UNSPECIFIED (1997) Reduced entropy motion compensation using variable sized blocks. In: 1997 Conference on Visual Communications and Image Processing, SAN JOSE, CA, FEB 12-14, 1997. Published in: VISUAL COMMUNICATIONS AND IMAGE PROCESSING '97, PTS 1-2, 3024 (Part 1 & 2). pp. 293-302.

Abstract

We describe a quad-tree based variable size block matching (VSBM) motion estimation algorithm which is as computationally efficient as fixed size block matching (FSBM) and yet provides a better quality prediction. The 'match and merge' scheme allows the dimensions of blocks to adapt to local activity within the image, and the total number of blocks in any frame can be varied while still representing true motion fairly accurately. This permits adaptive bit allocation between the representation of displacement and residual data, and the variation of the overall bit allowance on a frame-by-frame basis. The cost of coding the motion information from the VSBM technique is compared with the 2D motion vector prediction adopted by H.263 and MPEG-4 using FSBM with 16x16 macroblocks. 1D and 2D VSBM motion vector prediction strategies are described. The techniques are evaluated using two complete MPEG-4 test sequences. For similar quality prediction (same mean square error), 16% fewer bits are required to code the motion vectors from the 'Foreman' sequence using the VSBM technique and a 2D predictor. The saving increases to 68% for the 'Container Ship' sequence in which there is less disparate motion. The cost of including the quad-tree description is included in both cases.

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