Video motion analysis is a technique used to get information about moving objects from video. Examples of this include
gait analysis,
sport replays, speed and acceleration calculations and, in the case of team or individual sports, task performance analysis. The
motion analysis technique usually involves a
high-speed camera
A high-speed camera is a device capable of capturing moving images with exposures of less than 1/1,000 second or frame rates in excess of 250 fps. It is used for recording fast-moving objects as photographic images onto a storage medium. After r ...
and a computer that has software allowing frame-by-frame playback of the video.
Uses
Traditionally, video motion analysis has been used in scientific circles for calculation of speeds of projectiles, or in sport for improving play of athletes. Recently, computer technology has allowed other applications of video motion analysis to surface including things like teaching fundamental laws of physics to school students, or general educational projects in sport and science.
In sport, systems have been developed to provide a high level of task, performance and physiological data to coaches, teams and players. The objective is to improve individual and team performance and/or analyse opposition patterns of play to give tactical advantage. The repetitive and patterned nature of sports games lends itself to video analysis in that over a period of time real patterns, trends or habits can be discerned.
Police and forensic scientists analyse CCTV video when investigating criminal activity. Police use software, such as
Kinesense
Kinesense is computer vision and video analytics company based in Dublin, Ireland. The company is one of largest suppliers of computer vision products to the UK police, who use the technology to search CCTV content in the course of criminal invest ...
, which performs video motion analysis to search for key events in video and find suspects.
Technique
A digital video camera is mounted on a
tripod
A tripod is a portable three-legged frame or stand, used as a platform for supporting the weight and maintaining the stability of some other object. The three-legged (triangular stance) design provides good stability against gravitational loads ...
. The moving object of interest is filmed doing a motion with a scale in clear view on the camera. Using video motion analysis software, the image on screen can be calibrated to the size of the scale enabling measurement of real world values. The software also takes note of the time between frames to give a movement versus time data set. This is useful in calculating gravity for instance from a dropping ball.
Sophisticated sport analysis systems such as those by
Verusco Technologies in New Zealand use other methods such as direct feeds from satellite television to provide real-time analysis to coaches over the Internet and more detailed post game analysis after the game has ended.
Software
There are many commercial packages that enable frame by frame or real-time video motion analysis. There are also free packages available that provide the necessary software functions. These free packages include the relatively old but still functional Physvis, and a relatively new program called PhysMo which runs on Macintosh and Windows. Upmygame is a free
online
In computer technology and telecommunications, online indicates a state of connectivity and offline indicates a disconnected state. In modern terminology, this usually refers to an Internet connection, but (especially when expressed "on line" o ...
application. VideoStrobe is free software that creates a strobographic image from a video;
motion analysis can then be carried out with dynamic geometry software such a
GeoGebra
The objective for video motion analysis will determine the type of software used. Prozone and Amisco are expensive stadium-based camera installations focusing on player movement and patterns. Both of these provide a service to "tag" or "code" the video with the players' actions, and deliver the results after the match. In each of these services, the data is tagged according to the company's standards for defining actions.
Verusco Technologies are oriented more on task and performance and therefore can analyse games from any ground. Focus X2 and Sportscode systems rely on the team performing the analysis in house, allowing the results to be available immediately, and to the team's own coding standards.
MatchMatix takes the data output of video analysis software and analyses sequences of events. Live
HTML
The HyperText Markup Language or HTML is the standard markup language for documents designed to be displayed in a web browser. It can be assisted by technologies such as Cascading Style Sheets (CSS) and scripting languages such as JavaScri ...
reports are generated and shared across a LAN, giving updates to the manager on the touchline while the game is in progress.
References
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Film and video technology
Motion in computer vision