High-speed median filter designs using shiftable content-addressable memory

This paper presents a very efficient VLSI architecture for real-time median filtering as requested in many image/video applications. The median is obtained by first sorting input sequences and then selecting identified order according to the number of inputs. To reach the goal of high-speed data sorting, an optimized delete-and-insert algorithm is derived and then mapped onto shiftable content-addressable memory architecture. The complete design can be decomposed into a set of processor elements, where each processor element consists of two basic cells-sort-cell and compare-cell. Thus the design becomes very regular. More specifically any specified order can be obtained within one cycle and a high-speed clock rate can be achieved. A prototype chip for 64 samples based on this architecture has been implemented and tested. Results show that a clock rate up to 50 MHz can be achieved using a 1.2 μm CMOS double metal technology