Experiments On Image Coding With Distortion Below Visual Threshold
Éric Dubois, Y. Rahmouni, F. Lortie · Proceedings of SPIE, the International Society for Optical Engineering/Proceedings of SPIE · 1987
Two quantization methods for high quality image coding are presented. The goal in both methods is to keep subjective distortion below visual threshold. The first method is a discrete cosine transform coding system. The coefficients of the transformed blocks are quantized with a set. of uniform quantizers with step sizes determine by a parametric function. Subjective experiments were carried out to determine the parameter values which minimize output entropy while keeping distortion at about the threshold of perceptibility. The second method is a vector quantizer on small image blocks. A structured quantizer defined by a few parameters is described, and approximate parameter values for transparent, coding are given.