METHOD AND APPARATUS FOR PREVENTING ROUNDING ERRORS WHEN CONVERSION FACTORS REPRESENTING A SIGNAL ARE INVERSELY TRANSFORMED

摘要

Mismatch error can occur in MPEG decoders because of the lack of standards for rounding results of *. 5 ( where * is an integer),obtained when a set of conversion factors resulting from compressing the motion picture signal is inversely orthogonally transformed. Such errors are prevented by pre-processing the conversion factors prior to the inverse orthogonal transformation (15). The conversion factors are summed (23A) and the parity (odd or even) of the sum (21) is judged. If the sum parity is judged to be even, the parity of one of the conversion factors is inverted (28) to make the parity of the sum odd. Consequently, no conversion factor resulting from the inverse orthogonal transformation will have a value of *.5.