A novel approach for fast codebook re-quantization

  • Authors:

  • Chih-Tang Chang;Yi-Ching Liaw;Jim Z. C. Lai

  • Affiliations:

  • Department of Electrical Engineering, National Taiwan Ocean University, Keelung 202, Taiwan, ROC;Department of Computer Science and Information Engineering, Nanhua University, Chiayi 622, Taiwan, ROC;Department of Computer Science and Engineering, National Taiwan Ocean University, Keelung 202, Taiwan, ROC

  • Venue:
  • Pattern Recognition
  • Year:
  • 2008

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Abstract

In this paper, we present a fast codebook re-quantization algorithm (FCRA) using codewords of a codebook being re-quantized as the training vectors to generate the re-quantized codebook. Our method is different from the available approach, which uses the original training set to generate a re-quantized codebook. Compared to the traditional approach, our method can reduce the computing time dramatically, since the number of codewords of a codebook being re-quantized is usually much smaller than the number of original training vectors. Our method first classifies codewords of a re-quantized codebook into static and active groups. This approach uses the information of codeword displacements between successive partitions to reject impossible candidates in the partition process of codebook re-quantization. By implementing a fast search algorithm used for vector quantization encoding (MFAUPI) in the partition step of FCRA, the computational complexity of codebook re-quantization can be further reduced significantly. Using MFAUPI, the computing time of FCRA can be reduced by a factor of 1.55-3.78. Compared with the available approach OARC (optimization algorithm for re-quantization codebook), our proposed method can reduce the codebook re-quantization time by a factor of about 8005 using a training set of six real images. This reduction factor is increased when the re-quantized codebook size and/or training set size are increased. It is noted that our proposed algorithm can generate the same re-quantized codebook as that produced by the OARC.