Metadata Structures¶

group metadata_structures

Define structures that hold metadata.

Defines

MAX_USER_FIELDS: Defines the number of additional fields available to the user in the metadata structure.

MAX_RESERVED_FIELDS

MAX_LABEL_SIZE: Defines the maximum size of an array for storing a text result.

MAX_ELEMENTS_IN_DISPLAY_META: Defines the maximum number of elements that a given display meta can hold.

UNTRACKED_OBJECT_ID: Defines an untracked object ID.

Typedefs

typedef GList NvDsFrameMetaList

typedef GList NvDsUserMetaList

typedef GList NvDsObjectMetaList

typedef GList NvDisplayMetaList

typedef GList NvDsClassifierMetaList

typedef GList NvDsLabelInfoList

typedef GList NvDsMetaList

typedef void NvDsElementMeta

typedef gpointer (*NvDsMetaCopyFunc)(gpointer data, gpointer user_data)

Defines the type of a callback to copy metadata.

The callback is passed pointers to source metadata. It allocates the required memory, copies the content from the source metadata and returns a pointer to the destination.

Parameters

[in] data: A pointer to the source metadata.
[in] user_data: A pointer to user-specific data.

typedef void (*NvDsMetaReleaseFunc)(gpointer data, gpointer user_data)

Defines the type of a callback to free metadata.

The callback is passed a pointer to metadata created by NvDsMetaCopyFunc(). It frees the metadata and any other resources that the metadata uses.

Parameters

[in] data: A pointer to the metadata to be freed.
[in] user_data: A pointer to user-specific data.

typedef struct _NvDsComp_BboxInfo NvDsComp_BboxInfo: Holds unclipped positional bounding box coordinates of the object processed by the component.

typedef struct _NvDsMetaPool NvDsMetaPool: Holds information about a given metadata pool.

typedef struct _NvDsBaseMeta NvDsBaseMeta: Holds information about base metadata of a given metadata type.

typedef struct _NvDsBatchMeta NvDsBatchMeta: Holds information about a formed batch containing frames from different sources.

typedef struct _NvDsFrameMeta NvDsFrameMeta: Holds metadata for a frame in a batch.

typedef struct _NvDsObjectMeta NvDsObjectMeta: Holds metadata for an object in the frame.

typedef struct _NvDsClassifierMeta NvDsClassifierMeta: Holds classifier metadata for an object.

typedef struct _NvDsLabelInfo NvDsLabelInfo: Holds label metadata for the classifier.

typedef struct NvDsDisplayMeta NvDsDisplayMeta: Holds display metadata that the user can specify in the frame.

typedef struct _NvDsUserMeta NvDsUserMeta: Holds user metadata.

Enums

enum NvDsMetaType

Specifies the type of metadata.

All metadata types are subtypes of NvDsMetaType. Members that represent NVIDIA-defined types are in the range from NVDS_BATCH_META to NVDS_START_USER_META. User-defined types may be assigned values greater than or equal to NVDS_START_USER_META.

Values:

enumerator NVDS_INVALID_META

enumerator NVDS_BATCH_META: Specifies metadata type for formed batch.

enumerator NVDS_FRAME_META: Specifies metadata type for frame.

enumerator NVDS_OBJ_META: Specifies metadata type for a detected object.

enumerator NVDS_DISPLAY_META: Specifies metadata type for display.

enumerator NVDS_CLASSIFIER_META: Specifies metadata type for an object classifier.

enumerator NVDS_LABEL_INFO_META: Specifies metadata type for a label assigned by a classifier.

enumerator NVDS_USER_META: Reserved for internal use.

enumerator NVDS_PAYLOAD_META: Specifies metadata type for a payload generated by a message converter.

enumerator NVDS_EVENT_MSG_META: Specifies metadata type for a payload generated by a message broker.

enumerator NVDS_OPTICAL_FLOW_META: Specifies metadata type for an optical flow.

enumerator NVDS_LATENCY_MEASUREMENT_META: Specifies metadata type for a latency measurement.

enumerator NVDSINFER_TENSOR_OUTPUT_META

Specifies metadata type for raw inference output attached by Gst-nvinfer.

See: NvDsInferTensorMeta for details.

enumerator NVDSINFER_SEGMENTATION_META

Specifies metadata type for segmentation model output attached by Gst-nvinfer.

See: NvDsInferSegmentationMeta for details.

enumerator NVDS_CROP_IMAGE_META

Specifies metadata type for JPEG-encoded object crops.

See the deepstream-image-meta-test app for details.

enumerator NVDS_TRACKER_PAST_FRAME_META: metadata type to be set for tracking previous frames

enumerator NVDS_AUDIO_BATCH_META: Specifies metadata type for formed audio batch.

enumerator NVDS_AUDIO_FRAME_META: Specifies metadata type for audio frame.

enumerator NVDS_RESERVED_META: Reserved field.

enumerator NVDS_GST_CUSTOM_META

Specifies the start of a range of enum values that represent types of NVIDIA-defined Gst metas.

The range is from NVDS_GST_CUSTOM_META to NVDS_GST_CUSTOM_META+4096, inclusive.

enumerator NVDS_START_USER_META

Start adding user specific meta types from here.

Specifies the start of a range of enum values that represent custom (application-specific) Gst meta types. A custom meta type may be assigned any enum value equal to or larger than this.

Such Gst metas may be attached by GStreamer plugins upstream from Gst-nvstreammux. They may have any contents that is a superset of the metadata in an NvDsFrameMeta.

enumerator NVDS_FORCE32_META

Functions

void nvds_acquire_meta_lock(NvDsBatchMeta *batch_meta)

Acquires a lock before updating metadata.

Parameters

[in] batch_meta: A pointer to the NvDsBatchMeta structure to be locked.

void nvds_release_meta_lock(NvDsBatchMeta *batch_meta)

Releases the lock after updating metadata.

Parameters

[in] batch_meta: A pointer to NvDsBatchMeta structure to be unlocked.

NvDsBatchMeta *nvds_create_batch_meta(guint max_batch_size)

Creates a batch metadata structure for a batch of specified size.

Parameters

[in] max_batch_size: The maximum number of frames in the batch. @ return A pointer to the created structure.

gboolean nvds_destroy_batch_meta(NvDsBatchMeta *batch_meta)

Destroys a batch metadata structure.

Return

True if the object was successfully destroyed, or false otherwise.

Parameters

[in] batch_meta: A pointer to batch metadata structure to be destroyed.

NvDsFrameMeta *nvds_acquire_frame_meta_from_pool(NvDsBatchMeta *batch_meta)

Acquires a frame meta from a batch’s frame meta pool.

You must acquire a frame meta before you can fill it with frame metadata.

Return

A pointer to the acquired frame meta.

Parameters

[in] batch_meta: A pointer to batch meta from which to acquire a frame meta.

void nvds_add_frame_meta_to_batch(NvDsBatchMeta *batch_meta, NvDsFrameMeta *frame_meta)

Adds a frame meta to a batch meta.

Parameters

[in] batch_meta: A pointer to the NvDsBatchMeta to which frame_meta is to be added.
[in] frame_meta: A pointer to a frame meta to be added to batch_meta.

void nvds_remove_frame_meta_from_batch(NvDsBatchMeta *batch_meta, NvDsFrameMeta *frame_meta)

Removes a frame meta from a batch meta.

Parameters

[in] batch_meta: A pointer to the batch meta from which frame_meta is to be removed.
[in] frame_meta: A pointer to the frame meta to be removed from batch_meta.

NvDsObjectMeta *nvds_acquire_obj_meta_from_pool(NvDsBatchMeta *batch_meta)

Acquires an object meta from a batch meta’s object meta pool.

You must acquire an object meta before you can fill it with object metadata.

Return

A pointer to the acquired object meta.

Parameters

[in] batch_meta: A pointer to the batch meta from which to acquire an object meta.

void nvds_add_obj_meta_to_frame(NvDsFrameMeta *frame_meta, NvDsObjectMeta *obj_meta, NvDsObjectMeta *obj_parent)

Adds an object meta to a frame meta.

You must acquire the object meta with nvds_acquire_object_meta_from_pool() and fill it with metadata before you add to to the frame meta.

Parameters

[in] frame_meta: A pointer to the frame meta to which obj_meta is to be added.
[in] obj_meta: A pointer to an object meta to be added to frame_meta.
[in] obj_parent: A pointer to the this object meta’s parent object meta. This pointer is stored in obj_meta->parent.

void nvds_remove_obj_meta_from_frame(NvDsFrameMeta *frame_meta, NvDsObjectMeta *obj_meta)

Removes an object meta from the frame meta to which it is attached.

Parameters

[in] frame_meta: A pointer to frame meta from which obj_meta is to be removed.
[in] obj_meta: A pointer to the object meta to be removed from frame_meta.

NvDsClassifierMeta *nvds_acquire_classifier_meta_from_pool(NvDsBatchMeta *batch_meta)

Acquires a classifier meta from a batch meta’s classifier meta pool.

You must acquire a classifier meta from the classifier meta pool before you can fill it with classifier metadata.

Return

The classifier meta acquired from the batch meta’s classifier meta pool.

Parameters

[in] batch_meta: A pointer to the batch meta from which to acquire a classifier meta.

void nvds_add_classifier_meta_to_object(NvDsObjectMeta *obj_meta, NvDsClassifierMeta *classifier_meta)

Adds a classifier meta the appropriate object meta.

You must acquire a classifier meta with nvds_acquire_classifier_meta_from_pool() and fill it with classifier metadata before you add it to the object metadata.

Parameters

[in] obj_meta: A pointer to the object meta to which classifier_meta is to be added.
[in] classifier_meta: A pointer to the classifier meta to be added to obj_meta.

void nvds_remove_classifier_meta_from_obj(NvDsObjectMeta *obj_meta, NvDsClassifierMeta *classifier_meta)

Removes a classifier meta from the object meta to which it is attached.

Parameters

[in] obj_meta: A pointer to the object meta from which classifier_meta is to be removed.
[in] classifier_meta: A pointer to the classifier meta to be removed from obj_meta.

NvDsDisplayMeta *nvds_acquire_display_meta_from_pool(NvDsBatchMeta *batch_meta)

Acquires a display meta from a batch meta’s display meta pool.

You must acquire a display meta before you can fill it with display metadata.

Return

The display meta acquired from the batch meta’s display meta pool.

Parameters

[in] batch_meta: A pointer to the batch meta from which to acquire a display meta.

void nvds_add_display_meta_to_frame(NvDsFrameMeta *frame_meta, NvDsDisplayMeta *display_meta)

Adds a display meta to the appropriate frame meta.

You must acquire a display meta with nvds_)acquire_display_meta_from_pool() and fill it with display metadata before you can add it to the frame meta.

Parameters

[in] frame_meta: A pointer to frame meta to which display_meta is to be added.
[in] display_meta: A pointer to the display meta to be added to frame_meta.

void nvds_remove_display_meta_from_frame(NvDsFrameMeta *frame_meta, NvDsDisplayMeta *display_meta)

Removes a display meta from the frame meta to which it is attached.

Parameters

[in] frame_meta: A pointer to the frame meta from which display_meta is to be removed.
[in] display_meta: A pointer to the display meta to be removed from frame_meta.

NvDsLabelInfo *nvds_acquire_label_info_meta_from_pool(NvDsBatchMeta *batch_meta)

Acquires a label info meta from a batch meta’s label info meta pool.

You must acquire a label info meta before you can fill it and add it to a classifier meta.

Return

The label info meta acquired from the batch meta’s label info meta pool.

Parameters

[in] batch_meta: A pointer to the batch meta from which to acquire a label info meta.

void nvds_add_label_info_meta_to_classifier(NvDsClassifierMeta *classifier_meta, NvDsLabelInfo *label_info_meta)

Adds a label info meta to a classifier meta.

Parameters

[in] classifier_meta: A pointer to the classifier meta to which label_info_meta is to be added.
[in] label_info_meta: A pointer to the label info meta to be added to classifier_meta.

void nvds_remove_label_info_meta_from_classifier(NvDsClassifierMeta *classifier_meta, NvDsLabelInfo *label_info_meta)

Removes a label info meta from the classifier meta to which it is attached.

Parameters

[in] classifier_meta: A pointer to the classifier meta from which label_info_meta is to be removed.
[in] label_info_meta: A pointer to the label info meta to be removed from classifier_meta.

void nvds_add_user_meta_to_batch(NvDsBatchMeta *batch_meta, NvDsUserMeta *user_meta)

Add a user meta to a batch meta.

Parameters

[in] batch_meta: A pointer to batch meta to which user_meta is to be added.
[in] user_meta: A pointer to a user meta to be added to batch_meta.

void nvds_add_user_meta_to_frame(NvDsFrameMeta *frame_meta, NvDsUserMeta *user_meta)

Add a user meta to a frame meta.

Parameters

[in] frame_meta: A pointer to the frame meta to which user_meta is to be added.
[in] user_meta: A pointer to a user meta to be added to frame_meta.

void nvds_add_user_meta_to_obj(NvDsObjectMeta *obj_meta, NvDsUserMeta *user_meta)

Add a user meta user to an object meta.

Parameters

[in] obj_meta: A pointer to the object meta to which user_meta is to be added.
[in] user_meta: A pointer to the user meta to be added to obj_meta.

NvDsUserMeta *nvds_acquire_user_meta_from_pool(NvDsBatchMeta *batch_meta)

Acquires a user meta from a batch meta’s user meta pool.

You must acquire a user meta before you can fill it with user metdata and add it to a batch, frame, or object meta (call nvds_add_user_data_to_batch(), nvds_add_user_data_to_frame(), or nvds_add_user_data_to_obj()).

Parameters

[in] batch_meta: A pointer to the batch meta from which to acquire a user meta.

void nvds_remove_user_meta_from_batch(NvDsBatchMeta *batch_meta, NvDsUserMeta *user_meta)

Removes a user meta from a batch meta to which it is attached.

returns acquired

NvDsUserMeta pointer from user meta pool

Parameters

[in] batch_meta: A pointer to the batch meta from which user_meta is to be removed.
[in] user_meta: A pointer to the user meta to be removed from batch_meta.

void nvds_remove_user_meta_from_frame(NvDsFrameMeta *frame_meta, NvDsUserMeta *user_meta)

Removes a user meta from a frame meta to which it is attached.

Parameters

[in] frame_meta: A pointer to the frame meta from which user_meta is to be removed.
[in] user_meta: A pointer to the user meta to be removed from frame_meta.

void nvds_remove_user_meta_from_object(NvDsObjectMeta *obj_meta, NvDsUserMeta *user_meta)

Removes a user meta from an object meta to which it is attached.

Parameters

[in] obj_meta: A pointer to the object meta from which user_meta is to be removed.
[in] user_meta: A pointer to the user to be removed from obj_meta.

gboolean nvds_get_current_metadata_info(NvDsBatchMeta *batch_meta)

A debugging function; prints current metadata information available after inference.

This function should be called after inference.

Return

Parameters

[in] batch_meta: A pointer to a batch meta from which to print information.

gpointer nvds_batch_meta_copy_func(gpointer data, gpointer user_data)

Copies or transforms meta data from one buffer to another.

Return

A pointer to a metadata structure, to be cast to type NvDsBatchMeta.

Parameters

[in] data: A pointer to a batch meta (of type NvDsBatchMeta), cast to gpointer.
[in] user_data: Currently not in use and should be set to NULL.

void nvds_batch_meta_release_func(gpointer data, gpointer user_data)

Releases metadata from a batch meta.

Parameters

[in] data: A pointer to a batch meta (type NvDsBatchMeta), cast to gpointer.
[in] user_data: Currently not in use and should be set to NULL.

NvDsFrameMeta *nvds_get_nth_frame_meta(NvDsFrameMetaList *frame_meta_list, guint index)

Returns a pointer to a specified frame meta in the frame meta list.

Return

A pointer to the index’th frame meta in the frame meta list.

Parameters

[in] frame_meta_list: A pointer to a list of pointers to frame metas.
[in] index: The index of the frame meta to be returned.

void nvds_clear_frame_meta_list(NvDsBatchMeta *batch_meta, NvDsFrameMetaList *meta_list)

Removes all of the frame metadata attached to a batch meta.

Parameters

[in] batch_meta: A pointer to the batch whose frame meta list is to be cleared.
[in] meta_list: A pointer to the frame meta list to be cleared.

void nvds_clear_obj_meta_list(NvDsFrameMeta *frame_meta, NvDsObjectMetaList *meta_list)

Removes all the object metadata attached to a frame meta.

Parameters

[in] frame_meta: A pointer to the frame meta whose object meta list is to be cleared.
[in] meta_list: A pointer to the object meta list to be cleared.

void nvds_clear_classifier_meta_list(NvDsObjectMeta *obj_meta, NvDsClassifierMetaList *meta_list)

Removes all of the classifier metadata attached to an object meta.

Parameters

[in] obj_meta: A pointer to NvDsObjectMeta from which NvDsClassifierMetaList needs to be cleared
[in] meta_list: A pointer to NvDsClassifierMetaList which needs to be cleared

void nvds_clear_label_info_meta_list(NvDsClassifierMeta *classifier_meta, NvDsLabelInfoList *meta_list)

Removes all of the label info metadata attached to a classifier meta.

Parameters

[in] classifier_meta: A pointer to the classifier meta whose label info meta list is to be cleared.
[in] meta_list: A pointer to the label info meta list to be cleared.

void nvds_clear_display_meta_list(NvDsFrameMeta *frame_meta, NvDisplayMetaList *meta_list)

Removes all of the display metadata attached to a frame meta.

Parameters

[in] frame_meta: A pointer to the frame meta whose display meta list is to be cleared.
[in] meta_list: A pointer to the display meta list to be cleared.

void nvds_clear_batch_user_meta_list(NvDsBatchMeta *batch_meta, NvDsUserMetaList *meta_list)

Removes all of the user metadata attached to the batch meta.

Parameters

[in] batch_meta: A pointer to the batch meta whose user meta list is to be cleared.
[in] meta_list: A pointer to the user meta list to be cleared

void nvds_clear_frame_user_meta_list(NvDsFrameMeta *frame_meta, NvDsUserMetaList *meta_list)

Removes all of the user metadata attached to the frame meta.

Parameters

[in] frame_meta: A pointer to the frame meta whose user meta list is to be cleared.
[in] meta_list: A pointer to the user meta list to be cleared.

void nvds_clear_obj_user_meta_list(NvDsObjectMeta *object_meta, NvDsUserMetaList *meta_list)

Removes all of the user metadata attached to an object meta.

Parameters

[in] object_meta: A pointer to the object meta whose user meta list is to be cleared.
[in] meta_list: A pointer to the user meta list to be cleared.

NvDsMetaList *nvds_clear_meta_list(NvDsBatchMeta *batch_meta, NvDsMetaList *meta_list, NvDsMetaPool *meta_pool)

Removes all of the metadata elements attached to a metadata list.

Return

A pointer to the updated meta list.

Parameters

[in] batch_meta: A pointer to a batch meta.
[in] meta_list: A pointer to meta list to be cleared.
[in] meta_pool: A pointer to the meta pool that contains meta_list.

void nvds_copy_frame_meta(NvDsFrameMeta *src_frame_meta, NvDsFrameMeta *dst_frame_meta)

Makes a deep copy of a frame meta to another frame meta.

Parameters

[in] src_frame_meta: A pointer to the source frame meta.
[in] dst_frame_meta: A pointer to the destination frame meta.

void nvds_copy_obj_meta(NvDsObjectMeta *src_object_meta, NvDsObjectMeta *dst_object_meta)

Makes a deep copy of an object meta to another object meta.

Parameters

[in] src_object_meta: A pointer to the source object meta.
[in] dst_object_meta: A pointer to the destination object meta.

void nvds_copy_classifier_meta(NvDsClassifierMeta *src_classifier_meta, NvDsClassifierMeta *dst_classifier_meta)

Makes a deep copy of a classifier meta to another classifier meta.

Parameters

[in] src_classifier_meta: A pointer to the source classifier meta.
[in] dst_classifier_meta: A pointer to the destination classifier meta.

void nvds_copy_label_info_meta(NvDsLabelInfo *src_label_info, NvDsLabelInfo *dst_label_info)

Makes a deep copy of a label info meta to another label info meta.

Parameters

[in] src_label_info: A pointer to the source label info meta.
[in] dst_label_info: A pointer to the destination label info meta.

void nvds_copy_display_meta(NvDsDisplayMeta *src_display_meta, NvDsDisplayMeta *dst_display_meta)

Makes a deep copy of a display meta to another display meta.

Parameters

[in] src_display_meta: A pointer to the source display meta.
[in] dst_display_meta: A pointer to destination display meta.

void nvds_copy_batch_user_meta_list(NvDsUserMetaList *src_user_meta_list, NvDsBatchMeta *dst_batch_meta)

Makes a deep copy of a user meta list to the user meta list in a specified batch meta.

Parameters

[in] src_user_meta_list: A pointer to the source user meta list.
[in] dst_batch_meta: A pointer to the destination batch meta.

void nvds_copy_frame_user_meta_list(NvDsUserMetaList *src_user_meta_list, NvDsFrameMeta *dst_frame_meta)

Makes a deep copy of a source user meta list to the user meta list in a specified frame meta.

Parameters

[in] src_user_meta_list: A pointer to the source user meta list.
[in] dst_frame_meta: A pointer to the destination frame meta.

void nvds_copy_obj_user_meta_list(NvDsUserMetaList *src_user_meta_list, NvDsObjectMeta *dst_object_meta)

Makes a deep copy of a source user meta list to the user meta list in a specified object meta.

Parameters

[in] src_user_meta_list: A pointer to the source user meta list.
[in] dst_object_meta: A pointer to the destination object meta.

void nvds_copy_display_meta_list(NvDisplayMetaList *src_display_meta_list, NvDsFrameMeta *dst_frame_meta)

Makes a deep copy of a source display meta list to the display meta list in a specified frame meta.

Parameters

[in] src_display_meta_list: A pointer to the source display meta list.
[in] dst_frame_meta: A pointer to the destination frame meta.

void nvds_copy_frame_meta_list(NvDsFrameMetaList *src_frame_meta_list, NvDsBatchMeta *dst_batch_meta)

Makes a deep copy of a source frame meta list to the frame meta list in a specified batch meta.

Parameters

[in] src_frame_meta_list: A pointer to the source frame meta list.
[in] dst_batch_meta: A pointer to the destination batch meta.

void nvds_copy_obj_meta_list(NvDsObjectMetaList *src_obj_meta_list, NvDsFrameMeta *dst_frame_meta)

Makes a deep copy of a source object meta list to the object meta list in a specified frame meta.

Parameters

[in] src_obj_meta_list: A pointer to the source object meta list.
[in] dst_frame_meta: A pointer to the destination frame meta.

void nvds_copy_classification_list(NvDsClassifierMetaList *src_classifier_meta_list, NvDsObjectMeta *dst_object_meta)

Makes a deep copy of a source classifier meta list to the classifier meta list in a specified object meta.

Parameters

[in] src_classifier_meta_list: A pointer to the source classifier meta list.
[in] dst_object_meta: A pointer to the destination object meta.

void nvds_copy_label_info_list(NvDsLabelInfoList *src_label_info_list, NvDsClassifierMeta *dst_classifier_meta)

Makes a deep copy of a source label info meta list to the label info meta list in a specified classifier meta.

Parameters

[in] src_label_info_list: A pointer to the source label info meta list.
[in] dst_classifier_meta: A pointer to the destination classifier meta.

NvDsMetaType nvds_get_user_meta_type(gchar *meta_descriptor)

Generates a unique user metadata type from a specified string describing user-specific metadata.

Parameters

[in] meta_descriptor: A pointer to a string describing user-specific metadata. The string must be in the format ORG_NAME.COMPONENT_NAME.METADATA_DESCRIPTION, e.g. NVIDIA.NVINFER.TENSOR_METADATA.

struct _NvDsComp_BboxInfo: #include <nvdsmeta.h>
Holds unclipped positional bounding box coordinates of the object processed by the component.

struct _NvDsMetaPool: #include <nvdsmeta.h>
Holds information about a given metadata pool.

struct _NvDsBaseMeta: #include <nvdsmeta.h>
Holds information about base metadata of a given metadata type.

struct _NvDsBatchMeta: #include <nvdsmeta.h>
Holds information about a formed batch containing frames from different sources.

struct _NvDsFrameMeta: #include <nvdsmeta.h>
Holds metadata for a frame in a batch.

struct _NvDsObjectMeta: #include <nvdsmeta.h>
Holds metadata for an object in the frame.

struct _NvDsClassifierMeta: #include <nvdsmeta.h>
Holds classifier metadata for an object.

struct _NvDsLabelInfo: #include <nvdsmeta.h>
Holds label metadata for the classifier.

struct NvDsDisplayMeta: #include <nvdsmeta.h>
Holds display metadata that the user can specify in the frame.

struct _NvDsUserMeta: #include <nvdsmeta.h>
Holds user metadata.