A Non-Local CNN for Video Denoising

Non-local patch-based methods were until recently state-of-the-art for image denoising but are now outperformed by convolutional neural networks (CNNs). Yet they are still the best ones for video denoising, as video redundancy is a key factor to attain high denoising performance. In this work we propose a novel video denoising CNN. Non-local self-similarity is incorporated into the network via a first non-trainable layer which finds for each patch in the input image its most similar patches in a 3D spatio-temporal search region centered at the target patch. The central values of these patches are then gathered in a feature vector which is assigned to each image pixel. This information is presented to a CNN which is trained to predict a clean image. The proposed architecture achieves state-of-the-art results. To the best of our knowledge, this is the first successful application of CNNs to video denoising.