Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
CA 02559783 2006-09-15
A SYSTEM AND METHOD FOR GRAPHICALLY ENHANCING THE
VISIBILITY OF AN OBJECT/PERSON IN BROADCASTING
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to the video
broadcast of sporting events and, more particularly, to
graphically enhancing the perceptibility of objects/persons
in the broadcast of sporting events.
2. Background Art
1o The broadcast of sport events has constantly
evolved by the advent of new technologies in video
equipment. Live footage from new points of view, high-
resolution slow-motion replays and high-definition close-ups
are a few examples of recent improvements to the broadcast
of sporting events.
The use of graphics to enhance the visualization
of the events has also significantly modified sports event
broadcast. In addition to graphics displayed in replays to
support the commentator's interventions, graphics have been
added in real-time to depict movements of objects. For
instance, in order to facilitate the viewing of the puck in
hockey, a trajectory mark has been used to show puck
displacement. The trajectory mark results form the use of
transmitters inserted in the puck.
Similarly, virtual lines have been added as marker
lines in the live broadcast of football games. For example,
virtual lines mark the scrimmage line and the first-down
line on the football field.
U.S. Patent No. 5,413,345, issued to Nauck on
May 9, 1995, describes a system utilizing an array of fixed
high-speed video cameras to identify, track, display and
record the path of golf balls. The tracking information is
then displayed in video or audio replay. This system is
CA 02559783 2006-09-15
-2-
primarily used in driving ranges, for instance to compare
the trajectory of a ball with another ball or as a function
of the swing of the golfer, and to show trajectory data in
replay to the golfer. This system would require a very large
number of cameras (with fixed orientation and zoom) in order
to provide accurate 3-D positioning of a golf ball at an
event which covers a large site (i.e., 18-hole tournament).
U.S. Patent No. 6,449,010, issued to Tucker on
September 10, 2002, describes a system and method for
enhancing the display of a sporting event, such as golf. In
this system, video images are obtained from an overhead
large field of view, for instance using a blimp. The video
images are overlaid to present a trajectory of an object,
which trajectory is represented in two dimensions upon
background video images. This system does not provide 3-D
positioning of the golf ball.
The webpage http://www.imagotrackers.com/pdf/
Imagolf_sv_fin.pdf (June 28, 2006) describes a driving range
trajectory system. In this system, a video camera unit is
positioned behind the driver, and records video footage of a
golfer and of a driven golf ball. A graphical display
showing the trajectory of the ball may then be produced.
One of the issues with the prior art systems, is
that none enable the video enhancement of the 3-D trajectory
of the tracked object/person (i.e., golf ball) in real time.
Another issue is that these prior art systems use dedicated
video cameras which would have to be installed at the event
venue in addition to the broadcasting cameras. Therefore,
none has given rise to interest from the broadcasting
industry, either for the absence of 3-D trajectory data, for
the lack of precision in the calculation of trajectories, or
for the lack of flexibility in their use.
SUMMARY OF INVENTION
It is therefore an aim of the present invention to
provide a system and method for enhancing the visualization
CA 02559783 2006-09-15
-3-
of objects or persons in the broadcast of sporting events
that addresses issues associated with the prior art.
The present invention is especially useful in
situations where the object/person of interest is not
visible because of limited camera resolution. For instance,
during a golf tournament, it would be desirable to see in
real time the complete trajectory of the shot while showing
a global view of the golf hole.
Therefore, in accordance with the present
invention, there is provided a system for graphically
enhancing the position of an object/person on a video image
used in broadcasting a sport event. The system comprises a
video camera module having at least one video camera at the
sport event venue for taking a video image for broadcasting
the sport event, the video camera module providing view
parameters associated with the video camera. The system also
comprises a monitoring module passively tracking the
object/person and measuring a three-dimensional position of
the object/person in a global reference frame from the
tracking and a broadcasting image processing unit connected
to the video camera module and the monitoring module. The
broadcasting image processing unit has a projection renderer
and a graphical combiner. The projection renderer projects
the three-dimensional position in the global reference frame
to the video image by associating the view parameters to the
global reference frame. The graphical combiner adds a
graphical representation showing the projected position of
the object/person on the video image in a broadcast output.
In accordance with the present invention, there is
also provided a method for enhancing substantially in real-
time the position of an object/person on a video image in
broadcasting a sport event. The method comprises acquiring a
video image of the object/person for live broadcast of the
sport event; monitoring view parameters associating the
video image to a global reference frame; measuring a three-
dimensional position of the object/person in the global
reference frame by passively tracking the object/person;
CA 02559783 2006-09-15
-4-
projecting the three-dimensional position in the global
reference frame to the video image using the view
parameters; and graphically depicting the projected position
on the video image in a broadcast output.
The present invention provides a system and a
method for graphically enhancing the visibility of an
object/person on a video image used in broadcasting a sport
event. For broadcasting the sport event, one or a plurality
of video camera acquire video images of the event. The
object/person of which the trajectory is of relative
importance in the sport game is generally in the field of
view of the video camera but may or may not be visible on
the images. When the object/person travels, a monitoring
module passively tracks the object/person and measures the
3D position of the object/person. As the event is being
broadcast, a graphical representation of the object or of
its trajectory is depicted on the image to enhance the
visibility of the object/person on the broadcast image.
BRIEF DESCRIPTION OF THE DRAWINGS
Having thus generally described the nature of the
invention, reference will now be made to the accompanying
drawings, showing by way of illustration a preferred
embodiment thereof and in which:
Fig. 1 is a schematic illustrating a site where a
sport event takes place along with a system for monitoring
the position of an object/person, according to an embodiment
of the invention;
Fig. 2 is block diagram illustrating a system for
graphically enhancing the visibility of an object/person on
a video image used in broadcasting a sport event, according
to an embodiment of the invention;
Fig. 3 is a block diagram illustrating the
components of the broadcasting image processing unit of the
system of Fig. 2; and
CA 02559783 2006-09-15
-5-
Fig. 4 is a schematic view illustrating a
graphical representation of the trajectory of an
object/person superimposed on a video image of the sport
event during a broadcast of the event.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
Referring now to the drawings and more
particularly to Fig. 1, a system for monitoring the position
of an object/person as positioned at a sport event venue is
illustrated.
For broadcasting the sport event, one or a
plurality of video camera modules 12 are taking video images
of the event. The object/person A of which the trajectory is
of relative importance in the sport game is generally in the
field of view of the video camera module 12 but it may or
may not be visible (i.e., perceptible) in the video images
because of the limited resolution of the video images, for
example. When the object/person A travels, a monitoring
module 14 passively tracks the object/person and measures
the 3D position of the object/person A in time. As the event
is being broadcast, a graphical representation of the
trajectory or a graphical representation showing the
position of the object/person A as it travels is depicted on
the image to enhance the visibility of the object/person A
on the broadcast image.
As known in the art, passive tracking includes
methods where no special modification is required to the
object to be tracked. One example of a passive tracking
method is a stereoscopic method. In stereoscopic methods,
the object is tracked in video images using pattern
recognition. Active tracking methods includes methods where
the tracking is assisted by a transmitting device installed
on the object to be tracked.
In the embodiment of Fig. 1, the monitoring module
14 uses a stereoscopic method. In order to provide 3D
measurement, at least two tracking cameras 24 are provided
CA 02559783 2006-09-15
-6-
at the sport event venue. The cameras are used for
stereoscopic tracking, such that a minimum of two cameras
(e.g., including video cameras and tracking cameras) is
necessary to subsequently provide 3D measurement.
Additionally, more than two tracking cameras can be used to
cover a large site.
In the stereoscopic embodiment, the position,
orientation and zoom (i.e., tracking parameters) of the
tracking cameras 24 in a global reference frame are known
such that the three-dimensional position of the object in
the global reference frame is calculable using triangulation
techniques. In this embodiment, the orientation and the zoom
of the tracking cameras 24 are variable (e.g., operators
manually handling the cameras) as the object/person A
travels, to maintain the object/person A in the field of
view of the cameras 24. In an alternative embodiment, the
position of the tracking cameras 24 can also be varied. In
any case, as the object/person A moves along its trajectory,
the tracking parameters (position, orientation and/or zoom)
are monitored. In an embodiment, the tracking cameras 24 are
motorized and automatically controlled to track the
object/person A as it travels along its trajectory. All
tracking parameters need to be pre-calibrated using, for
instance, a pattern recognition method and known physical
locations (i.e., ground points).
As the event is being broadcast, the measured 3D
positions of the object/person A are cumulated as a function
of time to provide a 3D trajectory of the object/person. The
measured 3D position or trajectory is projected on the video
image and a graphical representation of the trajectory or of
the actual position of the object/person A is drawn on the
image to enhance the visualization of the object/person A on
the broadcast image. The graphical representation may be a
curve, series of points, ghost of the object/person A or
such, showing the trajectory of the object/person A or it
may be a point or an image of the object/person A showing
only the actual position of the object/person A. In an
CA 02559783 2006-09-15
-7-
embodiment, the graphical representation of the trajectory
is drawn in real-time on the video image, i.e., the up-to-
date trajectory is graphically added to the video image as
the object/person A travels. Alternatively, the graphical
representation of the trajectory could appear on the video
image at the end of the trajectory, e.g. when the ball
arrives at destination (e.g., touches the ground) or when
the athlete reaches the finish line.
In order to perform the projection, the view
parameters (i.e., the position, orientation and zoom) of the
video camera module 12, which provides the broadcast
footage, are monitored in the global reference frame. In
this embodiment, the orientation and zoom of the video
camera module 12 are varied to select the appropriate view
for broadcasting the event and the view parameters are
monitored. Alternatively, the video cameras 18 could be
fixed. In any case, all view parameters need to be pre-
calibrated using, for instance, a pattern recognition method
and known physical locations (i.e., ground points).
Fig. 2 illustrates a system 10 for graphically
enhancing the visibility of an object/person on a video
image used in broadcasting a sport event according to an
embodiment. The system 10 comprises a video camera module
12, a monitoring module 14, a broadcasting image processing
unit 16 and a statistic/storage module 34.
The video camera module 12 is provided for taking
a video image framing the object/person for live broadcast
of the event. As previously stated, the object/person may or
may not be visible (i.e., perceptible) in the video image
taken by the video camera module 12.
The monitoring module 14 measures a 3D position of
the object/person in time and provides the 3D trajectory of
the object/person.
The broadcasting image processing unit 16 renders
a graphical representation of the trajectory or a graphical
representation showing the position of the object/person A
as it travels, on the video image.
CA 02559783 2006-09-15
-8-
The statistic/storage module 34 stores a plurality
of object/person trajectories obtained at the sport event.
The video camera module 12 comprises at least one
video camera 18. Images from a plurality of video cameras 18
can also be combined when producing the broadcast program.
The view parameters of each video camera 18 can be varied
(i.e., manually or automatically) as the location of the
action of the game varies. More specifically, the position,
orientation and/or the zoom of the camera are variable as a
function of the footage gathered for the video broadcast.
Accordingly, a view parameter reader 22 is
provided for each video camera 18 for reading the varying
position, orientation and/or zoom. The view parameter reader
22 typically has encoders, inertial sensors and such for
reading the orientation of the camera 18, and encoders for
reading the zoom of the camera 18, i.e., the focal point of
the camera's lens. In embodiments where the position of the
video camera 18 is variable, the view parameter reader 22
typically has a positioning system (i.e., GPS or a local
implementation).
The monitoring module 14 is a three-dimension
measuring system. In an embodiment, the module 14 uses
stereoscopy to measure the 3D trajectory of the
object/person but any other 3D measuring method could
alternatively be used. The monitoring module 14 uses at
least two tracking camera modules 19 each having a tracking
camera 24 for acquiring tracking images of the
object/person, and an associated tracking parameter reader
23. The orientation and the zoom of the tracking cameras are
controlled (e.g., manually) to allow an operator to follow
the object/person A such that it is maintained in the field
of view of the camera as it travels along the trajectory.
The varying orientation and zoom of the tracking cameras in
the global reference frame are monitored using the tracking
parameter reader 23. Additionally, in an alternative
embodiment, the position of the cameras can also be manually
controlled and is monitored.
CA 02559783 2006-09-15
-9-
Like the view parameter reader 22, the tracking
parameter reader 23 typically has encoders, inertial sensors
and such for reading the orientation of the tracking camera
24, and encoders for reading the zoom of the tracking camera
24, i.e., the focal point of the camera's lens. In
embodiments where the position of the tracking camera 24 is
variable, the tracking parameter reader 23 also typically
has a positioning system (i.e., GPS or a local
implementation).
It is contemplated that, as the broadcast event
goes on, the role of a video camera module 12 and of a
tracking camera module 19 could be swapped at any time.
Accordingly, at one time, a first camera could be used for
providing the video image and, at another time, a second
camera could be used for providing the video image while the
first camera is used for providing a tracking image for
measuring the position of the object/person.
A 3D trajectory processing unit 26 calculates the
3D position of the object/person A as it travels and
comprises a trajectory memory 28, a 2D image processor 30,
and a global position calculator 32. The 2D image processor
passively tracks the location of the object/person A in
the tracking images using pattern recognition and provides a
2D position of the object/person in the image obtained from
25 each of the cameras 24. The handling of the tracking cameras
24 for the tracking of the object/person A may be completely
automated or may be operator assisted. For example, the
operator could point out the position of the object/person
on the image at the beginning of the trajectory, i.e., when
30 the object/person A is still, and the 2D image processor 30
tracks the object/person A from that location.
The global position calculator 32 calculates the
3D position of the object/person in the global reference
frame using triangulation techniques which are well known in
the art. These methods basically use the 2D positions and
the tracking parameters in order to obtain the 3D position
of the object/person. The 3D positions are cumulated in the
CA 02559783 2006-09-15
-10-
trajectory memory 28 to provide the 3D trajectory of the
object/person A. The 3D trajectory is updated in real-time
as the object/person travels and the up-to-date trajectory
can thus be rendered on the broadcast image in real-time.
The broadcasting image processor 16 adds a
graphical representation of the trajectory over the video
image to be broadcast. Alternatively, a graphical
representation showing the actual position only of the
object/person A could only be added. The broadcasting image
processor 16 is controlled by the operator of the system
through a user interface 36. The operator may turn on and
off the graphical representation and may add a statistic
graphical representation as will be discussed further below.
In this embodiment, a 3D model 38 of the event
venue is provided and taken into account in the graphic
rendering. On segments of the trajectory where the
object/person A is hidden by the 3D profile of the site (as
seen by the video camera 18), the graphical representation
is omitted. For example, if the object/person is behind a
hill or a building, the trajectory is not drawn on the video
image even though the trajectory is known (i.e., could be
displayed). The 3D model 38 is thus used to improve the
realism of the graphical representation.
As the sport event goes on, the various
trajectories performed by various players or on various
tries of the same player are typically stored in the
statistic/storage module 34. This feature provides the
option of superposing a graphical representation of the best
up-to-date performance, for example, on the broadcast image
for comparison purposes. The average performance of the
actual player or any other trajectory may also be
superposed. Superposing several trajectories on the live
event image may also be performed, i.e., when the
object/person starts its motion several trajectories are
started at the same time and comparisons between several
trajectories can be made in real-time. Any other statistic
or numerical data that can be determined from the measured
CA 02559783 2006-09-15
-11-
trajectory and that is relevant in the sport event can also
be stored in the statistic/storage module 34. Such statistic
includes the distance reached by the trajectory, the highest
point of the trajectory, the maximum speed of the
object/person along the trajectory, the time elapsed during
the trajectory, etc.
An operator of the system controls the choices of
displayed trajectories through an operator interface 36. The
operator interface 36 is also used to associate each
trajectory with the player that performed the trajectory and
to other statistic data. The operator interface 36 can also
be used to select between trajectory display and position
display or between various styles of graphical
representation.
It is contemplated that each 3D position may be
stored in the trajectory memory 28 along with its associated
time stamp for use, for example, in calculating statistic
data. The data provided by the tracking camera modules 19 is
preferably synchronized. Data provided by the video camera
module 12 from at least one video camera and communications
between the different modules of the system are preferably
synchronized. It is contemplated that any appropriate
synchronizing method known by one skilled in the art can be
used.
Referring to Fig. 3, greater detail is provided
with regard to the broadcasting image processing unit 16.
The broadcasting image processing unit 16 receives the 3D
trajectory data from the monitoring module 14, as well as
the video image from the video camera module 12.
The broadcasting image processing unit 16
comprises a 2D projection renderer 40 and a graphical
combiner 42. The 2D projection renderer 40 receives the 3D
trajectory and the view parameters and projects the 3D
trajectory in the global reference frame on the video image.
The graphical combiner 42 adds a graphical representation of
the trajectory on the video image or a graphical
CA 02559783 2006-09-15
12-
representation showing the actual position only of the
object/person.
In order to combine the- trajectory/position
information to the video image, a 2D projection renderer 40
must associate the video image to the global reference
frame. As discussed previously, the view parameters of the
video camera 18 are known, as provided by the video camera
module 12.
Accordingly, with the position, orientation and
zoom of the video camera 18 in the global reference frame,
provided from the view parameters, the 2D projection
renderer 40 determines the projection parameters associated
with the video image within the global frame of reference.
The 2D projection renderer 40 then projects the 3D
trajectory using the same projection parameters. A projected
trajectory is thereby provided as 2D points associated to
the video image.
The graphical combiner 42 adds a graphical
representation of the trajectory to the video image or,
alternatively, a graphical representation showing the actual
position of the object/person. The graphical representation
can for instance be a realistic rendering of the
object/person as it progresses along the trajectory, a curve
depicting the projected trajectory (i.e., a curve passing
through sampled 2D points) or dots distributed along the
projected trajectory (i.e., located on selected 2D points).
The broadcasting image is therefore the video image with a
graphical display representing the trajectory or,
alternatively, the object/person.
Moreover, statistic data is provided from the
statistic/storage module 34 to the 2D projection rendered
40. As commanded through the operator interface 36,
statistic information may be added to the video image using
the graphical combiner 42.
The system 10 for enhancing the visibility of an
object/person on a video image used in broadcasting a sport
event has numerous contemplated uses. For example, the
CA 02559783 2006-09-15
- 13-
system can be used in broadcasting a golf game or tournament
by drawing the trajectory of the golf ball in the air on the
video image. It can also be used for visualizing the object
thrown in broadcasting discus, hammer or javelin throw, for
visualizing the trajectory of the athlete in ski jump, the
trajectory of the ball hit in baseball or the trajectory of
the kicked ball in football or soccer. Another example is
the trajectory of the athlete in alpine skiing competition.
It should be contemplated that, if only the actual
position of the object/person is to be graphically displayed
on the broadcast image, a trajectory memory is not required
and the broadcasting image processing unit can rather
receive the actual 3D position of the object/person instead
of the 3D trajectory.
Fig. 4 illustrates an example of a graphical
representation of the trajectory of an object/person
superimposed on a video image of the sport event venue for
broadcasting the event. In this example, the sport event is
a golf tournament and the trajectory of a golf ball is
displayed on a broadcast image. It should be appreciated
that Fig. 4 is provided for illustration purposes and that,
while a schematic of a golf hole along with the enhanced
trajectory is shown in Fig. 4, a typical broadcast image
would be a two-dimensional video image with a contrasting
graphical representation of the trajectory.
While illustrated in the block diagrams as groups
of discrete components communicating with each other via
distinct data signal connections, it will be understood by
those skilled in the art that the preferred embodiments may
be provided by a combination of hardware and software
components, with some components being implemented by a
given function or operation of a hardware or software
system, and many of the data paths illustrated being
implemented by data communication within a computer
application or operating system. The structure illustrated
is thus provided for efficiency of teaching the present
preferred embodiment.
CA 02559783 2006-09-15
-14-
The embodiments of the invention described above
are intended to be exemplary only. The scope of the
invention is therefore intended to be limited solely by the
scope of the appended claims.
