Prototype prediction for colour update in object-based analysis-synthesis coding

Abstract

In an object-based analysis-synthesis coder each image of an image sequence is subdivided into arbitrarily shaped moving objects. The objects are described by three parameter sets defining their motion, shape and colour, where the colour parameters denote the luminance and chrominance values of the object surface. In order to increase the efficiency of the coder, a predictive technique for the coding of colour parameters is presented using image pattern prototypes for prediction. The prototypes are extracted from previously coded images and identically stored at the coder and the decoder. They can be used for the prediction of the colour parameters of an object by applying a suitably defined mapping function. The prediction error is coded by an adaptive combination of DCT and intraframe DPCM. For the reconstruction of the colour parameters at the decoder the address of the image pattern prototype and the parameters of the mapping function have to be transmitted as side information. Prototype prediction is only applied, when its data rate is lower than that of an extended hybrid scheme. At a transmission data rate of 61 kbit/s prototype prediction increases the PSNR by 2 dB in the areas of colour update. >