International audienceThis paper presents a new tensor motion descriptor only using optical flow and HOG3D information: no interest points are extracted and it is not based on a visual dictionary. We propose a new aggregation technique based on tensors. This is a double aggregation of tensor descriptors. The first one represents motion by using polynomial coefficients which approximates the optical flow. The other represents the accumulated data of all histograms of gradients of the video. The descriptor is evaluated by a classification of KTH, UCF11 and Hollywood2 datasets, using a SVM classifier. Our method reaches 93.2% of recognition rate with KTH, comparable to the best local ap- proaches. For the UCF11 and Hollywood2 datasets, our recognition achieves fairly competitive results compared to local and learning based approaches. Keywords: Global motion descriptor, optical flow, histogram of gradients, action recognitio

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In this paper we propose a new method to deal with the problem of automatic human skin segmentation in RGB color space model. The problem is modeled as a minimum cost graph cut problem on a graph whose vertices represent the image color characteristics. Skin and non-skin elements are assigned by evaluating label costs of vertices associated to the weight edges of the graph. A novel approach based on an energy function defined in terms of a database of skin and non-skin tones is used to define the costs of the edges of the graph. Finally, the graph cut problem is solved in Graphics Processing Units (GPU) using the Compute Unified Device Architecture (CUDA) technology yielding very promising skin segmentation results for standard resolution video sequences. Our method was evaluated under several conditions, indicating when correct or incorrect results are generated. The overall experiments have shown that this automatic method is simple, efficient, and yields very reliable results.

Motion is one of the main characteristics that describe the semantic information of videos. In this work, a global video descriptor based on orientation tensors is proposed. This descriptor is obtained by combining polynomial coefficients calculated for each image in a video. The coefficients are found through the projection of the optical flow on Legendre polynomials, reducing the dimension of per frame motion estimations. The sequence of coefficients are then combined using orientation tensors. The global tensor descriptor created is evaluated by a classification of the KTH video database with a SVM classifier.