DRAM Bandwidth Optimal Perspective Transform Engine

Abstract

Perspective transform (or Homography) is commonly used algorithms in ADAS and Automated Driving System. Perspective transform is used in multiple use-cases e.g. viewpoint change, fisheye lens distortion correction, chromatic aberration correction, stereo image pair rectification, This algorithm needs high external DRAM memory bandwidth due to inherent scaling, resulting in nonaligned two dimensional memory burst accesses, resulting in large degradation in system performance and latencies. In this paper, we propose a novel perspective transform engine to reduce external memory DRAM bandwidth to alleviate this problem. The proposed solution consists of multiple regions slicing of input video frame with block size tuned for each region. The paper also gives an algorithm for finding optimal region boundaries with corresponding block size tuned for each region. The proposed solution enables average BW reduction of 67% compared to traditional implementation and achieves clock up-to 720 MHz with output pixel throughput of 1 cycle/pixel in 16nm FinFET process node.