GstRegistry

GstRegistry — Abstract base class for management of GstPlugin objects

Functions

GstRegistry * gst_registry_get ()
GList * gst_registry_get_feature_list ()
guint32 gst_registry_get_feature_list_cookie ()
GList * gst_registry_get_feature_list_by_plugin ()
GList * gst_registry_get_plugin_list ()
gboolean gst_registry_add_plugin ()
void gst_registry_remove_plugin ()
GList * gst_registry_plugin_filter ()
GList * gst_registry_feature_filter ()
GstPlugin * gst_registry_find_plugin ()
GstPluginFeature * gst_registry_find_feature ()
GstPluginFeature * gst_registry_lookup_feature ()
void gst_registry_add_path ()
GList * gst_registry_get_path_list ()
gboolean gst_registry_scan_path ()
GstPlugin * gst_registry_lookup ()
void gst_registry_remove_feature ()
gboolean gst_registry_add_feature ()
gboolean gst_registry_check_feature_version ()

Signals

void feature-added Run Last
void plugin-added Run Last

Types and Values

struct GstRegistry

Object Hierarchy

    GObject
    ╰── GInitiallyUnowned
        ╰── GstObject
            ╰── GstRegistry

Includes

#include <gst/gst.h>

Description

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: $XDG_DATA_HOME/gstreamer-$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.

Functions

gst_registry_get ()

GstRegistry *
gst_registry_get (void);

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.

Returns

the GstRegistry.

[transfer none]

gst_registry_get_feature_list ()

GList *
gst_registry_get_feature_list (GstRegistry *registry,
                               GType type);

Retrieves a GList of GstPluginFeature of type .

Parameters

registry

a GstRegistry

  

type

a GType.

  

Returns

a GList of GstPluginFeature of type . Use gst_plugin_feature_list_free() after use

MT safe.

[transfer full][element-type Gst.PluginFeature]

gst_registry_get_feature_list_cookie ()

guint32
gst_registry_get_feature_list_cookie (GstRegistry *registry);

Returns the registry's feature list cookie. This changes every time a feature is added or removed from the registry.

Parameters

registry

the registry

  

Returns

the feature list cookie.

gst_registry_get_feature_list_by_plugin ()

GList *
gst_registry_get_feature_list_by_plugin
                               (GstRegistry *registry,
                                const gchar *name);

Retrieves a GList of features of the plugin with name name .

Parameters

registry

a GstRegistry.

  

name

a plugin name.

  

Returns

a GList of GstPluginFeature. Use gst_plugin_feature_list_free() after usage.

[transfer full][element-type Gst.PluginFeature]

gst_registry_get_plugin_list ()

GList *
gst_registry_get_plugin_list (GstRegistry *registry);

Get a copy of all plugins registered in the given registry. The refcount of each element in the list in incremented.

Parameters

registry

the registry to search

  

Returns

a GList of GstPlugin. Use gst_plugin_list_free() after usage.

MT safe.

[transfer full][element-type Gst.Plugin]

gst_registry_add_plugin ()

gboolean
gst_registry_add_plugin (GstRegistry *registry,
                         GstPlugin *plugin);

Add the plugin to the registry. The plugin-added signal will be emitted. This function will sink plugin .

Parameters

registry

the registry to add the plugin to

  

plugin

the plugin to add.

[transfer full]

Returns

TRUE on success.

MT safe.

gst_registry_remove_plugin ()

void
gst_registry_remove_plugin (GstRegistry *registry,
                            GstPlugin *plugin);

Remove the plugin from the registry.

MT safe.

Parameters

registry

the registry to remove the plugin from

  

plugin

the plugin to remove.

[transfer none]

gst_registry_plugin_filter ()

GList *
gst_registry_plugin_filter (GstRegistry *registry,
                            GstPluginFilter filter,
                            gboolean first,
                            gpointer user_data);

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.

Parameters

registry

registry to query

  

filter

the filter to use.

[scope call]

first

only return first match

  

user_data

user data passed to the filter function.

[closure]

Returns

a GList of GstPlugin. Use gst_plugin_list_free() after usage.

MT safe.

[transfer full][element-type Gst.Plugin]

gst_registry_feature_filter ()

GList *
gst_registry_feature_filter (GstRegistry *registry,
                             GstPluginFeatureFilter filter,
                             gboolean first,
                             gpointer user_data);

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).

Parameters

registry

registry to query

  

filter

the filter to use.

[scope call]

first

only return first match

  

user_data

user data passed to the filter function.

[closure]

Returns

a GList of GstPluginFeature. Use gst_plugin_feature_list_free() after usage.

MT safe.

[transfer full][element-type Gst.PluginFeature]

gst_registry_find_plugin ()

GstPlugin *
gst_registry_find_plugin (GstRegistry *registry,
                          const gchar *name);

Find the plugin with the given name in the registry. The plugin will be reffed; caller is responsible for unreffing.

Parameters

registry

the registry to search

  

name

the plugin name to find

  

Returns

the plugin with the given name or NULL if the plugin was not found. gst_object_unref() after usage.

MT safe.

[transfer full][nullable]

gst_registry_find_feature ()

GstPluginFeature *
gst_registry_find_feature (GstRegistry *registry,
                           const gchar *name,
                           GType type);

Find the pluginfeature with the given name and type in the registry.

Parameters

registry

the registry to search

  

name

the pluginfeature name to find

  

type

the pluginfeature type to find

  

Returns

the pluginfeature with the given name and type or NULL if the plugin was not found. gst_object_unref() after usage.

MT safe.

[transfer full][nullable]

gst_registry_lookup_feature ()

GstPluginFeature *
gst_registry_lookup_feature (GstRegistry *registry,
                             const char *name);

Find a GstPluginFeature with name in registry .

Parameters

registry

a GstRegistry

  

name

a GstPluginFeature name

  

Returns

a GstPluginFeature with its refcount incremented, use gst_object_unref() after usage.

MT safe.

[transfer full]

gst_registry_add_path ()

void
gst_registry_add_path (GstRegistry *registry,
                       const gchar *path);

Add the given path to the registry. The syntax of the path is specific to the registry. If the path has already been added, do nothing.

Parameters

registry

the registry to add the path to

  

path

the path to add to the registry

  

gst_registry_get_path_list ()

GList *
gst_registry_get_path_list (GstRegistry *registry);

Get the list of paths for the given registry.

Parameters

registry

the registry to get the pathlist of

  

Returns

A GList of paths as strings. g_list_free after use.

MT safe.

[transfer container][element-type char*]

gst_registry_scan_path ()

gboolean
gst_registry_scan_path (GstRegistry *registry,
                        const gchar *path);

Scan the given path for plugins to add to the registry. The syntax of the path is specific to the registry.

Parameters

registry

the registry to add found plugins to

  

path

the path to scan

  

Returns

TRUE if registry changed

gst_registry_lookup ()

GstPlugin *
gst_registry_lookup (GstRegistry *registry,
                     const char *filename);

Look up a plugin in the given registry with the given filename. If found, plugin is reffed.

Parameters

registry

the registry to look up in

  

filename

the name of the file to look up

  

Returns

the GstPlugin if found, or NULL if not. gst_object_unref() after usage.

[transfer full][nullable]

gst_registry_remove_feature ()

void
gst_registry_remove_feature (GstRegistry *registry,
                             GstPluginFeature *feature);

Remove the feature from the registry.

MT safe.

Parameters

registry

the registry to remove the feature from

  

feature

the feature to remove.

[transfer none]

gst_registry_add_feature ()

gboolean
gst_registry_add_feature (GstRegistry *registry,
                          GstPluginFeature *feature);

Add the feature to the registry. The feature-added signal will be emitted. This function sinks feature .

Parameters

registry

the registry to add the plugin to

  

feature

the feature to add.

[transfer full]

Returns

TRUE on success.

MT safe.

gst_registry_check_feature_version ()

gboolean
gst_registry_check_feature_version (GstRegistry *registry,
                                    const gchar *feature_name,
                                    guint min_major,
                                    guint min_minor,
                                    guint min_micro);

Checks whether a plugin feature by the given name exists in registry and whether its version is at least the version required.

Parameters

registry

a GstRegistry

  

feature_name

the name of the feature (e.g. "oggdemux")

  

min_major

the minimum major version number

  

min_minor

the minimum minor version number

  

min_micro

the minimum micro version number

  

Returns

TRUE if the feature could be found and the version is the same as the required version or newer, and FALSE otherwise.

Types and Values

struct GstRegistry

struct GstRegistry;

Opaque GstRegistry structure.

Signal Details

The “feature-added” signal

void
user_function (GstRegistry      *registry,
               GstPluginFeature *feature,
               gpointer          user_data)

Signals that a feature has been added to the registry (possibly replacing a previously-added one by the same name)

Parameters

registry

the registry that emitted the signal

  

feature

the feature that has been added

  

user_data

user data set when the signal handler was connected.

  

Flags: Run Last

The “plugin-added” signal

void
user_function (GstRegistry *registry,
               GstPlugin   *plugin,
               gpointer     user_data)

Signals that a plugin has been added to the registry (possibly replacing a previously-added one by the same name)

Parameters

registry

the registry that emitted the signal

  

plugin

the plugin that has been added

  

user_data

user data set when the signal handler was connected.

  

Flags: Run Last

See Also

GstPlugin, GstPluginFeature

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