GENERATOR FOR HIERARCHICAL DATA, ITS METHOD, GENERATION RECOVERY SYSTEM FOR HIERARCHICAL DATA AND ITS METHOD

摘要

PROBLEM TO BE SOLVED: To reduce errors without the need for expansion of the bit length or for additional bits in the case of hierarchical coding where high-order hierarchical data are generated by a sum or a mean value of four adjacent pixels in a low-order layer. SOLUTION: The sum T2 of four adjacent pixels of 1st hierarchical data is calculated and low-order 2 bits of the sum T2 are rounded off to generate a tentative pixel value Y2'. A rounding error D is calculated by using a value -T2=D=-1 resulting from adding '00' to the low-order 2-bits of the value Y2'. A correction value -1 is generated and -1 is added to a value X12. The rounding error is distributed from the 2nd layer to the 1st layer in this way. The round error is similarly distributed from the 3rd layer to the 2nd layer. A correction value -1 is respectively added to tentative pixel values Y1' Y3'. Furthermore, pixel values of the 1st layer are corrected attended with correction to pixel values Y1, Y2 of the 2nd layer. Each pixel value of each layer has a prescribed bit length and no additional code is required.