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Mega Pixel Resolution
Back To Main MenuThe higher the resolution, the more details can be seen in an image. This is a very important consideration in video surveillance applications, where a high-resolution image can enable a criminal to be identified. Using traditional analogue technology, a live image has no more than 0.4 megapixels and a recorded image only has 0.1 megapixels (CIF). The maximum resolution of NTSC and PAL, in analogue cameras, after the video signal has been digitized in a DVR or a video server, is 400,000 pixels (704x576 = 405,504). 400,000 equals 0.4 Mega Pixel.
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Even though the video surveillance industry has always managed to live
with these limitations, new network camera technology now makes higher
resolution possible. A common Mega Pixel format is 1280x1024, giving
1.3 Mega Pixel resolution, 3 times higher than analogue cameras. We
have cameras with 1 - 9 Mega Pixels.
Mega Pixel network cameras also bring the benefit of different aspect
ratios. In a standard CCTV an aspect ratio of 4:3 is used, while movies
and wide-screen TV use 16:9. The advantage of this aspect ratio is that,
in most images, the upper part and the lower part of the picture are
of no interest, yet they take up precious pixels, and therefore bandwidth
and storage space. In a network camera any aspect ratio can be used.
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In addition, digital pan/tilt/zoom can be achieved without losing resolution,
where the operator selects which part of the Mega Pixel images should
be shown. This does not imply any mechanical movement from the camera.
It ensures much higher reliability.
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Intelligence At The Camera
Intelligence at the camera level empowers a much more productive and effective means of video surveillance than is possible with a DVR or other centralised systems. The network camera also solves another emerging dilemma: the shortage of computing power to analyse more than a few channels in real time. Network cameras have purpose-built, highly integrated hardware that excels in image analysis tasks, thus enabling installation of large-scale intelligent video systems.
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In this scenario an IP camera renders the video and actually excludes regions from the video resulting in less bandwidth.
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Video Motion Detection (VMD)
Video Motion Detection (VMD) is a way of defining
activity in a scene by analysing image data and differences in series
of images.
Video Motion Detection in DVR systems
Cameras are connected to the DVR, which performs the VMD on each video
stream. This allows the DVR to decrease the amount of recorded video,
to prioritise recordings and to use motion in a specific area of the
image as a search term when searching for events. The downside of this
method is that performing VMD is a CPU intensive process and performing
VMD on many channels puts a heavy strain on the DVR system - and critical
channels or more specifically cameras are missed by the DVR.
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Video Motion Detection in Network Video Systems
Video Motion Detection as an integrated function of network cameras
or video servers offers substantial advantages over the scenario mentioned
above – the most significant being that the VMD is processed in the
network camera or video server itself. This alleviates the workload
for any recording devices in the system and makes “event-driven surveillance”
possible. In that case, no video (or only video with low frame rate)
is sent to the operator or recording system unless activity is detected
in the scene. VMD data with information about the activity can also
be included in the video stream to simplify activity searches in recorded
material. Video Motion Detection can also reside in the video management
software, thus providing VMD functionality to network cameras that do
not originally embed this feature.
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Power Over Ethernet Support
Power over Ethernet (PoE) is a technology that integrates
power into a standard LAN infrastructure. It enables power to be provided
to the network device, such as an IP phone or a network camera, using
the same cable as that used for network connection. It eliminates the
need for power outlets at the camera locations and enables easier application
of uninterruptible power supplies (UPS) to ensure 24 hours a day, 7
days a week operation.
PoE technology is regulated in a standard called IEEE 802.3af and is
designed in a way that does not degrade the network data communication
performance or decrease the network reach. The power delivered over
the LAN infrastructure is automatically activated when a compatible
terminal is identified, and blocked to legacy devices that are not compatible.
This feature allows users to freely and safely mix legacy and PoE-compatible
devices, on their network.
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PoE works across standard network cabling (i.e. cat-5) to supply power directly from the data ports to which networked devices are connected. Today, most manufacturers offer network switches with built-in PoE support. If an existing network /switch structure is in place, customers can benefit from the same functionality by adding a so-called Midspan to the switch, which will add power to the network cable. All network cameras without built-in PoE can be integrated in a PoE system using an Active Splitter.
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Audio Support
Audio can easily be integrated into network video
as the network can carry any type of data, which reduces the need for
extra cabling.
This is far better that analogue systems where an audio cable must
be installed from endpoint to endpoint.
A network camera captures audio at the camera, integrating it into the
video stream, and then sending it back for monitoring and/or recording
over the network. This makes it possible to use audio from remote locations.
For instance, monitoring personnel at a company’s headquarters can interact
with “surveillance scenes” at remote branch offices. They can inform
possible perpetrators that they are under surveillance and listen in
on situations using the audio as an additional confirmation method.
Audio can also be used in network cameras or video servers as an independent
detection method, which triggers video recordings and alarms when audio
levels above a certain threshold are detected.
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No Interlace Problems
There are two different techniques available to render
the video: Interlaced Scanning and Progressive Scanning. Progressive
Scanning is far better and particularly useful when the system is required
to capture moving objects and to allow viewing of detail within a moving
image.
Interlaced Scanning
Interlaced scan-based images use techniques developed for Cathode Ray
Tube (CRT) based TV monitor displays, made up of 576 visible vertical
lines across a standard TV screen - This antiquated technique is
over 60 years old! Interlacing divides these into odd and even lines
and then alternately refreshes them at 25/30 frames per second. The
slight delay between odd and even line refreshes creates some distortion
or ‘jaggedness’. This is because only half the lines keeps up with the
moving image while the other half waits to be refreshed.
Interlaced scanning has served the Analogue camera, television and VHS
video world very well for many years, however now that display technology
is changing with the advent of Liquid Crystal Display (LCD), Thin Film
Transistor (TFT) based monitors, DVDs and digital cameras, an alternative
method of bringing the image to the screen, known as Progressive scanning,
has been created.
Progressive Scanning
Progressive Scanning, as opposed to Interlaced, scans the entire image
line by line every 25/30 of a second. In other words, captured images
are not split into separate fields like in interlaced scanning. Computer
monitors do not need to interlace to show the picture on the screen.
It puts them on one line at a time in perfect order i.e. 1, 2, 3, 4,
5, 6, 7 etc. So there is virtually no "flickering" effect. As such,
in a video surveillance application it can be critical in viewing detail
within a moving image such as a person running away.
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Example: Capturing Moving Objects
Compare these JPEG images, captured by three different cameras using
Progressive Scan, Interlaced Scan (4CIF) and Interlaced Scan (2CIF)
respectively.
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The car was driving at 15 mph. The images produced by an IP Network Surveillance Camera are clearly much higher quality than those produced by a traditional analogue camera.
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Digital Input / Output
A unique feature of Digital Network Video products,
is their integrated digital inputs and outputs that are manageable over
the network. The output can be used to trigger mechanisms either from
a remote PC or automatically, using the camera’s built-in logic, while
inputs can be configured to respond to external sensors such as PIRs
or push button initiating video transfers.
The I/Os can be used in conjunction with alarm sensors for instance,
to eliminate unnecessary transfers of video, unless the sensor attached
to the camera triggers.
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Example - A camera attached to a window switch
and to an alarm system/siren.
Digital Inputs
The range of devices that can be connected to a network camera’s input
port is almost infinite. The basic rule is that any device that can
toggle between an open and closed circuit can be connected to a network
camera or a video server.
Examples of Alarm Devices and Their Usage
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Digital Outputs
The output port’s main function is to allow the camera to trigger external
devices, either automatically or by remote control from a human operator
or a software application.
Example of Devices That Can Be Connected To The Output Port
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Day / Night Functionality
Certain environments or situations restrict the use
of artificial light, making infrared (IR) cameras particularly useful.
These include low-light video surveillance applications, where light
conditions are less than optimal, as well as discreet and covert surveillance
situations. Infrared-sensitive cameras, which can make use of invisible
infrared light, can be applied, for instance, in a residential area
late at night without disturbing residents. They are also useful when
the cameras should not be evident.
Light Perception
Light is a form of radiation wave energy that exists in a spectrum.
The human eye can see, however, only a portion (between wavelengths
of ~400 – 700 nanometers or nm). Below blue, just outside the range
humans can see, is ultraviolet light, and above red is infrared light.
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Infrared energy (light) is emitted by all objects:
humans, animals and grass, for instance. Warmer objects such as people
and animals stand out from typically cooler backgrounds. In low light
conditions, for example at night, the human eye cannot perceive colour
and hue - only black, white and shades of gray.
How Does Day / Night Functionality Filtering Work?
While the human eye can only register light between the blue and red
spectrum, a colour camera’s image sensor can detect more. The image sensor
can sense long-wave infrared radiation and thus “see” infrared light
up to 1000 nm. Allowing infrared to hit the image sensor during daylight,
however, will distort colours as humans see them. This is why all colour
cameras are equipped with an IR-cut filter - an optical piece of glass
that is placed between the lens and the image sensor - to remove IR
light and to render colour images that humans are used to.
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As illumination is reduced and the image darkens, the IR-cut filter in a day and night camera can be removed automatically* to enable the camera to make use of IR light so that it can “see” even in a very dark environment. To avoid colour distortions, the camera often switches to black and white mode, and is thus able to generate high quality black and white images.
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Infra Red Illumination
Infra Red Illumination help cameras see what is going
in - even in complete darkness and low-light situations without attracting
attention. The inherent low power consumption of the solid-state LEDs
results in ultra long life time, and very low running cost of the system.
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| Camera With Infra Red Illumination | Camera Without Infra Red Illumination |
The high quality IR Illuminator can be used both indoors and outdoors, for both semi-covert and covert applications, and the adjustable power settings offer possibility to match the scene requirements.
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Flexible Infrastructure
Analogue video is typically transmitted by expensive coax where distance will influence image quality. Adding power, inputs/outputs and audio further complicates this situation. Network video systems surmount these obstacles at much lower cost and with many more options. A network camera produces digital images, so there’s no quality reduction due to distance. IP-based networking is an established, standardized technology meaning the resulting costs are comparatively low. Unlike analogue systems, IP-based video streams can be routed around the world, using a variety of interoperable infrastructure.
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Secure Communication
With any video surveillance system, privacy is a
very important consideration.
Unlike Analogue CCTV cameras that only send out one single video stream
that can be tapped into, a network camera can encrypt the video being
sent over the network to make sure it cannot be viewed or tampered with.
There are several ways to provide security within a wired or wireless
network and between different networks and clients. Providing secure
transmission of data is like using a courier to bring a valuable and
sensitive document from one person to another. When the courier arrives
to the sender, he would normally be asked to prove his identity. Once
this is done, the sender would decide if he is the one he claims to
be, and if he can be trusted. If everything seems to be correct, the
locked and sealed briefcase would be handed over to him, and he would
deliver it to the receiver. At the receiver, the same identification
procedure would take place, and the seal would be verified as “unbroken”.
Once the courier had left, the receiver would unlock the briefcase and
take out the document to read it.
A secure communication is created in the same way, and is divided into
three different steps:
Authentication
This initial step is for the user or device to identify itself to the
network and the remote end. This is done by providing some kind of identity
to the network/system, like a username and password, i.e. an SSL certificate.
Authorisation
The next step is to have this authentication authorised and accepted,
that is verifying whether the device is the one it claims to be. This
is done by verifying the provided identity within a database or list
of correct and approved identities. Once the authorisation is completed,
the device is fully connected and operational in the system.
Privacy
The final step is to apply the level of privacy required. This is done
by encrypting the communication, which prevents others from using/reading
the data. The use of encryption could provide a substantial decrease
in performance, depending on the kind of implementation and encryption
used. Privacy can be achieved in several ways. Two of the more commonly
used methods are VPN and HTTPS:
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VPN (Virtual Private Network)
A VPN creates a secure tunnel between the points within the VPN. Only
devices with the correct “key” will be able to work within the VPN.
Network devices between the client and the server will not be able to
access or view the data. With a VPN, different sites can be connected
together over the Internet in a safe and secure way.
SSL/TLS (HTTPS)
Another way to accomplish security is to apply encryption to the data
itself. In this case there is no secure tunnel like with the VPN solution,
but the actual data sent is secured. There are several different encryption
techniques available, like SSL, WEP and WPA, the later two being used
in wireless networks. When using SSL, also known as HTTPS, the device
or computer will install a certificate into the unit, which can be issued
locally by the user or by a third-party body such as Verisign.
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A True Digital Solution
With Analogue based systems every conversion in image
quality is lost:
Analogue signal digitized in camera’s DSP - Image Degradation
Analogue signal converted back to analogue for transport over coax - Image
Degradation
Signal once again digitized at the DVR for recording - Image Degradation
The CCD sensor in an analogue camera generates an analogue signal that
is digitized by an A/D converter to make possible the image improving
function in a DSP. The signal is then converted back to analogue for
transport over a coax cable. Finally, at the DVR the signal is once
again digitized for recording. That makes a total of three conversions,
and with every conversion image quality is lost. In the network camera
system, images are digitized once and they stay digital for the duration—no
unnecessary conversions and no image degradation.
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