In this paper, the authors propose a novel algorithm for block artifact reduction for which Pseudo random noise masking is used. In H.264 video compression standard, an in-loop deblocking filter is implemented to reduce the quantization noise around the block boundaries. But there would still remain artifacts within blocks. These artifacts are known as contour artifacts. These contour artifacts further are reduced by their proposed pseudo random noise masking method. This paper is selectively applied to macro-blocks damaged by block artifacts after H.264 deblocking filtering.