Many illegal copies of digital movies by camcorder capture are found on the Internet or on the black market before their official release. Due to the angle of the camcorder relative to the screen, the copied movies are captured with perspective distortion. In this paper, we present a watermarking scheme for tracking the pirate using local auto-correlation function (LACF) to estimate geometric distortion. The goals of watermarking are to find the suspected position of the camcorder in the theater and to extract the embedded forensic marking data which specifies theater information and time stamp. Therefore, our watermarking system provides conclusive evidence to take the pirate to the court. Experimental results demonstrate robustness of the LACF and accuracy of the proposed modeling.