Registry

One registry holds the metadata of a set of plugins.

Design:

The GstRegistry object is a list of plugins and some functions for dealing with them. Each GstPlugin is matched 1-1 with a file on disk, and may or may not be loaded at a given time.

The primary source, at all times, of plugin information is each plugin file itself. Thus, if an application wants information about a particular plugin, or wants to search for a feature that satisfies given criteria, the primary means of doing so is to load every plugin and look at the resulting information that is gathered in the default registry. Clearly, this is a time consuming process, so we cache information in the registry file. The format and location of the cache file is internal to gstreamer.

On startup, plugins are searched for in the plugin search path. The following locations are checked in this order:

location from --gst-plugin-path commandline option.

the GST_PLUGIN_PATH environment variable.

the GST_PLUGIN_SYSTEM_PATH environment variable.

default locations (if GST_PLUGIN_SYSTEM_PATH is not set). Those default locations are: ~/.gstreamer-$GST_API_VERSION/plugins/ and $prefix/libs/gstreamer-$GST_API_VERSION/.

The registry cache file is loaded from ~/.gstreamer-$GST_API_VERSION/registry-$ARCH.bin or the file listed in the GST_REGISTRY env var. One reason to change the registry location is for testing.

For each plugin that is found in the plugin search path, there could be 3 possibilities for cached information:

the cache may not contain information about a given file.

the cache may have stale information.

the cache may have current information.

In the first two cases, the plugin is loaded and the cache updated. In addition to these cases, the cache may have entries for plugins that are not relevant to the current process. These are marked as not available to the current process. If the cache is updated for whatever reason, it is marked dirty.

A dirty cache is written out at the end of initialization. Each entry is checked to make sure the information is minimally valid. If not, the entry is simply dropped.

Implementation notes:

The "cache" and "registry" are different concepts and can represent different sets of plugins. For various reasons, at init time, the cache is stored in the default registry, and plugins not relevant to the current process are marked with the GST_PLUGIN_FLAG_CACHED bit. These plugins are removed at the end of initialization.

Last reviewed on 2012-03-29 (0.11.3)

class Registry : ObjectGst {

protected

GstRegistry* gstRegistry;

GstRegistry* getRegistryStruct();

void* getStruct();

this(GstRegistry* gstRegistry);

void setStruct(GObject* obj);

int[string] connectedSignals;

void delegate(PluginFeature, Registry)[] onFeatureAddedListeners;

void addOnFeatureAdded(void delegate(PluginFeature, Registry) dlg, ConnectFlags connectFlags);

static void callBackFeatureAdded(GstRegistry* registryStruct, GstPluginFeature* feature, Registry _registry);

void delegate(Plugin, Registry)[] onPluginAddedListeners;

void addOnPluginAdded(void delegate(Plugin, Registry) dlg, ConnectFlags connectFlags);

static void callBackPluginAdded(GstRegistry* registryStruct, GstPlugin* plugin, Registry _registry);

static Registry get();

ListG getFeatureList(GType type);

uint getFeatureListCookie();

ListG getFeatureListByPlugin(string name);

ListG getPluginList();

int addPlugin(Plugin plugin);

void removePlugin(Plugin plugin);

ListG pluginFilter(GstPluginFilter filter, int first, void* userData);

ListG featureFilter(GstPluginFeatureFilter filter, int first, void* userData);

Plugin findPlugin(string name);

PluginFeature findFeature(string name, GType type);

PluginFeature lookupFeature(string name);

int scanPath(string path);

Plugin lookup(string filename);

void removeFeature(PluginFeature feature);

int addFeature(PluginFeature feature);

int checkFeatureVersion(string featureName, uint minMajor, uint minMinor, uint minMicro);

}

Constructors

this this(GstRegistry* gstRegistry): Sets our main struct and passes it to the parent class

Members

Functions

addFeature int addFeature(PluginFeature feature): Add the feature to the registry. The feature-added signal will be emitted. This function sinks feature.
addOnFeatureAdded void addOnFeatureAdded(void delegate(PluginFeature, Registry) dlg, ConnectFlags connectFlags): Signals that a feature has been added to the registry (possibly replacing a previously-added one by the same name)
addOnPluginAdded void addOnPluginAdded(void delegate(Plugin, Registry) dlg, ConnectFlags connectFlags): Signals that a plugin has been added to the registry (possibly replacing a previously-added one by the same name) See Also GstPlugin, GstPluginFeature
addPlugin int addPlugin(Plugin plugin): Add the plugin to the registry. The plugin-added signal will be emitted. This function will sink plugin.
checkFeatureVersion int checkFeatureVersion(string featureName, uint minMajor, uint minMinor, uint minMicro): Checks whether a plugin feature by the given name exists in registry and whether its version is at least the version required.
featureFilter ListG featureFilter(GstPluginFeatureFilter filter, int first, void* userData): Runs a filter against all features of the plugins in the registry and returns a GList with the results. If the first flag is set, only the first match is returned (as a list with a single object).
findFeature PluginFeature findFeature(string name, GType type): Find the pluginfeature with the given name and type in the registry.
findPlugin Plugin findPlugin(string name): Find the plugin with the given name in the registry. The plugin will be reffed; caller is responsible for unreffing.
getFeatureList ListG getFeatureList(GType type): Retrieves a GList of GstPluginFeature of type.
getFeatureListByPlugin ListG getFeatureListByPlugin(string name): Retrieves a GList of features of the plugin with name name.
getFeatureListCookie uint getFeatureListCookie(): Returns the registrys feature list cookie. This changes every time a feature is added or removed from the registry.
getPluginList ListG getPluginList(): Get a copy of all plugins registered in the given registry. The refcount of each element in the list in incremented.
getRegistryStruct GstRegistry* getRegistryStruct(): Get the main Gtk struct
getStruct void* getStruct(): the main Gtk struct as a void*
lookup Plugin lookup(string filename): Look up a plugin in the given registry with the given filename. If found, plugin is reffed.
lookupFeature PluginFeature lookupFeature(string name): Find a GstPluginFeature with name in registry.
pluginFilter ListG pluginFilter(GstPluginFilter filter, int first, void* userData): Runs a filter against all plugins in the registry and returns a GList with the results. If the first flag is set, only the first match is returned (as a list with a single object). Every plugin is reffed; use gst_plugin_list_free() after use, which will unref again.
removeFeature void removeFeature(PluginFeature feature): Remove the feature from the registry. MT safe.
removePlugin void removePlugin(Plugin plugin): Remove the plugin from the registry. MT safe.
scanPath int scanPath(string path): Scan the given path for plugins to add to the registry. The syntax of the path is specific to the registry.
setStruct void setStruct(GObject* obj): Undocumented in source. Be warned that the author may not have intended to support it.

Static functions

callBackFeatureAdded void callBackFeatureAdded(GstRegistry* registryStruct, GstPluginFeature* feature, Registry _registry): Undocumented in source. Be warned that the author may not have intended to support it.
callBackPluginAdded void callBackPluginAdded(GstRegistry* registryStruct, GstPlugin* plugin, Registry _registry): Undocumented in source. Be warned that the author may not have intended to support it.
get Registry get(): Retrieves the singleton plugin registry. The caller does not own a reference on the registry, as it is alive as long as GStreamer is initialized.

Variables

connectedSignals int[string] connectedSignals;
gstRegistry GstRegistry* gstRegistry;: the main Gtk struct
onFeatureAddedListeners void delegate(PluginFeature, Registry)[] onFeatureAddedListeners;: Undocumented in source.
onPluginAddedListeners void delegate(Plugin, Registry)[] onPluginAddedListeners;: Undocumented in source.

Inherited Members

From ObjectGst

gstObject GstObject* gstObject;: the main Gtk struct
getObjectGstStruct GstObject* getObjectGstStruct(): Get the main Gtk struct
getStruct void* getStruct(): the main Gtk struct as a void*
setStruct void setStruct(GObject* obj): Undocumented in source. Be warned that the author may not have intended to support it.
connectedSignals int[string] connectedSignals;
onDeepNotifyListeners void delegate(ObjectGst, ParamSpec, ObjectGst)[] onDeepNotifyListeners;: Undocumented in source.
addOnDeepNotify void addOnDeepNotify(void delegate(ObjectGst, ParamSpec, ObjectGst) dlg, ConnectFlags connectFlags): The deep notify signal is used to be notified of property changes. It is typically attached to the toplevel bin to receive notifications from all the elements contained in that bin.
callBackDeepNotify void callBackDeepNotify(GstObject* gstobjectStruct, GstObject* propObject, GParamSpec* prop, ObjectGst _objectGst): Undocumented in source. Be warned that the author may not have intended to support it.
setName int setName(string name): Sets the name of object, or gives object a guaranteed unique name (if name is NULL). This function makes a copy of the provided name, so the caller retains ownership of the name it sent.
getName string getName(): Returns a copy of the name of object. Caller should g_free() the return value after usage. For a nameless object, this returns NULL, which you can safely g_free() as well. Free-function: g_free
setParent int setParent(ObjectGst parent): Sets the parent of object to parent. The object's reference count will be incremented, and any floating reference will be removed (see gst_object_ref_sink()).
getParent ObjectGst getParent(): Returns the parent of object. This function increases the refcount of the parent object so you should gst_object_unref() it after usage.
unparent void unparent(): Clear the parent of object, removing the associated reference. This function decreases the refcount of object. MT safe. Grabs and releases object's lock.
defaultDeepNotify void defaultDeepNotify(ObjectG object, ObjectGst orig, ParamSpec pspec, string[] excludedProps): A default deep_notify signal callback for an object. The user data should contain a pointer to an array of strings that should be excluded from the notify. The default handler will print the new value of the property using g_print. MT safe. This function grabs and releases object's LOCK for getting its path string.
defaultError void defaultError(ErrorG error, char dbug): A default error function that uses g_printerr() to display the error message and the optional debug sting.. The default handler will simply print the error string using g_print.
checkUniqueness int checkUniqueness(ListG list, string name): Checks to see if there is any object named name in list. This function does not do any locking of any kind. You might want to protect the provided list with the lock of the owner of the list. This function will lock each GstObject in the list to compare the name, so be carefull when passing a list with a locked object.
hasAncestor int hasAncestor(ObjectGst ancestor): Check if object has an ancestor ancestor somewhere up in the hierarchy. One can e.g. check if a GstElement is inside a GstPipeline.
doref void* doref(void* object): Increments the reference count on object. This function does not take the lock on object because it relies on atomic refcounting. This object returns the input parameter to ease writing
unref void unref(void* object): Decrements the reference count on object. If reference count hits zero, destroy object. This function does not take the lock on object as it relies on atomic refcounting. The unref method should never be called with the LOCK held since this might deadlock the dispose function.
refSink void* refSink(void* object): Increase the reference count of object, and possibly remove the floating reference, if object has a floating reference. In other words, if the object is floating, then this call "assumes ownership" of the floating reference, converting it to a normal reference by clearing the floating flag while leaving the reference count unchanged. If the object is not floating, then this call adds a new normal reference increasing the reference count by one.
replace int replace(ObjectGst oldobj, ObjectGst newobj): Atomically modifies a pointer to point to a new object. The reference count of oldobj is decreased and the reference count of newobj is increased. Either newobj and the value pointed to by oldobj may be NULL.
getPathString string getPathString(): Generates a string describing the path of object in the object hierarchy. Only useful (or used) for debugging. Free-function: g_free
suggestNextSync GstClockTime suggestNextSync(): Returns a suggestion for timestamps where buffers should be split to get best controller results.
syncValues int syncValues(GstClockTime timestamp): Sets the properties of the object, according to the GstControlSources that (maybe) handle them and for the given timestamp. If this function fails, it is most likely the application developers fault. Most probably the control sources are not setup correctly.
hasActiveControlBindings int hasActiveControlBindings(): Check if the object has an active controlled properties.
setControlBindingsDisabled void setControlBindingsDisabled(int disabled): This function is used to disable all controlled properties of the object for some time, i.e. gst_object_sync_values() will do nothing.
setControlBindingDisabled void setControlBindingDisabled(string propertyName, int disabled): This function is used to disable the GstController on a property for some time, i.e. gst_controller_sync_values() will do nothing for the property.
addControlBinding int addControlBinding(ControlBinding binding): Attach the GstControlBinding to the object. If there already was a GstControlBinding for this property it will be replaced. The object will take ownership of the binding.
getControlBinding ControlBinding getControlBinding(string propertyName): Gets the corresponding GstControlBinding for the property. This should be unreferenced again after use.
removeControlBinding int removeControlBinding(ControlBinding binding): Removes the corresponding GstControlBinding. If it was the last ref of the binding, it will be disposed.
getValue Value getValue(string propertyName, GstClockTime timestamp): Gets the value for the given controlled property at the requested time.
getValueArray int getValueArray(string propertyName, GstClockTime timestamp, GstClockTime interval, void[] values): Gets a number of values for the given controlled property starting at the requested time. The array values need to hold enough space for n_values of the same type as the objects property's type. This function is useful if one wants to e.g. draw a graph of the control curve or apply a control curve sample by sample. The values are unboxed and ready to be used. The similar function gst_object_get_g_value_array() returns the array as GValues and is better suites for bindings.
getGValueArray int getGValueArray(string propertyName, GstClockTime timestamp, GstClockTime interval, uint nValues, Value values): Gets a number of GValues for the given controlled property starting at the requested time. The array values need to hold enough space for n_values of GValue. This function is useful if one wants to e.g. draw a graph of the control curve or apply a control curve sample by sample.
getControlRate GstClockTime getControlRate(): Obtain the control-rate for this object. Audio processing GstElement objects will use this rate to sub-divide their processing loop and call gst_object_sync_values() inbetween. The length of the processing segment should be up to control-rate nanoseconds. If the object is not under property control, this will return GST_CLOCK_TIME_NONE. This allows the element to avoid the sub-dividing. The control-rate is not expected to change if the element is in GST_STATE_PAUSED or GST_STATE_PLAYING.
setControlRate void setControlRate(GstClockTime controlRate): Change the control-rate for this object. Audio processing GstElement objects will use this rate to sub-divide their processing loop and call gst_object_sync_values() inbetween. The length of the processing segment should be up to control-rate nanoseconds. The control-rate should not change if the element is in GST_STATE_PAUSED or GST_STATE_PLAYING.