1. A method for estimating a boundary between a background and a user object in a video, comprising: (a) segmenting a user object from a background by estimating an initial contour of the user object in a first video frame for object segmentation; (b) estimating color probability density functions for the user object and the background that have been segmented from the first video frame; (c) generating an edge strip having a predetermined width based on an object contour of a previous frame in a current frame and estimating a coherence probability density function of the edge strip based on spatio-temporal correlation of the current video frame; and (d) segmenting the user object in the current frame by energy minimization.