Note: Descriptions are shown in the official language in which they were submitted.
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DIGITAL VIDEO SECURITY SYSTEM
FIELD OF THE INVENTION
The invention herein disclosed relates to the field
of security video monitoring. Specifically the invention is
a digital video surveillance system equipped with motion
sensing and solid state storage capabilities.
BACKGROUND OF THE INVENTION
Video surveillance systems are part of a continually
evolving field, wherein many techniques of image capture and
image storage have been employed. Conventional monitoring
techniques include a standard analog video camera with analog
recording devices such as a VCR. These types of surveillance
systems have many associated drawbacks including operation
and maintenance costs of VCR equipment and the limited
storage capacity of VCR tapes which becomes a significant
factor when used in a continuously operating surveillance
system. Several recently developed advances have attempted
to address these problems.
Innovations in hardware and compression algorithms
have made digital video storage a cost effective alternative
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to VCR's. The significant advantages of digital video
include the ability to process video information before or
after storing it and the increased flexibility of storage
media offered by digital information. The ability to process
digital video has led to the use of video motion detection as
a triggering mechanism for the capture of surveillance data,
thereby reducing the required storage capacity relative to
continuously recording systems.
Various methods of digital video motion detection are
discussed in several U.S. Patents including No's 5,754,225
(Naganuma), 5,731,832 (Ng), 5,602,585 (Dickinson et al.), and
5,751,345 (Dozier et al.). The basic algorithm for digital
video motion detection involves comparison of a reference
video image (i.e. one captured previously) to the incoming
video image and looking for changes. A detected motion
signal may be used to trigger storage of the video signal.
Thus storage space is conserved relative to continuously
recording systems.
U.S. Patent No. '225 (issued to Naganuma) discloses a
method of digital video motion detection that involves
partitioning the video signal into a plurality of areas and
calculating an evaluation value for the image within each of
the areas. The calculation of an evaluation value can have
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several forms including: integrating in a vertical direction
peak values of the video signal taken in a horizontal
direction, integrating the output of a slice circuit which
outputs the video signal when it is in between two
predetermined slice levels, and counting the number of pixels
in the video signal that are above a certain threshold level.
A micro-computer calculates reference evaluation values
obtained in an ordinary state and compares the reference
evaluation values to the incoming current evaluation values
to detect a motion of the image. The problem with the
Naganuma process is that its principal purpose is to reduce
hardware requirements and as such sacrifices accuracy because
of the integration done over each partitioned area as opposed
to the entire frame.
U.S. Patent No. '832 (issued to Ng) discloses a
method of digital video motion detection that involves
generating a difference array by comparing pixel luminescence
data for each of a new image and a reference image on a pixel
by pixel basis. A difference array is generated and then
partitioned into blocks and an average value for each block
is put into a difference matrix. Finally, a difference
profile of the difference matrix is calculated and compared
to a threshold. If the difference profile is greater than
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the threshold, then a motion is detected. Despite being more
accurate in detection, this technique suffers because it
requires a large amount of processing and, therefore, costly
implementation hardware.
U.S. Patent No. '585 ,issued to Dickinson et al.,
discloses a means of analog video motion detection involving
a grid of active pixel sensor arrays. Each active pixel
sensor array is operative to convert a detected quantity of
light into a corresponding voltage which is fed into an
output circuit. The output circuits are controlled so as to
produce output voltage signals in a serial fashion. The
output voltage signals are compared to a threshold level over
which a motion is detected. The Dickinson system of motion
detection is based on analog as opposed to digital video.
U.S. Patent No. '345 (issued to Dozier et al.)
discloses a method of digital video motion detection, but it
is based on pixel by pixel comparison of digital still images
rather than video. Although essentially the same problem,
the Dozier solution is not time limited as a true video
solution would be because the rate of capture of the digital
stills is substantially less than that of digital video.
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Digital video has also led to an increased array of
storage mechanisms including magnetic storage devices such as
disk drives and tape drives. Disk and tape drive storage
techniques are discussed in U.S. Patent No. 5,724,475
(Kirsten) and 5,751,345 (Dozier et al.). Similar to
conventional analog video tapes, digital magnetic media such
as disk and tape drives are also subject to wear over a
period of time. Wear on digital magnetic storage media is
particularly a concern when the same disk is written and
overwritten a number of times.
The aforementioned patents suffer from a common
drawback when used in surveillance systems. They all depend
on an external camera to capture the video images and/or
external storage mechanisms to record the retrieved data.
The systems are not integrated so that the camera, motion
detection and storage subsystems are in the same enclosure.
Consequently the subsystems are left exposed for potential
vandals and criminals who may easily disable the entire
surveillance system by damaging any one of its component
subsystems. Furthermore, systems which are PC based, rather
than embedded, require the additional costs associated with
the computer and are susceptible to network crashes, computer
transmitted viruses and other PC related problems.
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Installation of separated systems can also be a costly
problem, when complex cabling is required, particularly for
home users, who may not have facilities to run cabling
through their residence.
It is an object of the present invention to
integrate the three functions of digital image capture
(camera), digital video motion detection and digital video
storage into an embedded system that is sufficiently small
and robust to withstand severe conditions such as an impact,
high pressure water spray or other physical trauma.
Another object of the present invention is to provide
a cost effective embedded surveillance system with a user
interface and on-screen display so that it is operable
without any dependence on a PC or other external operational
unit, effectively eliminating the need for external cabling
and the other costs and problems associated with PC's.
Another object of the present invention is to provide
a cost effective solid state storage medium within an
embedded surveillance system that can be used to store
digital video information without the associated wear that
manifests itself in costly mechanical storage media.
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Another object of the present invention is to include
a motion detection subsystem within an embedded surveillance
system so as to reduce the total storage capacity
requirement. The motion detection subsystem may be of the
digital video type that combines accuracy with minimal
hardware requirements and will trigger a storage subsystem to
record data and may optionally produce an alarm signal to
trigger other devices.
Another object of the present invention is to provide
an embedded surveillance system with a total storage capacity
requirement that is further reduced by recording video data
in a time lapse fashion, where the images are recorded at a
reduced rate. The combination of motion detection and
reduced frame rate enables effortless retrieval of
significant events without poring over hours of useless
images.
SUMMARY OF THE INVENTION
An apparatus for an embedded security and
surveillance system is disclosed. The apparatus comprises a
video camera which captures video images and outputs them in
one of several industry standard video formats. The output
of the video camera is coupled to a digital video decoder
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which converts the video images into digital form at a
capture rate of approximately 30 frames per second. A
digital solid state storage subsystem is also included in the
apparatus. The digital solid state storage subsystem is
operative to store, electronically, the video images at a
storage rate which is a fraction of the capture rate, the
fraction being 1/n where n is an integer greater than or
equal to 1. The apparatus also includes a digital video
motion detection subsystem which triggers the digital solid
state storage subsystem when a motion is detected and also
outputs an alarm signal which may be used to trigger other
events and devices. A camera interface subsystem is also
included in the apparatus. The camera interface subsystem is
coupled to both the video camera and the video motion
detection subsystem and is operative to adjust the video
camera so as to consistently provide a clear video image and
to provide pre-processing for the digital video motion
detection subsystem. Finally, all of the aforementioned
parts and subsystems are housed in a small durable vandal
resistant enclosure to form a single embedded structure.
Advantageously, the apparatus may support many
various camera types including those which may have the
following video formats:
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(1) regular resolution EIA (monochrome)
(2) high resolution EIA (monochrome)
(3) regular resolution CCIR (monochrome)
(4) high resolution CCIR (monochrome)
(5) regular resolution NTSC (color)
(6) high resolution NTSC (color)
(7) regular resolution PAL (color)
(8) high resolution PAL (color)
The digital video decoder may convert any of the above
mentioned video formats into CCIR601, which is a popular
digital video format.
The solid state storage subsystem used by the
apparatus may be a FLASH type of memory, which may be
exchangeable so as to expand the memory capabilities of the
apparatus.
Advantageously, the durable vandal resistant
enclosure may be made of poly-carbonate material which is
highly resistant to impact and other extreme conditions.
Preferably, the digital video motion detection
subsystem may be operative to analyze certain user defined
sectors within the video images for motion and, based on a
user defined sensitivity threshold, make a decision whether
to trigger the digital solid state storage subsystem.
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The apparatus may also comprise a user interface
which provides user input and output from the embedded
security and surveillance system. User input may be received
from a keypad on the apparatus. User output may include a
video output signal with an overlaid on-screen display which
may provide the user with information such as: time, date,
and menuing functions for the user interface. The user
interface may allow the user to monitor and alter several
features including:
(a) the storage rate, which determines a rate at which
video images are stored when the digital video
storage subsystem is triggered;
(b) the user defined sectors within the video images,
which determine which sectors will be analyzed for
motion by the digital video motion detection
subsystem;
(c) a sensitivity threshold for the digital video
motion detection subsystem, which determines what
level of motion will trigger the digital video
storage subsystem; and
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(d) a digital video frame file size which determines
the resolution at which the digital video storage
subsystem records the video images.
The system may also include a programmer interface
such as a serial port which is operative to input and output
program and diagnostic information. Advantageously, the
apparatus may include a remote arm/disarm capability that
will allow the user to activate/deactivate the device without
having to contact it.
BRIEF DESCRIPTION OF THE DRAWINGS
Fig. 1-a and Fig. 1-b depict a preferred embodiment
of the invention. The video camera aperture and the vandal
resistant enclosure are shown.
Fig. 2 depicts schematically the electronic
architecture of the apparatus displaying all of the
subsystems.
DESCRIPTION OF THE PREFERRED EMBODIMENT
Fig. 1-a and Fig. 1-b depict the entire security and
surveillance apparatus with the vandal resistant enclosure 4.
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The camera aperture 1 and the microphone 3 are shown in the
front of the enclosure 4. The enclosure 4 is held together
with security bolts 6. Optional cables 5 lead directly into
a wall or ceiling (without exposure) and carry video
information to a monitor (not shown) for immediate monitoring
if desired by the user. Typically, however, the unit will
not include the cables 5 making it a truly stand alone
system, which can be detached and moved to a location with a
monitor for playback. The keypad 10 provides a user input
device which can be used to select the user-programmable
features with the aid of the on-screen display.
Fig. 2 shows a schematic diagram of the electronic
architecture of a preferred embodiment of the invention. The
video camera 1 captures video images in one of eight
different types of video formats which include regular and
high resolution EIA, CCIR, NTSC, and PAL analog video
standards.
The video decoder 2 converts the industry standard
EIA/CCIR/NTSC/PAL video into a standard digital format called
CCIR601. The circuit that performs this function is a
standard "off-the-shelf" integrated circuit.
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The solid state storage subsystem includes, the
compression/decompression block 4, the microprocessor 7, and
the storage chips 8. The compression/decompression block 4
takes the digital video (from the decoder 2) and compresses
it for storage in memory 8 and also takes the stored images
and decompresses them for playback via the user interface.
The compression algorithm employed is wavelet compression, as
opposed to the more standard schemes such as JPEG, MPEG, etc.
The microprocessor 7 is the central controlling unit for the
entire embedded system and one of its functions includes
controlling the memory access. The memory 8 is a non-
volatile memory used to store the compressed images. The
amount of memory 8 included in the solid state storage
subsystem determines the maximum number of video frames that
can be stored. The memory chips 8 may be exchangeable so as
to allow "plug-in" cartridges of memory that expand the total
storage capacity of the device.
The digital video motion detection subsystem
includes: the microprocessor 7 and the camera/motion
interface 6. The camera/motion interface 6 pre-processes the
information from the camera 1 to help detect motion in the
video scene. The microprocessor 7 analyzes the motion and
determines the significance of the motion in the video scene
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to control image recording. Motion detection is the key to
recording images, such that when a motion of significance is
detected, the microprocessor will interface with the solid
state storage subsystem to store the compressed images in
memory for retrieval later.
The camera interface subsystem consists of the
camera/motion interface 6 and the microprocessor 7. The
microprocessor 7 is continually analyzing the incoming video
images to determine lighting and other criteria to ensure
that the video images that are captured are clear. The
camera/motion interface chip 6 provides the interface from
the microprocessor 7 to the camera 1.
The user interface for the apparatus includes: the
keypad 11, the on-screen display 5, and the encoder 3. The
encoder 3 converts the digital video back to analog for
viewing on a monitor (not shown). The on-screen display 5 is
added into the video signal to provide overlaid information
such as the time, date and menuing options. The 4 button
keypad 11 is provided to allow a user to manipulate the on-
screen display 5 as well as to control the playback of stored
images. Other switches separate from the keypad 11 are also
included to allow for some simple setup features.
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A programmer interface 10 is also included to permit
software upgrades and other programmer related services.
In normal operational mode, the video camera 1 is
capturing video images which are decoded by the digital video
decoder 2 at a rate of 30 frames per second and compressed by
compressor 4 for processing and/or storage. The captured
frames are used by the camera interface subsystem to adjust
features such as camera aperture and other camera adjustments
in accordance with the present light conditions. The digital
video motion detection subsystem is continually comparing the
captured images for motion in the user defined sectors of the
frame. The digital video motion detection subsystem runs the
digital data through a low pass filter to reduce the
information content contained in the image. Each value in
the newly filtered digital image corresponds to information
from many original samples in the original composite video
input. The newly filtered digital image is then filtered
again in a Sobel filter implementation so as to extract edge
information. Thus the image is removed and only an edge
profile remains in the data. This second filtering operation
reduces the chances that false triggering may occur because
of amplitude differences from scene to scene being
interpreted as movement within the scene. The current
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filtered digital "image" is then compared to the last
filtered digital "image". If the number of pixels that
exceed a first threshold is higher than a second user defined
threshold level of "significance", then the digital solid
state storage subsystem is triggered and the compressed video
images are stored in memory 8 until required for playback.
TnThen a next digital image arrives, the current image is
assigned to being the old image and the process begins anew.
The digital video images are stored at a user defined storage
rate that is a fraction of the capture rate. The preferred
embodiment allows storage between 0.2 and 5 frames per
second. This preserves the motion video "feel", but reduces
the corresponding memory requirements. A user can also
select the file size that they want to store. The file size
of each image is variable, so that the user can trade off
image resolution to total capacity for the number of images
stored. Stored images can be retrieved from memory 8 for
playback on a monitor (not shown). The on-screen display 5
is overlaid onto the decoded video output so that the user is
provided information such as date and time of the recorded
images that they are viewing.
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