A Heterogeneous Architecture for the Vision Processing Unit with a Hybrid Deep Neural Network Accelerator.

The vision chip is widely used to acquire and process images. It connects the image sensor directly with the vision processing unit (VPU) to execute the vision tasks. Modern vision tasks mainly consist of image signal processing (ISP) algorithms and deep neural networks (DNNs). However, the traditional VPUs are unsuitable for the DNNs, and the DNN processing units (DNPUs) cannot process the ISP algorithms. Meanwhile, only the CNNs and the CNN-RNN frameworks are used in the vision tasks, and few DNPUs are specifically designed for this. In this paper, we propose a heterogeneous architecture for the VPU with a hybrid accelerator for the DNNs. It can process the ISP, CNNs, and hybrid DNN subtasks on one unit. Furthermore, we present a sharing scheme to multiplex the hardware resources for different subtasks. We also adopt a pipelined workflow for the vision tasks to fully use the different processing modules and achieve a high processing speed. We implement the proposed VPU on the field-programmable gate array (FPGA), and several vision tasks are tested on it. The experiment results show that our design can process the vision tasks efficiently with an average performance of 22.6 giga operations per second/W (GOPS/W).