DSP seminar: November 13, 1997
        
	Rate-Distortion Based Boundary Encoding

                Aggelos K. Katsaggelos
                Professor
                Ameritech Chair of Information Technology
                Northwestern University 
                Department of ECE 
                Evanston, IL 60208-3118

In this talk we address the problem of the efficient encoding of
object boundaries.  This problem is becoming increasingly important
in applications such as content-based storage and retrieval, studio
and television post-production and mobile multimedia applications.
MPEG-4 Visual, for example, will allow the transmission of arbitrarily shaped 
video objects.  The object boundaries are given as 8-connect chain codes,
and they are approximated by a curve of a given order, such as, a polygon
or a B-spline. Various criteria are considered for measuring the
distortion between a segment of the original curve and its approximation,
as well as, the total distortion.  For all these distortion criteria
the problem of finding the approximation to a given boundary
which results in the smallest distortion for a given number of bits is 
solved.  Experimental results are presented which demonstrate the
effectiveness of the proposed approaches and ouline the differences
among the various distortion criteria.