310,710 research outputs found
Contextual Action Recognition with R*CNN
There are multiple cues in an image which reveal what action a person is
performing. For example, a jogger has a pose that is characteristic for
jogging, but the scene (e.g. road, trail) and the presence of other joggers can
be an additional source of information. In this work, we exploit the simple
observation that actions are accompanied by contextual cues to build a strong
action recognition system. We adapt RCNN to use more than one region for
classification while still maintaining the ability to localize the action. We
call our system R*CNN. The action-specific models and the feature maps are
trained jointly, allowing for action specific representations to emerge. R*CNN
achieves 90.2% mean AP on the PASAL VOC Action dataset, outperforming all other
approaches in the field by a significant margin. Last, we show that R*CNN is
not limited to action recognition. In particular, R*CNN can also be used to
tackle fine-grained tasks such as attribute classification. We validate this
claim by reporting state-of-the-art performance on the Berkeley Attributes of
People dataset
Towards Contextual Action Recognition and Target Localization with Active Allocation of Attention
Exploratory gaze movements are fundamental for gathering the most relevant information regarding the partner during social interactions. We have designed and implemented a system for dynamic attention allocation which is able to actively control gaze movements during a visual action recognition task. During the observation of a partners reaching movement, the robot is able to contextually estimate the goal position of the partner hand and the location in space of the candidate targets, while moving its gaze around with the purpose of optimizing the gathering of information relevant for the task. Experimental results on a simulated environment show that active gaze control provides a relevant advantage with respect to typical passive observation, both in term of estimation precision and of time required for action recognition. © 2012 Springer-Verlag
Modeling Temporal Dynamics and Spatial Configurations of Actions Using Two-Stream Recurrent Neural Networks
Recently, skeleton based action recognition gains more popularity due to
cost-effective depth sensors coupled with real-time skeleton estimation
algorithms. Traditional approaches based on handcrafted features are limited to
represent the complexity of motion patterns. Recent methods that use Recurrent
Neural Networks (RNN) to handle raw skeletons only focus on the contextual
dependency in the temporal domain and neglect the spatial configurations of
articulated skeletons. In this paper, we propose a novel two-stream RNN
architecture to model both temporal dynamics and spatial configurations for
skeleton based action recognition. We explore two different structures for the
temporal stream: stacked RNN and hierarchical RNN. Hierarchical RNN is designed
according to human body kinematics. We also propose two effective methods to
model the spatial structure by converting the spatial graph into a sequence of
joints. To improve generalization of our model, we further exploit 3D
transformation based data augmentation techniques including rotation and
scaling transformation to transform the 3D coordinates of skeletons during
training. Experiments on 3D action recognition benchmark datasets show that our
method brings a considerable improvement for a variety of actions, i.e.,
generic actions, interaction activities and gestures.Comment: Accepted to IEEE International Conference on Computer Vision and
Pattern Recognition (CVPR) 201
An original framework for understanding human actions and body language by using deep neural networks
The evolution of both fields of Computer Vision (CV) and Artificial Neural Networks (ANNs) has allowed the development of efficient automatic systems for the analysis of people's behaviour.
By studying hand movements it is possible to recognize gestures, often used by people to communicate information in a non-verbal way.
These gestures can also be used to control or interact with devices without physically touching them. In particular, sign language and semaphoric hand gestures are the two foremost areas of interest due to their importance in Human-Human Communication (HHC) and Human-Computer Interaction (HCI), respectively.
While the processing of body movements play a key role in the action recognition and affective computing fields. The former is essential to understand how people act in an environment, while the latter tries to interpret people's emotions based on their poses and movements;
both are essential tasks in many computer vision applications, including event recognition, and video surveillance.
In this Ph.D. thesis, an original framework for understanding Actions and body language is presented. The framework is composed of three main modules: in the first one, a Long Short Term Memory Recurrent Neural Networks (LSTM-RNNs) based method for the Recognition of Sign Language and Semaphoric Hand Gestures is proposed; the second module presents a solution based on 2D skeleton and two-branch stacked LSTM-RNNs for action recognition in video sequences; finally, in the last module, a solution for basic non-acted emotion recognition by using 3D skeleton and Deep Neural Networks (DNNs) is provided.
The performances of RNN-LSTMs are explored in depth, due to their ability to model the long term contextual information of temporal sequences, making them suitable for analysing body movements.
All the modules were tested by using challenging datasets, well known in the state of the art, showing remarkable results compared to the current literature methods
Understanding dynamic situations through context explanation.
International audienceThis article presents advantages of using context to set up a pedagogical assistance for recognition of collectives situations in Virtual Environment for Training (VET). We are focusing on generation of explanations to the learner. Two assistances types have been envisaged thanks to context using, the first one consists in guiding the learner before action and the second can be used during action. Those assistances have been set up thanks to contextual graph and consists of animations in the virtual environment
Reconstructing Humpty Dumpty: Multi-feature Graph Autoencoder for Open Set Action Recognition
Most action recognition datasets and algorithms assume a closed world, where
all test samples are instances of the known classes. In open set problems, test
samples may be drawn from either known or unknown classes. Existing open set
action recognition methods are typically based on extending closed set methods
by adding post hoc analysis of classification scores or feature distances and
do not capture the relations among all the video clip elements. Our approach
uses the reconstruction error to determine the novelty of the video since
unknown classes are harder to put back together and thus have a higher
reconstruction error than videos from known classes. We refer to our solution
to the open set action recognition problem as "Humpty Dumpty", due to its
reconstruction abilities. Humpty Dumpty is a novel graph-based autoencoder that
accounts for contextual and semantic relations among the clip pieces for
improved reconstruction. A larger reconstruction error leads to an increased
likelihood that the action can not be reconstructed, i.e., can not put Humpty
Dumpty back together again, indicating that the action has never been seen
before and is novel/unknown. Extensive experiments are performed on two
publicly available action recognition datasets including HMDB-51 and UCF-101,
showing the state-of-the-art performance for open set action recognition.Comment: Accepted to WACV 202
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