Resource-Efficient and High-Throughput VLSI Design of Global Optical Flow Method for Mobile Systems

Abstract

Most very-large-scale integration (VLSI) designs of the global optical flow method focus on reducing external memory accesses due to global and iterative processes for low-power operation in mobile systems. However, to achieve this goal, considerable amounts of resources are used and the throughput is decreased. To address these issues, we propose a multirow-based propagation approach and an efficient VLSI architecture. This approach divides an image into multiple small subimages. The flow of each subimage is then estimated sequentially using a small amount of internal memory without accessing any external memory. To avoid discontinuity artifacts stemming from the boundaries of the subimages, boundary conditions are imposed based on the smoothness of the optical flow. In addition, the main equations of the global optical flow method are simplified to boost the processing speed. The experimental results demonstrate that the external memory bandwidth is reduced by 96.7% with negligible accuracy degradation. Furthermore, the proposed design uses 63.4%-98% less internal memory and achieves $1.9\times $ -$18.8\times $ higher throughput-per-watt compared to state-of-the-art designs of the global optical flow method.