The following factors can strongly affect the performance of face detection:
Face direction. Media Server detects only faces that are facing the camera in the image; the face detector cannot detect profile face views. In general, both eyes in a face should be clearly visible in order to be detected. Any deviation from looking directly at the camera reduces the probability of detection.
Face size. Media Server is less likely to detect smaller faces than larger ones, particularly in low resolution images or images affected by compression or other artifacts.
Facial features. Although the face detector can process a relatively wide range of facial expressions, neutral faces are always detected with the greatest reliability. Particularly unusual facial expressions might cause face detection to fail. In addition, spectacles or large amounts of facial hair increase the difficulty in detecting faces. Glasses with dark lenses are likely to cause detection to fail.
Lighting effects. Extreme lighting effects on a face in an image inhibit its detection.
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