Plumerai Familiar Face Identification API¶

This document describes the API for the Familiar Face Identification functionality.

Note that the software is built with either the Automatic Enrollment option or the Manual Enrollment option enabled. This page provides documentation for both options, but at runtime only one of the two will be available.

Face Identification¶

get_face_id¶

int plumerai_face_identification_get_face_id(
    CPlumeraiVideoIntelligence pvi, const BoxPrediction* person_box);

Retrieve the face ID that belongs to a person box.

Retrieves the face ID given a person box from the most recent video frame.

This function has three possible return values:

FACE_ID_UNIDENTIFIED when the provided box is not of CLASS_PERSON or when a face is not yet identified, e.g. the face is not fully visible.
FACE_ID_NOT_IN_LIBRARY when the face is visible but not found in the library, e.g. when a stranger is in view.
Any integer face ID provided previously to plumerai_face_enrollment_manual_add_embedding when a familiar face is identified.

This function should not be called directly after restoring from a previous state through plumerai_video_intelligence_restore_state.

This function should not be called with results of plumerai_video_intelligence_single_image calls.

Arguments:

pvi: An initialized CPlumeraiVideoIntelligence object.
person_box: A box from the most recent video frame with class_id equal to DetectionClass::CLASS_PERSON.

Returns:

An integer face ID as provided when calling plumerai_face_enrollment_manual_add_embedding when a face is identified, FACE_ID_UNIDENTIFIED or FACE_ID_NOT_IN_LIBRARY when it is not identified successfully, or FACE_ID_UNIDENTIFIED when the provided box is not a valid person box.

get_person_box_from_face_box¶

PlumeraiErrorCode
plumerai_face_identification_get_person_box_from_face_box(
    CPlumeraiVideoIntelligence pvi, const BoxPrediction* face_box,
    BoxPrediction* result_person_box);

Retrieve a person box corresponding to a face box.

This function should not be called with results of plumerai_video_intelligence_single_image calls.

Arguments:

pvi: An initialized CPlumeraiVideoIntelligence object.
face_box: The target face to find a match for. This has to be a box from the most recent video frame.
result_person_box: The resulting box, only valid if the return value is true (see below). The caller needs to allocate memory for this box prior to calling this function.

Returns:

Returns SUCCESS in case a match was found. Returns NO_BOX_MATCH if it was not possible to uniquely match a face box to a person box. Returns INVALID_BOX in case of invalid arguments.

get_face_box_from_person_box¶

PlumeraiErrorCode
plumerai_face_identification_get_face_box_from_person_box(
    CPlumeraiVideoIntelligence pvi, const BoxPrediction* person_box,
    BoxPrediction* result_face_box);

Retrieve a face box corresponding to a person box.

This function should not be called with results of plumerai_video_intelligence_single_image calls.

Arguments:

pvi: An initialized CPlumeraiVideoIntelligence object.
person_box: The target person to find a match for. This has to be a box from the most recent video frame.
result_face_box: The resulting box, only valid if the return value is true (see below). The caller needs to allocate memory for this box prior to calling this function.

Returns:

Returns SUCCESS in case a match was found. Returns NO_BOX_MATCH if it was not possible to uniquely match a face box to a person box. Returns INVALID_BOX in case of invalid arguments.

embedding_version¶

uint32_t plumerai_face_identification_embedding_version(void);

Returns a version number for the face embedding data used by the face identification logic.

This version can be used to check if the face embedding data generated with one version of the Plumerai software are compatible with those generated by another version of the Plumerai software.

Returns:

The version number of the face embedding data.

Face Enrollment Automatic¶

get_face_ids¶

PlumeraiErrorCode plumerai_face_enrollment_automatic_get_face_ids(
    CPlumeraiVideoIntelligence pvi, int* face_ids, size_t* num_face_ids);

Return the face IDs of all automatically enrolled faces.

This list of face IDs is not related to the faces currently in view. The face IDs returned by this function are all faces that have ever been enrolled into the face library. To retrieve information about the faces currently in view, use plumerai_face_identification_get_face_id.

The caller must provide a buffer of size at least plumerai_face_enrollment_automatic_max_face_library_size integers.

Arguments:

pvi: An initialized CPlumeraiVideoIntelligence object.
face_ids: A pointer to a user-allocated list that receives the enrolled face IDs. It must hold at least plumerai_face_enrollment_automatic_max_face_library_size integers.
num_face_ids: An output parameter that receives the number of returned values.

Returns:

Returns SUCCESS on success.

tag_face_id¶

PlumeraiErrorCode plumerai_face_enrollment_automatic_tag_face_id(
    CPlumeraiVideoIntelligence pvi, const int face_id, bool important);

Tag a face ID as 'important' to prevent it from being overwritten.

When the face library is full and a new face is encountered, the algorithm will overwrite the oldest face in the library that is not tagged as important. A typical use-case of this is to tag a face as important when the user has named them in a front-end application.

When all entries in the face library are tagged as important and a new face is encountered, then no new faces will be enrolled.

By default, an automatically enrolled face is not tagged as important. However, library entries created by plumerai_face_enrollment_automatic_restore_enrollment_data are automatically tagged as important.

Note that INVALID_FACE_ID can be returned when a face ID that was previously valid is overwritten with a new entry.

Arguments:

pvi: An initialized CPlumeraiVideoIntelligence object.
face_id: A non-negative integer face ID.
important: Whether to tag the face as important or to remove a previously applied tag.

Returns:

Returns SUCCESS on success, INVALID_FACE_ID when the specified face ID could not be found.

remove_face_id¶

PlumeraiErrorCode plumerai_face_enrollment_automatic_remove_face_id(
    CPlumeraiVideoIntelligence pvi, const int face_id);

Remove a face ID from the face library for any plumerai_video_intelligence_process_frame calls that follow.

Note that INVALID_FACE_ID can be returned when a face ID that was previously valid is overwritten with a new entry.

Arguments:

pvi: An initialized CPlumeraiVideoIntelligence object.
face_id: A non-negative integer face ID.

Returns:

Returns SUCCESS on success, INVALID_FACE_ID on failure.

remove_all_face_ids¶

PlumeraiErrorCode
plumerai_face_enrollment_automatic_remove_all_face_ids(
    CPlumeraiVideoIntelligence pvi);

Remove all face IDs from the face library.

Arguments:

pvi: An initialized CPlumeraiVideoIntelligence object.

Returns:

Returns SUCCESS on success.

merge_face_ids¶

PlumeraiErrorCode plumerai_face_enrollment_automatic_merge_face_ids(
    CPlumeraiVideoIntelligence pvi, const int face_id_dst,
    const int face_id_src);

Merge two entries of the face library.

If a single person is enrolled twice in the face library, this function can be used to merge their enrollments back to a single one. After calling this function face_id_src is no longer valid and face_id_dst will be updated with the additional information from face_id_src.

Arguments:

pvi: An initialized CPlumeraiVideoIntelligence object.
face_id_dst: A non-negative integer face ID.
face_id_src: A non-negative integer face ID, must be different from face_id_dst.

Returns:

Returns SUCCESS on success, INVALID_FACE_ID when either of the face IDs could not be found, or INTERNAL_ERROR in case of an unexpected error.

get_face_enrollment_track_ids¶

PlumeraiErrorCode
plumerai_face_enrollment_automatic_get_face_enrollment_track_ids(
    CPlumeraiVideoIntelligence pvi, const int face_id, int64_t* track_ids,
    size_t* num_track_ids);

Return the track IDs for an automatically enrolled face.

The caller must provide a buffer of size at least plumerai_face_enrollment_automatic_max_tracks_per_face_id integers.

A face enrollment (face ID) can be made up of multiple person tracks, each of which is identified with a track ID. When a person is re-identified and their new face information is considered relevant for the algorithm, the new person track will be added to the existing face enrollment, or replace a previous one.

This list of track IDs can therefore change after processing any video frame.

Arguments:

pvi: An initialized CPlumeraiVideoIntelligence object.
face_id: A non-negative integer face ID.
track_ids: A pointer to a user-allocated list that receives the track IDs. It must hold at least plumerai_face_enrollment_automatic_max_tracks_per_face_id integers.
num_track_ids: An output parameter that receives the number of returned values.

Returns:

Returns SUCCESS on success.

remove_face_enrollment_track¶

PlumeraiErrorCode
plumerai_face_enrollment_automatic_remove_face_enrollment_track(
    CPlumeraiVideoIntelligence pvi, const int face_id, const int64_t track_id);

Remove a track that is part of a face enrollment.

This can be used if the Plumerai library made a mistake with automatic enrollment, and a user wants to manually correct the face library. By inspecting the face snapshots of each track ID, the user can decide to remove a wrong track.

If this was the only track of face_id then this face ID is removed entirely.

Arguments:

pvi: An initialized CPlumeraiVideoIntelligence object.
face_id: A non-negative integer face ID that is the source of the track.
track_id: The track ID of the track to remove.

Returns:

One of SUCCESS, INVALID_FACE_ID or INVALID_TRACK_ID.

reassign_face_enrollment_track¶

PlumeraiErrorCode
plumerai_face_enrollment_automatic_reassign_face_enrollment_track(
    CPlumeraiVideoIntelligence pvi, const int face_id_src,
    const int64_t track_id_src, const int face_id_dst);

Reassign a face track from face ID face_id_src to a new or existing face id face_id_dst.

This can be used if the Plumerai library made a mistake with automatic enrollment, and a user wants to manually correct the face library. By inspecting the face snapshots of each track ID, the user can decide to reassign a track to the correct face ID.

If face_id_dst does not exist, it will be created. If the face library is full, this will overwrite the oldest library entry, unless all of them are tagged as important in which case this function returns FACE_LIBRARY_FULL.

Note the following special behavior:

If face_id_src has only one track and it is reassigned, then face_id_src is automatically removed entirely.

It is possible that one or more existing tracks of face_id_dst are overwritten depending on whether the algorithm think it will improve the overall quality of the face enrollment.

The algorithm may determine that the original tracks of face_id_dst provide a better enrollment without the newly reassigned track. In such cases, face_id_dst remains unchanged, but the track is still removed from face_id_src.

Arguments:

pvi: An initialized CPlumeraiVideoIntelligence object.
face_id_src: A non-negative integer face ID that is the source of the track.
track_id_src: The track ID of the track to reassign.
face_id_dst: A non-negative integer face ID that is the destination of the track. If this face ID does not exist, it will be created.

Returns:

One of SUCCESS, FACE_LIBRARY_FULL, INVALID_FACE_ID or INVALID_TRACK_ID.

configure_face_snapshots¶

PlumeraiErrorCode
plumerai_face_enrollment_automatic_configure_face_snapshots(
    CPlumeraiVideoIntelligence pvi, const CFaceSnapshotSettings* settings,
    uint8_t* buffer, size_t buffer_size);

Configure the face snapshots for automatic enrollment.

By default, face snapshots are disabled.

Calling this function will invalidate any stored face snapshots of faces that are already enrolled. Trying to retrieve those face snapshots will return uninitialized data. When buffer is NULL and buffer_size is 0, the function will allocate heap memory to store the face snapshots (default, recommended). Otherwise, the function will use a user-provided buffer to store the face snapshots.

Arguments:

pvi: An initialized CPlumeraiVideoIntelligence object.
settings: See FaceSnapshotSettings for more details.
buffer: An optional buffer to store face snapshots, must stay valid for the lifetime of the CPlumeraiVideoIntelligence object or until the next call to plumerai_face_enrollment_automatic_configure_face_snapshots. If NULL, the function will allocate heap memory.
buffer_size: The size of the buffer. The required size can be obtained through plumerai_face_enrollment_automatic_get_face_snapshots_required_memory_size.

Returns:

Returns SUCCESS on success, INVALID_ARGUMENT when the provided settings are not valid, or NOT_ENOUGH_MEMORY if the provided buffer is not large enough.

get_face_snapshots_required_memory_size¶

size_t
plumerai_face_enrollment_automatic_get_face_snapshots_required_memory_size(
    CPlumeraiVideoIntelligence pvi, const CFaceSnapshotSettings* settings);

Get the required memory size for the face snapshots.

This optional function can be used to determine the required memory size for the face snapshots on system without dynamic memory allocation. See plumerai_face_enrollment_automatic_configure_face_snapshots for details.

Arguments:

pvi: An initialized CPlumeraiVideoIntelligence object.
settings: See FaceSnapshotSettings for more details.

Returns:

The required memory size in bytes.

get_face_snapshot¶

PlumeraiErrorCode
plumerai_face_enrollment_automatic_get_face_snapshot(
    CPlumeraiVideoIntelligence pvi, const int face_id, const int64_t track_id,
    const uint8_t** face_snapshot_data);

Return a snapshot of an automatically enrolled face.

A face enrollment can be made up of multiple person tracks. Every snapshot originates from a single person track. Use plumerai_face_enrollment_automatic_get_face_enrollment_track_ids to get a list of track IDs to use in this function.

Note that INVALID_FACE_ID can be returned when a face ID that was previously valid is overwritten with a new entry.

After every processed frame the list of snapshots can change. New images might be used by the algorithm if they are of higher quality.

Arguments:

pvi: An initialized CPlumeraiVideoIntelligence object.
face_id: A non-negative integer face ID.
track_id: The track ID of the snapshot to retrieve.
face_snapshot_data: The pointer to the stored snapshot data is returned via this output argument.

Returns:

Returns SUCCESS on success, INVALID_FACE_ID when the specified face ID could not be found, INVALID_TRACK_ID when the track ID could not be found, or FACE_SNAPSHOTS_DISABLED when face snapshots were not configured using plumerai_face_enrollment_automatic_configure_face_snapshots.

max_face_library_size¶

size_t plumerai_face_enrollment_automatic_max_face_library_size(void);

Returns the maximum size of the face library.

When the library is full and new faces are detected, they will overwrite older faces, except for faces that are tagged as important using plumerai_face_enrollment_automatic_tag_face_id. When all faces are tagged as important, new faces will not be added to the library beyond this maximum size.

Returns:

The maximum size of the face library.

max_tracks_per_face_id¶

size_t
plumerai_face_enrollment_automatic_max_tracks_per_face_id(void);

Returns the maximum number of tracks that a single face ID in the library consists of.

See plumerai_face_enrollment_automatic_get_face_enrollment_track_ids for more information.

When a face ID already has the maximum number of tracks stored, then a new person track will only update this face ID if it is of better quality than the existing tracks.

Returns:

The maximum number of tracks for a single face ID.

Face Enrollment Manual¶

embedding_size¶

size_t plumerai_face_enrollment_manual_embedding_size(void);

Returns the size of the face embeddings obtained from plumerai_face_enrollment_manual_finish_enrollment and required by plumerai_face_enrollment_manual_add_embedding.

Returns:

The size of the face embeddings.

max_face_library_size¶

size_t plumerai_face_enrollment_manual_max_face_library_size(void);

Returns the maximum size of the face library.

When the library is full, plumerai_face_enrollment_manual_add_embedding will return FACE_LIBRARY_FULL and won't be able to add new embeddings, until plumerai_face_enrollment_manual_remove_embedding is called.

Returns:

The maximum size of the face library.

start_enrollment¶

PlumeraiErrorCode plumerai_face_enrollment_manual_start_enrollment(
    CPlumeraiVideoIntelligence pvi);

This starts the enrollment procedure for a new face.

During subsequent calls to plumerai_video_intelligence_process_frame or plumerai_video_intelligence_single_image, face embeddings will be computed. During enrollment there should be a single face in the image, or in the optional Region specified by region_of_interest (not available in the C API), ideally clearly and completely visible. The enrollment procedure can be finalized by calling plumerai_face_enrollment_manual_finish_enrollment.

Arguments:

pvi: An initialized CPlumeraiVideoIntelligence object.

Returns:

Returns ENROLLMENT_IN_PROGRESS if the enrollment procedure was started successfully, otherwise returns ALREADY_ENROLLING.

finish_enrollment¶

PlumeraiErrorCode plumerai_face_enrollment_manual_finish_enrollment(
    CPlumeraiVideoIntelligence pvi, int8_t* face_embedding);

Finalize the face enrollment procedure started by plumerai_face_enrollment_manual_start_enrollment and obtain the face embedding.

The caller must provide a buffer of size plumerai_face_enrollment_manual_embedding_size.

The application is responsible for storing this embedding on persistent storage and passing it to plumerai_face_enrollment_manual_add_embedding every time an instance of this class is created. The face enrollment procedure does not automatically call plumerai_face_enrollment_manual_add_embedding.

For an example, see the example under plumerai_face_enrollment_manual_start_enrollment above.

Arguments:

pvi: An initialized CPlumeraiVideoIntelligence object.
face_embedding: The resulting face embedding if the result is SUCCESS or LOW_QUALITY_ENROLLMENT.

Returns:

Returns SUCCESS when enrollment was successful. Otherwise, returns one of NOT_ENROLLING, ENROLLMENT_FAILED, LOW_QUALITY_ENROLLMENT. See the enum for more information.

add_embedding¶

PlumeraiErrorCode plumerai_face_enrollment_manual_add_embedding(
    CPlumeraiVideoIntelligence pvi, const int8_t* face_embedding,
    size_t face_embedding_size, int face_id);

Add a face embedding to the face library for any plumerai_video_intelligence_process_frame calls that follow.

A second embedding for the same face ID will overwrite the previous one. When calling plumerai_face_identification_get_face_id on a detected person box, it will use the face_id provided here as return value.

Arguments:

pvi: An initialized CPlumeraiVideoIntelligence object.
face_embedding: A face embedding as obtained from plumerai_face_enrollment_manual_finish_enrollment.
face_embedding_size: Only used in the case when face_embedding is a raw pointer: the size of the face embedding data.
face_id: An integer face ID, is not allowed to be equal to FACE_ID_UNIDENTIFIED or FACE_ID_NOT_IN_LIBRARY.

Returns:

Returns SUCCESS on success, INVALID_FACE_ID, FACE_LIBRARY_FULL, or INVALID_EMBEDDING on failure.

get_face_ids¶

PlumeraiErrorCode plumerai_face_enrollment_manual_get_face_ids(
    CPlumeraiVideoIntelligence pvi, int* face_ids, size_t* num_face_ids);

Return the face IDs of all enrolled faces.

This list of face IDs is not related to the faces currently in view. The face IDs returned by this function are all faces that have ever been enrolled into the face library. To retrieve information about the faces currently in view, use plumerai_face_identification_get_face_id.

The caller must provide a buffer of size at least max_library_size integers.

Arguments:

pvi: An initialized CPlumeraiVideoIntelligence object.
face_ids: A pointer to a user-allocated list that receives the enrolled face IDs. It must hold at least max_library_size integers.
num_face_ids: An output parameter that receives the number of returned values.

Returns:

Returns SUCCESS on success.

remove_embedding¶

PlumeraiErrorCode plumerai_face_enrollment_manual_remove_embedding(
    CPlumeraiVideoIntelligence pvi, int face_id);

Remove a face embedding from the face library for any plumerai_video_intelligence_process_frame calls that follow.

Arguments:

pvi: An initialized CPlumeraiVideoIntelligence object.
face_id: An integer face ID, previously used in plumerai_face_enrollment_manual_add_embedding.

Returns:

Returns SUCCESS on success, INVALID_FACE_ID on failure.

remove_all_embeddings¶

PlumeraiErrorCode
plumerai_face_enrollment_manual_remove_all_embeddings(
    CPlumeraiVideoIntelligence pvi);

Remove all face embeddings from the face library.

Arguments:

pvi: An initialized CPlumeraiVideoIntelligence object.

Returns:

Returns SUCCESS on success.

Constants¶

static const int FACE_ID_UNIDENTIFIED = -1;
static const int FACE_ID_NOT_IN_LIBRARY = -2;

If the face-identification model is not confident about a face, it will output FACE_ID_UNIDENTIFIED. If the model is confident that a face is not in the face library, it will output FACE_ID_NOT_IN_LIBRARY.