Complexity analysis of two-pass algorithm and elliptical weighted average filter for VLSI implementation of perspective texture warping

摘要

In this paper we present the Elliptical Weighted Average filtering algorithm and an optimized implementation of a two-pass algorithm and used in digital image and video warping. Two-pass algorithms are well suited for hardware implementation due to their reduced complexity in using 1-D re-sampling and anti-aliasing filters. But, the primary disadvantage is the need for a large buffer to store the temporary image since warping is performed in two passes. The size of the temporary buffer is equal to or greater than the size of the input image. A dedicated, hardware, implementation for this algorithm implies huge cost in terms of real estate on chip. In our approach, Wolberg-Boult's resampling algorithm is modified to use only two rows of temporary buffer thereby making the algorithm more amenable for hardware implementation. We present the complexity analysis based on number of arithmetic and logic operations (add, shift, compare, multiply, clip and divide) per macroblock. In the case of EWA filters, it is the most cost-effective high-quality filtering method because point inclusion testing can be done with one function evaluation and the filter weights can be stored in lookup tables for reduction in computation. For mapping the quadrilaterals, four equations were needed for the four lines of the quadrilaterals, which was computationally complex, wherein the computational cost was directly proportional to the number of input pixels accessed. Also we present the complexity analysis per macroblock.