Elimination of blocky artifacts in predictive video coding
Yoon-Seok Jung, Geun-Soo Park, Samuel Moon-Ho Song · Proceedings of SPIE, the International Society for Optical Engineering/Proceedings of SPIE · 1998
In a number of image compression standards, the motion vectors are generally obtained by the well-known block matching algorithm (BMA), the error image along with the computed motion vectors are encoded. Unfortunately, this widely used approach generates artificial block boundary discontinuities, called blocky artifacts, between the blocks. Since the blocky artifacts are caused by synthesizing the predicted frame using one constant motion vector per block, we propose an algorithm that interpolates the motion vectors before the construction of the predicted image. Naturally, using spatially smooth motion vectors completely eliminates the blocky artifact. However, we can no longer use the motion vectors as provided by the BMA. The optimum motion vectors must minimize the norm of the error image. The proposed algorithm computes the optimum motion vectors, with the interpolation process built into the algorithm. To obtain spatially smooth motion vectors, we use a band-limited interpolation, and thus, we refer to our algorithm as the band-limited motion compensation (BLMC). Our simulations indicate that the BLMC completely eliminates the blocky artifacts, as expected, and in addition provides higher peak-signal-to-noise-ratio in comparison to the traditional BMA based motion compensation (BMC) as well as the overlapped BMC.