Interscale prediction and subband decomposition for still image coding
Félix Henry, Pierre Duhamel · Proceedings of SPIE, the International Society for Optical Engineering/Proceedings of SPIE · 1998
It is commonly admitted that relying only on interscale redundancies, like pure fractal coders do, leads to inferior rate-distortion performance when compared to more classical designs (involving transform, quantization, and entropy coding). We address the problem of local efficiency of interscale coding in digital images. We design an interscale coding technique that predicts vectors of subband coefficients between adjacent resolution levels. This interscale coding scheme is applied in cooperation with zeroing and lattice vector quantization (LVQ) within the same compression scheme. To this end, we propose a rate allocation algorithm adapted to a signal partitioned into small vectors. The rate allocator chooses the best method according to the rate-distortion compromise. Side information is transmitted in a compressed form to indicate which of the three decoding methods is chosen on each block (zeroing, interscale prediction, or LVQ). Experiments show that interscale coding can locally outperform other methods. Unfortunately, due to the side information, its impact is globally negative. Switching off interscale coding leads to improved performance. Thus, we show in a rigorous framework that interscale prediction of blocks is not recommended for natural image coding.