Quadtree segmentation is a hierarchical spatial decomposition technique that partitions an image into variable-sized blocks based on a quadtree structure. Different coding strategies can be adopted to encode blocks of different perceptual significance. In this paper, an novel variable rate vector quantization scheme based on quadtree segmentation is proposed with which low-detailed blocks are adaptively encoded by the mean-subsampled vector quantization while high-detailed blocks by the traditional vector quantization scheme. The simulation results show that the proposed variable-block-sized vector quantization scheme achieves better subjective image quality with higher PSNR at low bit rates.
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