Reducing artifacts of intra-frame video coding via sequential denoising

In this work we propose a new postprocessing method for video sequences compressed using intra-frame coding techniques. The suggested method extends our previously published approach for handling compressed still-images. We rely on the Plug-and-Play Prior framework, which shows that a general inverse problem can be cast as a sequence of Gaussian denoising steps. We formulate the video recovery task as such an inverse problem, with a regularization that leverages on existing state-of-the-art video denoising algorithms. Our method's strength emerges from two origins: (i) the flexibility of using the best available video denoising algorithm; and (ii) the fact that, while intra-coding is treated, an inter-frame force is introduced via the denoising stage. As such, our scheme can be interpreted as belonging to the distributed video coding paradigm with an extended decompression procedure coupled with a relatively simple compression. A prominent part in our approach is a linearization of the nonlinear compression-decompression operation, while leveraging the intra-coding structure to obtain a block-diagonal matrix form. We demonstrate significant quality improvements for video sequences compressed using Motion-JPEG2000.