A Low Power Motion Estimation Engine with Adaptive Bit-Shifted SAD Calculation

This paper describes a motion estimation (ME) engine that achieves both power efficiency and coding quality for real-time ultra-high definition video encoders. Sum of absolute difference (SAD) calculations are performed with bit-shortened SAD engines to reduce power, and bit extraction positions are adaptively shifted in accordance with the flatness of picture luminance values to maintain calculation precision. Power simulations with a High Efficiency Video Coding encoder LSI design [2] show that the ME engine reduces power consumption by 18–39% with 4-bit shortened SAD calculation, while coding efficiency loss is suppressed by up to 57% with adaptive bit-shifting. The ME engine is especially effective for high dynamic range pictures with downscaled luminance values, which are suitable for today's 4K and 8K video contents.