An elastic software cache with fast prefetching for Motion Compensation in video decoding

Real-time decoding of ultrahigh resolution video using multicore architectures is important for future embedded systems. However, memory bandwidth is still a bottleneck of system performance. Video coding performs irregular DRAM access resulting in very low and unstable efficiency. The conventional cache approach is insufficient because it reduces only the redundant accesses to data that has already been fetched during prior-macroblock decoding. We present an Elastic Software Cache (ESC) for ultrahigh resolution video decoding on Scratchpad Memory (SPM)-based systems. Utilizing access region analysis, our latency-optimized prefetching scheme rearranges accesses to minimize both data redundancy and DRAM access latency. Compared to the conventional cache approach, our scheme requires only 4.6 Kbytes of SPM space but it can save up to 25% of memory access cycles resulting in both higher performance and lower power.