Video Motion Capture Research Articles

Method and apparatus for sensing and displaying tablature associated with a stringed musical instrument

A system and method of enhancing guitar instruction based on Tablature Plus encoding of playing techniques within a MIDI file or other data structure, that may be rendered on an associated player application that provides multimedia output of the piece being played including a number of playing techniques. The system hardware for encoding the information includes string motion monitoring, and optionally a hand motion and finger positioning sensor, such as a data glove or a video motion capture system, for simultaneously registering the actions of the guitarist while playing the piece. The software comprises algorithms for determining note pitch and duration, and for extracting playing techniques from the data being collected. Multimedia player software is also described which renders a visual and audio output for the Tablature Plus encoded file, wherein the encoded playing techniques are represented within the display output. The system is adaptable to instruction for any instrument.

Dynamic accuracy of inertial measurement units during simple pendulum motion

A motion measurement system based on inertial measurement units (IMUs) has been suggested as an alternative to contemporary video motion capture. This paper reports an investigation into the accuracy of IMUs in estimating 3D orientation during simple pendulum motion. The IMU vendor's (XSens Technologies) accuracy claim of 3° root mean squared (RMS) error is tested. IMUs are integrated electronic devices that contain accelerometers, magnetometers and gyroscopes. The motion of a pendulum swing was measured using both IMUs and video motion capture as a reference. The IMU raw data were processed by the Kalman filter algorithm supplied by the vendor and a custom fusion algorithm developed by the authors. The IMU measurement of pendulum motion using the vendor's Kalman filter algorithm did not compare well with the video motion capture with a RMS error of between 8.5° and 11.7° depending on the length and type of pendulum swing. The maximum orientation error was greater than 30°, occurring approximately eight seconds into the motion. The custom fusion algorithm estimation of orientation compared well with the video motion capture with a RMS error of between 0.8° and 1.3°. Future research should concentrate on developing a general purpose fusion algorithm and vendors of IMUs should provide details about the errors to be expected in different measurement situations, not just those in a ‘best case’ scenario.

Joint Angles at Heel Strike and Toe Off during Motorized and Non-Motorized Treadmill Locomotion

Treadmill exercise during spaceflight may mitigate cardio-respiratory, musculoskeletal, and neuromuscular deconditioning. The International Space Station (ISS) treadmill operates in a motorized (M) and non-motorized (NM) mode. Differences in peak vertical ground reaction forces (GRF) between M and NM treadmill locomotion have been demonstrated, however, lower body joint kinematics have not been compared between treadmill modes. PURPOSE: To compare hip, knee, and ankle joint angles at heel strike and toe off between M and NM treadmill while walking (1.34 m·s−1; 3 mph) and running (2.68 m·s−1; 6 mph). METHODS: Twenty subjects (10 men, 10 women; 31±5 yr, 172±10 cm, 68±13 kg) exercised on a ground-based version of the ISS treadmill. Subjects completed three 10-s trials at each speed on separate days in random order. Kinematic data were collected at 60 Hz with a multiple-camera infrared video motion capture system. Paired t-tests were used to assess differences between treadmill modes within each speed (p<0.05). RESULTS: Hip and knee flexion and ankle dorsiflexion at heel strike were greater for NM. At toe off, subjects had greater hip flexion and less knee flexion during NM locomotion.Table: Caption not availableCONCLUSION: Subjects altered their gait kinematics from M to NM, perhaps in response to the increased horizontal force required to propel the treadmill belt during NM locomotion. Kinematic differences between M and NM may influence neuromuscular activation patterns, resulting in different training adaptations in normal gravity and perhaps dissimilar protection against microgravity-induced deconditioning.

In Vivo Validation of a Realistic Kinematic Model for the Trapezio-Metacarpal Joint Using an Optoelectronic System

This article analyzes a realistic kinematic model of the trapezio-metacarpal (TM) joint in the human thumb that involves two non-orthogonal and non-intersecting rotation axes. The estimation of the model parameters, i.e. the position and orientation of the two axes with respect to an anatomical coordinate system, was carried out by processing the motion of nine retroreflective markers, externally attached to the hand surface, surveyed by a video motion capture system. In order to compute the model parameters, prototypical circumduction movements were processed within an evolutionary optimization approach. Quality and reproducibility in assessing the parameters were demonstrated across multiple testing sessions on 10 healthy subjects (both left and right thumbs), involving the complete removal of all markers and then retesting. Maximum errors of less than 5 mm in the axis position and less than 6 degrees in the orientation were found, respectively. The inter-subject mean distance between the two axes was 4.16 and 4.71 mm for right and left TM joints, respectively. The inter-subject mean relative orientation between the two axes was about 106 and 113 degrees for right and left TM joints, respectively. Generalization properties of the model were evaluated quantitatively on opposition movements in terms of distance between measured and predicted marker positions (maximum error less than 5 mm). The performance of the proposed model compared favorably with the one (maximum error in the range of 7-8 mm) obtained by applying a universal joint model (orthogonal and intersecting axes). The ability of in vivo estimating the parameters of the proposed kinematic model represents a significant improvement for the biomechanical analysis of the hand motion.

B25 傾斜路面走行用シューズ設計の為の基礎研究(スポーツ用具)

Currently, population of trail runners who run on non-flat surface is increasing to maintain their health and be fun. In trail running, there are many cases of running on various surfaces with slopes of different gradients, compared with usual running. Accordingly, it is predicted that trail running shoes require different functions from usual running shoes. Generally, high speed video and 3D motion capture system are used in an outside environment because there are fewer restrictions. However, in order to enhance the accuracy of designing, it is essential that mechanical information between shoes and ground be measured by using a force plate. The purpose of this study is to clarify fundamental functions for designing trail running shoes. In order to measure ground reaction force in various locations, a portable force plate is used. Then, ground reaction forces in down hill running, up hill running and flat running are compared. Furthermore, influence of sole stiffness to ground reaction force is also discussed.

An Apparatus and Protocol to Measure Shoulder Girdle Strength

Muscles actuating the shoulder girdle are important for stabilizing the scapula and coordinating phased kinematics of the shoulder complex. If these muscles become weak or imbalanced, joint instability and injury may result. Reliable measurement of shoulder strength is thus important for prevention, diagnosis, and rehabilitation of shoulder problems. To date, studies quantifying the strength of the shoulder girdle are limited. The purpose of this work was to design and evaluate a custom apparatus and corresponding protocol for measuring maximal, voluntary, isometric strength of the shoulder girdle during various forms of shrugging exercise. A custom apparatus was constructed as a rigid frame with a vertical post supporting a seat, seat back, and horizontal beam. The beam extends laterally on either side beyond and around the shoulders of a seated subject. A pair of arm extension members pivots on the beam about an axis aligned with the shoulder flexion-extension axis. These members can be locked in place at any angle. Between them is mounted a force-sensing grip assembly, which can be adjusted proximally or distally to accommodate varying shoulder girdle positions. Subjects grasp the grip assembly handles with extended elbows and push or pull as forcefully as possible. Nine female and ten male subjects participated in a protocol using the apparatus to measure maximum isometric force generated at three positions each for elevation, depression, protraction, and retraction of the shoulder girdle (3positions×4modes=12tests). A video motion capture system was used to measure shoulder girdle angles. The reliability of the approach was evaluated based on the repeatability of measured shoulder elevation angle, protraction angle, and total force over three days of testing. The apparatus performed well during the tests, providing a stable, rigid, yet adjustable platform for measuring shoulder girdle strength. Repeatability of force measurements was interpreted as very good to excellent, with intraclass correlation coefficient (ICC) (2,1) values ranging from 0.83 to 0.95 for all tests except one (ICC=0.79). Repeatability of angle measurements was interpreted as good to excellent. For tests measuring elevation and depression strength, the ICC of elevation angle ranged from 0.85 to 0.89. For tests measuring protraction and retraction strength, the ICC of protraction angle ranged from 0.68 to 0.88. This type of apparatus could be an effective clinical tool for measuring strength in the shoulder girdle muscles. Use of the video motion capture system is optional.

Combining vision and computer graphics for video motion capture

We describe innovative methods for extracting three-dimensional motion of humans and animals from unrestricted monocular video, using a combination of new and established computer vision and computer graphics techniques. We identity features using image processing and active contours. Active contours become anchored to model segments in specified image frames and automatically "pull" the segments to feature positions in other frames. Adjustments are subject to joint limits and may use inverse kinematics. Occluded contour points are detected using object geometry and do not participate in feature tracking. Interactive adjustments are possible at any time in the process, allowing extraction of complicated movements regardless of background, camera movement, or feature clarity.

Transformation of the Medial Arch of Human Foot Complex in Sagittal Plane. Measurement by X-Ray Digital Ragiography and Video Motion Capture System.

Transformation of the medial arch angle of human foot was observed at sagittal plane during gait cycle by two methods : X ray television and Computer Aided Video Motion Analysis (VICON). Although the X-ray television has access to measurement of angles between templates, the X ray television has problems such as exposure to radiation, human error in acquiring digital data out of the templates, and low sampling late of Digital Radiograph-Fluroscopy. The VICON is a method to measure 3D coordinates of markers attached at the surface of the foot by 3D video tracking system, then estimate medial arch angle of the templates from the 3D markers. Transformation of the medial arch angle at stance phase were measure by the X ray television and the VICON, and results of the two methods were compared. The transformation pattern estimated by the VICON was approximate to the transformation measured by the X ray. Use of the VICON for the estimation of the medial arch angle of human foot was confirmed.

Video motion capture in VBA—Video-based animation

Computer vision has very wide application in human motion capture research. This paper proposes a new approach to do motion capture in video. It is composed of image sequence based tracking of human feature points and the reconstruction of the three-dimension(3D) motion skeleton. First, every part of the human body from top to bottom is tracked on the basis of a human model. The image difference and a morph-block similarity algorithm based on subpixels are used. Then camera calibration is done using the line correspondences between the 3D model and the image. Finally the 3D motion skeleton is established by use of the model knowledge. This approach does not aim at a given mode of human motion. Rather, it analyzes large scale motion from frame to frame in complex, variational background, and sets up a 3D motion skeleton in the perspective projection. The experiment results are presented at the end of the paper.

Video motion capture in VBA—Video-based animation

Video motion capture in VBA—Video-based animation

O Design Generativo Integrado ao Espetáculo de Dança Contemporânea Glow

Este artigo aborda conceitos relacionados à dança contemporânea e à fusão de linguagem com o design generativo. Faz um breve relato sobre a dança contemporânea, enfocando o modo como os profissionais experimentara tecnologias e outras linguagens integradas a seus projetos coreográficos. Aborda o uso do design generativo e de algoritmos, como parte do processo de criação no espetáculo Glow, no qual o designer manipula e explora o uso de formas gráficas, obtendo resultados inesperados e complexos por meio de uma estrutura flexível que se adapta à projeção de vídeo e à captura de movimentos. A abordagem metodológica é qualitativa com viés cultural e histórico, complementada pela observação e estudo do processo criativo e técnico, em materiais gráficos, textos, vídeos exclusivos e imagens. Por fim, é realizada uma descrição do espetáculo, atentando-se ao uso dos elementos gráficos como extensões do movimento coreográfico.