Analysis and Hardware Architecture Design of Global Motion Estimation

Global motion estimation and compensation (GME/GMC) is an important video processing technique and has been applied to many applications including video segmentation, sprite/mosaic generation, and video coding. In MPEG-4 Advanced Simple Profile (ASP), GME/GMC is adopted to compensate camera motions. Since GME is important, many GME algorithms have been proposed. These algorithms have two common characteristics, huge computation complexity and ultra large memory bandwidth. Hence for realtime applications, a hardware accelerator of GME is required. However, there are many hardware design challenges of GME like irregular memory access and huge memory bandwidth, and only few hardware architectures have been proposed. In this paper, we first analyzed three typical algorithms of GME, and a fast GME algorithm is proposed. By using temporal prediction and skipping the redundant computation, 91% memory bandwidth and 80% iterations are saved, while the performance is kept, compared to Gradient Descent in MPEG-4 Verification Model. Based on our proposed algorithm, a hardware architecture of GME is also presented. A new scheduling, Reference-Based Scheduling, is developed to solve the irregular memory access problem. An interleaved memory arrangement is applied to satisfy the memory access requirement of interpolation. The total gate count of hardware implementation is 131 K with Artisan 0.18 um cell library, and the internal memory size is about 7.9 Kb. Its processing ability is MPEG-4 ASP@L3, which is 352×288 with 30 fps, at 30 MHz.