Generic 3-D Modeling for Content Analysis of Court-Net Sports Sequences

In this paper, we present a generic 3-D modeling for analyzing court-net sports videos, which enables to map points in the real-world coordinates to the image coordinates. To this end, we propose a two-step algorithm to extract the feature lines and points from two perpendicular planes (ground and net plane) for determining the camera calibration parameters. In the first step, we bridge the gap between the 2-D standard court model and the image coordinate system that is described by a plane-to-plane mapping. With this mapping, it is possible to distinguish the feature lines like court lines in the ground plane. The second step is to detect the net line located in the net plane, where the line is classified as net line if it passes several tests. The feature points at well-known positions within these two planes (e.g. intersection of two lines) are utilized to calculate the camera calibration parameters. We demonstrate the performance of the proposed algorithm by evaluating it for a variety of court-net sports videos including badminton, tennis and volleyball. Results show that the algorithm is robust to partial court views or bad lighting conditions, and can be applied to various applications.