Method and apparatus for decoding mpeg video data

Abstract

An MPEG video decoder adapted to decode an incoming MPEG coded video data stream to form decoded MPEG video data and to reconstruct from the decoded MPEG video data a raw video signal, utilizes: an n×n block of decoded video data discrete cosine transform values forming an original matrix having a non-zero value in a preselected corner location in the matrix; and a modified matrix forming apparatus adapted to form a modified matrix having the same content as the original matrix with the exception of a zero in the preselected corner value position; a dummy matrix forming apparatus adapted to form a dummy matrix having zero in each of its matrix positions with the exception of the preselected corner position; an inverse discrete cosine transform apparatus adapted to perform an inverse discrete cosine transform algorithm on the modified matrix and the dummy matrix; and an adder which adds the inverse discrete cosine transform of the modified matrix and the dummy matrix to produce the inverse discrete cosine transform for the original matrix. The matrix may be the typical 8x8 MPEG block. The inverse discrete cosine transform for the dummy matrix may be precomputed and stored and added to each inverse discrete cosine transform of each modified matrix.