We propose a new method of estimating object contours from thresholded binary edge images. Our work is motivated by the edge-based video object plane (VOP) generation proposed by Meier, targeted at MPEG-4 object-based video coding. When objects are detected in the form of binary edge images, we have to estimate the complete object contour from edges that do not form a closed contour. The proposed method is designed to carry out this task using only binary edge images. To achieve this, we first introduce a probability field representing the probability that the object contour lies on each pixel, and then take a modified geodesic active contour approach to make the initial contour converge with the contour of the object according to the probability field.