Single Video Camera Research Articles

Analysis of Directional Wave Spectra in Shallow Water Areas Using Video Image Data

In this study, a technique for analyzing directional wave spectra in shallow water areas using video image sequences is presented. The video image was obtained and collected by a single digital video camera. The technique was based on time series of the pixel brightness on video images. The pixel can be treated as a fixed instruments through use of the rectification process. The extended maximum likelihood method and the Bayesian directional method were used to estimate directional wave spectra using two different configurations of arrays from pixel brightness on video images. The study examined video image data at HORS pier on Hasaki Beach, Japan. The results indicate that video image data could be used to estimate surface wave spectra in very shallow water areas.

Does light explain damselfish Chromis viridis abundances observed over coral colonies?

A single autonomous video camera was used to record the abundances of Chromis viridis over a branching Acropora sp. colony eight times per day over a period of 50 days. The poor explanatory power of global radiation suggests the need for recording the light really available to the fish, especially in the UV range. The increasing number of C. viridis observed with increasing wind along shore and water level may correspond to individuals swimming further from their shelter in order to get closer to the food carried by the water currents.

Preliminary studies on an automated 3D fish tracking methodbased on a single video camera

The study of fish behavior lays an important foundation for comprehending of fish migration routes,improving fishing efficiency and the protection of fishery resources.A large number of data are necessary in the study,such as stress response,cluster,migration and other measured data.However,getting these data is a time-consuming process.As fish behavior is often recorded in the form of video and a stereo camera recording system is popularly used for measurement and observation in the laboratory study,how to extract the data of fish behavior efficiently from the video has been a major problem in the study of fish behavior.By far fish 3D coordinate is usually calculated by hand,or by self made software which turns an importing fish 2D coordinate into a 3D one.In order to improve fish behavior data extraction efficiency,this paper presents an automated 3D fish tracking method based on a single video camera.A waterproof mirror was set above the experimental aquaria to simulate a camera shooting from the top,which provided a way to use a single camera for 3D imaging.We extract the data of fish behavior automatically by 3D fish tracking method which is divided into four parts: distortion calibration of single camera system,transfer formula between image coordinate to world coordinate,the automated tracking algorithm of fish movement and the automated output of fish behavior 2D and 3D data.Tests find out that while the distance between the camera and the aquaria is 1.5 m,the distortion calibration result shows the pixel error is much more acceptable which is about 0.1 pixels.As the camera tilted slightly during the experiment,the shape of the aquaria in the images changed.So based on the processing of Free-Form Deformation,the deformation of images is rectified during coordinate transform process.Then we implemented the algorithm of Interacting Multiple Model Joint Probabilistic Data Association(IMMJPDA) to automatically track fishes in 3D and output fish behavior data.The result of 6 Hemigrammus rhodostomus tracking experiment shows that: IMMJPDA algorithm can deal with the key issues during fish tracking system,which enables the method to extract individual fish from video images,construct their tracks,output 3D positions and speeds,and finally generate a complete 3D movement track drawing for fish behavior analysis.In a dense clutter situation JPDA requires a fairly large amount of computation to evaluate the joint probabilities.We combined Nearest Neighbor algorithm and JPDA algorithm to reduce the computational burden.

Video face replacement

We present a method for replacing facial performances in video. Our approach accounts for differences in identity, visual appearance, speech, and timing between source and target videos. Unlike prior work, it does not require substantial manual operation or complex acquisition hardware, only single-camera video. We use a 3D multilinear model to track the facial performance in both videos. Using the corresponding 3D geometry, we warp the source to the target face and retime the source to match the target performance. We then compute an optimal seam through the video volume that maintains temporal consistency in the final composite. We showcase the use of our method on a variety of examples and present the result of a user study that suggests our results are difficult to distinguish from real video footage.

Changes in Craniocervical and Trunk Flexion Angles and Gluteal Pressure during VDT Work with Continuous Cross‐legged Sitting

This study investigated changes in craniocervical and trunk flexion angles and gluteal pressure on both sides during visual display terminal (VDT) work with continuous cross-legged sitting. The gluteal pressures of ten VDT workers, who were recruited from laboratories, were measured using a Teckscan system and videotaped using a single video camera to capture the craniocervical and trunk flexion angles during VDT work at 30 s, 10, 20 and 30 min. The craniocervical angle was significantly increased at 10 and 20 min compared with the initial angle (p<0.05). The trunk flexion angle was significantly decreased at 30 s, 10, 20 and 30 min (p<0.05). The gluteal pressure of the crossed-leg side significantly increased at 30 s, 10 and 20 min (p<0.05). The gluteal pressure of the uncrossed-leg side significantly decreased at 30 s (p<0.05). We found that cross-legged sitting during VDT work may exert disadvantageous postural effects resulting from craniocervical and trunk flexion angles and gluteal pressure. Therefore, this posture could not be recommended during long-term VDT work.

Automated Video Exposure Assessment of Repetitive Motion

A new method is described for automatically quantifying repetitive hand motion using digital video processing. The hand activity level (HAL) is widely used for evaluating repetitive hand work. Conventional methods using either a trained observer on site, or manual off site video analysis, are often considered inaccurate, cumbersome or impractical for routine work assessment. A simple paced load transfer task was used to simulate a repetitive industrial activity. Twelve participants were videoed performing the task for varying HAL conditions. The automatically predicted HAL was compared to the ground truth HAL measured using manual frame-by-frame video analysis. Hand kinematics using the marker-less single-camera video tracking algorithm were compared against an infrared 3D motion tracking system. This paper demonstrates proof-of-concept for automatic video-based direct exposure assessment.

A Single Video Camera Postural Assessment System to Measure Rotation of the Shoulder During Computer Use

The goal of this study was to evaluate the performance of a single video camera system for measuring shoulder rotation during computer work, and to quantify the work and postural space within which the system performs optimally. Shoulder rotation angles calculated using the video system were compared with angles calculated using an active infrared LED three-dimensional motion analysis system while 10 adult volunteers simulated postures for two different trials: typical of normal computer work (freestyle) and with forced shoulder abduction (constrained). Average and absolute errors were calculated to determine the accuracy and precision of the system, respectively, for each trial, for each position, and for both the right and left hands. For the right hand, mean values for the average and absolute errors were -1 and 0 degrees, respectively. Only the absolute error increased significantly to 12 degrees for the constrained posture compared with freestyle. During normal computer work, the video system provided shoulder rotation angle values similar to those of a three-dimensional system, thus making it a viable and simple instrument to use in field studies.

Supporting region-of-interest cropping through constrained compression

The ability to create super high-resolution video is becoming relative easy to do either through a single high-definition video camera or panoramic video that automatically stitches multiple views together. As an example of the former, the motion picture industry now has 6000 × 4000 pixel full-rate video cameras available. This means that supporting region-of-interest cropping will become more important in the future. In this article, we propose a mechanism to support region-of-interest adaptation of stored video. The proposed approach creates a compression-compliant stream (e.g., MPEG-2), while still allowing it to be cropped. Fortunately, video standards like MPEG-2 specify the format of a compliant stream, and not the algorithm to get there. As a result, there is an opportunity to allow system researchers and implementers ways to optimize for applications. We show various fundamental tradeoffs that are made in order to support region-of-interest cropping with super high-resolution video which we received from a local motion-picture firm.

Combining Wireless Neural Recording and Video Capture for the Analysis of Natural Gait.

Neural control of movement is typically studied in constrained environments where there is a reduced set of possible behaviors. This constraint may unintentionally limit the applicability of findings to the generalized case of unconstrained behavior. We hypothesize that examining the unconstrained state across multiple behavioral contexts will lead to new insights into the neural control of movement and help advance the design of neural prosthetic decode algorithms. However, to pursue electrophysiological studies in such a manner requires a more flexible framework for experimentation. We propose that head-mounted neural recording systems with wireless data transmission, combined with markerless computer-vision based motion tracking, will enable new, less constrained experiments. As a proof-of-concept, we recorded and wirelessly transmitted broadband neural data from 32 electrodes in premotor cortex while acquiring single-camera video of a rhesus macaque walking on a treadmill. We demonstrate the ability to extract behavioral kinematics using an automated computer vision algorithm without use of markers and to predict kinematics from the neural data. Together these advances suggest that a new class of "freely moving monkey" experiments should be possible and should help broaden our understanding of the neural control of movement.

Study on a Vision Sensing System for the Parameter Estimation of a Serial Construction Robot

In this paper, a vision sensing system was developed in order to measure the gesture of a serial construction robot and the cylinder displacement of each actuator. The system consists of a single CCD video camera and several light sources which were used to acquire the distance information of key points of the construction robot. The three-dimensional coordinates of key points were obtained from a two-dimensional video image by using image processing. The gesture of the construction robot and the cylinder displacement of each hydraulic actuator were calculated via the inverse kinematics method. In addition, the validity of the proposed method was confirmed through an experiment of parameter estimation for the friction characteristics of a hydraulic cylinder.

CSM 2011 Sports Physical Therapy Section Poster Presentations (Abstracts SPO2175–SPO2193)

CSM 2011 Sports Physical Therapy Section Poster Presentations (Abstracts SPO2175–SPO2193)

Imaging linear polarimetry using a single ferroelectric liquid crystal modulator

In the field of polarimetry, ferroelectric liquid crystal cells are mostly used as bistable polarization rotators suitable to analyze crossed polarizations. This paper shows that, provided such a cell is used at its nominal wavelength and correctly driven, its behavior is close to that of a tunable half-wave plate, and it can be used with much benefit in lightweight imaging polarimetric setups. A partial Stokes polarimeter using a single digital video camera and a single ferroelectric liquid crystal modulator is designed and implemented for linear polarization analysis. Polarization azimuthal angle and degree of linear polarization are available at 150 frames per second with a good accuracy.

Automation of Tracking Trajectories in a Crowded Situation

Studies on pedestrians using microscopic simulation require large amounts of trajectory data from real-world pedestrian crowds. The collection of such data, if done manually, involves tremendous efforts and is very time-consuming. Although many studies have asserted the possibility of automating this task using video cameras, we have found that only a few have demonstrated good performance in very crowded situations or from a top-angled view scene. This paper deals with tracking pedestrian crowd under heavy occlusion and from an angular scene using only a single non-stereo video camera. Our automated tracking system consists of three modules that are performed sequentially. The first module detects moving objects as blobs. The second module computes feature values from the blob information in order to generate what we call a possibility matrix. The third module is a tracking system, which employs a Bayesian update of the probability tree derived from the possibility matrix and from the detection of each pedestrian, in order to track the next position of the pedestrian. The result of such tracking is a database of pedestrian trajectories over time and space. With certain prior information, we show that the system is able to track a large number of people under occlusion and clutter scene.

Effect of Infraction Type on Head Impact Severity in Youth Ice Hockey

To identify the effects of infractions sustained during participation in youth ice hockey on biomechanical measures of head impact severity. Sixteen adolescent Bantam-aged male ice hockey players (age = 14.0 +/- 0.5 yr, height = 171.3 +/- 4.5 cm, mass = 63.7 +/- 6.6 kg) were equipped with accelerometer-instrumented helmets to collect biomechanical measures relating to head impacts (linear acceleration, rotational acceleration, and Head Impact Technology severity profile (HITsp)) sustained while participating in ice hockey. Single-camera video footage from 54 games was synchronized with the head impact data, and all viewable collisions (n = 665) were evaluated as resulting from a legal collision or an infraction. Infractions were further categorized into boarding or charging, checking from behind, and elbowing or intentional head contact. Statistical analyses included random-intercepts general linear mixed models. Infractions were observed in 17.3% (115/665) of all body collisions. Overall, collisions involving infractions had higher linear accelerations (P = 0.012) and HITsp (P = 0.021) than collisions with no infraction. Specifically, elbowing, head contact, and high sticking infractions resulted in greater linear acceleration (P = 0.005) and HITsp (P = 0.010) than collisions with no infraction. A strong trend for higher rotational accelerations in this infraction type compared with legal collisions was also present (P = 0.059). Infractions result in higher measures of head impact severity than noninfraction collisions. Athletes and coaches should conform to playing rules, and officials should enforce more stringently existing rules and assess more severe penalties to participants who purposefully attempt to foul an opponent at the youth ice hockey level.

Tracking Motion, Deformation, and Texture Using Conditionally Gaussian Processes

We present a generative model and inference algorithm for 3D nonrigid object tracking. The model, which we call G-flow, enables the joint inference of 3D position, orientation, and nonrigid deformations, as well as object texture and background texture. Optimal inference under G-flow reduces to a conditionally Gaussian stochastic filtering problem. The optimal solution to this problem reveals a new space of computer vision algorithms, of which classic approaches such as optic flow and template matching are special cases that are optimal only under special circumstances. We evaluate G-flow on the problem of tracking facial expressions and head motion in 3D from single-camera video. Previously, the lack of realistic video data with ground truth nonrigid position information has hampered the rigorous evaluation of nonrigid tracking. We introduce a practical method of obtaining such ground truth data and present a new face video data set that was created using this technique. Results on this data set show that G-flow is much more robust and accurate than current deterministic optic-flow-based approaches.

Eyegaze Detection from Monocular Camera Image for Eyegaze Communication System

An eyegaze interface is one of the key technologies as an input device in the ubiquitous-computing society. In particular, an eyegaze communication system is very important and useful for severely handicapped users such as quadriplegic patients. Most of the conventional eyegaze tracking algorithms require specific light sources, equipment and devices. In this study, a simple eyegaze detection algorithm is proposed using a single monocular video camera. The proposed algorithm works under the condition of fixed head pose, but slight movement of the face is accepted. In our system, we assume that all users have the same eyeball size based on physiological eyeball models. However, we succeed to calibrate the physiologic movement of the eyeball center depending on the gazing direction by approximating it as a change in the eyeball radius. In the gaze detection stage, the iris is extracted from a captured face frame by using the Hough transform. Then, the eyegaze angle is derived by calculating the Euclidean distance of the iris centers between the extracted frame and a reference frame captured in the calibration process. We apply our system to an eyegaze communication interface, and verified the performance through key typing experiments with a visual keyboard on display.

Estudos de Reaeração com Velocimetria por Imagens de Partículas - Sistema S-PIV-3D

Particle Image Velocimetry (PIV) é uma técnica recente de medição não-intrusiva de campos de velocidades em escoamentos. Neste trabalho, foi desenvolvido um equipamento de medição com características similares aos convencionais, porém com algumas características exclusivas, como o método óptico de aquisição de imagens e a calibração de coordenadas, que resultaram na utilização de uma única câmera convencional para obtenção de imagens e dados tridimensionais em escoamentos de baixa turbulência, proporcionando significativa economia na implantação. Foi desenvolvido um software específico e os resultados consistem em campos de velocidades tridimensionais. A aplicação destinou-se à medição de velocidades na superfície do escoamento em um tanque de grades oscilantes de forma a correlacionar a turbulência superficial com a capacidade de reaeração dos corpos da água.

The Typical Flight Performance of Blowflies: Measuring the Normal Performance Envelope of Calliphora vicina Using a Novel Corner-Cube Arena

Despite a wealth of evidence demonstrating extraordinary maximal performance, little is known about the routine flight performance of insects. We present a set of techniques for benchmarking performance characteristics of insects in free flight, demonstrated using a model species, and comment on the significance of the performance observed. Free-flying blowflies (Calliphora vicina) were filmed inside a novel mirrored arena comprising a large (1.6 m1.6 m1.6 m) corner-cube reflector using a single high-speed digital video camera (250 or 500 fps). This arrangement permitted accurate reconstruction of the flies' 3-dimensional trajectories without the need for synchronisation hardware, by virtue of the multiple reflections of a subject within the arena. Image sequences were analysed using custom-written automated tracking software, and processed using a self-calibrating bundle adjustment procedure to determine the subject's instantaneous 3-dimensional position. We illustrate our method by using these trajectory data to benchmark the routine flight performance envelope of our flies. Flight speeds were most commonly observed between 1.2 ms−1 and 2.3 ms−1, with a maximum of 2.5 ms−1. Our flies tended to dive faster than they climbed, with a maximum descent rate (−2.4 ms−1) almost double the maximum climb rate (1.2 ms−1). Modal turn rate was around 240°s−1, with maximal rates in excess of 1700°s−1. We used the maximal flight performance we observed during normal flight to construct notional physical limits on the blowfly flight envelope, and used the distribution of observations within that notional envelope to postulate behavioural preferences or physiological and anatomical constraints. The flight trajectories we recorded were never steady: rather they were constantly accelerating or decelerating, with maximum tangential accelerations and maximum centripetal accelerations on the order of 3 g.

New Measurement Method for Aerodynamic Force by a Single Video Camera

A method of motion reconstruction from a image streak taken by a single video camera, and a procedure to calculate aerodynamic force and moment from the motion are proposed. In this method the motion of an object is separately measured with translational and rotational motion. For the translational motion, the size and its location of a moving object is used to get the instantaneous position of the object. For the rotational motion, the attitude of the object is calculated by tracking featured points on the object. In addition to accomplish the aerodynamic measurement by this method, an evaluation was done for the measurement errors in the aerodynamic force, which are caused from image distortion by aberration of a lens. A series of the experiments for the flying ball showed the validity of the proposed method and the aerodynamic characteristics of the flying ball were analyzed using this method.

The Relationship between the Active Cervical Range of Motion and Changes in Head and Neck Posture after Continuous VDT Work

This study investigated the relationship between the active cervical range of motion (ROM) and changes in the head and neck posture after continuous visual display terminal (VDT) work. Twenty VDT workers were recruited from laboratories. The active cervical ROM of the participants was measured and videotaped to capture the craniocervical and cervicothoracic angles using a single video camera before and after VDT work. Pearson correlation coefficients were used to quantify the linear relationship between active cervical ROM measurements and the changes in the craniocervical and cervicothoracic angles after continuous VDT work. Active neck extension (r=-0.84, p<0.01) was negatively correlated with the mean craniocervical angle, and active neck flexion (r=-0.82, p<0.01) and left lateral flexion (r=-0.67, p<0.01) were negatively correlated with the mean cervicothoracic angle.