1. A method of detecting a person from an image provided by a digital video camera, the method comprising: (a) initializing parameters used for a user detection; (b) determining a current mode; (c) when it is determined that the current mode is the face detection mode, performing a face detection on each of a plurality of image frames, and when a face is not detected even after a predetermined number of face detection trials, selecting a motion detection mode and going back to step (b); and (d) when it is determined that the current mode is the motion detection mode, performing a motion detection on a predetermined number of image frames at a time, and when at least a predetermined number of motion detections are performed successfully within a predetermined period of time, going back to step (a).