565 research outputs found
A distributed camera system for multi-resolution surveillance
We describe an architecture for a multi-camera, multi-resolution surveillance system. The aim is to support a set of distributed static and pan-tilt-zoom (PTZ) cameras and visual tracking algorithms, together with a central supervisor unit. Each camera (and possibly pan-tilt device) has a dedicated process and processor.
Asynchronous interprocess communications and archiving of data are achieved in a simple and effective way via a central repository, implemented using an SQL database.
Visual tracking data from static views are stored dynamically into tables in the database via client calls to the SQL server. A supervisor process running on the SQL server determines if active zoom cameras should be dispatched to observe a particular target, and this message is effected via writing demands into another database table.
We show results from a real implementation of the system comprising one static camera overviewing the environment under consideration and a PTZ camera operating
under closed-loop velocity control, which uses a fast and robust level-set-based region tracker. Experiments demonstrate the effectiveness of our approach and its feasibility to multi-camera systems for intelligent surveillance
Staple: Complementary Learners for Real-Time Tracking
Correlation Filter-based trackers have recently achieved excellent
performance, showing great robustness to challenging situations exhibiting
motion blur and illumination changes. However, since the model that they learn
depends strongly on the spatial layout of the tracked object, they are
notoriously sensitive to deformation. Models based on colour statistics have
complementary traits: they cope well with variation in shape, but suffer when
illumination is not consistent throughout a sequence. Moreover, colour
distributions alone can be insufficiently discriminative. In this paper, we
show that a simple tracker combining complementary cues in a ridge regression
framework can operate faster than 80 FPS and outperform not only all entries in
the popular VOT14 competition, but also recent and far more sophisticated
trackers according to multiple benchmarks.Comment: To appear in CVPR 201
Fully Automatic and Real-Time Catheter Segmentation in X-Ray Fluoroscopy
Augmenting X-ray imaging with 3D roadmap to improve guidance is a common
strategy. Such approaches benefit from automated analysis of the X-ray images,
such as the automatic detection and tracking of instruments. In this paper, we
propose a real-time method to segment the catheter and guidewire in 2D X-ray
fluoroscopic sequences. The method is based on deep convolutional neural
networks. The network takes as input the current image and the three previous
ones, and segments the catheter and guidewire in the current image.
Subsequently, a centerline model of the catheter is constructed from the
segmented image. A small set of annotated data combined with data augmentation
is used to train the network. We trained the method on images from 182 X-ray
sequences from 23 different interventions. On a testing set with images of 55
X-ray sequences from 5 other interventions, a median centerline distance error
of 0.2 mm and a median tip distance error of 0.9 mm was obtained. The
segmentation of the instruments in 2D X-ray sequences is performed in a
real-time fully-automatic manner.Comment: Accepted to MICCAI 201
Automatic recognition of fingerspelled words in British Sign Language
We investigate the problem of recognizing words from
video, fingerspelled using the British Sign Language (BSL)
fingerspelling alphabet. This is a challenging task since the
BSL alphabet involves both hands occluding each other, and
contains signs which are ambiguous from the observer’s
viewpoint. The main contributions of our work include:
(i) recognition based on hand shape alone, not requiring
motion cues; (ii) robust visual features for hand shape
recognition; (iii) scalability to large lexicon recognition
with no re-training.
We report results on a dataset of 1,000 low quality webcam
videos of 100 words. The proposed method achieves a
word recognition accuracy of 98.9%
Visibility Constrained Generative Model for Depth-based 3D Facial Pose Tracking
In this paper, we propose a generative framework that unifies depth-based 3D
facial pose tracking and face model adaptation on-the-fly, in the unconstrained
scenarios with heavy occlusions and arbitrary facial expression variations.
Specifically, we introduce a statistical 3D morphable model that flexibly
describes the distribution of points on the surface of the face model, with an
efficient switchable online adaptation that gradually captures the identity of
the tracked subject and rapidly constructs a suitable face model when the
subject changes. Moreover, unlike prior art that employed ICP-based facial pose
estimation, to improve robustness to occlusions, we propose a ray visibility
constraint that regularizes the pose based on the face model's visibility with
respect to the input point cloud. Ablation studies and experimental results on
Biwi and ICT-3DHP datasets demonstrate that the proposed framework is effective
and outperforms completing state-of-the-art depth-based methods
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