gstreamer/gst/gstelementfactory.c

864 lines
26 KiB
C

/* GStreamer
* Copyright (C) 1999,2000 Erik Walthinsen <omega@cse.ogi.edu>
* 2000 Wim Taymans <wtay@chello.be>
* 2003 Benjamin Otte <in7y118@public.uni-hamburg.de>
*
* gstelementfactory.c: GstElementFactory object, support routines
*
* This library is free software; you can redistribute it and/or
* modify it under the terms of the GNU Library General Public
* License as published by the Free Software Foundation; either
* version 2 of the License, or (at your option) any later version.
*
* This library is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* Library General Public License for more details.
*
* You should have received a copy of the GNU Library General Public
* License along with this library; if not, write to the
* Free Software Foundation, Inc., 59 Temple Place - Suite 330,
* Boston, MA 02111-1307, USA.
*/
/**
* SECTION:gstelementfactory
* @short_description: Create GstElements from a factory
* @see_also: #GstElement, #GstPlugin, #GstPluginFeature, #GstPadTemplate.
*
* #GstElementFactory is used to create instances of elements. A
* GstElementfactory can be added to a #GstPlugin as it is also a
* #GstPluginFeature.
*
* Use the gst_element_factory_find() and gst_element_factory_create()
* functions to create element instances or use gst_element_factory_make() as a
* convenient shortcut.
*
* The following code example shows you how to create a GstFileSrc element.
*
* <example>
* <title>Using an element factory</title>
* <programlisting language="c">
* #include &lt;gst/gst.h&gt;
*
* GstElement *src;
* GstElementFactory *srcfactory;
*
* gst_init (&amp;argc, &amp;argv);
*
* srcfactory = gst_element_factory_find ("filesrc");
* g_return_if_fail (srcfactory != NULL);
* src = gst_element_factory_create (srcfactory, "src");
* g_return_if_fail (src != NULL);
* ...
* </programlisting>
* </example>
*
* Last reviewed on 2005-11-23 (0.9.5)
*/
#include "gst_private.h"
#include "gstelement.h"
#include "gstelementmetadata.h"
#include "gstinfo.h"
#include "gsturi.h"
#include "gstregistry.h"
#include "gst.h"
#include "glib-compat-private.h"
GST_DEBUG_CATEGORY_STATIC (element_factory_debug);
#define GST_CAT_DEFAULT element_factory_debug
static void gst_element_factory_finalize (GObject * object);
static void gst_element_factory_cleanup (GstElementFactory * factory);
/* static guint gst_element_factory_signals[LAST_SIGNAL] = { 0 }; */
/* this is defined in gstelement.c */
extern GQuark __gst_elementclass_factory;
#define _do_init \
{ \
GST_DEBUG_CATEGORY_INIT (element_factory_debug, "GST_ELEMENT_FACTORY", \
GST_DEBUG_BOLD | GST_DEBUG_FG_WHITE | GST_DEBUG_BG_RED, \
"element factories keep information about installed elements"); \
}
G_DEFINE_TYPE_WITH_CODE (GstElementFactory, gst_element_factory,
GST_TYPE_PLUGIN_FEATURE, _do_init);
static void
gst_element_factory_class_init (GstElementFactoryClass * klass)
{
GObjectClass *gobject_class = (GObjectClass *) klass;
gobject_class->finalize = gst_element_factory_finalize;
}
static void
gst_element_factory_init (GstElementFactory * factory)
{
factory->staticpadtemplates = NULL;
factory->numpadtemplates = 0;
factory->uri_type = GST_URI_UNKNOWN;
factory->uri_protocols = NULL;
factory->interfaces = NULL;
}
static void
gst_element_factory_finalize (GObject * object)
{
GstElementFactory *factory = GST_ELEMENT_FACTORY (object);
gst_element_factory_cleanup (factory);
G_OBJECT_CLASS (gst_element_factory_parent_class)->finalize (object);
}
/**
* gst_element_factory_find:
* @name: name of factory to find
*
* Search for an element factory of the given name. Refs the returned
* element factory; caller is responsible for unreffing.
*
* Returns: (transfer full): #GstElementFactory if found, NULL otherwise
*/
GstElementFactory *
gst_element_factory_find (const gchar * name)
{
GstPluginFeature *feature;
g_return_val_if_fail (name != NULL, NULL);
feature = gst_registry_find_feature (gst_registry_get (), name,
GST_TYPE_ELEMENT_FACTORY);
if (feature)
return GST_ELEMENT_FACTORY (feature);
/* this isn't an error, for instance when you query if an element factory is
* present */
GST_LOG ("no such element factory \"%s\"", name);
return NULL;
}
static void
gst_element_factory_cleanup (GstElementFactory * factory)
{
GList *item;
if (factory->metadata) {
gst_structure_free ((GstStructure *) factory->metadata);
factory->metadata = NULL;
}
if (factory->type) {
factory->type = G_TYPE_INVALID;
}
for (item = factory->staticpadtemplates; item; item = item->next) {
GstStaticPadTemplate *templ = item->data;
gst_static_caps_cleanup (&templ->static_caps);
g_slice_free (GstStaticPadTemplate, templ);
}
g_list_free (factory->staticpadtemplates);
factory->staticpadtemplates = NULL;
factory->numpadtemplates = 0;
factory->uri_type = GST_URI_UNKNOWN;
if (factory->uri_protocols) {
g_strfreev (factory->uri_protocols);
factory->uri_protocols = NULL;
}
g_list_free (factory->interfaces);
factory->interfaces = NULL;
}
#define CHECK_METADATA_FIELD(klass, name, key) \
G_STMT_START { \
const gchar *metafield = gst_element_class_get_metadata (klass, key); \
if (G_UNLIKELY (metafield == NULL || *metafield == '\0')) { \
g_warning ("Element factory metadata for '%s' has no valid %s field", name, key); \
goto detailserror; \
} \
} G_STMT_END;
/**
* gst_element_register:
* @plugin: (allow-none): #GstPlugin to register the element with, or NULL for
* a static element.
* @name: name of elements of this type
* @rank: rank of element (higher rank means more importance when autoplugging)
* @type: GType of element to register
*
* Create a new elementfactory capable of instantiating objects of the
* @type and add the factory to @plugin.
*
* Returns: TRUE, if the registering succeeded, FALSE on error
*/
gboolean
gst_element_register (GstPlugin * plugin, const gchar * name, guint rank,
GType type)
{
GstPluginFeature *existing_feature;
GstRegistry *registry;
GstElementFactory *factory;
GType *interfaces;
guint n_interfaces, i;
GstElementClass *klass;
GList *item;
g_return_val_if_fail (name != NULL, FALSE);
g_return_val_if_fail (g_type_is_a (type, GST_TYPE_ELEMENT), FALSE);
registry = gst_registry_get ();
/* check if feature already exists, if it exists there is no need to update it
* when the registry is getting updated, outdated plugins and all their
* features are removed and readded.
*/
existing_feature = gst_registry_lookup_feature (registry, name);
if (existing_feature) {
GST_DEBUG_OBJECT (registry, "update existing feature %p (%s)",
existing_feature, name);
factory = GST_ELEMENT_FACTORY_CAST (existing_feature);
factory->type = type;
existing_feature->loaded = TRUE;
g_type_set_qdata (type, __gst_elementclass_factory, factory);
gst_object_unref (existing_feature);
return TRUE;
}
factory =
GST_ELEMENT_FACTORY_CAST (g_object_newv (GST_TYPE_ELEMENT_FACTORY, 0,
NULL));
gst_plugin_feature_set_name (GST_PLUGIN_FEATURE_CAST (factory), name);
GST_LOG_OBJECT (factory, "Created new elementfactory for type %s",
g_type_name (type));
/* provide info needed during class structure setup */
g_type_set_qdata (type, __gst_elementclass_factory, factory);
klass = GST_ELEMENT_CLASS (g_type_class_ref (type));
CHECK_METADATA_FIELD (klass, name, GST_ELEMENT_METADATA_LONGNAME);
CHECK_METADATA_FIELD (klass, name, GST_ELEMENT_METADATA_KLASS);
CHECK_METADATA_FIELD (klass, name, GST_ELEMENT_METADATA_DESCRIPTION);
CHECK_METADATA_FIELD (klass, name, GST_ELEMENT_METADATA_AUTHOR);
factory->type = type;
factory->metadata = gst_structure_copy ((GstStructure *) klass->metadata);
for (item = klass->padtemplates; item; item = item->next) {
GstPadTemplate *templ = item->data;
GstStaticPadTemplate *newt;
gchar *caps_string = gst_caps_to_string (templ->caps);
newt = g_slice_new (GstStaticPadTemplate);
newt->name_template = g_intern_string (templ->name_template);
newt->direction = templ->direction;
newt->presence = templ->presence;
newt->static_caps.caps = NULL;
newt->static_caps.string = g_intern_string (caps_string);
factory->staticpadtemplates =
g_list_append (factory->staticpadtemplates, newt);
g_free (caps_string);
}
factory->numpadtemplates = klass->numpadtemplates;
/* special stuff for URI handling */
if (g_type_is_a (type, GST_TYPE_URI_HANDLER)) {
GstURIHandlerInterface *iface = (GstURIHandlerInterface *)
g_type_interface_peek (klass, GST_TYPE_URI_HANDLER);
if (!iface || !iface->get_type || !iface->get_protocols)
goto urierror;
if (iface->get_type)
factory->uri_type = iface->get_type (factory->type);
if (!GST_URI_TYPE_IS_VALID (factory->uri_type))
goto urierror;
if (iface->get_protocols) {
const gchar *const *protocols;
protocols = iface->get_protocols (factory->type);
factory->uri_protocols = g_strdupv ((gchar **) protocols);
}
if (!factory->uri_protocols)
goto urierror;
}
interfaces = g_type_interfaces (type, &n_interfaces);
for (i = 0; i < n_interfaces; i++) {
__gst_element_factory_add_interface (factory, g_type_name (interfaces[i]));
}
g_free (interfaces);
if (plugin && plugin->desc.name) {
GST_PLUGIN_FEATURE_CAST (factory)->plugin_name = plugin->desc.name;
GST_PLUGIN_FEATURE_CAST (factory)->plugin = plugin;
g_object_add_weak_pointer ((GObject *) plugin,
(gpointer *) & GST_PLUGIN_FEATURE_CAST (factory)->plugin);
} else {
GST_PLUGIN_FEATURE_CAST (factory)->plugin_name = "NULL";
GST_PLUGIN_FEATURE_CAST (factory)->plugin = NULL;
}
gst_plugin_feature_set_rank (GST_PLUGIN_FEATURE_CAST (factory), rank);
GST_PLUGIN_FEATURE_CAST (factory)->loaded = TRUE;
gst_registry_add_feature (registry, GST_PLUGIN_FEATURE_CAST (factory));
return TRUE;
/* ERRORS */
urierror:
{
GST_WARNING_OBJECT (factory, "error with uri handler!");
gst_element_factory_cleanup (factory);
return FALSE;
}
detailserror:
{
gst_element_factory_cleanup (factory);
return FALSE;
}
}
/**
* gst_element_factory_create:
* @factory: factory to instantiate
* @name: (allow-none): name of new element, or NULL to automatically create
* a unique name
*
* Create a new element of the type defined by the given elementfactory.
* It will be given the name supplied, since all elements require a name as
* their first argument.
*
* Returns: (transfer floating): new #GstElement or NULL if the element couldn't
* be created
*/
GstElement *
gst_element_factory_create (GstElementFactory * factory, const gchar * name)
{
GstElement *element;
GstElementClass *oclass;
GstElementFactory *newfactory;
g_return_val_if_fail (factory != NULL, NULL);
newfactory =
GST_ELEMENT_FACTORY (gst_plugin_feature_load (GST_PLUGIN_FEATURE
(factory)));
if (newfactory == NULL)
goto load_failed;
factory = newfactory;
if (name)
GST_INFO ("creating element \"%s\" named \"%s\"",
GST_OBJECT_NAME (factory), GST_STR_NULL (name));
else
GST_INFO ("creating element \"%s\"", GST_OBJECT_NAME (factory));
if (factory->type == 0)
goto no_type;
/* create an instance of the element, cast so we don't assert on NULL
* also set name as early as we can
*/
if (name)
element =
GST_ELEMENT_CAST (g_object_new (factory->type, "name", name, NULL));
else
element = GST_ELEMENT_CAST (g_object_newv (factory->type, 0, NULL));
if (G_UNLIKELY (element == NULL))
goto no_element;
/* fill in the pointer to the factory in the element class. The
* class will not be unreffed currently.
* Be thread safe as there might be 2 threads creating the first instance of
* an element at the same moment
*/
oclass = GST_ELEMENT_GET_CLASS (element);
if (!g_atomic_pointer_compare_and_exchange (&oclass->elementfactory, NULL,
factory))
gst_object_unref (factory);
GST_DEBUG ("created element \"%s\"", GST_OBJECT_NAME (factory));
return element;
/* ERRORS */
load_failed:
{
GST_WARNING_OBJECT (factory,
"loading plugin containing feature %s returned NULL!", name);
return NULL;
}
no_type:
{
GST_WARNING_OBJECT (factory, "factory has no type");
gst_object_unref (factory);
return NULL;
}
no_element:
{
GST_WARNING_OBJECT (factory, "could not create element");
gst_object_unref (factory);
return NULL;
}
}
/**
* gst_element_factory_make:
* @factoryname: a named factory to instantiate
* @name: (allow-none): name of new element, or NULL to automatically create
* a unique name
*
* Create a new element of the type defined by the given element factory.
* If name is NULL, then the element will receive a guaranteed unique name,
* consisting of the element factory name and a number.
* If name is given, it will be given the name supplied.
*
* Returns: (transfer floating): new #GstElement or NULL if unable to create element
*/
GstElement *
gst_element_factory_make (const gchar * factoryname, const gchar * name)
{
GstElementFactory *factory;
GstElement *element;
g_return_val_if_fail (factoryname != NULL, NULL);
g_return_val_if_fail (gst_is_initialized (), NULL);
GST_LOG ("gstelementfactory: make \"%s\" \"%s\"",
factoryname, GST_STR_NULL (name));
factory = gst_element_factory_find (factoryname);
if (factory == NULL)
goto no_factory;
GST_LOG_OBJECT (factory, "found factory %p", factory);
element = gst_element_factory_create (factory, name);
if (element == NULL)
goto create_failed;
gst_object_unref (factory);
return element;
/* ERRORS */
no_factory:
{
GST_INFO ("no such element factory \"%s\"!", factoryname);
return NULL;
}
create_failed:
{
GST_INFO_OBJECT (factory, "couldn't create instance!");
gst_object_unref (factory);
return NULL;
}
}
void
__gst_element_factory_add_static_pad_template (GstElementFactory * factory,
GstStaticPadTemplate * templ)
{
g_return_if_fail (factory != NULL);
g_return_if_fail (templ != NULL);
factory->staticpadtemplates =
g_list_append (factory->staticpadtemplates, templ);
factory->numpadtemplates++;
}
/**
* gst_element_factory_get_element_type:
* @factory: factory to get managed #GType from
*
* Get the #GType for elements managed by this factory. The type can
* only be retrieved if the element factory is loaded, which can be
* assured with gst_plugin_feature_load().
*
* Returns: the #GType for elements managed by this factory or 0 if
* the factory is not loaded.
*/
GType
gst_element_factory_get_element_type (GstElementFactory * factory)
{
g_return_val_if_fail (GST_IS_ELEMENT_FACTORY (factory), 0);
return factory->type;
}
/**
* gst_element_factory_get_metadata:
* @factory: a #GstElementFactory
* @key: a key
*
* Get the metadata on @factory with @key.
*
* Returns: the metadata with @key on @factory or %NULL when there was no
* metadata with the given @key.
*/
const gchar *
gst_element_factory_get_metadata (GstElementFactory * factory,
const gchar * key)
{
return gst_structure_get_string ((GstStructure *) factory->metadata, key);
}
/**
* gst_element_factory_get_metadata_keys:
* @factory: a #GstElementFactory
*
* Get the available keys for the metadata on @factory.
*
* Returns: (transfer full) (element-type utf8) (array zero-terminated=1):
* a %NULL-terminated array of key strings, or %NULL when there is no
* metadata. Free with g_strfreev() when no longer needed.
*/
gchar **
gst_element_factory_get_metadata_keys (GstElementFactory * factory)
{
GstStructure *metadata;
gchar **arr;
gint i, num;
g_return_val_if_fail (GST_IS_ELEMENT_FACTORY (factory), NULL);
metadata = (GstStructure *) factory->metadata;
if (metadata == NULL)
return NULL;
num = gst_structure_n_fields (metadata);
if (num == 0)
return NULL;
arr = g_new (gchar *, num + 1);
for (i = 0; i < num; ++i) {
arr[i] = g_strdup (gst_structure_nth_field_name (metadata, i));
}
arr[i] = NULL;
return arr;
}
/**
* gst_element_factory_get_num_pad_templates:
* @factory: a #GstElementFactory
*
* Gets the number of pad_templates in this factory.
*
* Returns: the number of pad_templates
*/
guint
gst_element_factory_get_num_pad_templates (GstElementFactory * factory)
{
g_return_val_if_fail (GST_IS_ELEMENT_FACTORY (factory), 0);
return factory->numpadtemplates;
}
/**
* __gst_element_factory_add_interface:
* @elementfactory: The elementfactory to add the interface to
* @interfacename: Name of the interface
*
* Adds the given interfacename to the list of implemented interfaces of the
* element.
*/
void
__gst_element_factory_add_interface (GstElementFactory * elementfactory,
const gchar * interfacename)
{
g_return_if_fail (GST_IS_ELEMENT_FACTORY (elementfactory));
g_return_if_fail (interfacename != NULL);
g_return_if_fail (interfacename[0] != '\0'); /* no empty string */
elementfactory->interfaces =
g_list_prepend (elementfactory->interfaces,
(gpointer) g_intern_string (interfacename));
}
/**
* gst_element_factory_get_static_pad_templates:
* @factory: a #GstElementFactory
*
* Gets the #GList of #GstStaticPadTemplate for this factory.
*
* Returns: (transfer none) (element-type Gst.StaticPadTemplate): the
* static pad templates
*/
const GList *
gst_element_factory_get_static_pad_templates (GstElementFactory * factory)
{
g_return_val_if_fail (GST_IS_ELEMENT_FACTORY (factory), NULL);
return factory->staticpadtemplates;
}
/**
* gst_element_factory_get_uri_type:
* @factory: a #GstElementFactory
*
* Gets the type of URIs the element supports or #GST_URI_UNKNOWN if none.
*
* Returns: type of URIs this element supports
*/
GstURIType
gst_element_factory_get_uri_type (GstElementFactory * factory)
{
g_return_val_if_fail (GST_IS_ELEMENT_FACTORY (factory), GST_URI_UNKNOWN);
return factory->uri_type;
}
/**
* gst_element_factory_get_uri_protocols:
* @factory: a #GstElementFactory
*
* Gets a NULL-terminated array of protocols this element supports or NULL if
* no protocols are supported. You may not change the contents of the returned
* array, as it is still owned by the element factory. Use g_strdupv() to
* make a copy of the protocol string array if you need to.
*
* Returns: (transfer none) (array zero-terminated=1): the supported protocols
* or NULL
*/
const gchar *const *
gst_element_factory_get_uri_protocols (GstElementFactory * factory)
{
g_return_val_if_fail (GST_IS_ELEMENT_FACTORY (factory), NULL);
return (const gchar * const *) factory->uri_protocols;
}
/**
* gst_element_factory_has_interface:
* @factory: a #GstElementFactory
* @interfacename: an interface name
*
* Check if @factory implements the interface with name @interfacename.
*
* Returns: #TRUE when @factory implement the interface.
*/
gboolean
gst_element_factory_has_interface (GstElementFactory * factory,
const gchar * interfacename)
{
GList *walk;
g_return_val_if_fail (GST_IS_ELEMENT_FACTORY (factory), FALSE);
for (walk = factory->interfaces; walk; walk = g_list_next (walk)) {
gchar *iname = (gchar *) walk->data;
if (!strcmp (iname, interfacename))
return TRUE;
}
return FALSE;
}
typedef struct
{
GstElementFactoryListType type;
GstRank minrank;
} FilterData;
/**
* gst_element_factory_list_is_type:
* @factory: a #GstElementFactory
* @type: a #GstElementFactoryListType
*
* Check if @factory is of the given types.
*
* Returns: %TRUE if @factory is of @type.
*/
gboolean
gst_element_factory_list_is_type (GstElementFactory * factory,
GstElementFactoryListType type)
{
gboolean res = FALSE;
const gchar *klass;
klass =
gst_element_factory_get_metadata (factory, GST_ELEMENT_METADATA_KLASS);
if (klass == NULL) {
GST_ERROR_OBJECT (factory, "element factory is missing klass identifiers");
return res;
}
/* Filter by element type first, as soon as it matches
* one type, we skip all other tests */
if (!res && (type & GST_ELEMENT_FACTORY_TYPE_SINK))
res = (strstr (klass, "Sink") != NULL);
if (!res && (type & GST_ELEMENT_FACTORY_TYPE_SRC))
res = (strstr (klass, "Source") != NULL);
if (!res && (type & GST_ELEMENT_FACTORY_TYPE_DECODER))
res = (strstr (klass, "Decoder") != NULL);
if (!res && (type & GST_ELEMENT_FACTORY_TYPE_ENCODER))
res = (strstr (klass, "Encoder") != NULL);
if (!res && (type & GST_ELEMENT_FACTORY_TYPE_MUXER))
res = (strstr (klass, "Muxer") != NULL);
if (!res && (type & GST_ELEMENT_FACTORY_TYPE_DEMUXER))
res = (strstr (klass, "Demux") != NULL);
/* FIXME : We're actually parsing two Classes here... */
if (!res && (type & GST_ELEMENT_FACTORY_TYPE_PARSER))
res = ((strstr (klass, "Parser") != NULL)
&& (strstr (klass, "Codec") != NULL));
if (!res && (type & GST_ELEMENT_FACTORY_TYPE_DEPAYLOADER))
res = (strstr (klass, "Depayloader") != NULL);
if (!res && (type & GST_ELEMENT_FACTORY_TYPE_PAYLOADER))
res = (strstr (klass, "Payloader") != NULL);
if (!res && (type & GST_ELEMENT_FACTORY_TYPE_FORMATTER))
res = (strstr (klass, "Formatter") != NULL);
/* Filter by media type now, we only test if it
* matched any of the types above. */
if (res
&& (type & (GST_ELEMENT_FACTORY_TYPE_MEDIA_AUDIO |
GST_ELEMENT_FACTORY_TYPE_MEDIA_VIDEO |
GST_ELEMENT_FACTORY_TYPE_MEDIA_IMAGE)))
res = ((type & GST_ELEMENT_FACTORY_TYPE_MEDIA_AUDIO)
&& (strstr (klass, "Audio") != NULL))
|| ((type & GST_ELEMENT_FACTORY_TYPE_MEDIA_VIDEO)
&& (strstr (klass, "Video") != NULL))
|| ((type & GST_ELEMENT_FACTORY_TYPE_MEDIA_IMAGE)
&& (strstr (klass, "Image") != NULL));
return res;
}
static gboolean
element_filter (GstPluginFeature * feature, FilterData * data)
{
gboolean res;
/* we only care about element factories */
if (G_UNLIKELY (!GST_IS_ELEMENT_FACTORY (feature)))
return FALSE;
res = (gst_plugin_feature_get_rank (feature) >= data->minrank) &&
gst_element_factory_list_is_type (GST_ELEMENT_FACTORY_CAST (feature),
data->type);
return res;
}
/**
* gst_element_factory_list_get_elements:
* @type: a #GstElementFactoryListType
* @minrank: Minimum rank
*
* Get a list of factories that match the given @type. Only elements
* with a rank greater or equal to @minrank will be returned.
* The list of factories is returned by decreasing rank.
*
* Returns: (transfer full) (element-type Gst.ElementFactory): a #GList of
* #GstElementFactory elements. Use gst_plugin_feature_list_free() after
* usage.
*/
GList *
gst_element_factory_list_get_elements (GstElementFactoryListType type,
GstRank minrank)
{
GList *result;
FilterData data;
/* prepare type */
data.type = type;
data.minrank = minrank;
/* get the feature list using the filter */
result = gst_registry_feature_filter (gst_registry_get (),
(GstPluginFeatureFilter) element_filter, FALSE, &data);
/* sort on rank and name */
result = g_list_sort (result, gst_plugin_feature_rank_compare_func);
return result;
}
/**
* gst_element_factory_list_filter:
* @list: (transfer none) (element-type Gst.ElementFactory): a #GList of
* #GstElementFactory to filter
* @caps: a #GstCaps
* @direction: a #GstPadDirection to filter on
* @subsetonly: whether to filter on caps subsets or not.
*
* Filter out all the elementfactories in @list that can handle @caps in
* the given direction.
*
* If @subsetonly is %TRUE, then only the elements whose pads templates
* are a complete superset of @caps will be returned. Else any element
* whose pad templates caps can intersect with @caps will be returned.
*
* Returns: (transfer full) (element-type Gst.ElementFactory): a #GList of
* #GstElementFactory elements that match the given requisits.
* Use #gst_plugin_feature_list_free after usage.
*/
GList *
gst_element_factory_list_filter (GList * list,
const GstCaps * caps, GstPadDirection direction, gboolean subsetonly)
{
GQueue results = G_QUEUE_INIT;
GST_DEBUG ("finding factories");
/* loop over all the factories */
for (; list; list = list->next) {
GstElementFactory *factory;
const GList *templates;
GList *walk;
factory = (GstElementFactory *) list->data;
GST_DEBUG ("Trying %s",
gst_plugin_feature_get_name ((GstPluginFeature *) factory));
/* get the templates from the element factory */
templates = gst_element_factory_get_static_pad_templates (factory);
for (walk = (GList *) templates; walk; walk = g_list_next (walk)) {
GstStaticPadTemplate *templ = walk->data;
/* we only care about the sink templates */
if (templ->direction == direction) {
GstCaps *tmpl_caps;
/* try to intersect the caps with the caps of the template */
tmpl_caps = gst_static_caps_get (&templ->static_caps);
/* FIXME, intersect is not the right method, we ideally want to check
* for a subset here */
/* check if the intersection is empty */
if ((subsetonly && gst_caps_is_subset (caps, tmpl_caps)) ||
(!subsetonly && gst_caps_can_intersect (caps, tmpl_caps))) {
/* non empty intersection, we can use this element */
g_queue_push_tail (&results, gst_object_ref (factory));
gst_caps_unref (tmpl_caps);
break;
}
gst_caps_unref (tmpl_caps);
}
}
}
return results.head;
}