variable block size (VBS) motion estimation techniques
The variable block size (VBS) motion estimation technique have recently been proposed to enhance the performance allows for larger blocks to be used when smaller blocks yield of the motion compensated transform coding system [3][4][5]. little gain, saving bit rates especially for areas containing more In the VBS motion estimation, the block size for estimating complex motion. However, the employment of the VBS motion the motion is varied according to the types of motion in estimation technique introduces a new optimization issue for the block. This technique is known to be very effective in the motion compensated transform coding, because an increase improving the motion vector precision for areas containing in bit rate allocation is necessary to accommodate VBS motion complex motions. Thus in our previous work [1], a VBS vectors. Hence, this paper will describe a rate-distortion (R-D) motion estimation technique with a hierarchical quadtree constrained approach for the hierarchical quadtree VBS motion motion structure is shown to be an efficient motion estimaestimation and displaced frame difference (DFD) coding. First, tor that reduces the bit rates necessary to encode the moin order to make the R-D tree search feasible, the hierarchical quadtree VBS motion structures are grouped into two-stage tion vectors. model structures coupled to an efficient R-D tree search However, the employment of the VBS motion estimamethod. Next, a R-D constrained solution based on Lagrange tion technique has raised a new optimization issue in the multiplier method controls the employed VBS motion vectors motion compensated transform coding system. Now, the in relation to the dependent DFD coding. Extensive computer bit rate allocation process must take into account encoding simulation employing the motion compensated transform codthe dependent displaced frame difference (DFD) signals ing technique shows that an overall improvement up to 1.0 dB as well as the VBS motion vectors. The term ''dependent'' is obtainable, compared to the fixed block size motion simply implies that, depending on the employed VBS moestimation. ยฉ 1998 Academic Press tion vectors, the DFD signal to be encoded varies. An alternative approach based on the entropy comparison has been proposed in [6]. However, it should be noted that 1 This work was presented at the SPIE's Visual Communication and VBS motion estimation techniques [1]. Next, in order to Image Processing '95,