This disclosure relates generally to video camera systems and more particularly to steerable video surveillance cameras.
Most currently available video surveillance analytics systems rely on background subtraction to detect objects of interest by comparing incoming frames of video with a background model that provides a reference representation of what a video camera should see if no moving objects were present. The background model is created by a background maintenance procedure that learns the normal appearance of each pixel or local area of the field of view of the camera. These types of video surveillance analytics systems work on the assumption that the camera does not move and that any pixel will continue to see the same region of the real world. If this assumption is violated, i.e., the camera is moved, then a pixel will receive light from a different part of the scene from the real world and differences not due to scene changes will be detected. The analytics component of the surveillance system detects these differences through background subtraction, and because the detected differences are not due to scene changes, the system generates many false positives, creating tracks for artifacts that are not due to moving objects. In addition, the system is quite likely to fail to track true moving objects because of the number of false tracks being generated.
Camera motions that can cause false positives to occur in video surveillance analytics systems that use background subtraction can occur for several reasons. For example, wind and vibration can cause the camera to make small movements that result in the camera oscillating around its normal position. Also, steerable surveillance cameras that are controlled by an operator such as a security guard or by an automated procedure that moves the camera can be subject to false positives because of the visual changes caused by the camera motion. Other reasons for camera motion can be the result of direct physical movement of the camera. For example, a maintenance worker could turn the camera, a truck could collide with the camera or an intruder could turn the camera so that it could no longer be used to observe activity in a certain area under surveillance.
Various approaches have been employed to stabilize camera motions that occur for the above-noted reasons. These stabilization approaches can use mechanical, electromechanical or electronic methods to remove the effects of movement from the images delivered to the background subtraction detection component of the video surveillance analytics systems. Mechanical and electromechanical methods may move the lens or sensor of the camera in such a way that the image formed on the sensor maintains the same alignment with it, while electronic methods may detect the offset in the obtained image and shift it back to counteract the detected motion.
These approaches work well in stabilizing small camera motions but are not effective in stabilizing large camera motions that are beyond the range of mechanical actuators' ability to move the lens or sensor to compensate or motions that are so great that compensation mechanisms introduce image distortions of other kinds that are in themselves problematic. In addition, these approaches fail to work well for camera motions that cannot be dealt with by a compensation method that can compensate for movements of the camera such as the twisting of the camera about its optical axis.
In one embodiment, there is a system for managing images generated from a movable camera. In this embodiment, the system comprises a motion estimation component configured to determine camera motion. A camera motion alert component is configured to generate an alert in response to a determination that the camera has moved or the camera has ceased moving.
In a second embodiment, there is a method for managing images generated from a movable camera. In this embodiment, the method comprises: determining whether the camera has moved; and generating an alert in response to a determination that the camera has moved or ceased moving.
In a third embodiment, there is a computer-readable medium storing computer instructions, which when executed, enables a computer system to manage images generated from a movable camera. In this embodiment, the computer instructions comprise determining whether the camera has moved; and generating an alert in response to a determination that the camera has moved or ceased moving.
In a fourth embodiment, there is a method for deploying a tool for use in a computer system that manages images generated from a movable camera. In this embodiment, a computer infrastructure is provided and is operable to determine whether the camera has moved; and generate an alert in response to a determination that the camera has moved or ceased moving.
Therefore, this disclosure provides a system, method, and computer-readable medium for managing images generated from a movable camera.
Embodiments of this disclosure are directed to a technique for managing images generated from a movable camera such as a camera used in a video surveillance analytics system. Although the description that follows pertains to a camera used in a video surveillance analytics system, the principles of this disclosure are suitable for use in any application where movable cameras are employed. The embodiments of this disclosure provide stabilization or motion compensation to images generated from the camera in instances in which the camera has experienced small motions and also has the capability to distinguish large camera motions from small motions and thus suspend operation of the camera upon detecting these large motions.
Although not expressly shown in
A motion estimation component 14 uses the point motion estimates generated by the point tracker component 12 to determine whether the camera 5 has moved. In particular, the motion estimation component 14 determines camera movement from the point motion estimates by using a technique such as estimating a best-fit motion that matches all the points after discarding outliers. In one embodiment, a well known method such as the RANSAC algorithm iterated on least-squares affine motion estimates is used. Those skilled in the art will recognize that other well known methods can be used to determine whether the camera has moved.
The motion estimation component 14 is configured to distinguish between small camera motions and large camera motions. As used herein, small camera motions are those motions which are generated by vibrations and wind movement, and for which the field of view of the camera still largely overlaps with the original view of the camera and thus still can generate acceptable images after motion compensation. On the other hand, large camera motions are due to a change in the position of the camera that results in the field of view changing significantly.
In one embodiment, the motion estimation component 14 distinguishes between small camera motions and large camera motions by comparing the point motion estimates against a predetermined threshold. The predetermined threshold will depend on the surveillance application and in particular how broadly the operator wants to define small and large camera motions. In an illustrative embodiment, if the point motion estimates are below the predetermined threshold, then the camera is deemed to have experienced a small camera motion, while estimates that are above the threshold are considered to be indicative of a large camera motion. As those skilled in the art will recognize, other comparison methodologies are suitable for use in determining whether the camera has experienced small camera motions or large camera motions. For example, in one embodiment, a large camera motion can be deemed to have occurred if the point motion estimates are below the predetermined threshold, while a small camera motion would be deemed to occur in instances where the estimates are above the threshold.
A motion compensation component 16 provides compensation to the image frames in response to a determination that the camera 5 has moved in small camera motions. In particular, the motion compensation component 16 provides compensation to the image frames by transforming the image frames (e.g., by an affine warp or translation) such that they match closely to the image frames from the unmoved camera.
A camera operations component 20 is configured to control operations of the camera 5. In particular, the camera operations component 20 will suspend operations if the motion estimation component 14 determines that the camera 5 has experienced large camera motions and also resume camera operations when the motions estimation component 14 determines that these large camera motions have ceased.
The system 10 as shown in
The system 10 of
If the camera 5 has not moved as determined at decision block 38 and noted at 40, then the system 10 continues with the next frame where points are tracked at 34 and estimates are generated again at 36. These acts as embodied in blocks 34-40 will continue in a loop fashion until it is determined at decision block 38 that the camera 5 has moved. If a movement occurs, then the extent of movement (e.g., size and direction of the movement) is recorded in the camera motion database 18 at 42 and made available for future searches. In particular, the recorded camera motion can be used as a search criterion for later database searches using parametric or geometric searches. Examples of possible searches could include determining when the camera moved; was the camera moved greater than 30 degrees/second; when did the camera point at that door.
At decision block 44, the motion estimation component 14 determines whether the camera motion is small or large. As mentioned above, the motion estimation component 14 distinguishes between small camera motions and large camera motions by comparing the point motion estimates against a predetermined threshold. In a preferred embodiment, if the point motion estimates are below the predetermined threshold, then the camera is deemed to have experienced a small camera motion and as result the motion compensation component 16 will provide compensation to the image frames at 46 by performing shifting or warping operations. In this instance, after the motion compensation component 16 has provided compensation, then the system 10 continues with the next frame where points are tracked at 34 and acts 36-44 are repeated until a large camera motion is indicated at 44.
If the point motion estimates are above the predetermined threshold, then the camera is deemed to have experienced a large camera motion and as result the camera operations component 20 will suspend operations at 48. In particular, the camera operations component 20 will suspend operations that depend on a stable image such as background subtraction and tracking operations. Generally, the suspension of operations may involve performing other processing operations such as storing system state variables (e.g., the position of the camera, information regarding the background model, currently tracked objects, etc.) and terminating current tracks in the tracking component 24, or discarding recent updates as unreliable.
In one embodiment, the camera motion alert component 22 will generate an alert at 50 indicating that the camera 5 has experienced large camera motions. In this case, the camera motion alert may be stored in the camera motion database 18 or delivered to an operator of the surveillance system to warn that the camera has moved. For example, the camera motion alert component 22 could send a real-time alert to a security guard in the event that the camera motion is triggered by an external agency such as an intruder turning the camera so that it cannot observe activity in a certain area.
While the camera is moving, the motion estimation component 14 will estimate camera movement parameters (e.g., pan and tilt measurements) from the point motion estimates using a technique such as for example, least squares or RANSAC at 52 and also record these parameters in the camera motion database 18 for later searches. In addition, the motion estimation component 14 determines whether the camera is still moving at 54. If the motion estimation component 14 determines that the camera is still moving, then it is determined at decision block 56 whether there are enough visible tracked points (i.e., whether the points that the system is attempting to track are still within the field of view the camera and are not occluded by moving objects).
If there are not enough visible tracked points, then additional points are chosen at 58 by running an algorithm such as a corner-finding algorithm. If there are enough visible tracked points as determined at 56 or as chosen at 58, then the motion estimation component 14 will estimate movement parameters again at 52. Process acts 52-58 will continue to cycle in a loop until it is determined at decision block 54 that the camera 5 is no longer moving.
When no motion is detected, the camera motion alert component 22 will generate an alert at 60 that large camera motions have ceased. In addition, the camera motion alert may be stored in the camera motion database 18 and made available for future use by searching the database. Furthermore, the camera operations component 20 will resume camera operations that require a stable camera at 62. In particular, the camera operations component 20 will resume operations such as background subtraction and tracking operations as well as resuming detection of small and large camera motions.
Resumption of background subtraction operation may involve the acquisition of a new background model, or it may involve the detection of the camera position with respect to an existing background model or models and the initialization of a new model based on old models (e.g., with image warping and parameter merging). The tracking operation may be initialized with a clean slate, but may also reload parameters for the detected scene, or even resume tracking of moving objects that were being tracked before the camera moved; particularly if the camera motion was of short duration and small net motion.
The foregoing flow chart shows some of the processing functions associated with managing images generated from a movable camera. In this regard, each block represents a process act associated with performing these functions. It should also be noted that in some alternative implementations, the acts noted in the blocks may occur out of the order noted in the figure or, for example, may in fact be executed substantially concurrently or in the reverse order, depending upon the act involved. Also, one of ordinary skill in the art will recognize that additional blocks that describe the processing functions may be added.
In the computing environment 100 there is a computer 102 which is operational with numerous other general purpose or special purpose computing system environments or configurations. Examples of well known computing systems, environments, and/or configurations that may be suitable for use with an illustrative computer 102 include, but are not limited to, personal computers, server computers, thin clients, thick clients, hand-held or laptop devices, multiprocessor systems, microprocessor-based systems, set top boxes, programmable consumer electronics, network PCs, minicomputers, mainframe computers, distributed computing environments that include any of the above systems or devices, and the like.
The illustrative computer 102 may be described in the general context of computer-executable instructions, such as program modules, being executed by a computer. Generally, program modules include routines, programs, objects, components, logic, data structures, and so on, that performs particular tasks or implements particular abstract data types. The illustrative computer 102 may be practiced in distributed computing environments where tasks are performed by remote processing devices that are linked through a communications network. In a distributed computing environment, program modules may be located in both local and remote computer storage media including memory storage devices.
As shown in
Bus 108 represents one or more of any of several types of bus structures, including a memory bus or memory controller, a peripheral bus, an accelerated graphics port, and a processor or local bus using any of a variety of bus architectures. By way of example, and not limitation, such architectures include Industry Standard Architecture (ISA) bus, Micro Channel Architecture (MCA) bus, Enhanced ISA (EISA) bus, Video Electronics Standards Association (VESA) local bus, and Peripheral Component Interconnects (PCI) bus.
The computer 102 typically includes a variety of computer readable media. Such media may be any available media that is accessible by computer 102, and it includes both volatile and non-volatile media, removable and non-removable media.
In
Computer 102 may further include other removable/non-removable, volatile/non-volatile computer storage media. By way of example only,
The drives and their associated computer-readable media provide nonvolatile storage of computer readable instructions, data structures, program modules, and other data for computer 102. Although the exemplary environment described herein employs a hard disk 116, a removable magnetic disk 118 and a removable optical disk 122, it should be appreciated by those skilled in the art that other types of computer readable media which can store data that is accessible by a computer, such as magnetic cassettes, flash memory cards, digital video disks, RAMs, ROM, and the like, may also be used in the exemplary operating environment.
A number of program modules may be stored on the hard disk 116, magnetic disk 120, optical disk 122, ROM 112, or RAM 110, including, by way of example, and not limitation, an operating system 128, one or more application programs 130, other program modules 132, and program data 134. Each of the operating system 128, one or more application programs 130 other program modules 132, and program data 134 or some combination thereof, may include an implementation of the system 10 of
A user may enter commands and information into computer 102 through optional input devices such as a keyboard 136 and a pointing device 138 (such as a “mouse”). Other input devices (not shown) may include a microphone, joystick, game pad, satellite dish, serial port, scanner, camera, or the like. These and other input devices are connected to the processor unit 104 through a user input interface 140 that is coupled to bus 108, but may be connected by other interface and bus structures, such as a parallel port, game port, or a universal serial bus (USB).
An optional monitor 142 or other type of display device is also connected to bus 108 via an interface, such as a video adapter 144. In addition to the monitor, personal computers typically include other peripheral output devices (not shown), such as speakers and printers, which may be connected through output peripheral interface 146.
Computer 102 may operate in a networked environment using logical connections to one or more remote computers, such as a remote server/computer 148. Remote computer 148 may include many or all of the elements and features described herein relative to computer 102.
Computer 102 may operate in a networked environment using logical connections to one or more remote computers, such as a remote server/computer 148. Remote computer 148 may include many or all of the elements and features described herein relative to computer 102.
Logical connections shown in
In a networked environment, program modules depicted relative to the personal computer 102, or portions thereof, may be stored in a remote memory storage device. By way of example, and not limitation,
An implementation of an exemplary computer 102 may be stored on or transmitted across some form of computer readable media. Computer readable media can be any available media that can be accessed by a computer. By way of example, and not limitation, computer readable media may comprise “computer storage media” and “communications media.”
“Computer storage media” include volatile and non-volatile, removable and non-removable media implemented in any method or technology for storage of information such as computer readable instructions, data structures, program modules, or other data. Computer storage media includes, but is not limited to, RAM, ROM, EEPROM, flash memory or other memory technology, CD-ROM, digital versatile disks (DVD) or other optical storage, magnetic cassettes, magnetic tape, magnetic disk storage or other magnetic storage devices, or any other medium which can be used to store the desired information and which can be accessed by a computer.
“Communication media” typically embodies computer readable instructions, data structures, program modules, or other data in a modulated data signal, such as carrier wave or other transport mechanism. Communication media also includes any information delivery media.
The term “modulated data signal” means a signal that has one or more of its characteristics set or changed in such a manner as to encode information in the signal. By way of example, and not limitation, communication media includes wired media such as a wired network or direct-wired connection, and wireless media such as acoustic, RF, infrared, and other wireless media. Combinations of any of the above are also included within the scope of computer readable media.
It is apparent that there has been provided with this disclosure a system and method for managing moving surveillance cameras. While the disclosure has been particularly shown and described in conjunction with a preferred embodiment thereof, it will be appreciated that variations and modifications will occur to those skilled in the art. Therefore, it is to be understood that the appended claims are intended to cover all such modifications and changes as fall within the true spirit of the invention.
For example, in another embodiment, there is a business method that performs the functionalities of the disclosure on a subscription, advertising, and/or fee basis. That is, a service provider could manage images generated from a movable camera. In this case, the service provider can create, deploy, maintain, support, etc., a system, such as system 10 (FIG. 1) that performs the processes described in the disclosure for one or more sellers of goods and/or services. In return, the service provider can receive payment from the seller(s) under a subscription and/or fee agreement and/or the service provider can receive payment from the sale of advertising content to one or more third parties.
In still another embodiment, this disclosure provides a method for using the system 10 within a computer system to manage images generated from a movable camera. In this case, a system, such as system 10 (
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Number | Date | Country | |
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