A motion compensated subband coder for very low bit-rates

Abstract

A motion compensated subband coder with block-based processing for very low bit-rate video coding is presented. The motion compensated prediction is realized by using overlapping blocks. A forward analysis is introduced to select the blocks to be updated. In contrast to the conventional subband coding which is applied to the whole image, the subband coding here is applied to selected blocks only. In order to reduce the number of samples to be coded, a symmetric-periodic extension technique is applied in each stage of the subband analysis and synthesis filtering. A psychovisual model of the human visual perception is used to control the bit allocation and the adaptive quantization. Experimental results obtained with the presented coder at transmission bit-rates of 8, 16 and 24 kbit/s are presented. A comparison of the presented coder with ITU-T TMN-3 coder shows, that a PSNR gain of about 2.0 dB is achieved for typical videophone sequences with head and shoulder scenes.