Multirate image sequence coding with quadtree segmentation and backward motion compensation
Ligang Lu, William A. Pearlman · Proceedings of SPIE, the International Society for Optical Engineering/Proceedings of SPIE · 1992
In this paper, we present a new image sequence coding scheme which employs backward motion compensation, quadtree segmentation, and pruned tree-structured vector quantization. Based only on the previous reconstructed frames, the backward motion compensation technique eliminates the necessity to transmit the motion displacement vectors as side information, and thus achieves a bit rate saving. Quadtree segmentation is used to exploit the regional characteristics of the signal. To take the advantage of the fact that many large areas of the motion compensated frame difference contain only low activity, the motion compensated frame difference is decomposed into large, low activity blocks and small, high activity blocks. The large blocks are encoded by their means while the small blocks are encoded by pruned tree-structured vector quantization (PTSVQ) at different rates. PTSVQ is both a multi-rate and variable rate coding technique and has the fast codebook search property due to its tree structure. It has been shown recently that PTSVQ may outperform full search unstructured VQ in the low bit rate range. Excellent results have been obtained in the computer simulation of this new scheme. When tested on the Salesman sequence, this interframe coding technique has achieved an average peak signal-to-noise ratio of 40.55 dB at an average bit rate of 0.43 bits per pixel, which indicates that the proposed scheme is suitable for low rate video applications.