An efficient VLSI processor chip for variable block size integer motion estimation in H.264/AVC

Motion estimation (ME) is the most critical component of a video coding standard. H.264/AVC adopts the variable block size motion estimation (VBSME) to obtain excellent coding efficiency, but the high computational complexity makes design difficult. This paper presents an effective processor chip for integer motion estimation (IME) in H264/AVC based on the full-search block-matching algorithm (FSBMA). It uses architecture with a configurable 2D systolic array to obtain a high data reuse of search area. This systolic array supports a three-direction scan format in which only one row of pixels is changed between the two adjacent subblocks, thus reducing the memory accesses and saving clock cycles. A computing array of 64 PEs calculates the SAD of basic 4 x 4 subblocks and a modified Lagrangian cost is used as matching criterion to find the best 41 variable-size blocks by means of a tree pipeline parallel architecture. Finally, a mode decision module uses serial data flow to find the best mode by comparing the total minimum Lagrangian costs. The IME processor chip was designed in UMC 0.18 mu m technology resulting in a circuit with only 32.3 k gates and 6 RAMs (total 59kBits on-chip memory). In typical working conditions (25 degrees C, 1.8 V), a clock frequency of 300 MHz can be estimated with a processing capacity for HDTV (1920 x 1088 @ 30 fps) and a search range of 32 x 32. (C) 2011 Elsevier B.V. All rights reserved.