A multiband signal generator generates multiband signals from 21 lines of input data by using a subset of N lines with each line delayed from 1 line to N lines respectively. M line buffers delay the multiband signals such that each line is delayed from 1 line to M lines respectively. An analyzer detects correlations between video data by selecting regions with a maximum size M×M in the multiband signals, and analyzes characteristics of the video data. A multiband signal generator generates multiband signals with cutoff frequencies based on an analysis result from the analyzer, by using the data from 1-line through N-line delayed multiband signal. An amplitude adjuster and synthesizer unit adjusts and synthesizes amplitudes of the multiband signals.