Patent ID: 6097756
Filing Date: 2000-08-01
Classification: G06T,H04N

Abstract:
A method for scalably inter-contour coding a video signal including a previous frame and a current frame, wherein each of the previous and the current frame contains a contour, the method comprising the steps of:(a) generating a predicted contour by motion estimating and compensating a previous base layer;(b) widening the predicted contour by a predetermined threshold D.sub.max (j), generating (j)th primary and secondary vertices to thereby store them as (j)th layer information, j being 0, and reconstructing a current base layer;(c) widening the predicted contour by a predetermined threshold D.sub.max (j+1), generating (j+1)st primary and secondary vertices to thereby store them as (j+1)st layer information, and updating the (j)th layer information by using the (j+1)st layer information;(d) encoding the (j)th primary and secondary vertices of the (j)th layer information;(e) formatting the encoded (j)th primary and secondary vertex information in a predetermined way; and(f) increasing j by 1, and repeating steps (c) to (e) until j becomes N, N being a positive integer, wherein said step (b) includes the steps of:(b1) detecting coincidence vertices, wherein each of the coincidence vertices is a crossing point between the predicted contour and the current contour or an end point of a portion where the predicted contour overlaps with the current contour;(b2) widening the predicted contour by the predetermined threshold D.sub.max (j) to thereby generate a (j)th widened contour band, and detecting (j)th matching portions where the current contour overlaps with the (j)th widened contour band between two of the coincidence vertices determined at step (b1), wherein j is 0;(b3) determining the (j)th matching portions whose lengths are longer than or equal to a predetermined nonnegative threshold TH as (j)th matched segments, and determining end points of the (j)th matched segments as the (j)th primary vertices;(b4) determining portions on the current contour which do not belong to any of the (j)th matched segments as the (j)th unmatched segments, determining the (j)th secondary vertices by applying a polygonal approximation method, based on the predetermined threshold D.sub.max (j), to the (j)th unmatched segments, and storing the (j)th primary and secondary vertices as the (j)th layer information; and(b5) reconstructing the current base layer by using the (j)th matched segments and the (j)th secondary vertices, and storing the current base layer, and said step (d) includes the steps of:(d1) calculating lengths of all the segments, each of which connects two adjacent (j)th primary vertices, and determining a maximum length m, wherein m is greater than or equal to 2.sup.n and smaller than 2.sup.n+1 ;(d2) encoding a (j)th primary vertex adjacent to a reference point RP in a predetermined direction by representing the length from RP to the (j)th primary vertex to be encoded by using n bits, encoding a next (j)th primary vertex by representing the length from the (j)th primary vertex just encoded to the (j)th primary vertex to be encoded by using n bits if d is greater than m, and encoding the next (j)th primary vertices by representing the length by using s bits otherwise, wherein d is the length from RP to the (j)th primary vertex just encoded, and d is greater than or equal to 2.sup.s and smaller than 2.sup.s+1 ; and(d3) encoding each of the (j)th secondary vertices by representing a 2 dimensional displacement from the closest (j)th primary of secondary vertex located in a predetermined direction to the (j)th secondary vertex to be encoded.