VIDEO CODING WITH R-D CONSTRAINED HIERARCHICAL VARIABLE BLOCK SIZE (VBS) MOTION ESTIMATION

The variable block size (VBS) motion estimation technique allows for l arger blocks to be used when smaller blocks yield little gain, saving bit rates especially for areas containing more complex motion, However , the employment of the VBS motion estimation technique introduces a n ew optimization issue for the motion compensated transform coding, bec ause an increase in bit rate allocation is necessary to accommodate VB S motion vectors. Hence, this paper will describe a rate-distortion (R -D) constrained approach for the hierarchical quadtree VBS motion esti mation and displaced frame difference (DFD) coding. First, in order to make the R-D tree search feasible, the hierarchical quadtree VBS moti on structures are grouped into two-stage model structures coupled to a n efficient R-D tree search method. Next, a R-D constrained solution b ased on Lagrange multiplier method controls the employed VBS motion ve ctors in relation to the dependent DFD coding. Extensive computer simu lation employing the motion compensated transform coding technique sho ws that an overall improvement up to 1.0 dB is obtainable, compared to the fixed block size motion estimation, (C) 1998 Academic Press