SHAPE REPRESENTATION AND CODING OF VISUAL OBJECTS IN MULTIMEDIA APPLICATIONS - AN OVERVIEW

Emerging multimedia applications hale created the need for new functio nalities in digital communications. Whereas existing compression stand ards only deal with the audio-visual scene at a frame level, it is now necessary to handle individual objects separately, thus allowing scal able transmission as well as interactive scene recomposition by the re ceiver. The future MPEG-4 standard aims at providing compression tools addressing these functionalities. Unlike existing frame-based standar ds, the corresponding coding schemes need to encode shape information explicitly. This paper reviews existing solutions to the problem of sh ape representation and coding. Region and contour coding techniques ar e presented and their performance is discussed, considering coding eff iciency and rare-distortion control capability: as well as flexibility to application requirements such res progressive transmission, low-de lay coding, and error robustness.