When a face detection tool is in use, the following requirements must be met:
- Minimum linear dimensions of a face to be detected are 24 pixels.
- Maximum speed of a face to be detected is not to be more than a half of linear dimensions in pixels per frame (i.e. face overlapping between two adjacent frames must be not less than half-width and half-height of face).
- A detection tool needs 8 frames to confirm face detection – otherwise, a face detection message won’t be sent.