Perceptual Relevance Measure for Generic Shape Coding

Approximation metric is a significant factor for subjective quality improvement of polygonal vertex-based shape codec. Usually this metric is defined by absolute distance measure (ADM). ADM only considers the shortest absolute distance from candidate vertices on the original object contour segment to corresponding approximating line segment and ignores other visual characteristics of the contour segment. Thus it cannot describe the original contour appropriately in visual aspects. As a result, it may severely degrade the subjective reconstruction quality, especially for contours with sharp salience. We propose perceptual relevance measure (PRM) to address this problem. We first describe the original relative position relationship between candidate vertex C and approximating line segment AB by three parameters having definite visual meanings, namely turn angle of and lengths of two adjacent line segments a and b. And then we provide the following three visual properties to find the exactly expression of PRM.