Experimentally Derived Weighting Function in Spatial Frequency Domain for Evaluating Still Pictures.
Seiichiro Hangai, T. Wada, Kazuhiro Miyauchi · The Journal of The Institute of Image Information and Television Engineers · 1992
A "weighting function" is defined for evaluating monochrome still-picture quality in the spatial frequency domain.The weighting values of the function can bedetermined from the relationship between the MOS (Mean Opinion Score) and the spatial-frequency-selective noise level.A hundred and six weighting values are calculated in the spatial frequency dommain of 256 (TV lines) x 256 (TV lines).When the ratio of viewing distance to picture height is 7 , the weighting value at 3 (cpd , cycle per degree) shows maximum value .The function is isotropic in the region from 3 (cpd) to 8 (cpd) and anisotropic at over 10 (cpd) .Using the weighting function, a new objective measure named WSNR (Weighted Signal-to-Noise Ratio) is also defined and applied to pictures degraded artificially .The picture quality is degraded by adding random noise, by passing through a two-dimensional low-pass filter , or by distorting blocks.Experiments using different portrait pictures show good correlation coefficients between the MOS and the WSNR, 0.93 -0.97.