Video surveillance systems are widely used to monitor critical locations of public or private buildings or institutes like private homes, museums, prisons, factories, hazardous areas and so on from one or more central surveillance rooms. Commonly, the surveillance rooms are equipped with a plurality of monitors each displaying one of the critical locations or a mosaic display, which is divided in a plurality of cameos, whereby each cameo displays one of the critical locations. Additionally audio signals corresponding to the images displayed on the single monitors or cameos can be played.
Document WO 99/59340 discloses an observation system with a plurality of observation cameras and an observation monitor unit which displays the images from the observation cameras in a plurality of cameos. In case of an occurrence a further cameo is superimposed on the observation monitor showing a recorded video stream in connection with the occurrence. This document comprises no disclosure about a processing of audio signals in connection with the images displayed on the monitor or cameos.
Document WO 00/68908 describes a surveillance system, which also comprises a plurality of cameras and a central station with a plurality of monitors for displaying the images captured by the cameras. Additionally the surveillance system includes detector devices for providing a signal when movement in the monitored areas is detected. The signals may be generated in the central control room as an audible alarm. This document is assumed to represent the closest prior art.
Audio-signal generating and forming is a wide technical field which is especially often used in the entertainment industry. Known concepts are stereophonic sounds to create a pleasant and natural impression of sound heard from various directions as in natural hearings. Also surround sound is known as a concept of expanding the spatial imaging of audio playback.
From the abstract of the document Patent Abstracts of Japan, publication number 2004023180 A with the title “voice transmission apparatus, voice transmission method and program” it might be concluded that this document discloses a concept whereby in a first step a speaking person is imaged with a camera, in a second step the face direction of the speaking person is derived via image processing and in a third step the camera is turned in the direction of a person in the face direction (=listening person) of the speaking person. Additionally the voice of the speaking person is transmitted to the listening person in form of a wireless audio signal.