FAST LATTICE-BASED GAIN-SHAPE VECTOR QUANTIZATION FOR IMAGE-SEQUENCE CODING

A fast lattice-based gain/shape vector-quantisation method (FLGSVQ) is presented. The proposed technique combines the basic ideas of gain/sh ape vector quantisation (GSVQ) with lattice codes to offer an encoding process which is extremely fast compared with the conventional GSVQ. The main aim is to show how vector quantisers designed using the LBG a lgorithm can be substituted by lattice-based ones with vast reductions in encoding complexity, at a competitive image quality. A simple sing le-/two-stage coding system based on lattice quantisation is tested fo r interframe predictive coding of image sequences. Simulation results are provided to compare the performance of the proposed method with th e conventional LBG-designed vector quantisation. These results, along with subjective evaluations, clearly demonstrate that lattice quantisa tion can be competitive with vector quantisation in terms of signal-to -noise performance, only at a very small fraction (4%) of the vector-q uantiser complexity.