An encoding process and a recompression process of encoded data are disclosed that appropriately select low-order bit planes and low-order sub bit planes, codes corresponding to which are not to be output. The low-order bit planes and low-order sub bit planes are selected based on an inverse value of the square root of the subband gain of inverse wavelet transform, such that the selected low-order bit planes and low-order sub bit planes are not encoded, or alternatively, are encoded, but later discarded during packet generation.