Moving Objects Detection in Video Sequences Captured by a PTZ Camera

To solve the problem of detecting moving objects in video sequences which are captured by a Pan-Tilt-Zoom (PTZ) camera, a modified ViBe (Visual Background Extractor) algorithm, which is a pixel-based background modelling algorithm, is proposed in this paper. We divide a changing background scene into three parts. The first part is the new background region if a PTZ camera's field of view has been changed and we re-initialize background model of this part. The second is the disappeared area in the current frame and we decide to discard their models to save memory. Then the third part is the overlapping background region of consecutive frames. Via matching SURF feature points which are extracted only in background region we obtain an accurate homography matrix between consecutive frames. To ensure that the corresponding model from the former frame can be used in the current pixel, the homographic matrix should show a forward mapping relationship between the adjacent frames. Efficiency figures show that compared with origin ViBe algorithm and some other state-of-the-art background subtraction methods, our method is more affective for video sequences captured by a PTZ camera. More importantly, our method can be used in most of pixel- based background modelling algorithms to enhance their performance when dealing with videos captured by a moving camera.