A pixel block is coded by both of a quadrature transform coding section and a block truncation coding section. A code amount counter determines a first code amount of one-block coded data produced by the quadrature transform coding section. A code amount judgment section compares the first code amount with a threshold that is smaller than or equal to a second code amount of one-block coded data produced by the block truncation coding section, and produces discrimination information indicating a comparison result. A selector selects the coded data that is output from the quadrature transform coding section if the first code amount is smaller than the threshold, and selects the coded data that is output from the block truncation coding section if the first code amount is larger than the threshold. A storage section stores the discrimination information for each pixel block and the coded data that is output from the selector and corresponds to the discrimination information. <IMAGE>
Image signal coding apparatus with switching between variable-length coding and fixed-length coding