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GstPlugin — Dynamically loadable Elements
#include <gst/gst.h> #define GST_PLUGIN_ERROR GQuark gst_plugin_error_quark (void); enum GstPluginError; struct GstPlugin; gboolean (*GstPluginInitFunc) (GstPlugin *plugin); struct GstPluginDesc; void gst_plugin_set_name (GstPlugin *plugin, const gchar *name); G_CONST_RETURN gchar* gst_plugin_get_name (GstPlugin *plugin); G_CONST_RETURN gchar* gst_plugin_get_longname (GstPlugin *plugin); G_CONST_RETURN gchar* gst_plugin_get_filename (GstPlugin *plugin); gboolean gst_plugin_is_loaded (GstPlugin *plugin); GList* gst_plugin_get_feature_list (GstPlugin *plugin); GstPluginFeature* gst_plugin_find_feature (GstPlugin *plugin, const gchar *name, GType type); gboolean gst_plugin_unload_plugin (GstPlugin *plugin); void gst_plugin_add_feature (GstPlugin *plugin, GstPluginFeature *feature); gboolean gst_plugin_load (const gchar *name); gboolean gst_library_load (const gchar *name);
GStreamer is extensible so GstElements can be loaded at runtime. A plugin system can provide one or more of the basic GStreamer GstPluginFeature subclasses.
A plugin should export a symbol plugin_desc that is a struct of type GstPluginDesc. the plugin loader will check the version of the core library the plugin was linked against and will create a new GstPlugin. It will then call the GstPluginInitFunc function that was provided in the plugin_desc.
Once you have a handle to a GstPlugin, you can add any object that subclasses GstPluginFeature.
use gst_plugin_find_feature() and gst_plugin_get_feature_list() to find features in a plugin.
Usually plugins are always automaticlly loaded so you don't need to call gst_plugin_load() explicitly to bring it into memory. There are options to statically link plugins to an app or even use GStreamer without a plugin repository in which case gst_plugin_load() can be needed to bring the plugin into memory.
GQuark gst_plugin_error_quark (void);
Get the error quark
Returns : | The error quark used in GError messages |
typedef enum { GST_PLUGIN_ERROR_MODULE, GST_PLUGIN_ERROR_DEPENDENCIES, GST_PLUGIN_ERROR_NAME_MISMATCH } GstPluginError;
The plugin loading errors
GST_PLUGIN_ERROR_MODULE | The plugin could not be loaded |
GST_PLUGIN_ERROR_DEPENDENCIES | The plugin has unresolved dependencies |
GST_PLUGIN_ERROR_NAME_MISMATCH |
struct GstPlugin { GstPluginDesc desc; gchar * filename; GList * features; /* list of features provided */ gint numfeatures; gpointer manager; /* managing registry */ GModule * module; /* contains the module if the plugin is loaded */ gpointer _gst_reserved[GST_PADDING]; };
The plugin object
gboolean (*GstPluginInitFunc) (GstPlugin *plugin);
A plugin should provide a pointer to a function of this type in the plugin_desc struct. It will be called by the loader at statup.
plugin : | The plugin object that can be used to register stuff for this plugin. |
Returns : | A boolean indicating success or failure. |
struct GstPluginDesc { gint major_version; /* major version of core that plugin was compiled for */ gint minor_version; /* minor version of core that plugin was compiled for */ gchar *name; /* unique name of plugin */ gchar *description; /* description of plugin */ GstPluginInitFunc plugin_init; /* pointer to plugin_init function */ GstPluginExitFunc plugin_exit; /* pointer to exiting function */ gchar *version; /* version of the plugin */ gchar *license; /* effective license of plugin */ gchar *package; /* package plugin belongs to */ gchar *origin; /* URL to provider of plugin */ gpointer _gst_reserved[GST_PADDING]; };
A plugins should export a variable of this type called plugin_desc. This plugin loaded will use this variable to initialize the plugin.
gint major_version | The minor version of the gstreamer library this plugin was created with |
gint minor_version | The minor version of the gstreamer library this plugin was created with |
gchar *name | The name of the plugin |
gchar *description | |
GstPluginInitFunc plugin_init | The init function of this plugin. |
GstPluginExitFunc plugin_exit | |
gchar *version | |
gchar *license | |
gchar *package | |
gchar *origin | |
gpointer _gst_reserved[GST_PADDING] |
void gst_plugin_set_name (GstPlugin *plugin, const gchar *name);
plugin : | |
name : |
G_CONST_RETURN gchar* gst_plugin_get_name (GstPlugin *plugin);
Get the short name of the plugin
plugin : | plugin to get the name of |
Returns : | the name of the plugin |
G_CONST_RETURN gchar* gst_plugin_get_longname (GstPlugin *plugin);
Get the long descriptive name of the plugin
plugin : | plugin to get long name of |
Returns : | the long name of the plugin |
G_CONST_RETURN gchar* gst_plugin_get_filename (GstPlugin *plugin);
get the filename of the plugin
plugin : | plugin to get the filename of |
Returns : | the filename of the plugin |
gboolean gst_plugin_is_loaded (GstPlugin *plugin);
queries if the plugin is loaded into memory
plugin : | plugin to query |
Returns : | TRUE is loaded, FALSE otherwise |
GList* gst_plugin_get_feature_list (GstPlugin *plugin);
get a list of all the features that this plugin provides
plugin : | the plugin to get the features from |
Returns : | a GList of features, use g_list_free to free the list. |
GstPluginFeature* gst_plugin_find_feature (GstPlugin *plugin, const gchar *name, GType type);
Find a feature of the given name and type in the given plugin.
plugin : | plugin to get the feature from |
name : | The name of the feature to find |
type : | The type of the feature to find |
Returns : | a GstPluginFeature or NULL if the feature was not found. |
gboolean gst_plugin_unload_plugin (GstPlugin *plugin);
Unload the given plugin.
plugin : | The plugin to unload |
Returns : | whether or not the plugin unloaded |
void gst_plugin_add_feature (GstPlugin *plugin, GstPluginFeature *feature);
Add feature to the list of those provided by the plugin. There is a separate namespace for each plugin feature type. See gst_plugin_get_feature_list
plugin : | plugin to add feature to |
feature : | feature to add |
gboolean gst_plugin_load (const gchar *name);
Load the named plugin.
name : | name of plugin to load |
Returns : | whether the plugin was loaded or not |
GstPluginFeature, GstType, GstAutoplug, GstElementFactory
<< GstPipeline | GstPluginFeature >> |