Registry

One registry holds the metadata of a set of plugins.

<emphasis role="bold">Design:</emphasis>

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: $XDG_DATA_HOME/gstreamer-$GST_API_VERSION/plugins/ and $prefix/libs/gstreamer-$GST_API_VERSION/. $XDG_DATA_HOME defaults to $HOME/.local/share.

The registry cache file is loaded from $XDG_CACHE_HOME/gstreamer-$GST_API_VERSION/registry-$ARCH.bin (where $XDG_CACHE_HOME defaults to $HOME/.cache) 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.

class Registry : ObjectGst {

protected

GstRegistry* gstRegistry;

GstRegistry* getRegistryStruct(bool transferOwnership);

void* getStruct();

this(GstRegistry* gstRegistry, bool ownedRef);

static GType getType();

static bool forkIsEnabled();

static void forkSetEnabled(bool enabled);

static Registry get();

bool addFeature(PluginFeature feature);

bool addPlugin(Plugin plugin);

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

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

PluginFeature findFeature(string name, GType type);

Plugin findPlugin(string name);

ListG getFeatureList(GType type);

ListG getFeatureListByPlugin(string name);

uint getFeatureListCookie();

ListG getPluginList();

Plugin lookup(string filename);

PluginFeature lookupFeature(string name);

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

void removeFeature(PluginFeature feature);

void removePlugin(Plugin plugin);

bool scanPath(string path);

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

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

}

Constructors

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

Members

Functions

addFeature bool addFeature(PluginFeature feature): Add the feature to the registry. The feature-added signal will be emitted.
addOnFeatureAdded gulong 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 gulong 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)
addPlugin bool addPlugin(Plugin plugin): Add the plugin to the registry. The plugin-added signal will be emitted.
checkFeatureVersion bool 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, bool 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 registry's 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(bool transferOwnership): 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, bool 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.
removePlugin void removePlugin(Plugin plugin): Remove the plugin from the registry.
scanPath bool scanPath(string path): Scan the given path for plugins to add to the registry. The syntax of the path is specific to the registry.

Static functions

forkIsEnabled bool forkIsEnabled(): By default GStreamer will perform scanning and rebuilding of the registry file using a helper child process.
forkSetEnabled void forkSetEnabled(bool enabled): Applications might want to disable/enable spawning of a child helper process when rebuilding the registry. See gst_registry_fork_is_enabled() for more information.
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.
getType GType getType()

Variables

gstRegistry GstRegistry* gstRegistry;: the main Gtk struct

Inherited Members

From ObjectGst

gstObject GstObject* gstObject;: the main Gtk struct
getObjectGstStruct GstObject* getObjectGstStruct(bool transferOwnership): Get the main Gtk struct
getStruct void* getStruct(): the main Gtk struct as a void*
getType GType getType()
checkUniqueness bool 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 careful when passing a list with a locked object.
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.
refSink void* refSink(void* object): Increase the reference count of @object, and possibly remove the floating reference, if @object has a floating reference.
replace bool 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.
addControlBinding bool addControlBinding(ControlBinding binding): Attach the #GstControlBinding to the object. If there already was a #GstControlBinding for this property it will be replaced.
defaultError void defaultError(ErrorG error, string dbg): A default error function that uses g_printerr() to display the error message and the optional debug sting..
getControlBinding ControlBinding getControlBinding(string propertyName): Gets the corresponding #GstControlBinding for the property. This should be unreferenced again after use.
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.
getGValueArray bool getGValueArray(string propertyName, GstClockTime timestamp, GstClockTime interval, 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.
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.
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.
getPathString string getPathString(): Generates a string describing the path of @object in the object hierarchy. Only useful (or used) for debugging.
getValue Value getValue(string propertyName, GstClockTime timestamp): Gets the value for the given controlled property at the requested time.
getValueArray bool getValueArray(string propertyName, GstClockTime timestamp, GstClockTime interval, uint nValues, 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.
hasActiveControlBindings bool hasActiveControlBindings(): Check if the @object has active controlled properties.
hasAncestor bool 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.
hasAsAncestor bool hasAsAncestor(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.
hasAsParent bool hasAsParent(ObjectGst parent): Check if @parent is the parent of @object. E.g. a #GstElement can check if it owns a given #GstPad.
doref ObjectGst doref(): Increments the reference count on @object. This function does not take the lock on @object because it relies on atomic refcounting.
removeControlBinding bool removeControlBinding(ControlBinding binding): Removes the corresponding #GstControlBinding. If it was the last ref of the binding, it will be disposed.
setControlBindingDisabled void setControlBindingDisabled(string propertyName, bool disabled): This function is used to disable the control bindings on a property for some time, i.e. gst_object_sync_values() will do nothing for the property.
setControlBindingsDisabled void setControlBindingsDisabled(bool 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.
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.
setName bool 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.
setParent bool 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()).
suggestNextSync GstClockTime suggestNextSync(): Returns a suggestion for timestamps where buffers should be split to get best controller results.
syncValues bool syncValues(GstClockTime timestamp): Sets the properties of the object, according to the #GstControlSources that (maybe) handle them and for the given timestamp.
unparent void unparent(): Clear the parent of @object, removing the associated reference. This function decreases the refcount of @object.
unref void unref(): 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.
addOnDeepNotify gulong 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.