Fast, modified Z-coding of wavelet pyramids

Abstract

[Summary form only given]. This paper describes a fast, low-complexity, entropy efficient coder for wavelet pyramids. This coder approaches the entropy-limited coding rate of video wavelet pyramids, is fast in both hardware and software implementations, and has low complexity for use in ASICs. It consists of a modified Z-coder used to code the zero/non-zero significance function without adaptation. The wavelet pyramid is further sharpened by scaling to match the characteristics of the human visual system (HVS). We derive the statistical characteristics of quantized wavelet pyramids from NTSC video viewed under standard conditions. These video pyramids have substantial runs of zeros and also substantial runs of non-zeros. To explore these we developed a modification of the Z-coder and explored an application of it to code zero versus non-zero. Z-codecs have the advantage of a simple (no multipliers) and fast implementation combined with coding performance approximating that of an arithmetic codec. Our experiments showed that this coder compares favorably with straight arithmetic coding. Our encoder has significant speed advantage due to low cost implementation.