Patent ID: 6275533
Filing Date: 2001-08-14
Classification: H04N

Abstract:
An image processing method in which an image signal forming an image space comprising plural pixels arranged in matrix in horizontal and vertical directions is divided into image signals corresponding to plural macroblocks of a rectangular shape into which the image space is divided, and image signals of subblocks of each macroblock are coded for each subblock, said method comprising the steps:rearranging horizontal pixel rows of an image signal of a macroblock so that a first field image formed by image signals on odd-numbered horizontal pixel rows is positioned at an upper side of the macroblock and a second field image formed by image signals on even-numbered horizontal pixel rows is positioned at a lower side of the macroblock;transforming one of the image signal of the macroblock in which rearrangement has been performed and an image signal of a macroblock in which rearrangement has not been performed, into frequency components by frequency transformation, for each of four subblocks positioned upper left, upper right, lower left, and lower right in the macroblock;generating prediction values of frequency components of a target subblock to be coded by referring to at least one of a coded subblock positioned above and adjacently to the target subblock, a coded subblock positioned at the left of and adjacently to the target subblock, a coded subblock positioned at the upper left of and adjacently to the target subblock, wherein when the prediction values of the frequency components of the target subblock are generated, it is decided that one of the coded subblock positioned above and adjacently to the target subblock and the coded subblock positioned at the left of and adjacently to the target subblock is referred to, based on direct current components of frequency components of the coded subblocks which are positioned above and adjacently to the target subblock, at the left of and adjacently to the target subblock, and at the upper left of and adjacently to the target subblock, respectively; andcoding difference values between the frequency components and the prediction values of the target subblock, wherein when an absolute value of difference of direct current components of frequency components between the coded subblock positioned above and the coded subblock positioned at the upper left is smaller than an absolute value of difference of direct current components of frequency components between the coded subblock positioned at the left and the coded subblock positioned at the upper left, the prediction values of the frequency components of the target subblock are generated by referring to frequency components of the coded subblock positioned at the left of the target subblock, andwhen an absolute value of difference of direct current components of frequency components between the coded subblock positioned at the left and the coded subblock positioned at the upper left is smaller than an absolute value of difference of direct current components of frequency components between the coded subblock positioned above and the coded subblock positioned at the upper left, the prediction values of the frequency components of the target subblock are generated by referring to frequency components of the coded subblock positioned above of the target subblock.