A low-complexity upsampling technique for H.264

A hybrid up-sampling algorithm based on the predicted modes of H.264/AVC is proposed in this paper. Other than video codecs like MPEG group, H.264/AVC utilizes variable block size for motion estimation and motion compensation, which results in better precision and compression efficiency. According to the mode decision built in H.264/AVC, the macroblocks of each frame are divided into intra mode, skip mode and others. For intra-mode macroblocks which contain more details, they are up-sampled by MAP (maximum a posteriori) since this method has best performance among existing super resolution algorithms. For macroblocks coded as skip mode, they are assumed to be highly correlated to macroblocks in the reference frame. Thus those blocks are duplicated from those referenced blocks. For the rest of the macroblocks, they not only have correspondence with blocks in other frames but also contain relatively complicated content so that they are further analyzed into variable block sizes, say 16x 16, 8x16,16x8, 8x8, 8x4, 4x8 and 4χ4. By adopting different up- sampling methods adaptively with variable block sizes, the proposed method saves computational efforts of smoother blocks for complicated blocks so that the overall complexity can be successfully reduced. Comparing to traditional frame-based up-sampling methods, the experimental results demonstrated that the proposed algorithm provides a more efficient way to up- sample videos and is capable of preserving satisfactory visual quality.