Browsing by Author "Juan, SC"

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Entropy-constrained gradient-match vector quantization for image coding
(1998)
Juan, SC
;
Lee, CY
;
電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
Side-match VQ(SMVQ) is a well-known class of FSVQ used for low-bit rate image/video coding. it exploits the spatial correlation between the neighboring blocks to select several codewords that are very close to the encoding block: from the master codebook. But if the block boundary is in the region edge area, the spatial correlations are not high and the SMVQ can't select proper codewords to encode blocks. In this paper, an Entropy-Constrained Gradient-Match VQ (ECGMVQ) is proposed. Instead of exploiting the spatial correlation, the ECGMVQ uses the gradient contiguity property to select the codewords. State function of ECGMVQ can select better codevectors than the SMVQ. In addition, the entropy-constrained rule is applied to the encoding process to reduce bit rate. Simulation results show that the improvement of ECGMVQ over the SMVQ is up to 4-5 dB at neatly the same bit rate. Further, the perceptual image quality is better than that of SMVQ, especially in the region edge area.
Finite state vector quantization with multipath tree search strategy for image/video coding
(1996-06-01)
Lee, CY
;
Juan, SC
;
Chao, YJ
;
電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
This paper presents a new vector quantization (VQ) algorithm exploiting the features of tree-search as well as finite state VQ's for image/video coding, In the tree-search VQ, multiple candidates are identified for ongoing search to optimally determine an index of the minimum distortion, In addition, the desired codebook has been reorganized hierarchically to meet the concept of multipath search of neighboring trees so that picture quality can be improved by 4 dB on the average, In the finite state VQ, adaptation to the state codebooks is added to enhance the hit ratio of the index produced by the tree-search VQ, Thus, compressed bits can be further reduced, An identifier code is then included to indicate to which output indexes belong, Therefore, this modified algorithm not only reaches a higher compression ratio, but also achieves better quality compared to conventional finite-state and tree-search VQ's, Finally, suitable VLSI architectures for real-time performance are proposed here 1) to remove the bottleneck of iteration bound in finite-state VQ and 2) to provide parallel computing structure for tree-search VQ to meet computational requirements.