A Study of Wavelet-Based Vector Quantization for Image Coding

• Main Authors: Ou, Fu-Chiang, 歐富江
• Other Authors: Chen Wen-Shiung
• Format: Others
• Language: zh-TW
• Published: 1998
• Online Access: http://ndltd.ncl.edu.tw/handle/88066275134279949429

碩士 === 逢甲大學 === 電機工程研究所 === 86 === Recently, the computer industry and communication technique rapidly develop, the internet has become an important tool in life of people. In this times, multimedia is popular, but under the restriction of finite frequency bandwidth, the transmission time is unacceptable, and the image compression technique become more and more important for transmission on internet. The important of image data is different with different people, the multiresolution of one of the characteristics of wavelet transform can help us to change the transmission rate with our request, and save the transmission time. In this paper we combine wavelet transform and vector quantization to design a code/decode system for still image. The first coding scheme proposed in this thesis, called wavelet- based adaptive vector quantization (WT-AVQ), updates the codebook on-line by GW dynamic codebook refining mechnism, such that the codebook becomes adaptive to the characteristics of input image, and improves the quality of reconstruction image. The experimental result shows that it indeed improves PSNR in low bit rate. Second coding scheme which has a hierarchical tree codebook structure, called wavelet-based hierarchical vector quantization (WT-HVQ), utilizes the correlation between wavelet transform coefficients of neighboring levels. Although this system does not improve the performance of the coding image which outside the training images, but it can reduce very much coding bit rate of the image inside training set. In the future we will improve this coding system to have adaptability.