Data dependence analysis and bit-level systolic arrays of the median filter

The data dependence of the delete-and-insert sort algorithm for median filtering is analyzed in this paper. It is shown that because of data dependence, the fastest throughput rate and the most efficient pipeline scheme cannot be used concurrently. A modified delete-and insert sort algorithm avoiding the above dilemma and its bit-level systolic array implementation are proposed in this paper. The throughput rate of the proposed architecture is equal to one-half (output/clocks) the maximum throughput allowed by the delete-and-insert sort algorithm, and the clock cycle time is equal to the propagation delay of a simple combinational circuit. Its speed is about 1.5 times faster than the existing bit-level systolic array designed by using the same delete-and-insert sort algorithm. The proposed architecture can be designed to operate at different word lengths and different window sizes. It is modular, regular, and of local interconnections and therefore amenable for VLSI implementation.