Edge-preserving ADPCM and ECVQ coding of image sub-bands using subjective criteria

We propose an adaptive sub-band image coder designed according to subjective criteria. A pre-processing technique is applied to the high subbands and discards local information irrelevant to the overall subjective quality. Pixels not removed by this technique are classified as edges and non-edges by means of a specific algorithm designed for each sub-band. The two classes in each high-frequency sub-band are quantized with entropy constrained vector quantizers (ECVQ). The low sub-band is encoded with an edge-preserving ADPCM. Both in terms of PSNR and visual quality the proposed codec offers meaningful improvements compared to the JPEG algorithm.