A Low-Power IDCT Macrocell for MPEG-2 MP@ML Exploiting Data Distribution Properties for Minimal Activity

A chip has been designed and tested to demonstrate the feasibility of an ultra-low-power, two-dimensional inverse discrete cosine transform (IDCT) computation unit in a standard 3.3-V process. A data-driven computation algorithm that exploits the relative occurrence of zero-valued DCT coefficients coupled with clock gating has been used to minimize switched capacitance. In addition, circuit and architectural techniques such as deep pipelining have been used to lower the voltage and reduce the energy dissipation per sample. A Verilog-based power tool has been developed and used for architectural exploration and power estimation. The chip has a measured power dissipation of 4.65 mW at 1.3 V and 14 MHz, which meets the sample rate requirements for MPEG-2 MP@ML. The power dissipation improves significantly at lower bit rates (coarser quantization), which makes this implementation ideal for emerging qualityon-demand protocols that trade off energy efficiency and video quality.