Victory with image processing! A sharp look at football players
19 Jun 2012
The IMPIRE company, based in Ismaning near Munich, developed the tracking system VIS.TRACK for the detailed analysis of soccer matches, which is based primarily of components manufactured by STEMMER IMAGING. The coaches of the soccer teams hope the statistical analysis will lead to greater success, comments IMPIRE board member Christian Holzer: "Since the 2011/12 season all stadiums in the German first and second divisions have been equipped with this system providing a detailed analysis of the football game. Successful football clubs, including the current German champion Borussia Dortmund, and the majority of other teams, work extensively with VIS.TRACK to document the performance of their players, not only subjectively, but also objectively with facts." According to Holzer, a number of top international teams are already customers of the IMPIRE system.
Match analysis in real-time
Data such as ball possession percentages, number of shots on goal, headers or corners have already been counted manually for some time. However, the objective and precise recording of individual running performance of players was not possible with this method. VIS.TRACK provides exactly this capability. Holzer explains: "Our tracking system provides the position coordinates for every player at all times during the game. This allows us to calculate data such as the total running performance, average and maximum speeds, number and intensity of sprints and the distance covered, and much more."
The volume of data per match is enormous: the system records the X/Y coordinates of every player 25 times per second and stores them. At the end of a match this results in approximately 4 million position logs. This data is prepared by IMPIRE for the clubs providing the coaching teams of all clubs with password-protected access via PC or a smartphone app.
A number of graphic representations of the data is possible. For example, speed graphs for each player which can document a player’s willingness to run over the course of a game. The radius of action of each player on the field can be represented by a so-called heat map.
"By summation of the individual values we can provide statistics for the entire team and these are available instantly and with maximum accuracy", adds Holzer. During half time or after the match, a coach is therefore able to document with numbers and graphs whether his team has, for example, neglected the left offense, has played too defensively or has run considerably less than the opposing team. The system provides the coach with tactical analyses in 2D and 3D, as well as a drawing tool to demonstrate his ideas to the players.
Holzer mentions another important feature of the VIS.TRACK product range: "VIS.TRACK ¬products can also be used to analyse training sessions. The resulting analyses provide the opportunity of adapting the training intensity for individual players, following injury, or to optimize their current performance levels."
Not only are the statistics available to coaches and football clubs, the media too, have great interest in communicating relevant data to football fans. Due to this demand, IMPIRE has acquired the rights from the DFL (German Soccer Association) to sell the recorded data to media companies. If, for example, a player is substituted during a match, his running performance in metres can be displayed on the TV screen, from data provided by the IMPIRE data base.
VIS.TRACK also records the distances the referees run, so that one can track the distances the referee ran during a match and at which speeds.
High-end imaging in the stadium
The technical key to realizing the VIS.TRACK system consists of a high performance vision system, which IMPIRE designed and implemented in close collaboration with STEMMER IMAGING. A high-resolution camera integrated in a weatherproof housing specially developed by IMPIRE, provides the image data per half pitch. The two camera housings of a system are positioned at the center line in all stadiums and usually mounted in a fixed position under the stadium roof. HD cameras by Danish manufacturer JAI are used.
The image data recorded by these two cameras is in part transmitted via glass- fiber cable per Gigabit Ethernet to the four high-performance image processing PCs which presently make up a complete system. Holzer comments this decision: "Due to the sometimes rather long transmission paths in the stadiums, Gigabit Ethernet technology was the only technology that made sense."
The main key for the success of the IMPIRE system is the optimal design and the assignment of tasks between the four computers. According to Holzer, the close collaboration between the developers at IMPIRE and STEMMER IMAGING proved decisive. The image processing software Common Vision Blox (CVB) of the Puchheim company plays a decisive role at several points.
Four PC’s and CVB ensure extreme performance
In the current system, data is recorded using the multicast mode, i.e. the video data are distributed in parallel to all 4 PC’s using the STEMMER IMAGING CVB GigE Vision Server. A recording PC acts as a video recorder which allows time-delayed and variable speed play back of the recording. This is also done in multicast mode so that tracking and analysis of a match can, for example, be done at any time for subsequent analysis of the game.
On the second PC, the tracking PC, the de-Bayering of the image data and further pre-processing steps are realized on the GPU, i.e. the graphic card, before a software package developed by IMPIRE based on Common Vision Blox takes over the tracking of the players. This computer also provides the displays on the monitors.
The third PC involved is responsible for Bayer conversion and the display, including the overlay provided by the tracking PC. The fourth computer in the system, the Panorama PC utilizes the performance of multi-core GPU processing based on CVB, to seamlessly compose the image data of the two full-HD cameras Bayer-decoded and graphically equalized, to transmit these to the CPU and then to transcribe this in its entirety to the hard disk as an mp4 file with double HD resolution in RGB format.
With the system architecture which is designed for extremely high performance, it is possible to display the video data without any appreciable delay on the total of five monitors of the system. These monitors are staffed by two IMPIRE employees during a game. The main task of these two scouts is to check the correct assignment of the individual players of a team. As a rule, the system masters this task independently: it tracks every player automatically and displays this on the monitor with coloured boxes which frame each player.
"If the system cannot identify players with the same kit accurately, for example, after tackles or the player celebrates after a goal, then the system changes the frame color of the players involved on the observer PC and indicates to the scout to intervene", is the way Holzer describes the procedure. The employee then restores the correct assignments for Robben and Ribery, Götze and Großkreutz or Huntelaar and Höwedes.
VIS.TRACK then immediately corrects the data of the players mistaken by the system and their paths in the tracking data base to keep the statistics error- free.
Set up and configured in 90 minutes!
An IMPIRE team requires approximately only 90 minutes set-up time for the preparations to analyze a game, i.e. connecting the computer and monitors to the already installed cameras, start-up and assignment of the players. To keep travel for setting up the mobile systems to a minimum and to cover all the matches of the two divisions, the existing IMPIRE systems are distributed across Germany. This way, the team from Ismaning covers 18 games of the division at each soccer weekend – on the last two days of play even nine games in parallel throughout Germany. For training sessions, the use of additional camera pairs on a computer system allows recording and analyzing the activities on several pitches at the same time.
Visions: additional applications
According to the IMPIRE board, the system has proved extremely successful in the 2011/12 season and will also be used for all league games in the coming 2012/13 season. According to Holzer, invitations to tender are in progress internationally and IMPIRE’s prospects are good.
He also sees a number of opportunities for optimizing the present system: "To obtain an improved display of both halves of the game in one picture, we have now integrated a further computer in the systems, which allows a panorama view of the entire playing field on a single monitor". Further progress in optimization will be the exact tracking of ball data, for example, to measure the distance of passes automatically.
Holzer’s vision, however, extends well beyond soccer in Germany: "Statistics in basketball or American Football are extremely popular with US sports fans, and similar systems are technically viable for other types of sport." IMPIRE is quite literally on the ball in preparing the system for the future.
For more than 50 years JAI has delivered industrial CCD and CMOS cameras with innovative engineering, high-end quality, and operational reliability and durability.
STEMMER IMAGING has been leading the machine vision market since 1987. It is Europe's largest technology provider in this field. In 1997 STEMMER IMAGING presented Common Vision Blox (CVB), a powerful programming library for fast and reliable development and implementation of vision solutions, which has been deployed successfully throughout the world in more than 40,000 imaging applications in various industries.