DCT 直流係数による交流成分の予測を用いた画像符号化

概要

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As is seen in international standards such as H.261, MPEG-2 and H.263, recent image coding techniques adopt block-based transform coding. This coding divides an image into small pieces, or blocks, applies the discrete cosine transform (DCT) to each one and quantizes and encodes the coefficients. However, as each block is coded independently with this method, there still remain the correlations among: inter-block coefficients (short basis length) and intra-block coefficients (non-optimality of DCT). 'AC and DC prediction', which is adopted by the verification model (VM) of the forthcoming image coding standard MPEG-4 (currently Working Draft), reduces the former type of correlation and gives better performance. In this paper, we propose a reduction method of the latter type of correlation by predicting AC components, using the DC coefficients of surrounding blocks. This also turns out to improve coding performance. Through the implementation of our method on existing codecs, coding performance is evaluated.
社団法人電子情報通信学会の論文
1997-08-13