1. A method of operating a system for unobtrusively measuring a person's respiration, the method comprising acts of: capturing images of a person lying down or lying in bed, by at least one video camera, analyzing the images, to determine the rotation of the head of the person about the longitudinal axis of a body of the person, determining by the video processor, from the images and rotation of the head which of at least two microphones is a microphone in a line-of-sight of the person's breathing and which of the at least two microphones is a microphone not in the line-of-sight of the person's breathing, computing from the images by the video processor, a distance from the person's head to each of the at least two microphones positioned on opposite sides of the person's head, and measuring by an audio analyzer, the person's respiration depending on the distances from the head to each microphone computed by the video processor and on the determination by the video processor of which of the at least two microphones is the microphone in the line-of-sight and which of the at least two microphones is the microphone not in the line-of-sight, as parameters.