Time-varying mesh, which is attracting a lot of attention as a new multimedia representation method, is a sequence of 3-dmodels that are composed of vertices, edges, and some attribute components such as color. Among...
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Time-varying mesh, which is attracting a lot of attention as a new multimedia representation method, is a sequence of 3-dmodels that are composed of vertices, edges, and some attribute components such as color. Among these components, vertices require large storage space. In conventional 2-d video compression algorithms, motion compensation (MC) using a block matching algorithm is frequently employed to reduce temporal redundancy between consecutive frames. However, there has been no such technology for 3-d time-varying mesh so far. Therefore, in this paper, we have developed an extended block matching algorithm (EBMA) to reduce the temporal redundancy of the geometry information in the time-varying mesh by extending the idea of the 2-d block matching algorithm to 3-d space. In our EBMA, a cubic block is used as a matching unit. MC in the 3-d space is achieved efficiently by matching the mean normal vectors calculated from partial surfaces in cubic blocks, which our experiments showed to be a suboptimal matching criterion. After MC, residuals are transformed by the discrete cosine transform, uniformly quantized, and then encoded. The extracted motion vectors are also entropy coded after differential pulse code modulation. As a result of our experiments, 10%-18% compression has been achieved.
In conventional predictive quantization schemes for 3-d mesh geometry, excessively large residuals or prediction errors, although occasional, lead to visually unacceptable geometric distortion. This is due to the fact...
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In conventional predictive quantization schemes for 3-d mesh geometry, excessively large residuals or prediction errors, although occasional, lead to visually unacceptable geometric distortion. This is due to the fact that they cannot Limit the maximum quantization error within a given bound. In order to completely eliminate the visually unacceptable distortion caused by large residuals, we propose a predictive two-stage quantization scheme. This scheme is very similar to the conventional dPCM, except that the embedded quantizer is replaced by a series of two quantizers. Each quantizer output is further compressed by an arithmetic code. When applied to typical 3-d mesh models, the scheme performs much better than the conventional predictive quantization methods and, depending upon input models, even than the MPEG-4 compression method for 3-d mesh geometry both in rate-distortion sense and in subjective viewing.
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