST_QUARK (ELEMENT_METADATA_LONGNAME), G_TYPE_STRING, longname,
1311 GST_QUARK (ELEMENT_METADATA_KLASS), G_TYPE_STRING, classification,
1312 GST_QUARK (ELEMENT_METADATA_DESCRIPTION), G_TYPE_STRING, description,
1313 GST_QUARK (ELEMENT_METADATA_AUTHOR), G_TYPE_STRING, author, NULL);
1317 * gst_element_class_set_static_metadata:
1318 * @klass: class to set metadata for
1319 * @longname: The long English name of the element. E.g. "File Sink"
1320 * @classification: String describing the type of element, as an unordered list
1321 * separated with slashes ('/'). See draft-klass.txt of the design docs
1322 * for more details and common types. E.g: "Sink/File"
1323 * @description: Sentence describing the purpose of the element.
1324 * E.g: "Write stream to a file"
1325 * @author: Name and contact details of the author(s). Use \n to separate
1326 * multiple author metadata. E.g: "Joe Bloggs <joe.blogs at foo.com>"
1328 * Sets the detailed information for a #GstElementClass.
1329 * <note>This function is for use in _class_init functions only.</note>
1331 * Same as gst_element_class_set_metadata(), but @longname, @classification,
1332 * @description, and @author must be static strings or inlined strings, as
1333 * they will not be copied. (GStreamer plugins will be made resident once
1334 * loaded, so this function can be used even from dynamically loaded plugins.)
1337 gst_element_class_set_static_metadata (GstElementClass * klass,
1338 const gchar * longname, const gchar * classification,
1339 const gchar * description, const gchar * author)
1341 GstStructure *s = (GstStructure *) klass->metadata;
1342 GValue val = G_VALUE_INIT;
1344 g_return_if_fail (GST_IS_ELEMENT_CLASS (klass));
1345 g_return_if_fail (longname != NULL && *longname != '\0');
1346 g_return_if_fail (classification != NULL && *classification != '\0');
1347 g_return_if_fail (description != NULL && *description != '\0');
1348 g_return_if_fail (author != NULL && *author != '\0');
1350 g_value_init (&val, G_TYPE_STRING);
1352 g_value_set_static_string (&val, longname);
1353 gst_structure_id_set_value (s, GST_QUARK (ELEMENT_METADATA_LONGNAME), &val);
1355 g_value_set_static_string (&val, classification);
1356 gst_structure_id_set_value (s, GST_QUARK (ELEMENT_METADATA_KLASS), &val);
1358 g_value_set_static_string (&val, description);
1359 gst_structure_id_set_value (s, GST_QUARK (ELEMENT_METADATA_DESCRIPTION),
1362 g_value_set_static_string (&val, author);
1363 gst_structure_id_take_value (s, GST_QUARK (ELEMENT_METADATA_AUTHOR), &val);
1367 * gst_element_class_get_metadata:
1368 * @klass: class to get metadata for
1369 * @key: the key to get
1371 * Get metadata with @key in @klass.
1373 * Returns: the metadata for @key.
1376 gst_element_class_get_metadata (GstElementClass * klass, const gchar * key)
1378 g_return_val_if_fail (GST_IS_ELEMENT_CLASS (klass), NULL);
1379 g_return_val_if_fail (key != NULL, NULL);
1381 return gst_structure_get_string ((GstStructure *) klass->metadata, key);
1385 * gst_element_class_get_pad_template_list:
1386 * @element_class: a #GstElementClass to get pad templates of.
1388 * Retrieves a list of the pad templates associated with @element_class. The
1389 * list must not be modified by the calling code.
1390 * <note>If you use this function in the #GInstanceInitFunc of an object class
1391 * that has subclasses, make sure to pass the g_class parameter of the
1392 * #GInstanceInitFunc here.</note>
1394 * Returns: (transfer none) (element-type Gst.PadTemplate): the #GList of
1398 gst_element_class_get_pad_template_list (GstElementClass * element_class)
1400 g_return_val_if_fail (GST_IS_ELEMENT_CLASS (element_class), NULL);
1402 return element_class->padtemplates;
1406 * gst_element_class_get_pad_template:
1407 * @element_class: a #GstElementClass to get the pad template of.
1408 * @name: the name of the #GstPadTemplate to get.
1410 * Retrieves a padtemplate from @element_class with the given name.
1411 * <note>If you use this function in the #GInstanceInitFunc of an object class
1412 * that has subclasses, make sure to pass the g_class parameter of the
1413 * #GInstanceInitFunc here.</note>
1415 * Returns: (transfer none) (nullable): the #GstPadTemplate with the
1416 * given name, or %NULL if none was found. No unreferencing is
1420 gst_element_class_get_pad_template (GstElementClass *
1421 element_class, const gchar * name)
1425 g_return_val_if_fail (GST_IS_ELEMENT_CLASS (element_class), NULL);
1426 g_return_val_if_fail (name != NULL, NULL);
1428 padlist = element_class->padtemplates;
1431 GstPadTemplate *padtempl = (GstPadTemplate *) padlist->data;
1433 if (strcmp (padtempl->name_template, name) == 0)
1436 padlist = g_list_next (padlist);
1442 static GstPadTemplate *
1443 gst_element_class_get_request_pad_template (GstElementClass *
1444 element_class, const gchar * name)
1446 GstPadTemplate *tmpl;
1448 tmpl = gst_element_class_get_pad_template (element_class, name);
1449 if (tmpl != NULL && tmpl->presence == GST_PAD_REQUEST)
1455 /* get a random pad on element of the given direction.
1456 * The pad is random in a sense that it is the first pad that is (optionaly) linked.
1459 gst_element_get_random_pad (GstElement * element,
1460 gboolean need_linked, GstPadDirection dir)
1462 GstPad *result = NULL;
1465 GST_CAT_DEBUG (GST_CAT_ELEMENT_PADS, "getting a random pad");
1469 GST_OBJECT_LOCK (element);
1470 pads = element->srcpads;
1473 GST_OBJECT_LOCK (element);
1474 pads = element->sinkpads;
1477 goto wrong_direction;
1479 for (; pads; pads = g_list_next (pads)) {
1480 GstPad *pad = GST_PAD_CAST (pads->data);
1482 GST_OBJECT_LOCK (pad);
1483 GST_CAT_DEBUG (GST_CAT_ELEMENT_PADS, "checking pad %s:%s",
1484 GST_DEBUG_PAD_NAME (pad));
1486 if (need_linked && !GST_PAD_IS_LINKED (pad)) {
1487 /* if we require a linked pad, and it is not linked, continue the
1489 GST_CAT_DEBUG (GST_CAT_ELEMENT_PADS, "pad %s:%s is not linked",
1490 GST_DEBUG_PAD_NAME (pad));
1491 GST_OBJECT_UNLOCK (pad);
1494 /* found a pad, stop search */
1495 GST_CAT_DEBUG (GST_CAT_ELEMENT_PADS, "found pad %s:%s",
1496 GST_DEBUG_PAD_NAME (pad));
1497 GST_OBJECT_UNLOCK (pad);
1503 gst_object_ref (result);
1505 GST_OBJECT_UNLOCK (element);
1509 /* ERROR handling */
1512 g_warning ("unknown pad direction %d", dir);
1518 gst_element_default_send_event (GstElement * element, GstEvent * event)
1520 gboolean result = FALSE;
1523 pad = GST_EVENT_IS_DOWNSTREAM (event) ?
1524 gst_element_get_random_pad (element, TRUE, GST_PAD_SINK) :
1525 gst_element_get_random_pad (element, TRUE, GST_PAD_SRC);
1528 GST_CAT_DEBUG (GST_CAT_ELEMENT_PADS,
1529 "pushing %s event to random %s pad %s:%s",
1530 GST_EVENT_TYPE_NAME (event),
1531 (GST_PAD_DIRECTION (pad) == GST_PAD_SRC ? "src" : "sink"),
1532 GST_DEBUG_PAD_NAME (pad));
1534 result = gst_pad_send_event (pad, event);
1535 gst_object_unref (pad);
1537 GST_CAT_INFO (GST_CAT_ELEMENT_PADS, "can't send %s event on element %s",
1538 GST_EVENT_TYPE_NAME (event), GST_ELEMENT_NAME (element));
1539 gst_event_unref (event);
1545 * gst_element_send_event:
1546 * @element: a #GstElement to send the event to.
1547 * @event: (transfer full): the #GstEvent to send to the element.
1549 * Sends an event to an element. If the element doesn't implement an
1550 * event handler, the event will be pushed on a random linked sink pad for
1551 * downstream events or a random linked source pad for upstream events.
1553 * This function takes ownership of the provided event so you should
1554 * gst_event_ref() it if you want to reuse the event after this call.
1558 * Returns: %TRUE if the event was handled. Events that trigger a preroll (such
1559 * as flushing seeks and steps) will emit %GST_MESSAGE_ASYNC_DONE.
1562 gst_element_send_event (GstElement * element, GstEvent * event)
1564 GstElementClass *oclass;
1565 gboolean result = FALSE;
1567 g_return_val_if_fail (GST_IS_ELEMENT (element), FALSE);
1568 g_return_val_if_fail (event != NULL, FALSE);
1570 oclass = GST_ELEMENT_GET_CLASS (element);
1572 GST_STATE_LOCK (element);
1573 if (oclass->send_event) {
1574 GST_CAT_DEBUG (GST_CAT_ELEMENT_PADS, "send %s event on element %s",
1575 GST_EVENT_TYPE_NAME (event), GST_ELEMENT_NAME (element));
1576 result = oclass->send_event (element, event);
1578 GST_STATE_UNLOCK (element);
1585 * @element: a #GstElement to send the event to.
1586 * @rate: The new playback rate
1587 * @format: The format of the seek values
1588 * @flags: The optional seek flags.
1589 * @start_type: The type and flags for the new start position
1590 * @start: The value of the new start position
1591 * @stop_type: The type and flags for the new stop position
1592 * @stop: The value of the new stop position
1594 * Sends a seek event to an element. See gst_event_new_seek() for the details of
1595 * the parameters. The seek event is sent to the element using
1596 * gst_element_send_event().
1600 * Returns: %TRUE if the event was handled. Flushing seeks will trigger a
1601 * preroll, which will emit %GST_MESSAGE_ASYNC_DONE.
1604 gst_element_seek (GstElement * element, gdouble rate, GstFormat format,
1605 GstSeekFlags flags, GstSeekType start_type, gint64 start,
1606 GstSeekType stop_type, gint64 stop)
1611 g_return_val_if_fail (GST_IS_ELEMENT (element), FALSE);
1614 gst_event_new_seek (rate, format, flags, start_type, start, stop_type,
1616 result = gst_element_send_event (element, event);
1622 gst_element_default_query (GstElement * element, GstQuery * query)
1624 gboolean result = FALSE;
1627 pad = gst_element_get_random_pad (element, FALSE, GST_PAD_SRC);
1629 result = gst_pad_query (pad, query);
1631 gst_object_unref (pad);
1633 pad = gst_element_get_random_pad (element, TRUE, GST_PAD_SINK);
1635 GstPad *peer = gst_pad_get_peer (pad);
1638 result = gst_pad_query (peer, query);
1640 gst_object_unref (peer);
1642 gst_object_unref (pad);
1649 * gst_element_query:
1650 * @element: a #GstElement to perform the query on.
1651 * @query: (transfer none): the #GstQuery.
1653 * Performs a query on the given element.
1655 * For elements that don't implement a query handler, this function
1656 * forwards the query to a random srcpad or to the peer of a
1657 * random linked sinkpad of this element.
1659 * Please note that some queries might need a running pipeline to work.
1661 * Returns: %TRUE if the query could be performed.
1666 gst_element_query (GstElement * element, GstQuery * query)
1668 GstElementClass *klass;
1669 gboolean res = FALSE;
1671 g_return_val_if_fail (GST_IS_ELEMENT (element), FALSE);
1672 g_return_val_if_fail (query != NULL, FALSE);
1674 GST_TRACER_ELEMENT_QUERY_PRE (element, query);
1676 klass = GST_ELEMENT_GET_CLASS (element);
1678 GST_CAT_DEBUG (GST_CAT_ELEMENT_PADS, "send query on element %s",
1679 GST_ELEMENT_NAME (element));
1680 res = klass->query (element, query);
1683 GST_TRACER_ELEMENT_QUERY_POST (element, res);
1688 gst_element_post_message_default (GstElement * element, GstMessage * message)
1691 gboolean result = FALSE;
1693 g_return_val_if_fail (GST_IS_ELEMENT (element), FALSE);
1694 g_return_val_if_fail (message != NULL, FALSE);
1696 GST_OBJECT_LOCK (element);
1699 if (G_UNLIKELY (bus == NULL))
1702 gst_object_ref (bus);
1703 GST_OBJECT_UNLOCK (element);
1705 /* we release the element lock when posting the message so that any
1706 * (synchronous) message handlers can operate on the element */
1707 result = gst_bus_post (bus, message);
1708 gst_object_unref (bus);
1715 GST_CAT_DEBUG_OBJECT (GST_CAT_MESSAGE, element,
1716 "not posting message %p: no bus", message);
1717 GST_OBJECT_UNLOCK (element);
1718 gst_message_unref (message);
1724 * gst_element_post_message:
1725 * @element: a #GstElement posting the message
1726 * @message: (transfer full): a #GstMessage to post
1728 * Post a message on the element's #GstBus. This function takes ownership of the
1729 * message; if you want to access the message after this call, you should add an
1730 * additional reference before calling.
1732 * Returns: %TRUE if the message was successfully posted. The function returns
1733 * %FALSE if the element did not have a bus.
1738 gst_element_post_message (GstElement * element, GstMessage * message)
1740 GstElementClass *klass;
1741 gboolean res = FALSE;
1743 g_return_val_if_fail (GST_IS_ELEMENT (element), FALSE);
1744 g_return_val_if_fail (message != NULL, FALSE);
1746 GST_TRACER_ELEMENT_POST_MESSAGE_PRE (element, message);
1748 klass = GST_ELEMENT_GET_CLASS (element);
1749 if (klass->post_message)
1750 res = klass->post_message (element, message);
1752 GST_TRACER_ELEMENT_POST_MESSAGE_POST (element, res);
1757 * _gst_element_error_printf:
1758 * @format: (allow-none): the printf-like format to use, or %NULL
1760 * This function is only used internally by the gst_element_error() macro.
1762 * Returns: (transfer full) (nullable): a newly allocated string, or
1763 * %NULL if the format was %NULL or ""
1768 _gst_element_error_printf (const gchar * format, ...)
1779 va_start (args, format);
1781 len = __gst_vasprintf (&buffer, format, args);
1792 * gst_element_message_full:
1793 * @element: a #GstElement to send message from
1794 * @type: the #GstMessageType
1795 * @domain: the GStreamer GError domain this message belongs to
1796 * @code: the GError code belonging to the domain
1797 * @text: (allow-none) (transfer full): an allocated text string to be used
1798 * as a replacement for the default message connected to code,
1800 * @debug: (allow-none) (transfer full): an allocated debug message to be
1801 * used as a replacement for the default debugging information,
1803 * @file: the source code file where the error was generated
1804 * @function: the source code function where the error was generated
1805 * @line: the source code line where the error was generated
1807 * Post an error, warning or info message on the bus from inside an element.
1809 * @type must be of #GST_MESSAGE_ERROR, #GST_MESSAGE_WARNING or
1810 * #GST_MESSAGE_INFO.
1814 void gst_element_message_full
1815 (GstElement * element, GstMessageType type,
1816 GQuark domain, gint code, gchar * text,
1817 gchar * debug, const gchar * file, const gchar * function, gint line)
1819 GError *gerror = NULL;
1823 gboolean has_debug = TRUE;
1824 GstMessage *message = NULL;
1827 GST_CAT_DEBUG_OBJECT (GST_CAT_MESSAGE, element, "start");
1828 g_return_if_fail (GST_IS_ELEMENT (element));
1829 g_return_if_fail ((type == GST_MESSAGE_ERROR) ||
1830 (type == GST_MESSAGE_WARNING) || (type == GST_MESSAGE_INFO));
1832 /* check if we send the given text or the default error text */
1833 if ((text == NULL) || (text[0] == 0)) {
1834 /* text could have come from g_strdup_printf (""); */
1836 sent_text = gst_error_get_message (domain, code);
1840 /* construct a sent_debug with extra information from source */
1841 if ((debug == NULL) || (debug[0] == 0)) {
1842 /* debug could have come from g_strdup_printf (""); */
1846 name = gst_object_get_path_string (GST_OBJECT_CAST (element));
1848 sent_debug = g_strdup_printf ("%s(%d): %s (): %s:\n%s",
1849 file, line, function, name, debug);
1851 sent_debug = g_strdup_printf ("%s(%d): %s (): %s",
1852 file, line, function, name);
1856 /* create gerror and post message */
1857 GST_CAT_INFO_OBJECT (GST_CAT_ERROR_SYSTEM, element, "posting message: %s",
1859 gerror = g_error_new_literal (domain, code, sent_text);
1862 case GST_MESSAGE_ERROR:
1864 gst_message_new_error (GST_OBJECT_CAST (element), gerror, sent_debug);
1866 case GST_MESSAGE_WARNING:
1867 message = gst_message_new_warning (GST_OBJECT_CAST (element), gerror,
1870 case GST_MESSAGE_INFO:
1871 message = gst_message_new_info (GST_OBJECT_CAST (element), gerror,
1875 g_assert_not_reached ();
1878 gst_element_post_message (element, message);
1880 GST_CAT_INFO_OBJECT (GST_CAT_ERROR_SYSTEM, element, "posted %s message: %s",
1881 (type == GST_MESSAGE_ERROR ? "error" : "warning"), sent_text);
1884 g_error_free (gerror);
1885 g_free (sent_debug);
1890 * gst_element_is_locked_state:
1891 * @element: a #GstElement.
1893 * Checks if the state of an element is locked.
1894 * If the state of an element is locked, state changes of the parent don't
1895 * affect the element.
1896 * This way you can leave currently unused elements inside bins. Just lock their
1897 * state before changing the state from #GST_STATE_NULL.
1901 * Returns: %TRUE, if the element's state is locked.
1904 gst_element_is_locked_state (GstElement * element)
1908 g_return_val_if_fail (GST_IS_ELEMENT (element), FALSE);
1910 GST_OBJECT_LOCK (element);
1911 result = GST_ELEMENT_IS_LOCKED_STATE (element);
1912 GST_OBJECT_UNLOCK (element);
1918 * gst_element_set_locked_state:
1919 * @element: a #GstElement
1920 * @locked_state: %TRUE to lock the element's state
1922 * Locks the state of an element, so state changes of the parent don't affect
1923 * this element anymore.
1927 * Returns: %TRUE if the state was changed, %FALSE if bad parameters were given
1928 * or the elements state-locking needed no change.
1931 gst_element_set_locked_state (GstElement * element, gboolean locked_state)
1935 g_return_val_if_fail (GST_IS_ELEMENT (element), FALSE);
1937 GST_OBJECT_LOCK (element);
1938 old = GST_ELEMENT_IS_LOCKED_STATE (element);
1940 if (G_UNLIKELY (old == locked_state))
1944 GST_CAT_DEBUG (GST_CAT_STATES, "locking state of element %s",
1945 GST_ELEMENT_NAME (element));
1946 GST_OBJECT_FLAG_SET (element, GST_ELEMENT_FLAG_LOCKED_STATE);
1948 GST_CAT_DEBUG (GST_CAT_STATES, "unlocking state of element %s",
1949 GST_ELEMENT_NAME (element));
1950 GST_OBJECT_FLAG_UNSET (element, GST_ELEMENT_FLAG_LOCKED_STATE);
1952 GST_OBJECT_UNLOCK (element);
1958 GST_CAT_DEBUG (GST_CAT_STATES,
1959 "elements %s was already in locked state %d",
1960 GST_ELEMENT_NAME (element), old);
1961 GST_OBJECT_UNLOCK (element);
1968 * gst_element_sync_state_with_parent:
1969 * @element: a #GstElement.
1971 * Tries to change the state of the element to the same as its parent.
1972 * If this function returns %FALSE, the state of element is undefined.
1974 * Returns: %TRUE, if the element's state could be synced to the parent's state.
1979 gst_element_sync_state_with_parent (GstElement * element)
1983 GstStateChangeReturn ret;
1985 g_return_val_if_fail (GST_IS_ELEMENT (element), FALSE);
1987 if ((parent = GST_ELEMENT_CAST (gst_element_get_parent (element)))) {
1988 GstState parent_current, parent_pending;
1990 GST_OBJECT_LOCK (parent);
1991 parent_current = GST_STATE (parent);
1992 parent_pending = GST_STATE_PENDING (parent);
1993 GST_OBJECT_UNLOCK (parent);
1995 /* set to pending if there is one, else we set it to the current state of
1997 if (parent_pending != GST_STATE_VOID_PENDING)
1998 target = parent_pending;
2000 target = parent_current;
2002 GST_CAT_DEBUG_OBJECT (GST_CAT_STATES, element,
2003 "syncing state (%s) to parent %s %s (%s, %s)",
2004 gst_element_state_get_name (GST_STATE (element)),
2005 GST_ELEMENT_NAME (parent), gst_element_state_get_name (target),
2006 gst_element_state_get_name (parent_current),
2007 gst_element_state_get_name (parent_pending));
2009 ret = gst_element_set_state (element, target);
2010 if (ret == GST_STATE_CHANGE_FAILURE)
2013 gst_object_unref (parent);
2017 GST_CAT_DEBUG_OBJECT (GST_CAT_STATES, element, "element has no parent");
2024 GST_CAT_DEBUG_OBJECT (GST_CAT_STATES, element,
2025 "syncing state failed (%s)",
2026 gst_element_state_change_return_get_name (ret));
2027 gst_object_unref (parent);
2033 static GstStateChangeReturn
2034 gst_element_get_state_func (GstElement * element,
2035 GstState * state, GstState * pending, GstClockTime timeout)
2037 GstStateChangeReturn ret = GST_STATE_CHANGE_FAILURE;
2038 GstState old_pending;
2040 GST_CAT_DEBUG_OBJECT (GST_CAT_STATES, element, "getting state, timeout %"
2041 GST_TIME_FORMAT, GST_TIME_ARGS (timeout));
2043 GST_OBJECT_LOCK (element);
2044 ret = GST_STATE_RETURN (element);
2045 GST_CAT_DEBUG_OBJECT (GST_CAT_STATES, element, "RETURN is %s",
2046 gst_element_state_change_return_get_name (ret));
2048 /* we got an error, report immediately */
2049 if (ret == GST_STATE_CHANGE_FAILURE)
2052 /* we got no_preroll, report immediately */
2053 if (ret == GST_STATE_CHANGE_NO_PREROLL)
2056 /* no need to wait async if we are not async */
2057 if (ret != GST_STATE_CHANGE_ASYNC)
2060 old_pending = GST_STATE_PENDING (element);
2061 if (old_pending != GST_STATE_VOID_PENDING) {
2065 /* get cookie to detect state changes during waiting */
2066 cookie = element->state_cookie;
2068 GST_CAT_INFO_OBJECT (GST_CAT_STATES, element,
2069 "waiting for element to commit state");
2071 /* we have a pending state change, wait for it to complete */
2072 if (timeout != GST_CLOCK_TIME_NONE) {
2074 /* make timeout absolute */
2075 end_time = g_get_monotonic_time () + (timeout / 1000);
2076 signaled = GST_STATE_WAIT_UNTIL (element, end_time);
2078 GST_STATE_WAIT (element);
2083 GST_CAT_INFO_OBJECT (GST_CAT_STATES, element, "timed out");
2084 /* timeout triggered */
2085 ret = GST_STATE_CHANGE_ASYNC;
2087 if (cookie != element->state_cookie)
2090 /* could be success or failure */
2091 if (old_pending == GST_STATE (element)) {
2092 GST_CAT_DEBUG_OBJECT (GST_CAT_STATES, element, "got success");
2093 ret = GST_STATE_CHANGE_SUCCESS;
2095 GST_CAT_DEBUG_OBJECT (GST_CAT_STATES, element, "got failure");
2096 ret = GST_STATE_CHANGE_FAILURE;
2099 /* if nothing is pending anymore we can return SUCCESS */
2100 if (GST_STATE_PENDING (element) == GST_STATE_VOID_PENDING) {
2101 GST_CAT_LOG_OBJECT (GST_CAT_STATES, element, "nothing pending");
2102 ret = GST_STATE_CHANGE_SUCCESS;
2108 *state = GST_STATE (element);
2110 *pending = GST_STATE_PENDING (element);
2112 GST_CAT_DEBUG_OBJECT (GST_CAT_STATES, element,
2113 "state current: %s, pending: %s, result: %s",
2114 gst_element_state_get_name (GST_STATE (element)),
2115 gst_element_state_get_name (GST_STATE_PENDING (element)),
2116 gst_element_state_change_return_get_name (ret));
2117 GST_OBJECT_UNLOCK (element);
2124 *state = GST_STATE_VOID_PENDING;
2126 *pending = GST_STATE_VOID_PENDING;
2128 GST_CAT_INFO_OBJECT (GST_CAT_STATES, element, "interruped");
2130 GST_OBJECT_UNLOCK (element);
2132 return GST_STATE_CHANGE_FAILURE;
2137 * gst_element_get_state:
2138 * @element: a #GstElement to get the state of.
2139 * @state: (out) (allow-none): a pointer to #GstState to hold the state.
2141 * @pending: (out) (allow-none): a pointer to #GstState to hold the pending
2142 * state. Can be %NULL.
2143 * @timeout: a #GstClockTime to specify the timeout for an async
2144 * state change or %GST_CLOCK_TIME_NONE for infinite timeout.
2146 * Gets the state of the element.
2148 * For elements that performed an ASYNC state change, as reported by
2149 * gst_element_set_state(), this function will block up to the
2150 * specified timeout value for the state change to complete.
2151 * If the element completes the state change or goes into
2152 * an error, this function returns immediately with a return value of
2153 * %GST_STATE_CHANGE_SUCCESS or %GST_STATE_CHANGE_FAILURE respectively.
2155 * For elements that did not return %GST_STATE_CHANGE_ASYNC, this function
2156 * returns the current and pending state immediately.
2158 * This function returns %GST_STATE_CHANGE_NO_PREROLL if the element
2159 * successfully changed its state but is not able to provide data yet.
2160 * This mostly happens for live sources that only produce data in
2161 * %GST_STATE_PLAYING. While the state change return is equivalent to
2162 * %GST_STATE_CHANGE_SUCCESS, it is returned to the application to signal that
2163 * some sink elements might not be able to complete their state change because
2164 * an element is not producing data to complete the preroll. When setting the
2165 * element to playing, the preroll will complete and playback will start.
2167 * Returns: %GST_STATE_CHANGE_SUCCESS if the element has no more pending state
2168 * and the last state change succeeded, %GST_STATE_CHANGE_ASYNC if the
2169 * element is still performing a state change or
2170 * %GST_STATE_CHANGE_FAILURE if the last state change failed.
2174 GstStateChangeReturn
2175 gst_element_get_state (GstElement * element,
2176 GstState * state, GstState * pending, GstClockTime timeout)
2178 GstElementClass *oclass;
2179 GstStateChangeReturn result = GST_STATE_CHANGE_FAILURE;
2181 g_return_val_if_fail (GST_IS_ELEMENT (element), GST_STATE_CHANGE_FAILURE);
2183 oclass = GST_ELEMENT_GET_CLASS (element);
2185 if (oclass->get_state)
2186 result = (oclass->get_state) (element, state, pending, timeout);
2192 * gst_element_abort_state:
2193 * @element: a #GstElement to abort the state of.
2195 * Abort the state change of the element. This function is used
2196 * by elements that do asynchronous state changes and find out
2197 * something is wrong.
2199 * This function should be called with the STATE_LOCK held.
2204 gst_element_abort_state (GstElement * element)
2208 #ifndef GST_DISABLE_GST_DEBUG
2212 g_return_if_fail (GST_IS_ELEMENT (element));
2214 GST_OBJECT_LOCK (element);
2215 pending = GST_STATE_PENDING (element);
2217 if (pending == GST_STATE_VOID_PENDING ||
2218 GST_STATE_RETURN (element) == GST_STATE_CHANGE_FAILURE)
2219 goto nothing_aborted;
2221 #ifndef GST_DISABLE_GST_DEBUG
2222 old_state = GST_STATE (element);
2224 GST_CAT_INFO_OBJECT (GST_CAT_STATES, element,
2225 "aborting state from %s to %s", gst_element_state_get_name (old_state),
2226 gst_element_state_get_name (pending));
2230 GST_STATE_RETURN (element) = GST_STATE_CHANGE_FAILURE;
2232 GST_STATE_BROADCAST (element);
2233 GST_OBJECT_UNLOCK (element);
2239 GST_OBJECT_UNLOCK (element);
2244 /* Not static because GstBin has manual state handling too */
2246 _priv_gst_element_state_changed (GstElement * element, GstState oldstate,
2247 GstState newstate, GstState pending)
2249 GstElementClass *klass = GST_ELEMENT_GET_CLASS (element);
2250 GstMessage *message;
2252 GST_CAT_INFO_OBJECT (GST_CAT_STATES, element,
2253 "notifying about state-changed %s to %s (%s pending)",
2254 gst_element_state_get_name (oldstate),
2255 gst_element_state_get_name (newstate),
2256 gst_element_state_get_name (pending));
2258 if (klass->state_changed)
2259 klass->state_changed (element, oldstate, newstate, pending);
2261 message = gst_message_new_state_changed (GST_OBJECT_CAST (element),
2262 oldstate, newstate, pending);
2263 gst_element_post_message (element, message);
2267 * gst_element_continue_state:
2268 * @element: a #GstElement to continue the state change of.
2269 * @ret: The previous state return value
2271 * Commit the state change of the element and proceed to the next
2272 * pending state if any. This function is used
2273 * by elements that do asynchronous state changes.
2274 * The core will normally call this method automatically when an
2275 * element returned %GST_STATE_CHANGE_SUCCESS from the state change function.
2277 * If after calling this method the element still has not reached
2278 * the pending state, the next state change is performed.
2280 * This method is used internally and should normally not be called by plugins
2283 * Returns: The result of the commit state change.
2287 GstStateChangeReturn
2288 gst_element_continue_state (GstElement * element, GstStateChangeReturn ret)
2290 GstStateChangeReturn old_ret;
2291 GstState old_state, old_next;
2292 GstState current, next, pending;
2293 GstStateChange transition;
2295 GST_OBJECT_LOCK (element);
2296 old_ret = GST_STATE_RETURN (element);
2297 GST_STATE_RETURN (element) = ret;
2298 pending = GST_STATE_PENDING (element);
2300 /* check if there is something to commit */
2301 if (pending == GST_STATE_VOID_PENDING)
2302 goto nothing_pending;
2304 old_state = GST_STATE (element);
2305 /* this is the state we should go to next */
2306 old_next = GST_STATE_NEXT (element);
2307 /* update current state */
2308 current = GST_STATE (element) = old_next;
2310 /* see if we reached the final state */
2311 if (pending == current)
2314 next = GST_STATE_GET_NEXT (current, pending);
2315 transition = (GstStateChange) GST_STATE_TRANSITION (current, next);
2317 GST_STATE_NEXT (element) = next;
2319 GST_STATE_RETURN (element) = GST_STATE_CHANGE_ASYNC;
2320 GST_OBJECT_UNLOCK (element);
2322 GST_CAT_INFO_OBJECT (GST_CAT_STATES, element,
2323 "committing state from %s to %s, pending %s, next %s",
2324 gst_element_state_get_name (old_state),
2325 gst_element_state_get_name (old_next),
2326 gst_element_state_get_name (pending), gst_element_state_get_name (next));
2328 _priv_gst_element_state_changed (element, old_state, old_next, pending);
2330 GST_CAT_INFO_OBJECT (GST_CAT_STATES, element,
2331 "continue state change %s to %s, final %s",
2332 gst_element_state_get_name (current),
2333 gst_element_state_get_name (next), gst_element_state_get_name (pending));
2335 ret = gst_element_change_state (element, transition);
2341 GST_CAT_INFO_OBJECT (GST_CAT_STATES, element, "nothing pending");
2342 GST_OBJECT_UNLOCK (element);
2347 GST_STATE_PENDING (element) = GST_STATE_VOID_PENDING;
2348 GST_STATE_NEXT (element) = GST_STATE_VOID_PENDING;
2350 GST_CAT_INFO_OBJECT (GST_CAT_STATES, element,
2351 "completed state change to %s", gst_element_state_get_name (pending));
2352 GST_OBJECT_UNLOCK (element);
2354 /* don't post silly messages with the same state. This can happen
2355 * when an element state is changed to what it already was. For bins
2356 * this can be the result of a lost state, which we check with the
2357 * previous return value.
2358 * We do signal the cond though as a _get_state() might be blocking
2360 if (old_state != old_next || old_ret == GST_STATE_CHANGE_ASYNC)
2361 _priv_gst_element_state_changed (element, old_state, old_next,
2362 GST_STATE_VOID_PENDING);
2364 GST_STATE_BROADCAST (element);
2371 * gst_element_lost_state:
2372 * @element: a #GstElement the state is lost of
2374 * Brings the element to the lost state. The current state of the
2375 * element is copied to the pending state so that any call to
2376 * gst_element_get_state() will return %GST_STATE_CHANGE_ASYNC.
2378 * An ASYNC_START message is posted. If the element was PLAYING, it will
2379 * go to PAUSED. The element will be restored to its PLAYING state by
2380 * the parent pipeline when it prerolls again.
2382 * This is mostly used for elements that lost their preroll buffer
2383 * in the %GST_STATE_PAUSED or %GST_STATE_PLAYING state after a flush,
2384 * they will go to their pending state again when a new preroll buffer is
2385 * queued. This function can only be called when the element is currently
2386 * not in error or an async state change.
2388 * This function is used internally and should normally not be called from
2389 * plugins or applications.
2392 gst_element_lost_state (GstElement * element)
2394 GstState old_state, new_state;
2395 GstMessage *message;
2397 g_return_if_fail (GST_IS_ELEMENT (element));
2399 GST_OBJECT_LOCK (element);
2400 if (GST_STATE_RETURN (element) == GST_STATE_CHANGE_FAILURE)
2403 if (GST_STATE_PENDING (element) != GST_STATE_VOID_PENDING)
2404 goto only_async_start;
2406 old_state = GST_STATE (element);
2408 /* when we were PLAYING, the new state is PAUSED. We will also not
2409 * automatically go to PLAYING but let the parent bin(s) set us to PLAYING
2410 * when we preroll. */
2411 if (old_state > GST_STATE_PAUSED)
2412 new_state = GST_STATE_PAUSED;
2414 new_state = old_state;
2416 GST_CAT_DEBUG_OBJECT (GST_CAT_STATES, element,
2417 "lost state of %s to %s", gst_element_state_get_name (old_state),
2418 gst_element_state_get_name (new_state));
2420 GST_STATE (element) = new_state;
2421 GST_STATE_NEXT (element) = new_state;
2422 GST_STATE_PENDING (element) = new_state;
2423 GST_STATE_RETURN (element) = GST_STATE_CHANGE_ASYNC;
2424 GST_OBJECT_UNLOCK (element);
2426 _priv_gst_element_state_changed (element, new_state, new_state, new_state);
2428 message = gst_message_new_async_start (GST_OBJECT_CAST (element));
2429 gst_element_post_message (element, message);
2435 GST_OBJECT_UNLOCK (element);
2440 GST_OBJECT_UNLOCK (element);
2442 message = gst_message_new_async_start (GST_OBJECT_CAST (element));
2443 gst_element_post_message (element, message);
2449 * gst_element_set_state:
2450 * @element: a #GstElement to change state of.
2451 * @state: the element's new #GstState.
2453 * Sets the state of the element. This function will try to set the
2454 * requested state by going through all the intermediary states and calling
2455 * the class's state change function for each.
2457 * This function can return #GST_STATE_CHANGE_ASYNC, in which case the
2458 * element will perform the remainder of the state change asynchronously in
2460 * An application can use gst_element_get_state() to wait for the completion
2461 * of the state change or it can wait for a %GST_MESSAGE_ASYNC_DONE or
2462 * %GST_MESSAGE_STATE_CHANGED on the bus.
2464 * State changes to %GST_STATE_READY or %GST_STATE_NULL never return
2465 * #GST_STATE_CHANGE_ASYNC.
2467 * Returns: Result of the state change using #GstStateChangeReturn.
2471 GstStateChangeReturn
2472 gst_element_set_state (GstElement * element, GstState state)
2474 GstElementClass *oclass;
2475 GstStateChangeReturn result = GST_STATE_CHANGE_FAILURE;
2477 g_return_val_if_fail (GST_IS_ELEMENT (element), GST_STATE_CHANGE_FAILURE);
2479 oclass = GST_ELEMENT_GET_CLASS (element);
2481 if (oclass->set_state)
2482 result = (oclass->set_state) (element, state);
2488 * default set state function, calculates the next state based
2489 * on current state and calls the change_state function
2491 static GstStateChangeReturn
2492 gst_element_set_state_func (GstElement * element, GstState state)
2494 GstState current, next, old_pending;
2495 GstStateChangeReturn ret;
2496 GstStateChange transition;
2497 GstStateChangeReturn old_ret;
2499 g_return_val_if_fail (GST_IS_ELEMENT (element), GST_STATE_CHANGE_FAILURE);
2501 GST_CAT_DEBUG_OBJECT (GST_CAT_STATES, element, "set_state to %s",
2502 gst_element_state_get_name (state));
2504 /* state lock is taken to protect the set_state() and get_state()
2505 * procedures, it does not lock any variables. */
2506 GST_STATE_LOCK (element);
2508 /* now calculate how to get to the new state */
2509 GST_OBJECT_LOCK (element);
2510 old_ret = GST_STATE_RETURN (element);
2511 /* previous state change returned an error, remove all pending
2512 * and next states */
2513 if (old_ret == GST_STATE_CHANGE_FAILURE) {
2514 GST_STATE_NEXT (element) = GST_STATE_VOID_PENDING;
2515 GST_STATE_PENDING (element) = GST_STATE_VOID_PENDING;
2516 GST_STATE_RETURN (element) = GST_STATE_CHANGE_SUCCESS;
2519 current = GST_STATE (element);
2520 next = GST_STATE_NEXT (element);
2521 old_pending = GST_STATE_PENDING (element);
2523 /* this is the (new) state we should go to. TARGET is the last state we set on
2525 if (state != GST_STATE_TARGET (element)) {
2526 GST_CAT_DEBUG_OBJECT (GST_CAT_STATES, element,
2527 "setting target state to %s", gst_element_state_get_name (state));
2528 GST_STATE_TARGET (element) = state;
2529 /* increment state cookie so that we can track each state change. We only do
2530 * this if this is actually a new state change. */
2531 element->state_cookie++;
2533 GST_STATE_PENDING (element) = state;
2535 GST_CAT_DEBUG_OBJECT (GST_CAT_STATES, element,
2536 "current %s, old_pending %s, next %s, old return %s",
2537 gst_element_state_get_name (current),
2538 gst_element_state_get_name (old_pending),
2539 gst_element_state_get_name (next),
2540 gst_element_state_change_return_get_name (old_ret));
2542 /* if the element was busy doing a state change, we just update the
2543 * target state, it'll get to it async then. */
2544 if (old_pending != GST_STATE_VOID_PENDING) {
2545 /* upwards state change will happen ASYNC */
2546 if (old_pending <= state)
2548 /* element is going to this state already */
2549 else if (next == state)
2551 /* element was performing an ASYNC upward state change and
2552 * we request to go downward again. Start from the next pending
2554 else if (next > state
2555 && GST_STATE_RETURN (element) == GST_STATE_CHANGE_ASYNC) {
2559 next = GST_STATE_GET_NEXT (current, state);
2560 /* now we store the next state */
2561 GST_STATE_NEXT (element) = next;
2562 /* mark busy, we need to check that there is actually a state change
2563 * to be done else we could accidentally override SUCCESS/NO_PREROLL and
2564 * the default element change_state function has no way to know what the
2565 * old value was... could consider this a FIXME...*/
2566 if (current != next)
2567 GST_STATE_RETURN (element) = GST_STATE_CHANGE_ASYNC;
2569 transition = (GstStateChange) GST_STATE_TRANSITION (current, next);
2571 GST_CAT_DEBUG_OBJECT (GST_CAT_STATES, element,
2572 "%s: setting state from %s to %s",
2573 (next != state ? "intermediate" : "final"),
2574 gst_element_state_get_name (current), gst_element_state_get_name (next));
2576 /* now signal any waiters, they will error since the cookie was incremented */
2577 GST_STATE_BROADCAST (element);
2579 GST_OBJECT_UNLOCK (element);
2581 ret = gst_element_change_state (element, transition);
2583 GST_STATE_UNLOCK (element);
2585 GST_CAT_DEBUG_OBJECT (GST_CAT_STATES, element, "returned %s",
2586 gst_element_state_change_return_get_name (ret));
2592 GST_STATE_RETURN (element) = GST_STATE_CHANGE_ASYNC;
2593 GST_CAT_DEBUG_OBJECT (GST_CAT_STATES, element,
2594 "element was busy with async state change");
2595 GST_OBJECT_UNLOCK (element);
2597 GST_STATE_UNLOCK (element);
2599 return GST_STATE_CHANGE_ASYNC;
2604 * gst_element_change_state:
2605 * @element: a #GstElement
2606 * @transition: the requested transition
2608 * Perform @transition on @element.
2610 * This function must be called with STATE_LOCK held and is mainly used
2613 * Returns: the #GstStateChangeReturn of the state transition.
2615 GstStateChangeReturn
2616 gst_element_change_state (GstElement * element, GstStateChange transition)
2618 GstElementClass *oclass;
2619 GstStateChangeReturn ret = GST_STATE_CHANGE_SUCCESS;
2621 oclass = GST_ELEMENT_GET_CLASS (element);
2623 /* call the state change function so it can set the state */
2624 if (oclass->change_state)
2625 ret = (oclass->change_state) (element, transition);
2627 ret = GST_STATE_CHANGE_FAILURE;
2630 case GST_STATE_CHANGE_FAILURE:
2631 GST_CAT_INFO_OBJECT (GST_CAT_STATES, element,
2632 "have FAILURE change_state return");
2633 /* state change failure */
2634 gst_element_abort_state (element);
2636 case GST_STATE_CHANGE_ASYNC:
2640 GST_CAT_DEBUG_OBJECT (GST_CAT_STATES, element,
2641 "element will change state ASYNC");
2643 target = GST_STATE_TARGET (element);
2645 if (target > GST_STATE_READY)
2648 /* else we just continue the state change downwards */
2649 GST_CAT_INFO_OBJECT (GST_CAT_STATES, element,
2650 "forcing commit state %s <= %s",
2651 gst_element_state_get_name (target),
2652 gst_element_state_get_name (GST_STATE_READY));
2654 ret = gst_element_continue_state (element, GST_STATE_CHANGE_SUCCESS);
2657 case GST_STATE_CHANGE_SUCCESS:
2658 GST_CAT_DEBUG_OBJECT (GST_CAT_STATES, element,
2659 "element changed state SUCCESS");
2660 /* we can commit the state now which will proceeed to
2662 ret = gst_element_continue_state (element, ret);
2664 case GST_STATE_CHANGE_NO_PREROLL:
2665 GST_CAT_DEBUG_OBJECT (GST_CAT_STATES, element,
2666 "element changed state NO_PREROLL");
2667 /* we can commit the state now which will proceeed to
2669 ret = gst_element_continue_state (element, ret);
2672 goto invalid_return;
2675 GST_CAT_LOG_OBJECT (GST_CAT_STATES, element, "exit state change %d", ret);
2680 GST_CAT_LOG_OBJECT (GST_CAT_STATES, element, "exit async state change %d",
2688 GST_OBJECT_LOCK (element);
2689 /* somebody added a GST_STATE_ and forgot to do stuff here ! */
2690 g_critical ("%s: unknown return value %d from a state change function",
2691 GST_ELEMENT_NAME (element), ret);
2693 /* we are in error now */
2694 ret = GST_STATE_CHANGE_FAILURE;
2695 GST_STATE_RETURN (element) = ret;
2696 GST_OBJECT_UNLOCK (element);
2702 /* gst_iterator_fold functions for pads_activate
2703 * Stop the iterator if activating one pad failed, but only if that pad
2704 * has not been removed from the element. */
2706 activate_pads (const GValue * vpad, GValue * ret, gboolean * active)
2708 GstPad *pad = g_value_get_object (vpad);
2709 gboolean cont = TRUE;
2711 if (!gst_pad_set_active (pad, *active)) {
2712 if (GST_PAD_PARENT (pad) != NULL) {
2714 g_value_set_boolean (ret, FALSE);
2721 /* returns false on error or early cutout of the fold, true if all
2722 * pads in @iter were (de)activated successfully. */
2724 iterator_activate_fold_with_resync (GstIterator * iter,
2725 GstIteratorFoldFunction func, gpointer user_data)
2727 GstIteratorResult ires;
2730 /* no need to unset this later, it's just a boolean */
2731 g_value_init (&ret, G_TYPE_BOOLEAN);
2732 g_value_set_boolean (&ret, TRUE);
2735 ires = gst_iterator_fold (iter, func, &ret, user_data);
2737 case GST_ITERATOR_RESYNC:
2738 /* need to reset the result again */
2739 g_value_set_boolean (&ret, TRUE);
2740 gst_iterator_resync (iter);
2742 case GST_ITERATOR_DONE:
2743 /* all pads iterated, return collected value */
2746 /* iterator returned _ERROR or premature end with _OK,
2747 * mark an error and exit */
2748 g_value_set_boolean (&ret, FALSE);
2753 /* return collected value */
2754 return g_value_get_boolean (&ret);
2757 /* is called with STATE_LOCK
2759 * Pads are activated from source pads to sinkpads.
2762 gst_element_pads_activate (GstElement * element, gboolean active)
2767 GST_CAT_DEBUG_OBJECT (GST_CAT_ELEMENT_PADS, element,
2768 "%s pads", active ? "activate" : "deactivate");
2770 iter = gst_element_iterate_src_pads (element);
2772 iterator_activate_fold_with_resync (iter,
2773 (GstIteratorFoldFunction) activate_pads, &active);
2774 gst_iterator_free (iter);
2775 if (G_UNLIKELY (!res))
2778 iter = gst_element_iterate_sink_pads (element);
2780 iterator_activate_fold_with_resync (iter,
2781 (GstIteratorFoldFunction) activate_pads, &active);
2782 gst_iterator_free (iter);
2783 if (G_UNLIKELY (!res))
2786 GST_CAT_DEBUG_OBJECT (GST_CAT_ELEMENT_PADS, element,
2787 "pad %sactivation successful", active ? "" : "de");
2794 GST_CAT_DEBUG_OBJECT (GST_CAT_ELEMENT_PADS, element,
2795 "pad %sactivation failed", active ? "" : "de");
2800 GST_CAT_DEBUG_OBJECT (GST_CAT_ELEMENT_PADS, element,
2801 "sink pads_activate failed");
2806 /* is called with STATE_LOCK */
2807 static GstStateChangeReturn
2808 gst_element_change_state_func (GstElement * element, GstStateChange transition)
2810 GstState state, next;
2811 GstStateChangeReturn result = GST_STATE_CHANGE_SUCCESS;
2813 g_return_val_if_fail (GST_IS_ELEMENT (element), GST_STATE_CHANGE_FAILURE);
2815 state = (GstState) GST_STATE_TRANSITION_CURRENT (transition);
2816 next = GST_STATE_TRANSITION_NEXT (transition);
2818 /* if the element already is in the given state, we just return success */
2819 if (next == GST_STATE_VOID_PENDING || state == next)
2822 GST_CAT_LOG_OBJECT (GST_CAT_STATES, element,
2823 "default handler tries setting state from %s to %s (%04x)",
2824 gst_element_state_get_name (state),
2825 gst_element_state_get_name (next), transition);
2827 switch (transition) {
2828 case GST_STATE_CHANGE_NULL_TO_READY:
2830 case GST_STATE_CHANGE_READY_TO_PAUSED:
2831 if (!gst_element_pads_activate (element, TRUE)) {
2832 result = GST_STATE_CHANGE_FAILURE;
2835 case GST_STATE_CHANGE_PAUSED_TO_PLAYING:
2837 case GST_STATE_CHANGE_PLAYING_TO_PAUSED:
2839 case GST_STATE_CHANGE_PAUSED_TO_READY:
2840 case GST_STATE_CHANGE_READY_TO_NULL:{
2843 /* deactivate pads in both cases, since they are activated on
2844 ready->paused but the element might not have made it to paused */
2845 if (!gst_element_pads_activate (element, FALSE)) {
2846 result = GST_STATE_CHANGE_FAILURE;
2849 /* Remove all non-persistent contexts */
2850 GST_OBJECT_LOCK (element);
2851 for (l = element->contexts; l;) {
2852 GstContext *context = l->data;
2854 if (!gst_context_is_persistent (context)) {
2857 gst_context_unref (context);
2859 element->contexts = g_list_delete_link (element->contexts, l);
2865 GST_OBJECT_UNLOCK (element);
2869 /* this will catch real but unhandled state changes;
2870 * can only be caused by:
2871 * - a new state was added
2872 * - somehow the element was asked to jump across an intermediate state
2874 g_warning ("Unhandled state change from %s to %s",
2875 gst_element_state_get_name (state),
2876 gst_element_state_get_name (next));
2883 GST_OBJECT_LOCK (element);
2884 result = GST_STATE_RETURN (element);
2885 GST_CAT_DEBUG_OBJECT (GST_CAT_STATES, element,
2886 "element is already in the %s state",
2887 gst_element_state_get_name (state));
2888 GST_OBJECT_UNLOCK (element);
2895 * gst_element_get_factory:
2896 * @element: a #GstElement to request the element factory of.
2898 * Retrieves the factory that was used to create this element.
2900 * Returns: (transfer none): the #GstElementFactory used for creating this
2901 * element. no refcounting is needed.
2904 gst_element_get_factory (GstElement * element)
2906 g_return_val_if_fail (GST_IS_ELEMENT (element), NULL);
2908 return GST_ELEMENT_GET_CLASS (element)->elementfactory;
2912 gst_element_dispose (GObject * object)
2914 GstElement *element = GST_ELEMENT_CAST (object);
2917 GstElementClass *oclass;
2920 oclass = GST_ELEMENT_GET_CLASS (element);
2922 GST_CAT_INFO_OBJECT (GST_CAT_REFCOUNTING, element, "dispose");
2924 if (GST_STATE (element) != GST_STATE_NULL)
2927 /* start by releasing all request pads, this might also remove some dynamic
2929 walk = element->pads;
2931 GstPad *pad = GST_PAD_CAST (walk->data);
2935 if (oclass->release_pad && GST_PAD_PAD_TEMPLATE (pad) &&
2936 GST_PAD_TEMPLATE_PRESENCE (GST_PAD_PAD_TEMPLATE (pad))
2937 == GST_PAD_REQUEST) {
2938 GST_CAT_DEBUG_OBJECT (GST_CAT_ELEMENT_PADS, element,
2939 "removing request pad %s:%s", GST_DEBUG_PAD_NAME (pad));
2940 oclass->release_pad (element, pad);
2942 /* in case the release_pad function removed the next pad too */
2943 if (walk && g_list_position (element->pads, walk) == -1)
2944 walk = element->pads;
2947 /* remove the remaining pads */
2948 while (element->pads) {
2949 GstPad *pad = GST_PAD_CAST (element->pads->data);
2950 GST_CAT_DEBUG_OBJECT (GST_CAT_ELEMENT_PADS, element,
2951 "removing pad %s:%s", GST_DEBUG_PAD_NAME (pad));
2952 if (!gst_element_remove_pad (element, pad)) {
2953 /* only happens when someone unparented our pad.. */
2954 g_critical ("failed to remove pad %s:%s", GST_DEBUG_PAD_NAME (pad));
2959 GST_OBJECT_LOCK (element);
2960 clock_p = &element->clock;
2961 bus_p = &element->bus;
2962 gst_object_replace ((GstObject **) clock_p, NULL);
2963 gst_object_replace ((GstObject **) bus_p, NULL);
2964 g_list_free_full (element->contexts, (GDestroyNotify) gst_context_unref);
2965 GST_OBJECT_UNLOCK (element);
2967 GST_CAT_INFO_OBJECT (GST_CAT_REFCOUNTING, element, "parent class dispose");
2969 G_OBJECT_CLASS (parent_class)->dispose (object);
2978 is_locked = GST_ELEMENT_IS_LOCKED_STATE (element);
2980 ("\nTrying to dispose element %s, but it is in %s%s instead of the NULL"
2982 "You need to explicitly set elements to the NULL state before\n"
2983 "dropping the final reference, to allow them to clean up.\n"
2984 "This problem may also be caused by a refcounting bug in the\n"
2985 "application or some element.\n",
2986 GST_OBJECT_NAME (element),
2987 gst_element_state_get_name (GST_STATE (element)),
2988 is_locked ? " (locked)" : "");
2994 gst_element_finalize (GObject * object)
2996 GstElement *element = GST_ELEMENT_CAST (object);
2998 GST_CAT_INFO_OBJECT (GST_CAT_REFCOUNTING, element, "finalize");
3000 g_cond_clear (&element->state_cond);
3001 g_rec_mutex_clear (&element->state_lock);
3003 GST_CAT_INFO_OBJECT (GST_CAT_REFCOUNTING, element, "finalize parent");
3005 G_OBJECT_CLASS (parent_class)->finalize (object);
3009 gst_element_set_bus_func (GstElement * element, GstBus * bus)
3013 g_return_if_fail (GST_IS_ELEMENT (element));
3015 GST_CAT_DEBUG_OBJECT (GST_CAT_PARENTAGE, element, "setting bus to %p", bus);
3017 GST_OBJECT_LOCK (element);
3018 bus_p = &GST_ELEMENT_BUS (element);
3019 gst_object_replace ((GstObject **) bus_p, GST_OBJECT_CAST (bus));
3020 GST_OBJECT_UNLOCK (element);
3024 * gst_element_set_bus:
3025 * @element: a #GstElement to set the bus of.
3026 * @bus: (transfer none): the #GstBus to set.
3028 * Sets the bus of the element. Increases the refcount on the bus.
3029 * For internal use only, unless you're testing elements.
3034 gst_element_set_bus (GstElement * element, GstBus * bus)
3036 GstElementClass *oclass;
3038 g_return_if_fail (GST_IS_ELEMENT (element));
3040 oclass = GST_ELEMENT_GET_CLASS (element);
3042 if (oclass->set_bus)
3043 oclass->set_bus (element, bus);
3047 * gst_element_get_bus:
3048 * @element: a #GstElement to get the bus of.
3050 * Returns the bus of the element. Note that only a #GstPipeline will provide a
3051 * bus for the application.
3053 * Returns: (transfer full): the element's #GstBus. unref after usage.
3058 gst_element_get_bus (GstElement * element)
3060 GstBus *result = NULL;
3062 g_return_val_if_fail (GST_IS_ELEMENT (element), result);
3064 GST_OBJECT_LOCK (element);
3065 if ((result = GST_ELEMENT_BUS (element)))
3066 gst_object_ref (result);
3067 GST_OBJECT_UNLOCK (element);
3069 GST_CAT_DEBUG_OBJECT (GST_CAT_BUS, element, "got bus %" GST_PTR_FORMAT,
3076 gst_element_set_context_default (GstElement * element, GstContext * context)
3078 const gchar *context_type;
3081 GST_OBJECT_LOCK (element);
3082 context_type = gst_context_get_context_type (context);
3083 for (l = element->contexts; l; l = l->next) {
3084 GstContext *tmp = l->data;
3085 const gchar *tmp_type = gst_context_get_context_type (tmp);
3087 /* Always store newest context but never replace
3088 * a persistent one by a non-persistent one */
3089 if (strcmp (context_type, tmp_type) == 0 &&
3090 (gst_context_is_persistent (context) ||
3091 !gst_context_is_persistent (tmp))) {
3092 gst_context_replace ((GstContext **) & l->data, context);
3096 /* Not found? Add */
3099 g_list_prepend (element->contexts, gst_context_ref (context));
3101 GST_OBJECT_UNLOCK (element);
3105 * gst_element_set_context:
3106 * @element: a #GstElement to set the context of.
3107 * @context: (transfer none): the #GstContext to set.
3109 * Sets the context of the element. Increases the refcount of the context.
3114 gst_element_set_context (GstElement * element, GstContext * context)
3116 GstElementClass *oclass;
3118 g_return_if_fail (GST_IS_ELEMENT (element));
3120 oclass = GST_ELEMENT_GET_CLASS (element);
3122 GST_CAT_DEBUG_OBJECT (GST_CAT_CONTEXT, element,
3123 "set context %p %" GST_PTR_FORMAT, context,
3124 gst_context_get_structure (context));
3126 if (oclass->set_context)
3127 oclass->set_context (element, context);
3131 * gst_element_get_contexts:
3132 * @element: a #GstElement to set the context of.
3134 * Gets the contexts set on the element.
3138 * Returns: (element-type Gst.Context) (transfer full): List of #GstContext
3143 gst_element_get_contexts (GstElement * element)
3147 g_return_val_if_fail (GST_IS_ELEMENT (element), NULL);
3149 GST_OBJECT_LOCK (element);
3150 ret = g_list_copy_deep (element->contexts, (GCopyFunc) gst_context_ref, NULL);
3151 GST_OBJECT_UNLOCK (element);
3157 _match_context_type (GstContext * c1, const gchar * context_type)
3159 const gchar *c1_type;
3161 c1_type = gst_context_get_context_type (c1);
3163 return g_strcmp0 (c1_type, context_type);
3167 * gst_element_get_context_unlocked:
3168 * @element: a #GstElement to get the context of.
3169 * @context_type: a name of a context to retrieve
3171 * Gets the context with @context_type set on the element or NULL.
3173 * Returns: (transfer full): A #GstContext or NULL
3178 gst_element_get_context_unlocked (GstElement * element,
3179 const gchar * context_type)
3181 GstContext *ret = NULL;
3184 g_return_val_if_fail (GST_IS_ELEMENT (element), NULL);
3187 g_list_find_custom (element->contexts, context_type,
3188 (GCompareFunc) _match_context_type);
3189 if (node && node->data)
3190 ret = gst_context_ref (node->data);
3196 * gst_element_get_context:
3197 * @element: a #GstElement to get the context of.
3198 * @context_type: a name of a context to retrieve
3200 * Gets the context with @context_type set on the element or NULL.
3204 * Returns: (transfer full): A #GstContext or NULL
3209 gst_element_get_context (GstElement * element, const gchar * context_type)
3211 GstContext *ret = NULL;
3213 g_return_val_if_fail (GST_IS_ELEMENT (element), NULL);
3215 GST_OBJECT_LOCK (element);
3216 ret = gst_element_get_context_unlocked (element, context_type);
3217 GST_OBJECT_UNLOCK (element);