Hierarchical encoding of image sequences using multistage vector quantization

Vector quantization is a promising encoding technique especially for low data rate image transmission. Due to the exponential growing of its computational complexity with the block dimension, however, only small blocksizes have been used in practical applications. This restricts the coding efficiency and produces some blockiness in the reconstructed images. Our proposal solves this problems by a combination of a block-overlapping pyramidal transform with multistage VQ. This concept enables VQ of large blocks in a hierarchical manner with small computational costs, while the block-overlapping principle gives rise to a smooth image reconstruction. The simulation results proved that picture phone sequences are reconstructed without any annoying artifacts.