Facial action unit (AU) recognition is a crucial task for facial expressions analysis and has attracted extensive attention in the field of artificial intelligence and computer vision. Existing works have either focused on designing or learning complex regional feature representations, or delved into various types of AU relationship modeling. Albeit with varying degrees of progress, it is still arduous for existing methods to handle complex situations. In this paper, we investigate how to integrate the semantic relationship propagation between AUs in a deep neural network framework to enhance the feature representation of facial regions, and propose an AU semantic relationship embedded representation learning (SRERL) framework. Specifically, by analyzing the symbiosis and mutual exclusion of AUs in various facial expressions, we organize the facial AUs in the form of structured knowledge-graph and integrate a Gated Graph Neural Network (GGNN) in a multi-scale CNN framework to propagate node information through the graph for generating enhanced AU representation. As the learned feature involves both the appearance characteristics and the AU relationship reasoning, the proposed model is more robust and can cope with more challenging cases, e.g., illumination change and partial occlusion. Extensive experiments on the two public benchmarks demonstrate that our method outperforms the previous work and achieves state of the art performance.
Traditional feature representation based AU recognition methods focus on the design of more discriminative hand-crafted features. For instance, @cite_2 proposed to analyze the temporal behavior of action units in video and used individual feature GentleBoost templates built from Gabor wavelet features for SVM based AU classification. @cite_24 designed a facial AU intensity estimation and occurrence detection system based on the fusion of appearance and geometry features. However, these hand-crafted low level feature based algorithms are relatively fragile and difficult to deal with various types of complex situations. In recent years, deep convolutional neural networks have been widely used in a variety of computer vision tasks and have achieved unprecedented progress @cite_1 @cite_8 @cite_0 @cite_14 . There are also attempts to apply deep CNN to facial AU recognition @cite_12 @cite_11 @cite_23 @cite_4 . @cite_12 proposed a unified architecture for facial AU detection which incorporates a deep regional feature learning and multi-label learning modules. @cite_11 proposed an ROI framework for AU detection by cropping CNN feature maps with facial landmarks information. However, non of these methods explicitly take into consideration the linkage relationship between different AUs.
@cite_14 @cite_4 @cite_8 @cite_1 @cite_24 @cite_0 @cite_23 @cite_2 @cite_12 @cite_11
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Action Unit (AU) detection becomes essential for facial analysis. Many proposed approaches face challenging problems in dealing with the alignments of different face regions, in the effective fusion of temporal information, and in training a model for multiple AU labels. To better address these problems, we propose a deep learning framework for AU detection with region of interest (ROI) adaptation, integrated multi-label learning, and optimal LSTM-based temporal fusing. First, an ROI cropping net is designed to make sure specific interested regions of faces are learned independently, each sub-region has a local convolutional neural network (CNN) whose convolutional filters will only be trained for the corresponding region. Second, multi-label learning is employed to integrate the outputs of those individual ROI cropping nets, which learns the inter-relationships of various AUs and acquires global features across sub-regions for AU detection. Finally, the optimal selection of multiple LSTM layers are carried out to best fuse temporal features, in order to make the AU prediction the most accurate. The proposed approach is evaluated on two popular AU detection datasets, BP4D and DISFA, outperforming the state of the art significantly, with an average improvement of around 13 in BP4D and 25 in DISFA, respectively. Action Unit (AU) detection becomes essential for facial analysis. Many proposed approaches face challenging problems in dealing with the alignments of different face regions, in the effective fusion of temporal information, and in training a model for multiple AU labels. To better address these problems, we propose a deep learning framework for AU detection with region of interest (ROI) adaptation, integrated multi-label learning, and optimal LSTM-based temporal fusing. First, ROI cropping nets (ROI Nets) are designed to make sure specifically interested regions of faces are learned independently; each sub-region has a local convolutional neural network (CNN) - an ROI Net, whose convolutional filters will only be trained for the corresponding region. Second, multi-label learning is employed to integrate the outputs of those individual ROI cropping nets, which learns the inter-relationships of various AUs and acquires global features across sub-regions for AU detection. Finally, the optimal selection of multiple LSTM layers to form the best LSTM Net is carried out to best fuse temporal features, in order to make the AU prediction the most accurate. The proposed approach is evaluated on two popular AU detection datasets, BP4D and DISFA, outperforming the state of the art significantly, with an average improvement of around 13 on BP4D and 25 on DISFA, respectively. In this work we report on the progress of building a system that enables fully automated fast and robust facial expression recognition from face video. We analyse subtle changes in facial expression by recognizing facial muscle action units (AUs) and analysing their temporal behavior. By detecting AUs from face video we enable the analysis of various facial communicative signals including facial expressions of emotion, attitude and mood. For an input video picturing a facial expression we detect per frame whether any of 15 different AUs is activated, whether that facial action is in the onset, apex, or offset phase, and what the total duration of the activation in question is. We base this process upon a set of spatio-temporal features calculated from tracking data for 20 facial fiducial points. To detect these 20 points of interest in the first frame of an input face video, we utilize a fully automatic, facial point localization method that uses individual feature GentleBoost templates built from Gabor wavelet features. Then, we exploit a particle filtering scheme that uses factorized likelihoods and a novel observation model that combines a rigid and a morphological model to track the facial points. The AUs displayed in the input video and their temporal segments are recognized finally by Support Vector Machines trained on a subset of most informative spatio-temporal features selected by AdaBoost. For Cohn-Kanade andMMI databases, the proposed system classifies 15 AUs occurring alone or in combination with other AUs with a mean agreement rate of 90.2 with human FACS coders. Although both feature dependencies and label dependencies are crucial for facial action unit (AU) recognition, little work addresses them simultaneously till now. To address this limitation, we propose a 4-layer Restrict Boltzmann Machine (RBM) to simultaneously capture feature level and AU level dependencies to recognize multiple AUs. Specifically, the bottom two layers of the RBM model capture dependencies among image features, while the top two layers capture the high order dependencies among AU labels. An efficient learning algorithm is introduced to jointly learn all layers to leverage the interactions among different layers. Experiments on two benchmark databases demonstrate the effectiveness of the proposed approach in modelling complex AU relationships from both features and labels jointly, and its improved performance over the existing methods.