Rounding Mismatch Between Spatial-Domain and Transform-Domain Video Codecs

The mismatch between a spatial-domain encoder and a transform-domain decoder due to rounding can cause serious video quality degradation after a series of inter-coded frames. The mismatch is rooted on the fact that rounding is a nonlinear operation, and hence its equivalent in the transform domain does not exist. We analyze the mathematical property of the rounding operation and propose a practical solution that provides an optimal approximation of the rounding operation in the transform-domain. The proposed solution is able to reduce the mismatch and preserve image quality. Experimental results are shown to demonstrate the effectiveness of the solution