Recently, fractal and subband coding were combined to achieve good picture quality at very low bit rates, and the technique was named predictive pyramid coding (PPC) [5]. In this paper, we improve PPC performance by utilizing the inter-subband correlation between different groups of subbands. As a result, we can reduce the bit rate by 0.011?0.043 bpp without degrading the coded picture quality, or we can increase the coded picture quality by 0.29?0.63 dB without increasing the bit rate.

Keywords: fractal coding, subband coding, predictive pyramid coding, prediction, quadrature mirror filter

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Received January 24, 2000; revised May 20, 2000; accepted June 27, 2000.
Communicated by Mark H. Y. Liao.