Constrained two-bit transform for low complexity motion estimation

In transforming the original image frames into two-bit representations, the typical two-bit transform (2BT) needs to calculate the variances of the local blocks. This calculation of variances inevitably involves multiplication operations and renders the computational complexity of typical 2BT somewhat high. In this paper, we propose a constrained two-bit transform (C2BT) for low complexity motion estimation (ME). By exploiting the advantages of the typical constrained one-bit transform (C1BT) and the typical 2BT, the proposed algorithm significantly reduces the computational complexity of transformation of image frames into two-bit representations. Experimental results show that the proposed algorithm enhances the ME accuracy by 0.35dB and 0.28dB compared with the 2BT-based ME and the C1BT-based ME, respectively.