2 * Copyright (C) 1999,2000 Erik Walthinsen <omega@cse.ogi.edu>
3 * 2000 Wim Taymans <wtay@chello.be>
4 * 2003 Benjamin Otte <in7y118@public.uni-hamburg.de>
6 * gstelementfactory.c: GstElementFactory object, support routines
8 * This library is free software; you can redistribute it and/or
9 * modify it under the terms of the GNU Library General Public
10 * License as published by the Free Software Foundation; either
11 * version 2 of the License, or (at your option) any later version.
13 * This library is distributed in the hope that it will be useful,
14 * but WITHOUT ANY WARRANTY; without even the implied warranty of
15 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
16 * Library General Public License for more details.
18 * You should have received a copy of the GNU Library General Public
19 * License along with this library; if not, write to the
20 * Free Software Foundation, Inc., 59 Temple Place - Suite 330,
21 * Boston, MA 02111-1307, USA.
25 * SECTION:gstelementfactory
26 * @short_description: Create GstElements from a factory
27 * @see_also: #GstElement, #GstPlugin, #GstPluginFeature, #GstPadTemplate.
29 * #GstElementFactory is used to create instances of elements. A
30 * GstElementfactory can be added to a #GstPlugin as it is also a
33 * Use the gst_element_factory_find() and gst_element_factory_create()
34 * functions to create element instances or use gst_element_factory_make() as a
35 * convenient shortcut.
37 * The following code example shows you how to create a GstFileSrc element.
40 * <title>Using an element factory</title>
41 * <programlisting language="c">
42 * #include <gst/gst.h>
45 * GstElementFactory *srcfactory;
47 * gst_init (&argc, &argv);
49 * srcfactory = gst_element_factory_find ("filesrc");
50 * g_return_if_fail (srcfactory != NULL);
51 * src = gst_element_factory_create (srcfactory, "src");
52 * g_return_if_fail (src != NULL);
57 * Last reviewed on 2005-11-23 (0.9.5)
60 #include "gst_private.h"
62 #include "gstelement.h"
63 #include "gstelementmetadata.h"
66 #include "gstregistry.h"
69 #include "glib-compat-private.h"
71 GST_DEBUG_CATEGORY_STATIC (element_factory_debug);
72 #define GST_CAT_DEFAULT element_factory_debug
74 static void gst_element_factory_finalize (GObject * object);
75 static void gst_element_factory_cleanup (GstElementFactory * factory);
77 /* static guint gst_element_factory_signals[LAST_SIGNAL] = { 0 }; */
79 /* this is defined in gstelement.c */
80 extern GQuark _gst_elementclass_factory;
84 GST_DEBUG_CATEGORY_INIT (element_factory_debug, "GST_ELEMENT_FACTORY", \
85 GST_DEBUG_BOLD | GST_DEBUG_FG_WHITE | GST_DEBUG_BG_RED, \
86 "element factories keep information about installed elements"); \
89 G_DEFINE_TYPE_WITH_CODE (GstElementFactory, gst_element_factory,
90 GST_TYPE_PLUGIN_FEATURE, _do_init);
93 gst_element_factory_class_init (GstElementFactoryClass * klass)
95 GObjectClass *gobject_class = (GObjectClass *) klass;
97 gobject_class->finalize = gst_element_factory_finalize;
101 gst_element_factory_init (GstElementFactory * factory)
103 factory->staticpadtemplates = NULL;
104 factory->numpadtemplates = 0;
106 factory->uri_type = GST_URI_UNKNOWN;
107 factory->uri_protocols = NULL;
109 factory->interfaces = NULL;
113 gst_element_factory_finalize (GObject * object)
115 GstElementFactory *factory = GST_ELEMENT_FACTORY (object);
117 gst_element_factory_cleanup (factory);
118 G_OBJECT_CLASS (gst_element_factory_parent_class)->finalize (object);
122 * gst_element_factory_find:
123 * @name: name of factory to find
125 * Search for an element factory of the given name. Refs the returned
126 * element factory; caller is responsible for unreffing.
128 * Returns: (transfer full): #GstElementFactory if found, NULL otherwise
131 gst_element_factory_find (const gchar * name)
133 GstPluginFeature *feature;
135 g_return_val_if_fail (name != NULL, NULL);
137 feature = gst_registry_find_feature (gst_registry_get_default (), name,
138 GST_TYPE_ELEMENT_FACTORY);
140 return GST_ELEMENT_FACTORY (feature);
142 /* this isn't an error, for instance when you query if an element factory is
144 GST_LOG ("no such element factory \"%s\"", name);
149 gst_element_factory_cleanup (GstElementFactory * factory)
153 if (factory->metadata) {
154 gst_structure_free ((GstStructure *) factory->metadata);
155 factory->metadata = NULL;
158 factory->type = G_TYPE_INVALID;
161 for (item = factory->staticpadtemplates; item; item = item->next) {
162 GstStaticPadTemplate *templ = item->data;
163 GstCaps *caps = (GstCaps *) & (templ->static_caps);
165 /* FIXME: this is not threadsafe */
166 if (GST_CAPS_REFCOUNT_VALUE (caps) == 1) {
167 GstStructure *structure;
170 for (i = 0; i < caps->structs->len; i++) {
171 structure = (GstStructure *) gst_caps_get_structure (caps, i);
172 gst_structure_set_parent_refcount (structure, NULL);
173 gst_structure_free (structure);
175 g_ptr_array_free (caps->structs, TRUE);
176 GST_CAPS_REFCOUNT (caps) = 0;
178 g_slice_free (GstStaticPadTemplate, templ);
180 g_list_free (factory->staticpadtemplates);
181 factory->staticpadtemplates = NULL;
182 factory->numpadtemplates = 0;
183 factory->uri_type = GST_URI_UNKNOWN;
184 if (factory->uri_protocols) {
185 g_strfreev (factory->uri_protocols);
186 factory->uri_protocols = NULL;
189 g_list_free (factory->interfaces);
190 factory->interfaces = NULL;
194 * gst_element_register:
195 * @plugin: (allow-none): #GstPlugin to register the element with, or NULL for
196 * a static element (note that passing NULL only works in GStreamer 0.10.13
198 * @name: name of elements of this type
199 * @rank: rank of element (higher rank means more importance when autoplugging)
200 * @type: GType of element to register
202 * Create a new elementfactory capable of instantiating objects of the
203 * @type and add the factory to @plugin.
205 * Returns: TRUE, if the registering succeeded, FALSE on error
208 gst_element_register (GstPlugin * plugin, const gchar * name, guint rank,
211 GstPluginFeature *existing_feature;
212 GstRegistry *registry;
213 GstElementFactory *factory;
215 guint n_interfaces, i;
216 GstElementClass *klass;
219 g_return_val_if_fail (name != NULL, FALSE);
220 g_return_val_if_fail (g_type_is_a (type, GST_TYPE_ELEMENT), FALSE);
222 registry = gst_registry_get_default ();
224 /* check if feature already exists, if it exists there is no need to update it
225 * when the registry is getting updated, outdated plugins and all their
226 * features are removed and readded.
228 existing_feature = gst_registry_lookup_feature (registry, name);
229 if (existing_feature) {
230 GST_DEBUG_OBJECT (registry, "update existing feature %p (%s)",
231 existing_feature, name);
232 factory = GST_ELEMENT_FACTORY_CAST (existing_feature);
233 factory->type = type;
234 existing_feature->loaded = TRUE;
235 g_type_set_qdata (type, _gst_elementclass_factory, factory);
236 gst_object_unref (existing_feature);
241 GST_ELEMENT_FACTORY_CAST (g_object_newv (GST_TYPE_ELEMENT_FACTORY, 0,
243 gst_plugin_feature_set_name (GST_PLUGIN_FEATURE_CAST (factory), name);
244 GST_LOG_OBJECT (factory, "Created new elementfactory for type %s",
247 /* provide info needed during class structure setup */
248 g_type_set_qdata (type, _gst_elementclass_factory, factory);
249 klass = GST_ELEMENT_CLASS (g_type_class_ref (type));
252 if ((klass->details.longname == NULL) ||
253 (klass->details.klass == NULL) || (klass->details.author == NULL))
257 factory->type = type;
258 factory->metadata = gst_structure_copy ((GstStructure *) klass->metadata);
260 for (item = klass->padtemplates; item; item = item->next) {
261 GstPadTemplate *templ = item->data;
262 GstStaticPadTemplate *newt;
263 gchar *caps_string = gst_caps_to_string (templ->caps);
265 newt = g_slice_new (GstStaticPadTemplate);
266 newt->name_template = g_intern_string (templ->name_template);
267 newt->direction = templ->direction;
268 newt->presence = templ->presence;
269 newt->static_caps.caps.mini_object.refcount = 0;
270 newt->static_caps.string = g_intern_string (caps_string);
271 factory->staticpadtemplates =
272 g_list_append (factory->staticpadtemplates, newt);
274 g_free (caps_string);
276 factory->numpadtemplates = klass->numpadtemplates;
278 /* special stuff for URI handling */
279 if (g_type_is_a (type, GST_TYPE_URI_HANDLER)) {
280 GstURIHandlerInterface *iface = (GstURIHandlerInterface *)
281 g_type_interface_peek (klass, GST_TYPE_URI_HANDLER);
283 if (!iface || (!iface->get_type && !iface->get_type_full) ||
284 (!iface->get_protocols && !iface->get_protocols_full))
287 factory->uri_type = iface->get_type ();
288 else if (iface->get_type_full)
289 factory->uri_type = iface->get_type_full (factory->type);
290 if (!GST_URI_TYPE_IS_VALID (factory->uri_type))
292 if (iface->get_protocols)
293 factory->uri_protocols = g_strdupv (iface->get_protocols ());
294 else if (iface->get_protocols_full)
295 factory->uri_protocols = iface->get_protocols_full (factory->type);
296 if (!factory->uri_protocols)
300 interfaces = g_type_interfaces (type, &n_interfaces);
301 for (i = 0; i < n_interfaces; i++) {
302 __gst_element_factory_add_interface (factory, g_type_name (interfaces[i]));
306 if (plugin && plugin->desc.name) {
307 GST_PLUGIN_FEATURE_CAST (factory)->plugin_name = plugin->desc.name;
308 GST_PLUGIN_FEATURE_CAST (factory)->plugin = plugin;
309 g_object_add_weak_pointer ((GObject *) plugin,
310 (gpointer *) & GST_PLUGIN_FEATURE_CAST (factory)->plugin);
312 GST_PLUGIN_FEATURE_CAST (factory)->plugin_name = "NULL";
313 GST_PLUGIN_FEATURE_CAST (factory)->plugin = NULL;
315 gst_plugin_feature_set_rank (GST_PLUGIN_FEATURE_CAST (factory), rank);
316 GST_PLUGIN_FEATURE_CAST (factory)->loaded = TRUE;
318 gst_registry_add_feature (registry, GST_PLUGIN_FEATURE_CAST (factory));
325 GST_WARNING_OBJECT (factory, "error with uri handler!");
326 gst_element_factory_cleanup (factory);
333 GST_WARNING_OBJECT (factory,
334 "The GstElementDetails don't seem to have been set properly");
335 gst_element_factory_cleanup (factory);
342 * gst_element_factory_create:
343 * @factory: factory to instantiate
344 * @name: name of new element
346 * Create a new element of the type defined by the given elementfactory.
347 * It will be given the name supplied, since all elements require a name as
348 * their first argument.
350 * Returns: (transfer full): new #GstElement or NULL if the element couldn't
354 gst_element_factory_create (GstElementFactory * factory, const gchar * name)
357 GstElementClass *oclass;
358 GstElementFactory *newfactory;
360 g_return_val_if_fail (factory != NULL, NULL);
363 GST_ELEMENT_FACTORY (gst_plugin_feature_load (GST_PLUGIN_FEATURE
366 if (newfactory == NULL)
369 factory = newfactory;
372 GST_INFO ("creating element \"%s\" named \"%s\"",
373 GST_PLUGIN_FEATURE_NAME (factory), GST_STR_NULL (name));
375 GST_INFO ("creating element \"%s\"", GST_PLUGIN_FEATURE_NAME (factory));
377 if (factory->type == 0)
380 /* create an instance of the element, cast so we don't assert on NULL
381 * also set name as early as we can
385 GST_ELEMENT_CAST (g_object_new (factory->type, "name", name, NULL));
387 element = GST_ELEMENT_CAST (g_object_newv (factory->type, 0, NULL));
388 if (G_UNLIKELY (element == NULL))
391 /* fill in the pointer to the factory in the element class. The
392 * class will not be unreffed currently.
393 * Be thread safe as there might be 2 threads creating the first instance of
394 * an element at the same moment
396 oclass = GST_ELEMENT_GET_CLASS (element);
397 if (!g_atomic_pointer_compare_and_exchange (
398 (gpointer) & oclass->elementfactory, NULL, factory))
399 gst_object_unref (factory);
401 GST_DEBUG ("created element \"%s\"", GST_PLUGIN_FEATURE_NAME (factory));
408 GST_WARNING_OBJECT (factory,
409 "loading plugin containing feature %s returned NULL!", name);
414 GST_WARNING_OBJECT (factory, "factory has no type");
415 gst_object_unref (factory);
420 GST_WARNING_OBJECT (factory, "could not create element");
421 gst_object_unref (factory);
427 * gst_element_factory_make:
428 * @factoryname: a named factory to instantiate
429 * @name: (allow-none): name of new element
431 * Create a new element of the type defined by the given element factory.
432 * If name is NULL, then the element will receive a guaranteed unique name,
433 * consisting of the element factory name and a number.
434 * If name is given, it will be given the name supplied.
436 * Returns: (transfer full): new #GstElement or NULL if unable to create element
439 gst_element_factory_make (const gchar * factoryname, const gchar * name)
441 GstElementFactory *factory;
444 g_return_val_if_fail (factoryname != NULL, NULL);
445 g_return_val_if_fail (gst_is_initialized (), NULL);
447 GST_LOG ("gstelementfactory: make \"%s\" \"%s\"",
448 factoryname, GST_STR_NULL (name));
450 factory = gst_element_factory_find (factoryname);
454 GST_LOG_OBJECT (factory, "found factory %p", factory);
455 element = gst_element_factory_create (factory, name);
459 gst_object_unref (factory);
465 GST_INFO ("no such element factory \"%s\"!", factoryname);
470 GST_INFO_OBJECT (factory, "couldn't create instance!");
471 gst_object_unref (factory);
477 __gst_element_factory_add_static_pad_template (GstElementFactory * factory,
478 GstStaticPadTemplate * templ)
480 g_return_if_fail (factory != NULL);
481 g_return_if_fail (templ != NULL);
483 factory->staticpadtemplates =
484 g_list_append (factory->staticpadtemplates, templ);
485 factory->numpadtemplates++;
489 * gst_element_factory_get_element_type:
490 * @factory: factory to get managed #GType from
492 * Get the #GType for elements managed by this factory. The type can
493 * only be retrieved if the element factory is loaded, which can be
494 * assured with gst_plugin_feature_load().
496 * Returns: the #GType for elements managed by this factory or 0 if
497 * the factory is not loaded.
500 gst_element_factory_get_element_type (GstElementFactory * factory)
502 g_return_val_if_fail (GST_IS_ELEMENT_FACTORY (factory), 0);
504 return factory->type;
507 G_CONST_RETURN gchar *
508 gst_element_factory_get_metadata (GstElementFactory * factory,
511 return gst_structure_get_string ((GstStructure *) factory->metadata, key);
515 * gst_element_factory_get_num_pad_templates:
516 * @factory: a #GstElementFactory
518 * Gets the number of pad_templates in this factory.
520 * Returns: the number of pad_templates
523 gst_element_factory_get_num_pad_templates (GstElementFactory * factory)
525 g_return_val_if_fail (GST_IS_ELEMENT_FACTORY (factory), 0);
527 return factory->numpadtemplates;
531 * __gst_element_factory_add_interface:
532 * @elementfactory: The elementfactory to add the interface to
533 * @interfacename: Name of the interface
535 * Adds the given interfacename to the list of implemented interfaces of the
539 __gst_element_factory_add_interface (GstElementFactory * elementfactory,
540 const gchar * interfacename)
542 g_return_if_fail (GST_IS_ELEMENT_FACTORY (elementfactory));
543 g_return_if_fail (interfacename != NULL);
544 g_return_if_fail (interfacename[0] != '\0'); /* no empty string */
546 elementfactory->interfaces =
547 g_list_prepend (elementfactory->interfaces,
548 (gpointer) g_intern_string (interfacename));
552 * gst_element_factory_get_static_pad_templates:
553 * @factory: a #GstElementFactory
555 * Gets the #GList of #GstStaticPadTemplate for this factory.
557 * Returns: (transfer none) (element-type Gst.StaticPadTemplate): the
558 * static pad templates
560 G_CONST_RETURN GList *
561 gst_element_factory_get_static_pad_templates (GstElementFactory * factory)
563 g_return_val_if_fail (GST_IS_ELEMENT_FACTORY (factory), NULL);
565 return factory->staticpadtemplates;
569 * gst_element_factory_get_uri_type:
570 * @factory: a #GstElementFactory
572 * Gets the type of URIs the element supports or #GST_URI_UNKNOWN if none.
574 * Returns: type of URIs this element supports
577 gst_element_factory_get_uri_type (GstElementFactory * factory)
579 g_return_val_if_fail (GST_IS_ELEMENT_FACTORY (factory), GST_URI_UNKNOWN);
581 return factory->uri_type;
585 * gst_element_factory_get_uri_protocols:
586 * @factory: a #GstElementFactory
588 * Gets a NULL-terminated array of protocols this element supports or NULL if
589 * no protocols are supported. You may not change the contents of the returned
590 * array, as it is still owned by the element factory. Use g_strdupv() to
591 * make a copy of the protocol string array if you need to.
593 * Returns: (transfer none) (array zero-terminated=1): the supported protocols
597 gst_element_factory_get_uri_protocols (GstElementFactory * factory)
599 g_return_val_if_fail (GST_IS_ELEMENT_FACTORY (factory), NULL);
601 return factory->uri_protocols;
605 * gst_element_factory_has_interface:
606 * @factory: a #GstElementFactory
607 * @interfacename: an interface name
609 * Check if @factory implements the interface with name @interfacename.
611 * Returns: #TRUE when @factory implement the interface.
616 gst_element_factory_has_interface (GstElementFactory * factory,
617 const gchar * interfacename)
621 g_return_val_if_fail (GST_IS_ELEMENT_FACTORY (factory), FALSE);
623 for (walk = factory->interfaces; walk; walk = g_list_next (walk)) {
624 gchar *iname = (gchar *) walk->data;
626 if (!strcmp (iname, interfacename))
635 GstElementFactoryListType type;
641 * gst_element_factory_list_is_type:
642 * @factory: a #GstElementFactory
643 * @type: a #GstElementFactoryListType
645 * Check if @factory if of the given types.
647 * Returns: %TRUE if @factory is of @type.
652 gst_element_factory_list_is_type (GstElementFactory * factory,
653 GstElementFactoryListType type)
655 gboolean res = FALSE;
659 gst_element_factory_get_metadata (factory, GST_ELEMENT_METADATA_KLASS);
661 /* Filter by element type first, as soon as it matches
662 * one type, we skip all other tests */
663 if (!res && (type & GST_ELEMENT_FACTORY_TYPE_SINK))
664 res = (strstr (klass, "Sink") != NULL);
666 if (!res && (type & GST_ELEMENT_FACTORY_TYPE_SRC))
667 res = (strstr (klass, "Source") != NULL);
669 if (!res && (type & GST_ELEMENT_FACTORY_TYPE_DECODER))
670 res = (strstr (klass, "Decoder") != NULL);
672 if (!res && (type & GST_ELEMENT_FACTORY_TYPE_ENCODER))
673 res = (strstr (klass, "Encoder") != NULL);
675 if (!res && (type & GST_ELEMENT_FACTORY_TYPE_MUXER))
676 res = (strstr (klass, "Muxer") != NULL);
678 if (!res && (type & GST_ELEMENT_FACTORY_TYPE_DEMUXER))
679 res = (strstr (klass, "Demux") != NULL);
681 /* FIXME : We're actually parsing two Classes here... */
682 if (!res && (type & GST_ELEMENT_FACTORY_TYPE_PARSER))
683 res = ((strstr (klass, "Parser") != NULL)
684 && (strstr (klass, "Codec") != NULL));
686 if (!res && (type & GST_ELEMENT_FACTORY_TYPE_DEPAYLOADER))
687 res = (strstr (klass, "Depayloader") != NULL);
689 if (!res && (type & GST_ELEMENT_FACTORY_TYPE_PAYLOADER))
690 res = (strstr (klass, "Payloader") != NULL);
692 if (!res && (type & GST_ELEMENT_FACTORY_TYPE_FORMATTER))
693 res = (strstr (klass, "Formatter") != NULL);
695 /* Filter by media type now, we only test if it
696 * matched any of the types above. */
698 && (type & (GST_ELEMENT_FACTORY_TYPE_MEDIA_AUDIO |
699 GST_ELEMENT_FACTORY_TYPE_MEDIA_VIDEO |
700 GST_ELEMENT_FACTORY_TYPE_MEDIA_IMAGE)))
701 res = ((type & GST_ELEMENT_FACTORY_TYPE_MEDIA_AUDIO)
702 && (strstr (klass, "Audio") != NULL))
703 || ((type & GST_ELEMENT_FACTORY_TYPE_MEDIA_VIDEO)
704 && (strstr (klass, "Video") != NULL))
705 || ((type & GST_ELEMENT_FACTORY_TYPE_MEDIA_IMAGE)
706 && (strstr (klass, "Image") != NULL));
712 element_filter (GstPluginFeature * feature, FilterData * data)
716 /* we only care about element factories */
717 if (G_UNLIKELY (!GST_IS_ELEMENT_FACTORY (feature)))
720 res = (gst_plugin_feature_get_rank (feature) >= data->minrank) &&
721 gst_element_factory_list_is_type (GST_ELEMENT_FACTORY_CAST (feature),
728 * gst_element_factory_list_get_elements:
729 * @type: a #GstElementFactoryListType
730 * @minrank: Minimum rank
732 * Get a list of factories that match the given @type. Only elements
733 * with a rank greater or equal to @minrank will be returned.
734 * The list of factories is returned by decreasing rank.
736 * Returns: (transfer full) (element-type Gst.ElementFactory): a #GList of
737 * #GstElementFactory elements. Use gst_plugin_feature_list_free() after
743 gst_element_factory_list_get_elements (GstElementFactoryListType type,
751 data.minrank = minrank;
753 /* get the feature list using the filter */
754 result = gst_default_registry_feature_filter ((GstPluginFeatureFilter)
755 element_filter, FALSE, &data);
757 /* sort on rank and name */
758 result = g_list_sort (result, gst_plugin_feature_rank_compare_func);
764 * gst_element_factory_list_filter:
765 * @list: (transfer none) (element-type Gst.ElementFactory): a #GList of
766 * #GstElementFactory to filter
768 * @direction: a #GstPadDirection to filter on
769 * @subsetonly: whether to filter on caps subsets or not.
771 * Filter out all the elementfactories in @list that can handle @caps in
772 * the given direction.
774 * If @subsetonly is %TRUE, then only the elements whose pads templates
775 * are a complete superset of @caps will be returned. Else any element
776 * whose pad templates caps can intersect with @caps will be returned.
778 * Returns: (transfer full) (element-type Gst.ElementFactory): a #GList of
779 * #GstElementFactory elements that match the given requisits.
780 * Use #gst_plugin_feature_list_free after usage.
785 gst_element_factory_list_filter (GList * list,
786 const GstCaps * caps, GstPadDirection direction, gboolean subsetonly)
788 GList *result = NULL;
790 GST_DEBUG ("finding factories");
792 /* loop over all the factories */
793 for (; list; list = list->next) {
794 GstElementFactory *factory;
795 const GList *templates;
798 factory = (GstElementFactory *) list->data;
800 GST_DEBUG ("Trying %s",
801 gst_plugin_feature_get_name ((GstPluginFeature *) factory));
803 /* get the templates from the element factory */
804 templates = gst_element_factory_get_static_pad_templates (factory);
805 for (walk = (GList *) templates; walk; walk = g_list_next (walk)) {
806 GstStaticPadTemplate *templ = walk->data;
808 /* we only care about the sink templates */
809 if (templ->direction == direction) {
812 /* try to intersect the caps with the caps of the template */
813 tmpl_caps = gst_static_caps_get (&templ->static_caps);
815 /* FIXME, intersect is not the right method, we ideally want to check
816 * for a subset here */
818 /* check if the intersection is empty */
819 if ((subsetonly && gst_caps_is_subset (caps, tmpl_caps)) ||
820 (!subsetonly && gst_caps_can_intersect (caps, tmpl_caps))) {
821 /* non empty intersection, we can use this element */
822 result = g_list_prepend (result, gst_object_ref (factory));
823 gst_caps_unref (tmpl_caps);
826 gst_caps_unref (tmpl_caps);
830 return g_list_reverse (result);