# GstMeta

The GstMeta structure should be included as the first member of a GstBuffer metadata structure. The structure defines the API of the metadata and should be accessible to all elements using the metadata.

A metadata API is registered with gst_meta_api_type_register which takes a name for the metadata API and some tags associated with the metadata. With gst_meta_api_type_has_tag one can check if a certain metadata API contains a given tag.

Multiple implementations of a metadata API can be registered. To implement a metadata API, gst_meta_register should be used. This function takes all parameters needed to create, free and transform metadata along with the size of the metadata. The function returns a GstMetaInfo structure that contains the information for the implementation of the API.

A specific implementation can be retrieved by name with gst_meta_get_info.

See GstBuffer for how the metadata can be added, retrieved and removed from buffers.

## GstMeta

Base structure for metadata. Custom metadata will put this structure as the first member of their structure.

### Members

`flags` (GstMetaFlags) –

extra flags for the metadata

`info` (const GstMetaInfo *) –

pointer to the GstMetaInfo

## GstMeta

Base structure for metadata. Custom metadata will put this structure as the first member of their structure.

### Members

`flags` (GstMetaFlags) –

extra flags for the metadata

`info` (GstMetaInfo) –

pointer to the GstMetaInfo

## GstMeta

Base structure for metadata. Custom metadata will put this structure as the first member of their structure.

### Members

`flags` (GstMetaFlags) –

extra flags for the metadata

`info` (GstMetaInfo) –

pointer to the GstMetaInfo

### Methods

#### gst_meta_compare_seqnum

    gint
    gst_meta_compare_seqnum (const GstMeta * meta1,
                             const GstMeta * meta2)

Meta sequence number compare function. Can be used as GCompareFunc or a GCompareDataFunc.

Parameters:

`meta1` –

a GstMeta

`meta2` –

a GstMeta

Returns –

a negative number if meta1 comes before meta2, 0 if both metas have an equal sequence number, or a positive integer if meta1 comes after meta2.

Since : 1.16

#### Gst.Meta.prototype.compare_seqnum

    function Gst.Meta.prototype.compare_seqnum(meta2: Gst.Meta): {
        // javascript wrapper for 'gst_meta_compare_seqnum'
    }

Meta sequence number compare function. Can be used as GLib.CompareFunc or a GLib.CompareDataFunc.

Parameters:

`meta1` ( Gst.Meta ) –

a Gst.Meta

`meta2` ( Gst.Meta ) –

a Gst.Meta

Returns ( Number ) –

a negative number if meta1 comes before meta2, 0 if both metas have an equal sequence number, or a positive integer if meta1 comes after meta2.

Since : 1.16

#### Gst.Meta.compare_seqnum

    def Gst.Meta.compare_seqnum (self, meta2):
        #python wrapper for 'gst_meta_compare_seqnum'

Meta sequence number compare function. Can be used as GLib.CompareFunc or a GLib.CompareDataFunc.

Parameters:

`meta1` ( Gst.Meta ) –

a Gst.Meta

`meta2` ( Gst.Meta ) –

a Gst.Meta

Returns ( int ) –

a negative number if meta1 comes before meta2, 0 if both metas have an equal sequence number, or a positive integer if meta1 comes after meta2.

Since : 1.16

#### gst_meta_get_seqnum

    guint64
    gst_meta_get_seqnum (const GstMeta * meta)

Gets seqnum for this meta.

Parameters:

`meta` –

a GstMeta

Returns –
No description available

Since : 1.16

#### Gst.Meta.prototype.get_seqnum

    function Gst.Meta.prototype.get_seqnum(): {
        // javascript wrapper for 'gst_meta_get_seqnum'
    }

Gets seqnum for this meta.

Parameters:

`meta` ( Gst.Meta ) –

a Gst.Meta

Returns ( Number ) –
No description available

Since : 1.16

#### Gst.Meta.get_seqnum

    def Gst.Meta.get_seqnum (self):
        #python wrapper for 'gst_meta_get_seqnum'

Gets seqnum for this meta.

Parameters:

`meta` ( Gst.Meta ) –

a Gst.Meta

Returns ( int ) –
No description available

Since : 1.16

### Functions

#### gst_meta_api_type_get_tags

    const gchar*const **
    gst_meta_api_type_get_tags (GType api)

Parameters:

`api` –

an API

Returns ( [transfer: none] [array zero-terminated=1] [element-type utf8] ) –

an array of tags as strings.

Since : 1.2

#### Gst.prototype.meta_api_type_get_tags

    function Gst.prototype.meta_api_type_get_tags(api: GObject.Type): {
        // javascript wrapper for 'gst_meta_api_type_get_tags'
    }

Parameters:

`api` ( GObject.Type ) –

an API

Returns ( [ String ] ) –

an array of tags as strings.

Since : 1.2

#### Gst.meta_api_type_get_tags

    def Gst.meta_api_type_get_tags (api):
        #python wrapper for 'gst_meta_api_type_get_tags'

Parameters:

`api` ( GObject.Type ) –

an API

Returns ( [ str ] ) –

an array of tags as strings.

Since : 1.2

#### gst_meta_api_type_has_tag

    gboolean
    gst_meta_api_type_has_tag (GType api,
                               GQuark tag)

Check if api was registered with tag.

Parameters:

`api` –

an API

`tag` –

the tag to check

Returns –

TRUE if api was registered with tag.

#### Gst.prototype.meta_api_type_has_tag

    function Gst.prototype.meta_api_type_has_tag(api: GObject.Type, tag: GLib.Quark): {
        // javascript wrapper for 'gst_meta_api_type_has_tag'
    }

Check if api was registered with tag.

Parameters:

`api` ( GObject.Type ) –

an API

`tag` ( GLib.Quark ) –

the tag to check

Returns ( Number ) –

true if api was registered with tag.

#### Gst.meta_api_type_has_tag

    def Gst.meta_api_type_has_tag (api, tag):
        #python wrapper for 'gst_meta_api_type_has_tag'

Check if api was registered with tag.

Parameters:

`api` ( GObject.Type ) –

an API

`tag` ( GLib.Quark ) –

the tag to check

Returns ( bool ) –

True if api was registered with tag.

#### gst_meta_api_type_register

    GType
    gst_meta_api_type_register (const gchar * api,
                                const gchar ** tags)

Register and return a GType for the api and associate it with tags.

Parameters:

`api` –

an API to register

`tags` ( [array zero-terminated=1] ) –

tags for api

Returns –

a unique GType for api.

#### Gst.prototype.meta_api_type_register

    function Gst.prototype.meta_api_type_register(api: String, tags: [ String ]): {
        // javascript wrapper for 'gst_meta_api_type_register'
    }

Register and return a GType for the api and associate it with tags.

Parameters:

`api` ( String ) –

an API to register

`tags` ( [ String ] ) –

tags for api

Returns ( GObject.Type ) –

a unique GType for api.

#### Gst.meta_api_type_register

    def Gst.meta_api_type_register (api, tags):
        #python wrapper for 'gst_meta_api_type_register'

Register and return a GType for the api and associate it with tags.

Parameters:

`api` ( str ) –

an API to register

`tags` ( [ str ] ) –

tags for api

Returns ( GObject.Type ) –

a unique GType for api.

#### gst_meta_get_info

    const GstMetaInfo *
    gst_meta_get_info (const gchar * impl)

Lookup a previously registered meta info structure by its implementation name impl.

Parameters:

`impl` –

the name

Returns ( [transfer: none] [nullable] ) –

a GstMetaInfo with impl, or NULL when no such metainfo exists.

#### Gst.prototype.meta_get_info

    function Gst.prototype.meta_get_info(impl: String): {
        // javascript wrapper for 'gst_meta_get_info'
    }

Lookup a previously registered meta info structure by its implementation name impl.

Parameters:

`impl` ( String ) –

the name

Returns ( Gst.MetaInfo ) –

a Gst.MetaInfo with impl, or null when no such metainfo exists.

#### Gst.meta_get_info

    def Gst.meta_get_info (impl):
        #python wrapper for 'gst_meta_get_info'

Lookup a previously registered meta info structure by its implementation name impl.

Parameters:

`impl` ( str ) –

the name

Returns ( Gst.MetaInfo ) –

a Gst.MetaInfo with impl, or None when no such metainfo exists.

#### gst_meta_register

    const GstMetaInfo *
    gst_meta_register (GType api,
                       const gchar * impl,
                       gsize size,
                       GstMetaInitFunction init_func,
                       GstMetaFreeFunction free_func,
                       GstMetaTransformFunction transform_func)

Register a new GstMeta implementation.

The same info can be retrieved later with gst_meta_get_info by using impl as the key.

Parameters:

`api` –

the type of the GstMeta API

`impl` –

the name of the GstMeta implementation

`size` –

the size of the GstMeta structure

`init_func` ( [scope async] ) –

a GstMetaInitFunction

`free_func` ( [scope async] ) –

a GstMetaFreeFunction

`transform_func` ( [scope async] ) –

a GstMetaTransformFunction

Returns ( [transfer: none] [nullable] ) –

a GstMetaInfo that can be used to access metadata.

#### Gst.prototype.meta_register

    function Gst.prototype.meta_register(api: GObject.Type, impl: String, size: Number, init_func: Gst.MetaInitFunction, free_func: Gst.MetaFreeFunction, transform_func: Gst.MetaTransformFunction): {
        // javascript wrapper for 'gst_meta_register'
    }

Register a new Gst.Meta implementation.

The same info can be retrieved later with Gst.prototype.meta_get_info by using impl as the key.

Parameters:

`api` ( GObject.Type ) –

the type of the Gst.Meta API

`impl` ( String ) –

the name of the Gst.Meta implementation

`size` ( Number ) –

the size of the Gst.Meta structure

`init_func` ( Gst.MetaInitFunction ) –

a Gst.MetaInitFunction

`free_func` ( Gst.MetaFreeFunction ) –

a Gst.MetaFreeFunction

`transform_func` ( Gst.MetaTransformFunction ) –

a Gst.MetaTransformFunction

Returns ( Gst.MetaInfo ) –

a Gst.MetaInfo that can be used to access metadata.

#### Gst.meta_register

    def Gst.meta_register (api, impl, size, init_func, free_func, transform_func):
        #python wrapper for 'gst_meta_register'

Register a new Gst.Meta implementation.

The same info can be retrieved later with Gst.meta_get_info by using impl as the key.

Parameters:

`api` ( GObject.Type ) –

the type of the Gst.Meta API

`impl` ( str ) –

the name of the Gst.Meta implementation

`size` ( int ) –

the size of the Gst.Meta structure

`init_func` ( Gst.MetaInitFunction ) –

a Gst.MetaInitFunction

`free_func` ( Gst.MetaFreeFunction ) –

a Gst.MetaFreeFunction

`transform_func` ( Gst.MetaTransformFunction ) –

a Gst.MetaTransformFunction

Returns ( Gst.MetaInfo ) –

a Gst.MetaInfo that can be used to access metadata.

## GstMetaInfo

The GstMetaInfo provides information about a specific metadata structure.

### Members

`api` (GType) –

tag identifying the metadata structure and api

`type` (GType) –

type identifying the implementor of the api

`size` (gsize) –

size of the metadata

## Gst.MetaInfo

The Gst.MetaInfo provides information about a specific metadata structure.

### Members

`api` (GObject.Type) –

tag identifying the metadata structure and api

`type` (GObject.Type) –

type identifying the implementor of the api

`size` (Number) –

size of the metadata

## Gst.MetaInfo

The Gst.MetaInfo provides information about a specific metadata structure.

### Members

`api` (GObject.Type) –

tag identifying the metadata structure and api

`type` (GObject.Type) –

type identifying the implementor of the api

`size` (int) –

size of the metadata

## GstMetaTransformCopy

Extra data passed to a "gst-copy" transform GstMetaTransformFunction.

### Members

`region` (gboolean) –

TRUE if only region is copied

`offset` (gsize) –

the offset to copy, 0 if region is FALSE, otherwise > 0

`size` (gsize) –

the size to copy, -1 or the buffer size when region is FALSE

## Gst.MetaTransformCopy

Extra data passed to a "gst-copy" transform Gst.MetaTransformFunction.

### Members

`region` (Number) –

true if only region is copied

`offset` (Number) –

the offset to copy, 0 if region is false, otherwise > 0

`size` (Number) –

the size to copy, -1 or the buffer size when region is false

## Gst.MetaTransformCopy

Extra data passed to a "gst-copy" transform Gst.MetaTransformFunction.

### Members

`region` (bool) –

True if only region is copied

`offset` (int) –

the offset to copy, 0 if region is False, otherwise > 0

`size` (int) –

the size to copy, -1 or the buffer size when region is False

## Function Macros

### GST_META_CAST

    #define GST_META_CAST(meta)   ((GstMeta *)(meta))

### GST_META_FLAGS

    #define GST_META_FLAGS(meta)  (GST_META_CAST (meta)->flags)

A flags word containing GstMetaFlags flags set on meta

Parameters:

`meta` –

a GstMeta.

### GST_META_FLAG_IS_SET

    #define GST_META_FLAG_IS_SET(meta,flag)        !!(GST_META_FLAGS (meta) & (flag))

Gives the status of a specific flag on a metadata.

Parameters:

`meta` –

a GstMeta.

`flag` –

the GstMetaFlags to check.

### GST_META_FLAG_SET

    #define GST_META_FLAG_SET(meta,flag)           (GST_META_FLAGS (meta) |= (flag))

Sets a metadata flag on a metadata.

Parameters:

`meta` –

a GstMeta.

`flag` –

the GstMetaFlags to set.

### GST_META_FLAG_UNSET

    #define GST_META_FLAG_UNSET(meta,flag)         (GST_META_FLAGS (meta) &= ~(flag))

Clears a metadata flag.

Parameters:

`meta` –

a GstMeta.

`flag` –

the GstMetaFlags to clear.

### GST_META_TRANSFORM_IS_COPY

    #define GST_META_TRANSFORM_IS_COPY(type) ((type) == _gst_meta_transform_copy)

Check if the transform type is a copy transform

Parameters:

`type` –

a transform type

## Enumerations

### GstMetaFlags

Extra metadata flags.

##### Members

`GST_META_FLAG_NONE` (0) –

no flags

`GST_META_FLAG_READONLY` (1) –

metadata should not be modified

`GST_META_FLAG_POOLED` (2) –

metadata is managed by a bufferpool

`GST_META_FLAG_LOCKED` (4) –

metadata should not be removed

`GST_META_FLAG_LAST` (65536) –

additional flags can be added starting from this flag.

### Gst.MetaFlags

Extra metadata flags.

##### Members

`Gst.MetaFlags.NONE` (0) –

no flags

`Gst.MetaFlags.READONLY` (1) –

metadata should not be modified

`Gst.MetaFlags.POOLED` (2) –

metadata is managed by a bufferpool

`Gst.MetaFlags.LOCKED` (4) –

metadata should not be removed

`Gst.MetaFlags.LAST` (65536) –

additional flags can be added starting from this flag.

### Gst.MetaFlags

Extra metadata flags.

##### Members

`Gst.MetaFlags.NONE` (0) –

no flags

`Gst.MetaFlags.READONLY` (1) –

metadata should not be modified

`Gst.MetaFlags.POOLED` (2) –

metadata is managed by a bufferpool

`Gst.MetaFlags.LOCKED` (4) –

metadata should not be removed

`Gst.MetaFlags.LAST` (65536) –

additional flags can be added starting from this flag.

## Constants

### GST_META_TAG_MEMORY

    #define GST_META_TAG_MEMORY (_gst_meta_tag_memory)

Metadata tagged with this tag depends on the particular memory or buffer that it is on.

### GST_META_TAG_MEMORY_STR

    #define GST_META_TAG_MEMORY_STR "memory"

This metadata stays relevant as long as memory layout is unchanged.

### Gst.META_TAG_MEMORY_STR

This metadata stays relevant as long as memory layout is unchanged.

### Gst.META_TAG_MEMORY_STR

This metadata stays relevant as long as memory layout is unchanged.

## Callbacks

### GstMetaFreeFunction

    (*GstMetaFreeFunction) (GstMeta * meta,
                            GstBuffer * buffer)

Function called when meta is freed in buffer.

Parameters:

`meta` –

a GstMeta

`buffer` –

a GstBuffer

### Gst.MetaFreeFunction

    function Gst.MetaFreeFunction(meta: Gst.Meta, buffer: Gst.Buffer): {
        // javascript wrapper for 'GstMetaFreeFunction'
    }

Function called when meta is freed in buffer.

Parameters:

`meta` ( Gst.Meta ) –

a Gst.Meta

`buffer` ( Gst.Buffer ) –

a Gst.Buffer

### Gst.MetaFreeFunction

    def Gst.MetaFreeFunction (meta, buffer):
        #python wrapper for 'GstMetaFreeFunction'

Function called when meta is freed in buffer.

Parameters:

`meta` ( Gst.Meta ) –

a Gst.Meta

`buffer` ( Gst.Buffer ) –

a Gst.Buffer

### GstMetaInitFunction

    gboolean
    (*GstMetaInitFunction) (GstMeta * meta,
                            gpointer params,
                            GstBuffer * buffer)

Function called when meta is initialized in buffer.

Parameters:

`meta` –

a GstMeta

`params` –

parameters passed to the init function

`buffer` –

a GstBuffer

Returns –
No description available

### Gst.MetaInitFunction

    function Gst.MetaInitFunction(meta: Gst.Meta, params: Object, buffer: Gst.Buffer): {
        // javascript wrapper for 'GstMetaInitFunction'
    }

Function called when meta is initialized in buffer.

Parameters:

`meta` ( Gst.Meta ) –

a Gst.Meta

`params` ( Object ) –

parameters passed to the init function

`buffer` ( Gst.Buffer ) –

a Gst.Buffer

Returns ( Number ) –
No description available

### Gst.MetaInitFunction

    def Gst.MetaInitFunction (meta, params, buffer):
        #python wrapper for 'GstMetaInitFunction'

Function called when meta is initialized in buffer.

Parameters:

`meta` ( Gst.Meta ) –

a Gst.Meta

`params` ( object ) –

parameters passed to the init function

`buffer` ( Gst.Buffer ) –

a Gst.Buffer

Returns ( bool ) –
No description available

### GstMetaTransformFunction

    gboolean
    (*GstMetaTransformFunction) (GstBuffer * transbuf,
                                 GstMeta * meta,
                                 GstBuffer * buffer,
                                 GQuark type,
                                 gpointer data)

Function called for each meta in buffer as a result of performing a transformation on transbuf. Additional type specific transform data is passed to the function as data.

Implementations should check the type of the transform and parse additional type specific fields in data that should be used to update the metadata on transbuf.

Parameters:

`transbuf` –

a GstBuffer

`meta` –

a GstMeta

`buffer` –

a GstBuffer

`type` –

the transform type

`data` –

transform specific data.

Returns –

TRUE if the transform could be performed

### Gst.MetaTransformFunction

    function Gst.MetaTransformFunction(transbuf: Gst.Buffer, meta: Gst.Meta, buffer: Gst.Buffer, type: GLib.Quark, data: Object): {
        // javascript wrapper for 'GstMetaTransformFunction'
    }

Function called for each meta in buffer as a result of performing a transformation on transbuf. Additional type specific transform data is passed to the function as data.

Implementations should check the type of the transform and parse additional type specific fields in data that should be used to update the metadata on transbuf.

Parameters:

`transbuf` ( Gst.Buffer ) –

a Gst.Buffer

`meta` ( Gst.Meta ) –

a Gst.Meta

`buffer` ( Gst.Buffer ) –

a Gst.Buffer

`type` ( GLib.Quark ) –

the transform type

`data` ( Object ) –

transform specific data.

Returns ( Number ) –

true if the transform could be performed

### Gst.MetaTransformFunction

    def Gst.MetaTransformFunction (transbuf, meta, buffer, type, data):
        #python wrapper for 'GstMetaTransformFunction'

Function called for each meta in buffer as a result of performing a transformation on transbuf. Additional type specific transform data is passed to the function as data.

Implementations should check the type of the transform and parse additional type specific fields in data that should be used to update the metadata on transbuf.

Parameters:

`transbuf` ( Gst.Buffer ) –

a Gst.Buffer

`meta` ( Gst.Meta ) –

a Gst.Meta

`buffer` ( Gst.Buffer ) –

a Gst.Buffer

`type` ( GLib.Quark ) –

the transform type

`data` ( object ) –

transform specific data.

Returns ( bool ) –

True if the transform could be performed

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