Methods and apparatus for preventing rounding errors when transf

Details Methods and apparatus for preventing rounding errors when transf Methods and apparatus for preventing rounding errors when transf

1994-02-28

1996-01-02

Baker, Stephen M.

Excavating

348403, 348415, 364725, H04N 1415

Patent

active

054815533

ABSTRACT:
Mismatch errors occur in the local decoder of a MPEG-standard compressor for a motion picture signal, and in an MPEG-standard expander for a compressed motion picture signal. This is because of the lack of a standard for rounding results of *0.5 (* is an integer) obtained when a set of transform coefficients resulting from compressing the motion picture signal is inversely orthogonally transformed. The invention prevents mismatch errors by pre-processing the set of transform coefficients prior to the inverse orthogonal transform. The transform coefficients in the set are summed, and the parity (odd or even) of the sum is judged. When the parity of the sum is judged to be even, the parity of one of the transform coefficients in the set is inverted to provide a parity-inverted transform coefficient. This makes the parity of the sum odd. Then, when the set of transform coefficients including the parity-inverted transform coefficient is inversely orthogonally transformed, none of the results of the orthogonal transform will have a value of *0.5.

REFERENCES:
patent: 4463377 (1984-07-01), Meyer-Ebrecht et al.
patent: 4807033 (1989-02-01), Keesen et al.
patent: 5218650 (1993-06-01), Blonstein et al.
"Oddification Problem for iDCT Miss-match," International Organization for Standardization--Coding of Moving Pictures and Associated Audio, ISO/IEC JTC1/SC2/WG11, MPEG93/278, Mar. 29, 1993.
"Information Technology--Generic Coding of Moving Pictures and Associated Audio," Recommendation H.26x, ISO/IEC xxxxx, Third working draft (preparation for Jul. 1993 meeting).

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