80,178 research outputs found
Efficient Action Detection in Untrimmed Videos via Multi-Task Learning
This paper studies the joint learning of action recognition and temporal
localization in long, untrimmed videos. We employ a multi-task learning
framework that performs the three highly related steps of action proposal,
action recognition, and action localization refinement in parallel instead of
the standard sequential pipeline that performs the steps in order. We develop a
novel temporal actionness regression module that estimates what proportion of a
clip contains action. We use it for temporal localization but it could have
other applications like video retrieval, surveillance, summarization, etc. We
also introduce random shear augmentation during training to simulate viewpoint
change. We evaluate our framework on three popular video benchmarks. Results
demonstrate that our joint model is efficient in terms of storage and
computation in that we do not need to compute and cache dense trajectory
features, and that it is several times faster than its sequential ConvNets
counterpart. Yet, despite being more efficient, it outperforms state-of-the-art
methods with respect to accuracy.Comment: WACV 2017 camera ready, minor updates about test time efficienc
FCN-rLSTM: Deep Spatio-Temporal Neural Networks for Vehicle Counting in City Cameras
In this paper, we develop deep spatio-temporal neural networks to
sequentially count vehicles from low quality videos captured by city cameras
(citycams). Citycam videos have low resolution, low frame rate, high occlusion
and large perspective, making most existing methods lose their efficacy. To
overcome limitations of existing methods and incorporate the temporal
information of traffic video, we design a novel FCN-rLSTM network to jointly
estimate vehicle density and vehicle count by connecting fully convolutional
neural networks (FCN) with long short term memory networks (LSTM) in a residual
learning fashion. Such design leverages the strengths of FCN for pixel-level
prediction and the strengths of LSTM for learning complex temporal dynamics.
The residual learning connection reformulates the vehicle count regression as
learning residual functions with reference to the sum of densities in each
frame, which significantly accelerates the training of networks. To preserve
feature map resolution, we propose a Hyper-Atrous combination to integrate
atrous convolution in FCN and combine feature maps of different convolution
layers. FCN-rLSTM enables refined feature representation and a novel end-to-end
trainable mapping from pixels to vehicle count. We extensively evaluated the
proposed method on different counting tasks with three datasets, with
experimental results demonstrating their effectiveness and robustness. In
particular, FCN-rLSTM reduces the mean absolute error (MAE) from 5.31 to 4.21
on TRANCOS, and reduces the MAE from 2.74 to 1.53 on WebCamT. Training process
is accelerated by 5 times on average.Comment: Accepted by International Conference on Computer Vision (ICCV), 201
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