Method and apparatus for improved video decompression using previous frame DCT coefficients

摘要

An video decoder system, such as for use with MPEG video compression, uses a previous B-frame as an additional prediction source for the current B-frame. In one embodiment, a given block within a current B- frame "N" reuses IDCT result terms from the previous B-frame "N-1" if they are determined to be "similar enough" to the anticipated IDCT result terms which would otherwise need to be computed. For a given block, each of the "M" lowest-frequency DCT coefficients for B-frame "N" and B-frame "N-1" are respectively compared: if they differ by less than a similarity threshold value, then the IDCT result terms from the previous B-frame "N- 1" are reused without further computation. The similarity threshold may be adaptively adjusted to reduce the computational burden of video decompression, while affording a gradual degradation of picture quality, rather than wholesale skipping of entire frames.