Directional frame interpolation for MPEG compressed video

Image interpolation is one of the most elementary imaging research topics. A number of image interpolation methods have been developed for uncompressed images in the literature. However, a lot of videos have already been stored in MPEG-2 format or have to be transmitted in MPEG-2 format due to bandwidth limitation. The image interpolation methods developed for uncompressed images may not be effective when directly applied to compressed videos, because on the one hand, they do not utilize the information existed in the coded bitstreams; on the other hand, they do not consider quantization error, which may be dominant in some cases. Inspired by the success of the intra prediction in H.264/AVC and the edge-directed image interpolation methods (such as LAZA and NEDI), we propose a directional frame interpolation for MPEG compressed video. In the proposed method, 8×8 intra blocks in I frames are first classified to the nine block directions in transform domain. Then the interpolation on each block is performed along its block direction. For each block direction, an optimal Wiener filter is trained based on the representative video sequences and then used for its interpolation. In the similar way, for each pixel in an inter block in P or B frames, the interpolation is performed along the direction of its corresponding reference block. The experimental results demonstrate that the proposed method achieves better performance than the traditional linear methods such as Bicubic and Bilinear and the edge-directed methods such as LAZA and NEDI, while keeping low computational complexity which meets the requirement of practical applications.