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Proceedings Paper

Comparison Of Coding Performance Of Image Transforms Under Vector Quantization Of Optimized Subbands
Author(s): Yonggang Du; Jurgen Halfmann
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Paper Abstract

To exploit the remaining statistical dependencies between the spectral coefficients of an image transform, techniques applying vector quantization (VQ) to small subbands of the spectral domain have been introduced in recent years. Unfortunately, up to now these techniques are only viewed as a straightforward extension of the traditional transform coding (TC). The interplay of the VQ and the TC is more or less disregarded, leading to the consequence that statements which are made to the traditional transform coding are likely to be taken over to the new VQ based scheme. Thus, the well known superiority of the DCT - although only proven in connection with scalar quantization (SQ) - might be the reason why almost all new subband VQ based coders prefer the DCT, too. It is the purpose of this paper to introduce a method which enables a theoretical comparison of the coding performance of image transforms, specially for the case of subband VQ. It will be shown that this comparison can only be meaningful if the partition of the spectral domain is optimized. For this optimization a suboptimal iterative algorithm is described. Based on this algorithm it is shown that the performance difference between the DCT and Hadamard transform is considerably reduced even at strongly limited expense of VQ. Finally, the theoretical results are confirmed by an experimental bit rate evaluation of two subband VQ coders, one uses the DCT and the other the Hadamard transform, but otherwise both have the same structure.

Paper Details

Date Published: 1 November 1989
PDF: 12 pages
Proc. SPIE 1199, Visual Communications and Image Processing IV, (1 November 1989); doi: 10.1117/12.970150
Show Author Affiliations
Yonggang Du, Aachen University of Technology (Germany)
Jurgen Halfmann, Aachen University of Technology (Germany)

Published in SPIE Proceedings Vol. 1199:
Visual Communications and Image Processing IV
William A. Pearlman, Editor(s)

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