OPTIMIZATION AND EFFICIENCY OF AN OBJECT-ORIENTED ANALYSIS-SYNTHESIS CODER

In this paper, an object-oriented analysis-synthesis coder is presented the first time in its entity concentrating on an optimal relationship of its components image analysis, image synthesis and parameter coding and on a comparison of its coding efficiency to block-oriented hybrid coding. As block-oriented hybrid coder, the RM8 of the CCITT is used. The presented object-oriented analysis-synthesis coder is based on the source model of moving flexible 2D-objects and encodes arbitrarily shaped objects instead of rectangular blocks. The objects are described by three parameter sets defining their motion, shape and colour (colour parameters denoting luminance as well as chrominance values of the object surface). The parameter sets of each object are obtained by image analysis and coded by an object dependent parameter coding. Using the coded parameter sets, an image can be reconstructed by model-based image synthesis. Experimental results show that transmitting shape information and allowing small position errors (geometrical distortions) avoid the mosquito and blocking artefacts of a block-oriented coder. Furthermore, important image areas such as facial areas can be reconstructed with an image quality improvement up to 4 dB using the image analysis. As a whole, the reconstructed image of an object-oriented analysis-synthesis coder appears sharper compared to block-oriented hybrid coding.