Evaluating the Impact of Architectural Decisions on the Energy Efficiency of FDCT/IDCT Configurable IP Cores

Abstract

The development of mobile multimedia devices follows the platform-based design methodology in which IP cores are the building blocks. In the context of mobile devices there is a concern of battery lifetime which leads to the need of energy-efficient IP cores. This paper presents four energy-efficient FDCT/IDCT configurable IP cores. These architectures are based on Massimino’s algorithm, which was chosen due to its high accuracy and parallelism. The four architectures were built by combining fully-combinational or pipelined datapaths, using either a single or two 1-D DCT blocks with a transpose buffer that assures the optimal minimum latency of eight cycles. Synthesis results for 90nm showed that our most efficient architecture, which uses two pipelined 1-D blocks, achieved 250 MHz as maximum frequency at a total power of 14.03 mW. Such frequency was enough to process 16x 1080p@30fps videos in real time (nearly 2 GigaPixels/s). Comparisons with related work, in terms of energy efficiency (μJ/MPixels), revealed that our most energy-efficient architecture is at least 2 times as efficient as other DCT architectures. Moreover, the four designed architectures were also synthesized by using common low-power techniques. These results showed that pipelined versions at high throughput tend to take more benefit from using Low-Vdd and High-Vt combined than the combinational ones, thus becoming the most energy efficient.