Video decoder apparatus using non-reference frame as an additional prediction source and method therefor

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, along with the past and future reference frames as defined by the MPEG specification. In one embodiment a given macroblock within a current B-frame "N" reuses pixel values from the previous B-frame "N-1" if they are "similar enough" to the anticipated pixels which would otherwise need to be computed. For a given macroblock, motion vectors for both B-frames are compared: if they differ by less than a similarity threshold value, then the pixel values from the previous B-frame 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.