GstMeta

GstCustomMeta

Since : 1.20

gst_custom_meta_get_structure

GstStructure *
gst_custom_meta_get_structure (GstCustomMeta * meta)

Retrieve the GstStructure backing a custom meta, the structure's mutability is conditioned to the writability of the GstBuffer meta is attached to.

Since : 1.20

gst_custom_meta_has_name

gboolean
gst_custom_meta_has_name (GstCustomMeta * meta,
                          const gchar * name)

Checks whether the name of the custom meta is name

Since : 1.20

GstMeta

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.

Since : 1.16

gst_meta_get_seqnum

guint64
gst_meta_get_seqnum (const GstMeta * meta)

Gets seqnum for this meta.

Since : 1.16

gst_meta_serialize

gboolean
gst_meta_serialize (const GstMeta * meta,
                    GstByteArrayInterface * data)

Serialize meta into a format that can be stored or transmitted and later deserialized by gst_meta_deserialize.

This is only supported for meta that implements serialize_func, FALSE is returned otherwise.

Upon failure, data->data pointer could have been reallocated, but data->len won't be modified. This is intended to be able to append multiple metas into the same GByteArray.

Since serialization size is often the same for every buffer, caller may want to remember the size of previous data to preallocate the next.

Since : 1.24

gst_meta_serialize_simple

gboolean
gst_meta_serialize_simple (const GstMeta * meta,
                           GByteArray * data)

Same as gst_meta_serialize but with a GByteArray instead of GstByteArrayInterface.

Since : 1.24

gst_meta_api_type_aggregate_params

gboolean
gst_meta_api_type_aggregate_params (GType api,
                                    GstStructure ** aggregated_params,
                                    const GstStructure * params0,
                                    const GstStructure * params1)

When a element like tee decides the allocation, each downstream element may fill different parameters and pass them to gst_query_add_allocation_meta. In order to keep these parameters, a merge operation is needed. This aggregate function can combine the parameters from params0 and param1, and write the result back into aggregated_params.

Since : 1.26

gst_meta_api_type_get_tags

const gchar*const **
gst_meta_api_type_get_tags (GType api)

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.

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.

gst_meta_api_type_set_params_aggregator

gst_meta_api_type_set_params_aggregator (GType api,
                                         GstAllocationMetaParamsAggregator aggregator)

This function sets the aggregator function for a specific API type.

Since : 1.26

gst_meta_deserialize

GstMeta *
gst_meta_deserialize (GstBuffer * buffer,
                      const guint8 * data,
                      gsize size,
                      guint32 * consumed)

Recreate a GstMeta from serialized data returned by gst_meta_serialize and add it to buffer.

Note that the meta must have been previously registered by calling one of gst_*_meta_get_info () functions.

consumed is set to the number of bytes that can be skipped from data to find the next meta serialization, if any. In case of parsing error that does not allow to determine that size, consumed is set to 0.

Since : 1.24

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.

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.

gst_meta_register_custom

const GstMetaInfo *
gst_meta_register_custom (const gchar * name,
                          const gchar ** tags,
                          GstCustomMetaTransformFunction transform_func,
                          gpointer user_data,
                          GDestroyNotify destroy_data)

Register a new custom GstMeta implementation, backed by an opaque structure holding a GstStructure.

The registered info can be retrieved later with gst_meta_get_info by using name as the key.

The backing GstStructure can be retrieved with gst_custom_meta_get_structure, its mutability is conditioned by the writability of the buffer the meta is attached to.

When transform_func is NULL, the meta and its backing GstStructure will always be copied when the transform operation is copy, other operations are discarded, copy regions are ignored.

Since : 1.20

gst_meta_register_custom_simple

const GstMetaInfo *
gst_meta_register_custom_simple (const gchar * name)

Simplified version of gst_meta_register_custom, with no tags and no transform function.

Since : 1.24

GstMetaInfo

gst_meta_info_is_custom

gboolean
gst_meta_info_is_custom (const GstMetaInfo * info)

Since : 1.20

gst_meta_info_register

const GstMetaInfo *
gst_meta_info_register (GstMetaInfo * info)

Registers a new meta.

Use the structure returned by gst_meta_info_new, it consumes it and the structure shouldnt be used after. The one returned by the function can be kept.

Since : 1.24

gst_meta_info_new

GstMetaInfo *
gst_meta_info_new (GType api,
                   const gchar * impl,
                   gsize size)

Creates a new structure that needs to be filled before being registered. This structure should filled and then registered with gst_meta_info_register.

Example:

const GstMetaInfo *
gst_my_meta_get_info (void)
{
  static const GstMetaInfo *meta_info = NULL;

  if (g_once_init_enter ((GstMetaInfo **) & meta_info)) {
    GstMetaInfo *info = gst_meta_info_new (
      gst_my_meta_api_get_type (),
        "GstMyMeta",
       sizeof (GstMyMeta));
    const GstMetaInfo *meta = NULL;

    info->init_func = my_meta_init;
    info->free_func = my_meta_free;
    info->transform_func = my_meta_transform;
    info->serialize_func = my_meta_serialize;
    info->deserialize_func = my_meta_deserialize;
    meta = gst_meta_info_register (info);
    g_once_init_leave ((GstMetaInfo **) & meta_info, (GstMetaInfo *) meta);
  }

  return meta_info;
}

Since : 1.24

GstMetaTransformCopy

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

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.

GST_META_FLAG_SET

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

Sets a metadata flag on a metadata.

GST_META_FLAG_UNSET

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

Clears a metadata flag.

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

GstMetaFlags

Extra metadata flags.

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.

deprecated : The GQuarks are not exported by any public API, use GST_META_TAG_MEMORY_STR instead.

GST_META_TAG_MEMORY_REFERENCE_STR

#define GST_META_TAG_MEMORY_REFERENCE_STR "memory-reference"

This metadata stays relevant until a deep copy is made.

Since : 1.20.4

GST_META_TAG_MEMORY_STR

#define GST_META_TAG_MEMORY_STR "memory"

This metadata stays relevant as long as memory layout is unchanged. In hindsight, this tag should have been called "memory-layout".

Since : 1.2

GstAllocationMetaParamsAggregator

gboolean
(*GstAllocationMetaParamsAggregator) (GstStructure ** aggregated_params,
                                      const GstStructure * params0,
                                      const GstStructure * params1)

The aggregator function will combine the parameters from params0 and param1 and write the result back into aggregated_params.

Since : 1.26

GstCustomMetaTransformFunction

gboolean
(*GstCustomMetaTransformFunction) (GstBuffer * transbuf,
                                   GstCustomMeta * meta,
                                   GstBuffer * buffer,
                                   GQuark type,
                                   gpointer data,
                                   gpointer user_data)

Function called for each meta in buffer as a result of performing a transformation that yields 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.

Since : 1.20

GstMetaClearFunction

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

Clears the content of the meta. This will be called by the GstBufferPool when a pooled buffer is returned.

Since : 1.24

GstMetaDeserializeFunction

GstMeta *
(*GstMetaDeserializeFunction) (const GstMetaInfo * info,
                               GstBuffer * buffer,
                               const guint8 * data,
                               gsize size,
                               guint8 version)

Recreate a GstMeta from serialized data returned by GstMetaSerializeFunction and add it to buffer.

Since : 1.24

GstMetaFreeFunction

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

Function called when meta is freed in buffer.

GstMetaInitFunction

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

Function called when meta is initialized in buffer.

GstMetaSerializeFunction

gboolean
(*GstMetaSerializeFunction) (const GstMeta * meta,
                             GstByteArrayInterface * data,
                             guint8 * version)

Serialize meta into a format that can be stored or transmitted and later deserialized by GstMetaDeserializeFunction.

By default version is set to 0, it should be bumped if incompatible changes are made to the format so GstMetaDeserializeFunction can deserialize each version.

Since : 1.24

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.