Low-power techniques for video decoding

Abstract

The H.264 video coding standard can deliver high compression efficiency at a cost of large complexity and power. The increasing popularity of video capture and playback on portable devices requires that the energy of the video processing be kept to a minimum. This work implements several architecture optimizations that reduce the system power of a high-definition video decoder. In order to decode high resolutions at low voltages and low frequencies, we employ techniques such as pipelining, unit parallelism, multiple cores, and multiple voltage/frequency domains. For example, a 3-core decoder can reduce the required clock frequency by 2.91 x, which enables a power reduction of 61% relative to a full-voltage single-core decoder. To reduce the total memory system power, several caching techniques are demonstrated that can dramatically reduce the off-chip memory bandwidth and power at the cost of increased chip area. A 123 kB data-forwarding cache can reduce the read bandwidth from external memory by 53%, which leads to 44% power savings in the memory reads. To demonstrate these low-power ideas, a H.264/AVC Baseline Level 3.2 decoder ASIC was fabricated in 65 nm CMOS and verified. It operates down to 0.7 V and has a measured power down to 1.8 mW when decoding a high definition 720p video at 30 frames per second, which is over an order of magnitude lower than previously published results.