等分割サブバンド符号化における動き補償フレーム間予測の周波数領域実現

抄録

A new type of hybrid subband coding method using motion compensation (MC) is described in this paper. Energy compaction of lapped transforms and analysis/synthesis filter banks such as QMF are higher than that of Discrete Cosine Transform. However, when we combine the intraframe/MC-interframe adaptive prediction and filter banks, the problems of 1) level gaps between two successive MC blocks (caused by block matching process), and 2) level gaps between intraframe and interframe blocks should be solved. Because those level gaps contain very high frequency components, they reduce the efficiency of subband codings. Thus, we propose a hybrid coding structure, where motion estimation is carried out in the image domain, and interframe differences are taken in the frequency domain. In this method, interframe prediction and intra/inter switching can be carried out in the frequency domain. Thus, level gap problem does not appear. In addition, we show that the process of loop filtering can be carried out by only discarding high frequency band data of prediction images. By using this method, the coding efficiency of proposed MC+subband coding can be enhanced. Also, an adaptive loop filtering can be performed by varying the number of bands to be used for interframe prediction.