Extracting moving objects from a video by sequential background detection employing a local correlation map

This paper describes a technique for extracting moving objects from a video image sequence taken by a fixed or slowly moving camera by background subtraction. The background subtraction method is effective for extracting moving objects from a video provided by a fixed camera. But the latest background image should be employed for the subtraction in order not to be influenced by the light intensity change. A temporal median filter is proposed in this paper which detects the latest background images sequentially. From a video image stream provided by a slowly moving camera, the camera motion is estimated using a registration algorithm and the temporal median filter is applied to the common image area among a set of successive image frames to extract the background. In order that the camera motion estimation may become more exact effective, local correlation maps are calculated which can exclude outliers in estimated motion vectors. The technique was applied to the video images obtained from a hand-held camera and those taken from a camera set at the front seat of a car, and satisfactory results were obtained.