GstPlugin: GStreamer Core Reference Manual

## GstPlugin GstPlugin — Container for features loaded from a shared object module |

## Functions

GQuark | gst_plugin_error_quark ()
gboolean | (*GstPluginInitFunc) ()
gboolean | (*GstPluginInitFullFunc) ()
#define | GST_PLUGIN_DEFINE()
#define | GST_PLUGIN_STATIC_DECLARE()
#define | GST_PLUGIN_STATIC_REGISTER()
gboolean | (*GstPluginFilter) ()
const gchar * | gst_plugin_get_name ()
const gchar * | gst_plugin_get_description ()
const gchar * | gst_plugin_get_filename ()
const gchar * | gst_plugin_get_license ()
const gchar * | gst_plugin_get_package ()
const gchar * | gst_plugin_get_origin ()
const gchar * | gst_plugin_get_source ()
const gchar * | gst_plugin_get_version ()
const gchar * | gst_plugin_get_release_date_string ()
gboolean | gst_plugin_is_loaded ()
const GstStructure * | gst_plugin_get_cache_data ()
void | gst_plugin_set_cache_data ()
GstPlugin * | gst_plugin_load_file ()
GstPlugin * | gst_plugin_load ()
GstPlugin * | gst_plugin_load_by_name ()
void | gst_plugin_list_free ()
gboolean | gst_plugin_register_static ()
gboolean | gst_plugin_register_static_full ()
void | gst_plugin_add_dependency ()
void | gst_plugin_add_dependency_simple ()

## Types and Values

#define | GST_PLUGIN_ERROR
enum | GstPluginError
| GstPlugin
struct | GstPluginDesc
#define | GST_LICENSE_UNKNOWN
enum | GstPluginFlags
enum | GstPluginDependencyFlags

## Object Hierarchy

        GObject
        ╰── GInitiallyUnowned
            ╰── GstObject
                ╰── GstPlugin

## Includes

    #include <gst/gst.h>

## Description

GStreamer is extensible, so GstElement instances 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 gst_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

gst_plugin_desc.

Once you have a handle to a GstPlugin (e.g. from the GstRegistry), you can add any object that subclasses GstPluginFeature.

Usually plugins are always automatically 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.

## Functions

### gst_plugin_error_quark ()

    GQuark
    gst_plugin_error_quark (void);

Get the error quark.

#### Returns

The error quark used in GError messages

### GstPluginInitFunc ()

    gboolean
    (*GstPluginInitFunc) (GstPlugin *plugin);

A plugin should provide a pointer to a function of this type in the plugin_desc struct. This function will be called by the loader at startup. One would then register each GstPluginFeature.

#### Parameters

plugin | The plugin object |

#### Returns

`TRUE` if plugin initialised successfully

### GstPluginInitFullFunc ()

    gboolean
    (*GstPluginInitFullFunc) (GstPlugin *plugin,
                              gpointer user_data);

A plugin should provide a pointer to a function of either GstPluginInitFunc or this type in the plugin_desc struct. The function will be called by the loader at startup. One would then register each GstPluginFeature. This version allows user data to be passed to init function (useful for bindings).

#### Parameters

plugin | The plugin object |
user_data | extra data |

#### Returns

`TRUE` if plugin initialised successfully

### GST_PLUGIN_DEFINE()

    #define             GST_PLUGIN_DEFINE(major,minor,name,description,init,version,license,package,origin)

This macro needs to be used to define the entry point and meta data of a plugin. One would use this macro to export a plugin, so that it can be used by other applications.

The macro uses a define named PACKAGE for the GstPluginDesc,source field. When using autoconf, this is usually set automatically via the AC_INIT macro, and set in config.h. If you are not using autoconf, you will need to define PACKAGE yourself and set it to a short mnemonic string identifying your application/package, e.g. 'someapp' or 'my-plugins-foo.

If defined, the GST_PACKAGE_RELEASE_DATETIME will also be used for the GstPluginDesc,release_datetime field.

#### Parameters

major | major version number of the gstreamer-core that plugin was compiled for |
minor | minor version number of the gstreamer-core that plugin was compiled for |
name | short, but unique name of the plugin |
description | information about the purpose of the plugin |
init | function pointer to the plugin_init method with the signature of `static gboolean plugin_init (GstPlugin * plugin)`. |
version | full version string (e.g. VERSION from config.h) |
license | under which licence the package has been released, e.g. GPL, LGPL. |
package | the package-name (e.g. PACKAGE_NAME from config.h) |
origin | a description from where the package comes from (e.g. the homepage URL) |

### GST_PLUGIN_STATIC_DECLARE()

    #define             GST_PLUGIN_STATIC_DECLARE(name)

This macro can be used to initialize statically linked plugins. It is necessary to call this macro before the plugin can be used. It has to be used in combination with GST_PLUGIN_STATIC_REGISTER and must be placed outside any block to declare the plugin initialization function.

#### Parameters

name | short, but unique name of the plugin |

Since: 1.2

### GST_PLUGIN_STATIC_REGISTER()

    #define GST_PLUGIN_STATIC_REGISTER(name) G_PASTE(gst_plugin_, G_PASTE(name, _register)) ()

This macro can be used to initialize statically linked plugins. It is necessary to call this macro before the plugin can be used. It has to be used in combination with GST_PLUGIN_STATIC_DECLARE and calls the plugin initialization function.

#### Parameters

name | short, but unique name of the plugin |

Since: 1.2

### GstPluginFilter ()

    gboolean
    (*GstPluginFilter) (GstPlugin *plugin,
                        gpointer user_data);

A function that can be used with e.g. `gst_registry_plugin_filter()` to get a list of plugins that match certain criteria.

#### Parameters

plugin | the plugin to check |
user_data | the user_data that has been passed on e.g. `gst_registry_plugin_filter()` |

#### Returns

`TRUE` for a positive match, `FALSE` otherwise

### gst_plugin_get_name ()

    const gchar *
    gst_plugin_get_name (GstPlugin *plugin);

Get the short name of the plugin

#### Parameters

plugin | plugin to get the name of |

#### Returns

the name of the plugin

### gst_plugin_get_description ()

    const gchar *
    gst_plugin_get_description (GstPlugin *plugin);

Get the long descriptive name of the plugin

#### Parameters

plugin | plugin to get long name of |

#### Returns

the long name of the plugin

### gst_plugin_get_filename ()

    const gchar *
    gst_plugin_get_filename (GstPlugin *plugin);

get the filename of the plugin

#### Parameters

plugin | plugin to get the filename of |

#### Returns

the filename of the plugin.

[type filename]

### gst_plugin_get_license ()

    const gchar *
    gst_plugin_get_license (GstPlugin *plugin);

get the license of the plugin

#### Parameters

plugin | plugin to get the license of |

#### Returns

the license of the plugin

### gst_plugin_get_package ()

    const gchar *
    gst_plugin_get_package (GstPlugin *plugin);

get the package the plugin belongs to.

#### Parameters

plugin | plugin to get the package of |

#### Returns

the package of the plugin

### gst_plugin_get_origin ()

    const gchar *
    gst_plugin_get_origin (GstPlugin *plugin);

get the URL where the plugin comes from

#### Parameters

plugin | plugin to get the origin of |

#### Returns

the origin of the plugin

### gst_plugin_get_source ()

    const gchar *
    gst_plugin_get_source (GstPlugin *plugin);

get the source module the plugin belongs to.

#### Parameters

plugin | plugin to get the source of |

#### Returns

the source of the plugin

### gst_plugin_get_version ()

    const gchar *
    gst_plugin_get_version (GstPlugin *plugin);

get the version of the plugin

#### Parameters

plugin | plugin to get the version of |

#### Returns

the version of the plugin

### gst_plugin_get_release_date_string ()

    const gchar *
    gst_plugin_get_release_date_string (GstPlugin *plugin);

Get the release date (and possibly time) in form of a string, if available.

For normal GStreamer plugin releases this will usually just be a date in the form of "YYYY-MM-DD", while pre-releases and builds from git may contain a time component after the date as well, in which case the string will be formatted like "YYYY-MM-DDTHH:MMZ" (e.g. "2012-04-30T09:30Z").

There may be plugins that do not have a valid release date set on them.

#### Parameters

plugin | plugin to get the release date of |

#### Returns

the date string of the plugin, or `NULL` if not available.

[nullable]

### gst_plugin_is_loaded ()

    gboolean
    gst_plugin_is_loaded (GstPlugin *plugin);

queries if the plugin is loaded into memory

#### Parameters

plugin | plugin to query |

#### Returns

`TRUE` is loaded, `FALSE` otherwise

### gst_plugin_get_cache_data ()

    const GstStructure *
    gst_plugin_get_cache_data (GstPlugin *plugin);

Gets the plugin specific data cache. If it is `NULL` there is no cached data stored. This is the case when the registry is getting rebuilt.

#### Parameters

plugin | a plugin |

#### Returns

The cached data as a GstStructure or `NULL`.

[transfer none][nullable]

### gst_plugin_set_cache_data ()

    void
    gst_plugin_set_cache_data (GstPlugin *plugin,
                               GstStructure *cache_data);

Adds plugin specific data to cache. Passes the ownership of the structure to the `plugin` .

The cache is flushed every time the registry is rebuilt.

#### Parameters

plugin | a plugin |
cache_data | a structure containing the data to cache. | [transfer full]

### gst_plugin_load_file ()

    GstPlugin *
    gst_plugin_load_file (const gchar *filename,
                          GError **error);

Loads the given plugin and refs it. Caller needs to unref after use.

#### Parameters

filename | the plugin filename to load. | [type filename]
error | pointer to a `NULL`-valued GError |

#### Returns

a reference to the existing loaded GstPlugin, a reference to the newly-loaded GstPlugin, or `NULL` if an error occurred.

[transfer full]

### gst_plugin_load ()

    GstPlugin *
    gst_plugin_load (GstPlugin *plugin);

Loads `plugin` . Note that the *return value* is the loaded plugin; `plugin` is untouched. The normal use pattern of this function goes like this:

    1
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    GstPlugin *loaded_plugin;
    loaded_plugin = gst_plugin_load (plugin);
    // presumably, we're no longer interested in the potentially-unloaded plugin
    gst_object_unref (plugin);
    plugin = loaded_plugin;

#### Parameters

plugin | plugin to load. | [transfer none]

#### Returns

a reference to a loaded plugin, or `NULL` on error.

[transfer full][nullable]

### gst_plugin_load_by_name ()

    GstPlugin *
    gst_plugin_load_by_name (const gchar *name);

Load the named plugin. Refs the plugin.

#### Parameters

name | name of plugin to load |

#### Returns

a reference to a loaded plugin, or `NULL` on error.

[transfer full][nullable]

### gst_plugin_list_free ()

    void
    gst_plugin_list_free (GList *list);

Unrefs each member of `list` , then frees the list.

#### Parameters

list | list of GstPlugin. | [transfer full][element-type Gst.Plugin]

### gst_plugin_register_static ()

    gboolean
    gst_plugin_register_static (gint major_version,
                                gint minor_version,
                                const gchar *name,
                                const gchar *description,
                                GstPluginInitFunc init_func,
                                const gchar *version,
                                const gchar *license,
                                const gchar *source,
                                const gchar *package,
                                const gchar *origin);

Registers a static plugin, ie. a plugin which is private to an application or library and contained within the application or library (as opposed to being shipped as a separate module file).

You must make sure that GStreamer has been initialised (with `gst_init()` or via `gst_init_get_option_group()`) before calling this function.

#### Parameters

major_version | the major version number of the GStreamer core that the plugin was compiled for, you can just use GST_VERSION_MAJOR here |
minor_version | the minor version number of the GStreamer core that the plugin was compiled for, you can just use GST_VERSION_MINOR here |
name | a unique name of the plugin (ideally prefixed with an application- or library-specific namespace prefix in order to avoid name conflicts in case a similar plugin with the same name ever gets added to GStreamer) |
description | description of the plugin |
init_func | pointer to the init function of this plugin. | [scope call]
version | version string of the plugin |
license | effective license of plugin. Must be one of the approved licenses (see GstPluginDesc above) or the plugin will not be registered. |
source | source module plugin belongs to |
package | shipped package plugin belongs to |
origin | URL to provider of plugin |

#### Returns

`TRUE` if the plugin was registered correctly, otherwise `FALSE`.

### gst_plugin_register_static_full ()

    gboolean
    gst_plugin_register_static_full (gint major_version,
                                     gint minor_version,
                                     const gchar *name,
                                     const gchar *description,
                                     GstPluginInitFullFunc init_full_func,
                                     const gchar *version,
                                     const gchar *license,
                                     const gchar *source,
                                     const gchar *package,
                                     const gchar *origin,
                                     gpointer user_data);

Registers a static plugin, ie. a plugin which is private to an application or library and contained within the application or library (as opposed to being shipped as a separate module file) with a GstPluginInitFullFunc which allows user data to be passed to the callback function (useful for bindings).

You must make sure that GStreamer has been initialised (with `gst_init()` or via `gst_init_get_option_group()`) before calling this function.

#### Parameters

major_version | the major version number of the GStreamer core that the plugin was compiled for, you can just use GST_VERSION_MAJOR here |
minor_version | the minor version number of the GStreamer core that the plugin was compiled for, you can just use GST_VERSION_MINOR here |
name | a unique name of the plugin (ideally prefixed with an application- or library-specific namespace prefix in order to avoid name conflicts in case a similar plugin with the same name ever gets added to GStreamer) |
description | description of the plugin |
init_full_func | pointer to the init function with user data of this plugin. | [scope call]
version | version string of the plugin |
license | effective license of plugin. Must be one of the approved licenses (see GstPluginDesc above) or the plugin will not be registered. |
source | source module plugin belongs to |
package | shipped package plugin belongs to |
origin | URL to provider of plugin |
user_data | gpointer to user data |

#### Returns

`TRUE` if the plugin was registered correctly, otherwise `FALSE`.

### gst_plugin_add_dependency ()

    void
    gst_plugin_add_dependency (GstPlugin *plugin,
                               const gchar **env_vars,
                               const gchar **paths,
                               const gchar **names,
                               GstPluginDependencyFlags flags);

Make GStreamer aware of external dependencies which affect the feature set of this plugin (ie. the elements or typefinders associated with it).

GStreamer will re-inspect plugins with external dependencies whenever any of the external dependencies change. This is useful for plugins which wrap other plugin systems, e.g. a plugin which wraps a plugin-based visualisation library and makes visualisations available as GStreamer elements, or a codec loader which exposes elements and/or caps dependent on what external codec libraries are currently installed.

#### Parameters

plugin | a GstPlugin |
env_vars | `NULL`-terminated array of environment variables affecting the feature set of the plugin (e.g. an environment variable containing paths where to look for additional modules/plugins of a library), or `NULL`. Environment variable names may be followed by a path component which will be added to the content of the environment variable, e.g. "HOME/.mystuff/plugins". | [allow-none][array zero-terminated=1]
paths | `NULL`-terminated array of directories/paths where dependent files may be, or `NULL`. | [allow-none][array zero-terminated=1]
names | `NULL`-terminated array of file names (or file name suffixes, depending on `flags` ) to be used in combination with the paths from `paths` and/or the paths extracted from the environment variables in `env_vars` , or `NULL`. | [allow-none][array zero-terminated=1]
flags | optional flags, or GST_PLUGIN_DEPENDENCY_FLAG_NONE |

### gst_plugin_add_dependency_simple ()

    void
    gst_plugin_add_dependency_simple (GstPlugin *plugin,
                                      const gchar *env_vars,
                                      const gchar *paths,
                                      const gchar *names,
                                      GstPluginDependencyFlags flags);

Make GStreamer aware of external dependencies which affect the feature set of this plugin (ie. the elements or typefinders associated with it).

GStreamer will re-inspect plugins with external dependencies whenever any of the external dependencies change. This is useful for plugins which wrap other plugin systems, e.g. a plugin which wraps a plugin-based visualisation library and makes visualisations available as GStreamer elements, or a codec loader which exposes elements and/or caps dependent on what external codec libraries are currently installed.

Convenience wrapper function for `gst_plugin_add_dependency()` which takes simple strings as arguments instead of string arrays, with multiple arguments separated by predefined delimiters (see above).

#### Parameters

plugin | the GstPlugin |
env_vars | one or more environment variables (separated by ':', ';' or ','), or `NULL`. Environment variable names may be followed by a path component which will be added to the content of the environment variable, e.g. "HOME/.mystuff/plugins:MYSTUFF_PLUGINS_PATH". | [allow-none]
paths | one ore more directory paths (separated by ':' or ';' or ','), or `NULL`. Example: "/usr/lib/mystuff/plugins". | [allow-none]
names | one or more file names or file name suffixes (separated by commas), or `NULL`. | [allow-none]
flags | optional flags, or GST_PLUGIN_DEPENDENCY_FLAG_NONE |

## Types and Values

### GST_PLUGIN_ERROR

    #define GST_PLUGIN_ERROR gst_plugin_error_quark ()

The error message category quark

### enum GstPluginError

The plugin loading errors

#### Members

GST_PLUGIN_ERROR_MODULE | The plugin could not be loaded |
GST_PLUGIN_ERROR_DEPENDENCIES | The plugin has unresolved dependencies |
GST_PLUGIN_ERROR_NAME_MISMATCH | The plugin has already be loaded from a different file |

### GstPlugin

    typedef struct _GstPlugin GstPlugin;

The opaque plugin object

### struct GstPluginDesc

    struct GstPluginDesc {
      gint major_version;
      gint minor_version;
      const gchar *name;
      const gchar *description;
      GstPluginInitFunc plugin_init;
      const gchar *version;
      const gchar *license;
      const gchar *source;
      const gchar *package;
      const gchar *origin;
      const gchar *release_datetime;
    };

A plugin should export a variable of this type called plugin_desc. The plugin loader will use the data provided there to initialize the plugin.

The `licence` parameter must be one of: LGPL, GPL, QPL, GPL/QPL, MPL, BSD, MIT/X11, Proprietary, unknown.

#### Members

gint `major_version`; | the major version number of core that plugin was compiled for |
gint `minor_version`; | the minor version number of core that plugin was compiled for |
const gchar *`name`; | a unique name of the plugin |
const gchar *`description`; | description of plugin |
GstPluginInitFunc `plugin_init`; | pointer to the init function of this plugin. |
const gchar *`version`; | version of the plugin |
const gchar *`license`; | effective license of plugin |
const gchar *`source`; | source module plugin belongs to |
const gchar *`package`; | shipped package plugin belongs to |
const gchar *`origin`; | URL to provider of plugin |
const gchar *`release_datetime`; | date time string in ISO 8601 format (or rather, a subset thereof), or `NULL`. Allowed are the following formats: "YYYY-MM-DD" and "YYY-MM-DDTHH:MMZ" (with 'T' a separator and 'Z' indicating UTC/Zulu time). This field should be set via the GST_PACKAGE_RELEASE_DATETIME preprocessor macro. | [allow-none]

### GST_LICENSE_UNKNOWN

    #define GST_LICENSE_UNKNOWN "unknown"

To be used in GST_PLUGIN_DEFINE if unsure about the licence.

### enum GstPluginFlags

The plugin loading state

#### Members

GST_PLUGIN_FLAG_CACHED | Temporarily loaded plugins |
GST_PLUGIN_FLAG_BLACKLISTED | The plugin won't be scanned (again) |

### enum GstPluginDependencyFlags

Flags used in connection with `gst_plugin_add_dependency()`.

#### Members

GST_PLUGIN_DEPENDENCY_FLAG_NONE | no special flags |
GST_PLUGIN_DEPENDENCY_FLAG_RECURSE | recurse into subdirectories |
GST_PLUGIN_DEPENDENCY_FLAG_PATHS_ARE_DEFAULT_ONLY | use paths argument only if none of the environment variables is set |
GST_PLUGIN_DEPENDENCY_FLAG_FILE_NAME_IS_SUFFIX | interpret filename argument as filter suffix and check all matching files in the directory |
GST_PLUGIN_DEPENDENCY_FLAG_FILE_NAME_IS_PREFIX | interpret filename argument as filter prefix and check all matching files in the directory. Since 1.8. |
GST_PLUGIN_DEPENDENCY_FLAG_PATHS_ARE_RELATIVE_TO_EXE | interpret non-absolute paths as relative to the main executable directory. Since 1.14. |

## See Also

GstPluginFeature, GstElementFactory