Alternatives in FPGA-based SAD implementations

In multimedia processing, it is well-known that the sum-of-absolute-differences (SAD) operation is the most time-consuming operation when implemented in software running on programmable processor cores. This is mainly due to the sequential characteristic of such an implementation. In this paper, we investigate several hardware implementations of the SAD operation and map the most promising one in FPGA. Our investigation shows that an adder tree based approach yields the best results in terms of speed and area requirements and has been implemented as such by writing high-level VHDL code. The design was functionally verified by utilizing the MAX+plus II 10.1 Baseline software package from Altera Corp. and then synthesized by utilizing the LeonardoSpectrum software package from Exemplar Logic Inc. Preliminary results show that the design can be clocked at 380 Mhz. This result translates into a faster than real-time full search in motion estimation for the main profile/main level of the MPEG-2 standard.