Masking and quantization laws in a visual subband coding scheme

To design psychovisual quantizers, experiments based on the visibility of the quantization noise have been conducted by Saadane, Senane and Barba (see Visual Communications and Image Processing, Oct. 1994). The results obtained show that for a given visual decomposition scheme and within a subband, the decision thresholds and reconstruction levels follow a linear law with an interval quantization varying with frequency and orientation. In this paper, and in order to examine the masking effects on the perception of quantization noise, further experiments have been conducted by keeping the same methodology and the same decomposition scheme as Saadane et. al. Two important results have been obtained. First the masking didn´t affect the linear behavior observed when no masking was considered. Secondly, with the contrast definition used, and even a slight increase in the quantization interval has been observed for the radial subbands, the masking was essentially due to the angular subbands