This paper presents a contour-based approach to efficiently code binary shape information in the context of object-based video coding. This approach meets some of the most important requirements identified for the MPE...
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This paper presents a contour-based approach to efficiently code binary shape information in the context of object-based video coding. This approach meets some of the most important requirements identified for the MPEG-4 standard, notably efficient coding and low delay. The proposed methods support both object-based lossless and quasi-lossless coding modes. For the cases where low delay is a primary requirement, a macroblock-based coding mode is proposed which can take advantage of inter-frame coding to improve the coding efficiency. The approach presented here relies on a grid different from that used for the pixels to represent the shape - the hexagonal grid - which simplifies the task of contour coding. Using this grid, an approach based on a differential chaincode (DCC) is proposed for the lossless mode while, for the quasi-lossless case, an approach based on the multiple grid chain code (MGCC) principle is proposed. The MGCC combines both contour simplification and contour prediction to reduce the number of bits needed to code the shapes. Results for alpha plane coding of MPEG-4 video test sequences are presented in order to illustrate the performance of the several modes of operation, and a comparison is made with the shape-coding tool chosen by MPEG-4. (C) 2000 Elsevier Science B.V. All rights reserved.
The multiplegrid(MG) chaincode which uses four different square grids is proposed to encode line drawings. The main processes adopted in the code are: 1) a grid selection algorithm which allocates quantization point...
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The multiplegrid(MG) chaincode which uses four different square grids is proposed to encode line drawings. The main processes adopted in the code are: 1) a grid selection algorithm which allocates quantization points only to the vicinity of the course of a line drawing, 2) labeling rule on quantization points which makes the frequency of some codes larger than that of other codes, and 3) quantization points allocation-not to the corners, but to the sides of a square which makes the straight line segments larger without increasing quantization error. A performance comparison of various chaincodes is made from the viewpoints of the encoding efficiency, naturalness of the encoded lines, and the rate distortion measure. Also, the superiority of the MG chaincode to other codes is shown. At last, application of the MG chaincode to the electronic blackboard system is explained.
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