.. _liveness:

Enable Face Liveness Detection
======================================


The FindFace Multi face liveness detector tells apart live faces from face representations, such as face images, videos, or masks. The liveness detector estimates face liveness with a certain level of confidence and returns the confidence score along with a binary result ``real/fake``, depending on the pre-defined liveness threshold.

The face liveness detector can be automatically enabled and configured during the :ref:`installation <installer>`. If you skipped this step, you can manually enable it later, following the instructions below.

.. note::
   The face liveness detector functions on both GPU- and CPU-acceleration. However, it is much slower on CPU. 
 

.. rubric:: In this section:

.. contents::
   :local:


Enable Face Liveness Detector
---------------------------------

To enable the face liveness detector, do the following:

#. Open the ``/opt/findface-multi/configs/findface-video-worker/findface-video-worker.yaml`` configuration file. In the ``liveness`` section, specify the neural network models as shown in the example:

   .. rubric:: GPU 

   .. code::

      sudo vi /opt/findface-multi/configs/findface-video-worker/findface-video-worker.yaml

      liveness:
        fnk: /usr/share/findface-data/models/faceattr/liveness.pacs.v2.gpu.fnk
        norm: /usr/share/findface-data/models/facenorm/facenorm.multicrop_full_crop2x_size400.gpu.fnk
      ...

   .. rubric:: CPU 

   .. code::

      sudo vi /opt/findface-multi/configs/findface-video-worker/findface-video-worker.yaml

      liveness:
        fnk: /usr/share/findface-data/models/faceattr/liveness.pacs.v2.cpu.fnk
        norm: /usr/share/findface-data/models/facenorm/facenorm.multicrop_full_crop2x_size400.cpu.fnk
      ...

#. Restart the ``findface-multi-findface-video-worker-1`` container.
 
   .. code::

      sudo docker container restart findface-multi-findface-video-worker-1

Configure Liveness Threshold
--------------------------------

If necessary, you can adjust the liveness threshold in the ``/opt/findface-multi/configs/findface-multi-legacy/findface-multi-legacy.py`` configuration file. The liveness detector will estimate face liveness with a certain level of confidence. Depending on the threshold value, it will return a binary result ``real`` or ``fake``. 

.. note::
   The default value is optimal. Before changing the threshold, we recommend that you seek advice from our experts at support@ntechlab.com.


.. code::

   sudo vi /opt/findface-multi/configs/findface-multi-legacy/findface-multi-legacy.py

   FFSECURITY = {
       ...
       # feature specific confidence thresholds
       'LIVENESS_THRESHOLD': 0.674,  # model: [liveness.pacs.v2]
       ...

Restart the ``findface-multi-findface-multi-legacy-1`` container if you have configured the liveness threshold.

.. code::

   sudo docker container restart findface-multi-findface-multi-legacy-1