The multi-frame super resolution (SR) problem is to generate high resolution (HR) images by referring to a sequence of low resolution (LR) images. However, traditional multi-frame SR methods fail to take full advantage of the redundancy in LR images. In this paper, we present a novel algorithm using a refined example-based SR framework to cope with this problem. The refined framework includes two innovative points. First, based upon a thorough study of multi-frame and single frame statistics, we extend the single frame example-based scheme to multi-frame. Instead of training an external dictionary, we search for examples in the image pyramids of the LR inputs, i.e., a set of multi-resolution images derived from the input LRs. Second, we propose a new metric to find similar image patches, which not only considers the intensity and structure features of a patch but also adaptively balances between these two parts. With the refined framework, we are able to make the utmost of the redundancy in LR images to facilitate the SR process. As can be seen from the experiments, it is efficient in preserving structural features. Experimental results also show that our algorithm outperforms state-of-the-art methods on test sequences, achieving the average PSNR gain by up to 1.2dB.
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