This paper presents a color demosaicing method by introducing iterative asymmetric average interpolation. Missing primary colors on a Bayer pattern color filter array (CFA) are estimated by an asymmetric average interpolation where less intensity variation is assumed to be of stronger significance, before sharpness of an initial estimate is further improved by an iterative procedure. The iteration is implemented by an observation process followed by a restoration process. The former is modeled by blurring followed by CFA sampling and the latter is completely as same as the color demosaicing method initially applied. Experimental results have shown a favorable performance in terms of PSNR and visual appearance, in particular, in sharpness recovery.

A unified polyphase representation of analysis and synthesis filter banks is introduced in this paper, and then the efficient implementation on digital signal processors (DSP) is investigated. Especially, the number of memory accesses, power consumption, processing accuracy and the required instruction cycles are discussed. Firstly, a unified representation is given, and then two types of procedures, SIMO system-based and MISO system-based procedures, are shown, where SIMO and MISO are abbreviations for single-input/multiple-output and multiple-input/single-output, respectively. These procedures are compared to each other. It is shown that the number of data load in SIMO system-based procedure is a half of that in MISO system-based procedure for two-channel filter banks. The implementation of M-channel filter banks is also discussed.