Memory-Efficient High-Speed Convolution-based Generic Structure for Multilevel 2-D DWT

In this paper, we have proposed a design strategy for the derivation of memory-efficient architecture for multilevel 2-D DWT. Using the proposed design scheme, we have derived a convolution-based generic architecture for the computation of three-level 2-D DWT based on Daubechies (Daub) as well as biorthogonal filters. The proposed structure does not involve frame-buffer. It involves line-buffers of size 3(K - 2) M/4 which is independent of throughput-rate, where K is the order of Daubechies/biorthogonal wavelet filter and M is the image height. This is a major advantage when the structure is implemented for higher throughput. The structure has regular data-flow, small cycle period T-M and 100% hardware utilization efficiency. As per theoretical estimate, for image size 512 x 512, the proposed structure for Daub-4 filter requires 152 more multipliers and 114 more adders, but involves 82 412 less memory words and takes 10.5 times less time to compute three-level 2-D DWT than the best of the existing convolution-based folded structures. Similarly, compared with the best of the existing lifting-based folded structures, proposed structure for 9/7-filter involves 93 more multipliers and 166 more adders, but uses 85 317 less memory words and requires 2.625 times less computation time for the same image size. It involves 90 (nearly 47.6%) more multipliers and 118 (nearly 40.1%) more adders, but requires 2723 less memory words than the recently proposed parallel structure and performs the computation in nearly half the time of the other. In-spite of having more arithmetic components than the lifting-based structures, the proposed structure offers significant saving of area and power over the other due to substantial reduction in memory size and smaller clock-period. ASIC synthesis result shows that, the proposed structure for Daub-4 involves 1.7 times less area-delay-product (ADP) and consumes 1.21 times less energy per image (EPI) than the corresponding best available convolution-based structure. It involves 2.6 times less ADP and consumes 1.48 times less EPI than the parallel lifting-based structure.(1)