GstRegistry: GStreamer Core Reference Manual

## 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.

`plugin` 's reference count will be incremented, and any floating reference will be removed (see `gst_object_ref_sink()`)

#### Parameters

registry | the registry to add the plugin to |
plugin | the plugin to add. | [transfer floating]

#### 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. | [type filename]

#### 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.

`feature` 's reference count will be incremented, and any floating reference will be removed (see `gst_object_ref_sink()`)

#### Parameters

registry | the registry to add the plugin to |
feature | the feature to add. | [transfer floating]

#### 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