Low-power motion vector estimation using iterative search block-matching methods and a high-speed non-destructive CMOS image sensor

In this paper, motion vector (MV) estimation methods with high-speed intermediate pictures for low-power video compression are proposed. The intermediate pictures are obtained by a special type of CMOS image sensor. An adaptive iterative-search block matching is proposed to obtain precise MVs of video-rate pictures from high-speed intermediate pictures with the reduced computational complexity. The sensor captures high-speed intermediate pictures without destructing signal charge and video-rate pictures with full signal accumulation time. The proposed active pixel sensor using bidirectional multiple charge transfer is useful for the nondestructive intermediate imaging with a reduced fixed pattern noise. The image sensor chip has been implemented by using 0.35-mum CMOS technology. It operates with 3.3 V and captures 480 frames/s high-speed nondestructive intermediate pictures and 30 frame/s fully accumulated video-rate pictures. The proposed adaptive iterative-search block matching has a comparable precision to a full search block matching with reduction of computational complexity by a factor of about 1113, on average. It also reduces the data-loading rate from the memory by a factor of about 1/4.