This paper presents a relative depth layer extraction system for monoscopic video, using multi-line filters and a layer selection algorithm. Main ideas are to extract multiple linear trajectory signals from videos and to determine their relative depths using the concept of motion parallax. The proposed superficial line model used for detecting slow moving objects provides sufficient taps within few frames to reduce frame buffer, while the closest-hit line model used for detecting fast motion objects provides few enough taps to prevent blurring. To increase the correctness of layer map, three-level layer map codecision is used to compensate low texture region defect.