COMPRESSOR FOR PICTURE DATA

摘要

PURPOSE:To suppress deterioration in picture quality while securing a high compression rate in picture data compression. CONSTITUTION:A characteristic quantity W(f) such as an absolute value is calculated from a conversion coefficient CO(f) obtained by applying cosine transformation to picture data divided into blocks (characteristic quantity calculation device 21). On the other hand, a threshold level T(f) is decided for each frequency (f) based on a border value decision parameter obtained from a statistic quantity for each block of the conversion coefficient CO(f) (threshold level decision device 22) and the characteristic quantity W(f) and the threshold level T(f) are compared (comparator 23). Then a highest frequency when the characteristic quantity W(f) exceeds the threshold level T(f)is obtained as a border fb of the frequency at which coding is cut off (Maximum value storage device 24) and coding is applied to only AC components at frequencies below the border fb.