An efficient real-time accelerator for high-accuracy DNN-based optical flow estimation in FPGA

Recently, accelerator architectures of deep neural networks (DNNs) have been designed to accelerate computer vision tasks, gaining the advantages of both accuracy and speed. However, DNNs-based optical flow estimation accelerators have not been successfully deployed due to the resource constraint. Existing hardware accelerators for optical flow estimation are all designed for non-DNN methods and generally perform poorly in estimated accuracy. In this paper, we present FlowAcc, a dedicated hardware accelerator for DNN-based optical flow estimation, adopting a pipelined hardware design for the real-time processing of image streams. We design an efficient multiplexing binary neural network (BNN) architecture for pyramidal feature extraction to significantly reduce the hardware cost and make it independent of the pyramid-level number. Furthermore, efficient designs such as hamming distance calculation and competent flow regularization are used for hierarchical optical flow estimation to greatly improve the system’s efficiency. Comprehensive experimental results demonstrate that FlowAcc achieves state-of-the-art estimation accuracy and real-time performance on the Middlebury dataset when compared with the existing optical flow accelerators.