Investigations on colour coding in an object-oriented analysis-synthesis coder

In this paper, a new colour coding algorithm called Hybrid Adaptive DCT/DPCM Colour Coding is presented which encodes the colour parameters of objects in an object-oriented analysis-synthesis coder with a hybrid scheme, where either a DPCM (Differential Pulse Code Modulation) technique or a DCT (Discrete Cosine Transform) is used whichever allows a more efficient coding. In experimental results, the coding efficiency of the Hybrid Adaptive DCT/DPCM Colour Coding is compared to purely block-oriented DCT coding and region-oriented transform coding for typical videophone sequences at data rates of about 64 kbit/s. The relative gain concerning the average bit-rate at a fixed image quality is about 5% compared to region-oriented transform coding and 41% compared to block-oriented DCT coding. Beside its coding efficiency, Hybrid Adaptive DCT/DPCM Coding can easily be realized by fast algorithms of low computational complexity.