All you wanted to know
Closed Circuit Television
But didn’t know what to ask.
By: Paul Broome
Table of Contents:
Forward: ............................................................................................................................ 3
Introduction: ..................................................................................................................... 4
Basic Video System Components - A history lesson: ..................................................... 5
Old CCTV parts that just won’t go away:...................................................................... 5
Time-lapse VCR: ........................................................................................................... 5
Manual switch: .............................................................................................................. 5
Sequential Switcher: ..................................................................................................... 6
Video Splitter: ............................................................................................................... 6
Picture in a picture: ...................................................................................................... 6
Motion detectors: .......................................................................................................... 6
Quads: ............................................................................................................................ 6
Multiplexers: ................................................................................................................. 7
Virtual Real-time VCR: ............................................................................................... 7
All in one VHS recorders: ............................................................................................ 7
Other video accessories of note:....................................................................................... 8
Video Line amplifiers: .................................................................................................. 8
Distribution amplifiers: ................................................................................................ 8
Coax cable: .................................................................................................................... 8
Video Baluns .................................................................................................................. 9
Power Supplies: ............................................................................................................. 9
UPS power supplies: ..................................................................................................... 9
KVM Switches:............................................................................................................ 10
Monitors: ..................................................................................................................... 10
Typical monitor displays: ........................................................................................... 11
Cameras: ...................................................................................................................... 12
Matrix Switches: ......................................................................................................... 14
DVR (Digital Video Recorders): ................................................................................ 15
NVR (Network Video Recorder): .............................................................................. 16
Is the latest and greatest always the best? .................................................................... 17
Notable Transitions in CCTV: ....................................................................................... 18
Why bother using alarms to increase record rates. Why not record all cameras as
fast a possible all the time? ............................................................................................. 20
Addendum #1: VCR101 and VCR102 .......................................................................... 21
Addendum #2: Pixels, record speed and CIF: ............................................................. 27
Addendum #3: “Picture Quality” .................................................................................. 32
Are you really going to learn all you wanted to know about CCTV by reading this paper?
It seems unlikely that such a relatively short document could contain all that much
detailed information. On the other hand, you may just be looking for a brief overview of
the history of a topic that could bring you to tears when hearing the long version. The
value in this brief description of old product solutions is that most of these same
functions are included with the latest DVRs. Shining the spotlight of truth on these items
one at a time may give you some insight into why people still want, or need these
functions in the digital age. If all you are looking for are basic facts, general information
and a few anecdotes, this may be just the kind of reference material you’re looking for.
A wise person once told me that if I wanted to quickly learn something about a subject I
should go to the children’s section of a library and see what books they had to offer. The
subject is described in simple terms, leaving out much of the excruciating detail, and
provided in a straight forward way that even a child can understand. About 80% of what
you would get from a detailed text is in the children’s version. Once you have worked
your way through the book you may find that you have discovered all you wanted to
know about the subject. This cursory review may give you the information you need to
sound knowledgeable and better able to understand the in-depth versions provided by
That thought is behind the title of a series of papers that I’ve written on several product
specific and other loosely related subjects. This document, “All you wanted to know
about… CCTV” provides a brief description of many hardware devices used in CCTV,
some background information where it is useful and an occasionally humorous slant on
an otherwise dry technical subject.
So kids, if you find yourself trapped on a plane, or the passenger in a car on your way to a
customer facing experience where your CCTV knowledge may be tested, this could be
just the thing to pass the time.
If you want just a little more detail on some of the items mentioned, I have written papers
on some of the individual subjects. Check the documents page on
CCTV (Closed Circuit Television) is a continually changing subject. New technologies
spring up to replace the old at a deafening rate. As soon as you hear about the newest
solution, another product is beating the drum for attention. You might think that the old
technology would recognize that it has been outdone and fade away. Of course some has.
The rest hangs on, still providing service as well as it always has in the past. These once
expensive solutions to individual applications are now only a fraction of their original
price. The original manufacturers may have long since abandoned the products due to
declining prices and newer replacements. New manufacturers have duplicated the
functionality (if not the original design) and are willing to proceed with limited margins.
Customers who were priced out of the original offerings are now seeing the benefit of the
technology at today’s price points, expanding the low end market for CCTV products.
The traditional higher end customers still have a working inventory of the old products
and like to purchase newer products that are compatible with their current investment.
Customer demand has required newer products to incorporate much of the functionality
of the older products into the newer designs. People often ask why this is true. This paper
attempts to answer this question and some others that you may not know to ask.
DVR (Digital Video Recorder) products provided by “old guard” CCTV manufacturers
typically provide most of the video features that existing customers are familiar with. For
a while, it looked like new manufacturers from Asia were going to pass the old guard by
with lower priced PC based DVR products touting bigger numbers for refresh rates and
record speeds. Although better in many respects, they lacked an established channel to
market (the main reason) and they were not tuned in to the customer requirements for
traditional CCTV capabilities. While they were figuring this out, the old guard
manufacturers came up to speed and added additional features. Some traditional US
manufacturers went the OEM route, partnering with Asian manufacturers.
This document is intended to provide a history lesson of information on past and present
products. If you are new to CCTV, or unaware of what products are out there, this is a
good starting point to make you aware of what you don’t know so you can do further
investigation where necessary.
Don’t feel bad if you aren’t familiar with the basic components used in CCTV. Most
people are not aware of all that is presented here. At first they don’t know what to ask.
After a while, they are too embarrassed to ask anyone. You will know much if you absorb
the cursory information provided in this paper. It may not be the easiest read from start to
finish, but it will be a valuable reference document to have around.
If you have questions, comments or would like to see other topics addressed, please email
me at firstname.lastname@example.org.
Basic Video System Components - A history lesson:
The products listed have been around for a while. Although you may be selling the most
up to date products, most of the functionality of these early product entries is included in
the latest DVR products. These features may be overlooked and unused by many, but
they would be sorely missed by “experienced” users.
The very basic video system consists of a camera, a cable and a monitor. The camera
captures images, the cable transmits the images to the place where you want to see them
and the monitor provides the visual display of the images. There are of course, many
verities of cameras, many different connection methods and a growing array of monitors
available. In the beginning…
Old CCTV parts that just won’t go away:
A CCTV system consists of a camera, a cable and a monitor. Would you like to add a
second camera to your video system? Just get another camera, another cable and another
It doesn’t take long to realize that you are going to need a lot of monitors as your system
grows. If you want to record the video on a VCR, you’ll also need a VCR for every
camera. The need is to create a way to view and record more than one camera on one
monitor and VCR.
Advantages: Full size, real-time image display on each monitor.
Disadvantages: You need lots of equipment as systems grow – size/space requirements.
Time-lapse VCR: Time-Lapse VCRs used in security are based on the standard home
VCR. These modified versions record for different lengths of time according to the mode
selected. Two-hour mode is like a standard VCR. 24-hour mode typically records five
images per second (rather than the 60 available from the camera). This is fine for a single
camera but may cause issues when used with a multiplexer that also time divides the
Advantages: You can record for extended periods of time on a single VHS tape (up to
Disadvantages: The longer the record mode, the more time between each recorded image
and more information is missed.
Manual switch: Not to be overlooked, a basic manual switch is a valuable tool in this
basic application and for selected uses in the most complex solutions.
Advantages: Simple easy solution that anyone can install.
Disadvantages: Someone must manually press the button when required.
Sequential Switcher: (Not to be confused with a Matrix Switch discussed later.) A
sequential switcher is a black box that has several camera inputs and one monitor output.
Connect multiple cameras to the inputs and each will alternately display on the monitor.
Sequential switchers can have a variety of options. You may have wired alarm inputs to
allow an alarm device (PIR, door contact, etc.) to switch to the alarmed camera when
activated. You may be able to select the viewed dwell time of each displayed camera.
Advantages: You see any camera on one monitor and record on one VCR.
Disadvantages: While you are watching and recording one camera, the others are not
available. You could miss important information.
Video Splitter: A video splitter is a black box that allows two cameras to display on one
monitor. Analog versions typically split the two images vertically, or horizontally. Half
of each image is eliminated. The remaining halves are displayed on the monitor. This
may seem odd at first, but it can be very effective at displaying the meaningful areas of
cameras aimed at narrow rows, like hallways and parking areas. Some video splitters
allow control of the size of each image.
Advantages: You see two cameras on one monitor and record on one VCR.
Disadvantages: Smaller images often oddly shaped.
Picture in a picture: A digital version of a video splitter is often called a picture in
picture. The second camera is typically a smaller (quad size) image overlaid on the larger
image. Most allow you to move the insert picture to the desired location.
Advantages: View and record two images on one monitor and VCR.
Disadvantages: One image is smaller and obscures part of the larger image.
Motion detectors: You can get a black box with as little as one camera input that
provides video motion detection.
Advantages: Provide an alarm device with no wiring necessary.
Disadvantages: Difficult setup and may not be as reliable as expected.
You can wire a motion sensing device to the alarm inputs on a variety of equipment. A
PIR (Passive Infra Red) sensor will provide a contact closure to trigger an alarm when
someone enters the field of view. Any device that provides a contact closure when
activated can trigger an alarm on most products.
Quads: Quads digitize four camera inputs, resize them and display all four as a single
image on the monitor. Quads have been around for about thirty years. Dual Quads have
eight camera inputs. They are a combination of quad and sequential switcher digitizing
cameras one through four and five through eight separately, then sequencing the quad
Advantages: View and record four images on one monitor and VCR.
Disadvantages: Each image is smaller. Zoomed playback images have low quality.
Multiplexers: Video multiplexers have been around in their current form since 1993.
This was a first digital step into time divided video as a trade off for accommodating
more video channels with less equipment. Multiplexers are the control center for a small
video system with up to 16 cameras on a single monitor and recording them on a single
VCR. This was a major “killer App” in its time. This was the first device to display 16
cameras on a single screen.
Advantages: One box to control most small installations. Minimum space requirements:
Put the multiplexer on top of a monitor on a single shelf and still accommodate 16
Disadvantages: Less than real-time update for live and playback.
The traditional application for a small video system using VCR recording relies on an
operator changing the tape on a rigid schedule. In many applications this means
changing the tape every day for week day operation using a time-lapse VCR in 24 hour
mode and switching to 72 hour mode to run through the weekend. Of course fewer
images are captured over the weekend, but requirements are less because no one is
supposed to be working. The updates of individual cameras get pretty far apart when a
multiplexer with 16 cameras is involved.
Virtual Real-time VCR: Like other CCTV hardware, VCRs have improved over time.
The first 24 hour virtual real-real time recorders hit the market soon after the multiplexer
gained in popularity. The original multiplexers had a 20 image per second maximum
switch rate (slow by today’s standards). Time-lapse VCRs recorded 5ips in 24-hour
mode. With everything timed perfectly, you get a recorded image of each camera every
3.2 seconds. Although there are a lot of alarm tricks you can do to increase the recording
of alarmed cameras, this is done at the expense of the other cameras. Besides that, most
people don’t use them (or can’t figure out how). The 24 hour virtual real-time recorder
was designed to maximize recording with a multiplexer. It recorded at 20ips capturing all
the available images from the multiplexer and bringing the time between updates of each
camera to .8 seconds. This product combination is very popular with retail and other
businesses where there is someone there to changes tapes seven days a week.
All in one VHS recorders: You can still buy the individual types of VCRs used in
CCTV. This is an extremely price driven product. The most popular models now have all
the different modes in a single box including standard time-lapse and high density time
lapse modes. Explaining all the VCR modes is complex so either see the addendum for a
copy of VCR 101, or stick to selling all digital products.
Other video accessories of note: There are catalogues filled with parts used
in CCTV installations. Many will help you out of an installation jam, or enable a special
feature that a customer just has to have. I mention a few products here because they are
often essential to camera installations. All the items mentioned here and previously are
still important to you even if you are concentrating on selling new digital products. The
functionality of most of the individual products mentioned is also included in the more
sophisticated devices. So you can’t really get away from them.
Video Line amplifiers: There is a limit to how far you can transmit a video signal
through coax cable (usually 800 feet using RG59 cable). A line amplifier boosts the
signal amplitude to allow as much as 5,000 feet of cable to be used.
Advantage: It can rescue you from that one camera that ended up further from the control
room than you expected.
Disadvantages: Additional cost that my not have been anticipated.
Distribution amplifiers: If you need to send the same camera video to more than one
place, your options are to loop the video through one device to the next (removing the
termination from the first device) or using a distribution amp. A single camera input is
isolated and distributed to several outputs. D/As come in a variety of sizes (one in/four
out, four in/16 out, 16 in/16out, etc). Despite the name distribution “amplifier” it is rare
to find one that actually amplifies. Don’t expect it to extend the distance rules for cable
length. A distribution system is a necessity in large installations where the same cameras
are viewed from multiple locations.
Advantages: Makes sense out of complex installations. Distribution allows central control
of all video inputs so you can manage termination issues.
Disadvantages: Additional cost and space requirements.
Coax cable: Cable sounds simple and it should be. It’s not. If you are buying cable and
connectors for the first time, you may find that the connectors don’t fit on your cable.
One cable manufacturer lists 20 different types of RG-59 cable. There are differences in
the size of center conductor, insulation, shielding and outer cover depending on a variety
of factors. Don’t expect to find cable manufacturers making connectors. Connector
manufacturers numbering systems have no relation to the cable numbers. Buying cable
and connectors from the same supplier is a good idea. If they don’t fit, you have one
person to blame. Once you find the parts that work together, hold on to that invoice for
reference the next time you order.
There are a lot of connector types available. Some are relatively easy to install on the
cable ends and some require some mechanical dexterity and expertise. It is tempting to
use the easiest methods in a pinch. Before you install a large application with inexpensive
parts, remember that most problems with CCTV systems are because of poor cable
connections. The connectors are usually the cause either immediately, or over time as
they fail one at a time.
Video Baluns: Want to avoid as much of the coax cable as you can? Video baluns are
small connectors that allow you to transmit video signals using twisted pair wire (usually
CAT5). This is a growing trend. CAT5 cable can be easier to work with than coax and it
is less expensive. The baluns come in passive and active versions depending on the wire
lengths required. The manufacturers quote distances based on a camera at one end and a
monitor on the other. DVRs don’t seem to be as forgiving as monitors and the usable
distances are considerably shorter. Color gives up first. Active baluns have gain
adjustments to optimize the video presentation. Expect one third the quoted distance.
The products range from single baluns (you need one at each end) to multi-channel rack
mounted devices. One very large installation has hundreds of video feeds using cabinets
of rack mount devices using CAT5 bundles of 26 twisted pairs.
Manufactures of other devices (cameras and DVRs) are seeing the value in CAT5 and are
installing baluns in their devices.
Advantages: Simple and easy to use in both small and large installations. Existing wire
may be available to add some cameras (phone wire will do).
Disadvantages: Adds another wrinkle to a complex installation. Some may require
adjustment for each camera to accommodate for cable distance.
Power Supplies: Many devices use an external “wall mount” power supply. These are
the plastic cubes that never seem to fit in a standard power strip. These simplify
manufacturing and development by pushing the most failure prone part of a device
outside the main unit. Regulatory testing is simplified because the main unit is considered
a low voltage device. This type of power supply is fine with a small number of units.
Things get messy when a large number of them are lying on the floor, or in the bottom of
equipment racks. Cameras typically require 12 volts DC, or 24 volts AC. “Wall wart”
power supplies are commonly used. These are convenient when there is an AC outlet
near each camera. They are not so convenient when the unit falls out of the outlet,
although a trip to the roof can be relaxing on a warm sunny day.
Multi-output power supplies in NEMA enclosures are the professional way to go for most
installations. The power supply can be mounted on the wall in the equipment room (right
next to the distribution amps). These come in a variety of configurations (12VDC,
24VAC, 4, 8, 12, 16, 32 outputs, etc). Do make sure you have sufficient current rating to
power the desired equipment and use the proper gauge wire for the distance involved.
Advantages: Clean professional looking installation. Central access for maintenance
Disadvantages: Cost, space and long wire runs.
UPS power supplies: UPS (Uninterruptible Power Supplies,) isolate equipment from the
incoming power line. They were originally very expensive. Modern versions (like most
equipment) have better features at lower prices. Most do some degree of line filtering. A
battery backup will continue power to the unit for a short time when AC line power is
interrupted. Most provide only a few minutes of continued power and sound an alarm to
let you know to correctly shut down power to the protected equipment before the battery
discharges. A UPS is very important in mission critical systems. Some will automatically
perform a proper shutdown to an attached PC (or DVR). A UPS is essential to guard
against data corruption with DVRs and network storage.
Advantages: Power “insurance” to protect against power glitches and failures.
Disadvantages: Additional cost and space requirement.
KVM Switches: KVM stands for Keyboard, Video and Mouse. It allows multiple PCs to
be operated by a single operator using one keyboard, monitor and mouse. You will need a
lot of cables to connect all the PCs to the KVM switch. Finding the right cables for your
PCs used to be a problem. Many smaller models now come with the needed cables and
most PCs have PS2 connectors for both mouse and keyboard. KVM switches range in
size from 2, 4 and 8 input desk top models to large rack mount models with 16 inputs.
You can daisy chain four (or more) units together to accommodate very large systems. I
know of at least one user with over one hundred DVRs connected to a single operator
Advantages: KVM switch can save on lots of monitors and the space needed to house
them. One operator can control all systems from one control station. DVR normal
operation is typically done from the remote software in these applications.
Disadvantages: Not user friendly when several operators want access the equipment room
for maintenance. There are lots of cables to contend with.
Monitors: Monitors come in a variety of sizes, shapes and types. Tube monitors, LCD’s/
TFT’s, VGA and projection systems are used to display video. Combinations of all are
found in large and sometimes in smaller applications. Some are better for specific
purposes. The size required often indicates the type of display required. LCDs and TFTs
look alike, LCD’s peak at about 37”. Larger than that is probably a TFT. Tube monitors
range up to about 27”. Standard televisions go a little larger if you can deal with the
quality. Very large displays are usually projection systems. The size is adjustable and can
often accommodate a 12’x9’ wall display with appropriate lighting.
LCD’s and projection systems often have multiple inputs allowing display of composite
video (analog) as well as computer video (digital). The devil is in the details when it
comes to the quality of the video produced. Nothing beats an analog monitor for fast
moving video directly from a camera.
Things to look for:
- Fast moving video looks great on a traditional analog monitor. If you’re wielding
the joystick of a matrix keyboard following a suspect around a retail store, you
will see all the action in fluid motion with no hesitation. The same keyboard and
switcher viewed on an LCD monitor may produce some irritating hesitations.
- If you line up a variety of monitors viewing the same video, you will probably
have a favorite. A different scene with different movement, detail and complexity
may look better to you on one of the other displays.
- Connecting the same monitor array to different equipment may produce different
quality results. The only way to ensure that a particular monitor will look good
with a particular piece of equipment is to test it yourself. You can either rely on
the product provider to have done the testing, or build your own experience by
viewing the products yourself. It is always a good idea to test a sample before
installing hundreds of them.
- LCD, TFT and projection monitors typically run at a variety of screen formats
(800x600, 1024x768, etc.). This does not necessarily mean that they will look
good at all the available settings. Most have a “native format” they were designed
for and then modify the display to accommodate additional formats. Some look
pretty bad when some formats are selected. This is another reason to make sure all
the selected equipment works together before quoting it and certainly before
installing it at the customer site.
- Some LCD, TFT and projection monitors look good with composite video. Some
look bad. If the application calls for more than one video type to be displayed,
better make sure it all works to the customer’s satisfaction first.
So when would you use each type of display? The rules change continuously but here is a
typical multi use application. A large control room seats eight operator stations and two
supervisor stations. Hundreds of cameras are installed controlled by a Matrix Switch and
recorded on DVRs. The size of the required display often indicates the type of monitor to
- Technicians in the DVR room use a standard VGA monitor connected to a large
KVM switch to view any DVR.
- Operators in the control room view a series of 4x4 multi-screen 12’x9’ wall
displays provided with ceiling mounted projection systems connected to
- Each operator station utilizes a 17” LCD display to view DVR remote software.
- Each operator station uses a 21” tube monitor to view the Matrix Switch cameras.
The surveillance operators are responsible for a number of locations that are displayed on
the large wall displays. When the operator sees activity in one of his cameras he calls that
camera to his matrix display and takes a closer look. He can use the LCD display to
review recorded video from that camera as needed.
Typical monitor displays:
Display type: Typical inputs: Typical size: Where used:
CCTV monitor, Composite video. Hand held to about Standard for
(tube). One or two inputs. 27”. security and
Standard Television. RF. Line input on 12” to about 32”. Inexpensive
AUX channel moderate sized
and/or RCA inputs display used in a
for accessories. variety of
VGA (Vector VGA (from 15” to 21” Computer displays.
Graphics Array) computer)
LCD (Liquid VGA, composite 15” to 37” Computer display
Crystal Diode) and/or composite.
TFT (Thin Film VGA, composite Up to 50” Computer display
Transistor - a higher and composite.
quality and size Often used to
version of LCD) display multi
Plasma (PDP) VGA, composite 37 to 61” Computer display
Often used to
Projection system VGA, composite Variable, depending Computer and video
on size adjustment presentations. Large
and distance from video displays often
the wall/display incorporating multi
screen. 12’ by 9’ is windows and or
usually obtainable. cameras.
Cameras: The image quality produced by a security system will never be better than the
original image captured by the camera. A good camera does not guarantee a good final
result. A bad camera will limit what can be done with the image passed on the other
components in the system.
Tube cameras: Tube cameras are thankfully gone from the CCTV landscape. There are a
few people hanging on to tube cameras in old installations, but they are a rare find.
CCD cameras: CCD (Charged Coupled Device) cameras are still the predominant
camera type in CCTV. They are very reliable. Many have been in service for nearly a
generation. The size of the CCD and the cameras has diminished over the years. The one
half inch diameter CCD prevailed for most of the time. One third and one quarter inch
versions have allowed for smaller housings. Most CCD cameras are camera bodies that
require a separate lens.
Lens: The lens determines the field of view presented by a camera. They come in a
variety of types. Manual lenses typically have an adjustable iris to control the amount of
light entering the camera and striking the CCD. The iris is adjusted to accommodate the
amount of ambient light available. Close the iris and you have blackness. Open it too far
and you have a white image. The trick is to leave it at just the right position to produce an
acceptable image. This is usually fine for indoor use with controlled lighting.
With variable light conditions (like outdoors) you will want to use an auto iris lens. This
lens is wired to the camera and the camera causes the lens to adjust to the light
requirements. So the rule of thumb is manual is OK indoors and auto iris is needed
Vari-focal lenses change the field of view presented. A typical vari-focal lens can adjust
from 6mm to 12mm and some can be found at a reasonable price at 5-50mm. Some
installers still use charts to try to figure out the precise lens size required for all cameras
in an installation. Most people just quote a variety of vari-focal lenses and adjust them
when they are installed.
Housings and mounts: Housings and mounts are important for protecting cameras from
the elements and from vandals. A good mount also secures the camera so it doesn’t
vibrate and shake. This is not so much an issue with indoor installations and short focal
lengths. An outdoor speed dome on a building or a pole will sway in the wind, especially
when you zoom in on a target. The movement you couldn’t notice in a wide view will be
quite obvious when zoomed in on a target. Large standard housings are sometimes used
to mount more than one camera (like a color and B/W for day/night operation).
PTZ units: PTZ (Pan, Tilt, Zoom) devices allow a camera to be moved in any direction
(up, down, left, right). Earlier units required a receiver driver box mounted nearby to
provide control and power. Modern units have this circuitry inside the device. Speed
Domes have replaced the need for many of these devices. They are still a good choice for
selected applications. They can look up as well as down. Speed Domes typically aim
Speed Domes: An early 1990’s “killer App,” the speed dome is an all in one device
containing camera, lens and PTZ control. The original units had a camera ball about the
size of a volley ball. Newer units have shrunk to baseball size. They typically rotate 360
degrees and can complete a revolution in a second or two. This device replaced most
indoor applications of PTZ units because of size, concealed movement and one piece
installation. Just look up and you will see these domes everywhere, inside and out. PTZ
units have one advantage over speed domes. They can look up.
Dome cameras: Not to be confused with speed domes, dome cameras are fixed cameras
inside a small dome shaped housing. They are easily installed in a ceiling, or on a wall.
They are very popular because of the one piece design incorporating all you need for
installation without the normal scavenger hunt required to find the lens, mounting
hardware and ancillary items needed with other camera types.
Black and white versus color cameras: B/W cameras still work better in low light
conditions. They are also less expensive than color cameras. You will find B/W cameras
in applications where lighting is an issue as well as where cost is important. Of course
color is better for overall identification while B/W may give you the edge in seeing
something in the shadows that a color camera can’t.
IR Illuminators: IR illuminating LEDs have brought night capabilities to some
inexpensive cameras whether B/W, or color. A series of IR LEDS are installed in the
camera body, or the housing to provide enough Infrared light to see images in total
darkness. The picture may not be beautiful but it can be very advantageous at a bargain
IR cameras: IR cameras are in a different (high price) category. These cameras see
outside the visible human spectrum and provide a black and white image that highlights
objects with higher heat content than their surroundings. These are true see in the dark
capable cameras. A normal camera won’t show you someone hiding in the bushes but an
IR camera will.
Day/Night cameras: Day night cameras typically switch from color in the day light to
B/W when the light diminishes. This provides better night images in black and white
provided some level of lighting is available.
IP Cameras: IP (Internet Protocol) cameras are the growing trend. Each camera is a
video server. Just connect an Ethernet cable and power and you’re in business. You don’t
even need the power connection if you’re using POE (Power Over Ethernet). Browser
based remote software will allow configuration and viewing of the camera video. IP
camera manufacturers and DVR (NVR) manufacturers are partnering to allow
compatibility between products.
Progressive Scan Cameras: Progressive scan cameras are still a mystery in traditional
CCTV applications. Most CCTV products are based on NTSC/PAL 2:1 interlaced
cameras. Progressive scan cameras can provide faster full frame images that can’t be used
to advantage with traditional DVRs. Most have a switch setting to select 2:1 operation.
Matrix Switches: A Matrix Switch is a control system for connecting an operator to a
camera view. Matrix Switches come in a variety of size capabilities from as few as 16
camera inputs with four monitors and keyboards to over a thousand camera inputs with
128 monitors and keyboards.
The purpose of a full cross point Matrix Switch is to allow any keyboard to select any
monitor and any camera while other operators can do the same. Matrix Switchers have
been around since the 1970s and some of the original units are still in service today at
high profile installations.
Large switches are designed to be rugged and reliable. Keyboards withstand considerable
misuse over time. Processor units and power supplies are often redundant systems,
switching immediately to the back up unit to avoid unexpected interruptions. Don’t think
box here. Think long rows of equipment racks filled with card cages of circuit boards.
You would find a difference if you looked inside the minds of a Matrix Switch person
and a DVR person. Matrix is a live interaction between man and machine. Schooled by
years of TV viewing, the operator sees fluid motion of the action and can immediately
select another view and follow a target through a large facility watching every move.
Using domes, he can zoom out for a wide view of the surroundings, and then zoom in on
five o’clock shadow. Anything less than real-time is not only unacceptable, it’s
unimaginable. Recording all this is sort of an afterthought to be considered once the
adrenalin of following the action has subsided.
His DVR cousin is a little more laid back, knowing that all the action is being recorded
while he attends to other tasks. The fact that the DVR isn’t recording fluid motion on all
cameras is of little consequence as he knows that only a few well timed images are
important for suspect identification. This may be attributed to the DVR guy’s casual
attention to TV and avid connection with computer video downloads.
If you wanted to record all the cameras in the early days your only option was the VCR.
A peek into a casino back room might reveal hundreds of standard VCRs recording each
camera individually. Don’t stand in the doorway at tape changing time as a crew of fast
moving individuals will be rushing through to change the tapes in all the machines. This
scenario still takes place at many casinos today (every six or eight hours). Many state
gaming commission rules require real-time, or near real-time recording of all important
cameras (read anything looking a gaming table, or slot machine). The video evidence is
held for a specified period of time (30, 60 days, or more). The main purpose here is so the
gaming commission can review the tapes at their leisure to ensure that the proper taxes
have been collected. The tape method still serves well for this purpose. This does not
prevent them from using newer methods as well.
Virtual Matrix: Many DVR manufacturers are integrating “Matrix” capabilities into
their products. Using a matrix keyboard connected to a PC running remote software
allows an operator to select cameras into individual cameos of multi-screen displays. You
could select several “windows” on the same computer screen to display a larger number
of cameras in small display windows. Some allow four monitors to be connected to the
same PC to distribute the video. You may elect to use a large display monitor to provide
more viewing real estate for multiple windows. You will need a leading edge PC to
provide the horsepower to make all this happen. Otherwise things grind to a slow crawl
when multiple windows are opened. The technology isn’t quite there yet to make this all
run smoothly. This is yet another “advanced feature” that will take some more time for
PCs to get fast enough to make this seem like a good idea to a real Matrix operator.
DVR (Digital Video Recorders): DVRs started appearing in the mid 1990’s. Sure, there
were phone line transmission systems in place years before then that recorded images to
PC hard drives, but the first DVRs with 16 cameras connected directly to the device
showed up in the US at the end of 1995. Enthusiasm for the new technology was high,
but sales were initially low because the first round of DVRs weren’t very good. Large
video file sizes and limited disk drive capabilities combined to product an expensive
product that didn’t produce as much an improvement over Multiplexers and DVRs as
The first DVR I was involved with had a standard unit with a two gigabyte drive and a
premium version with six GB (three 2GB drives). A two gig drive holds about the same
amount of recorded video as a standard VHS tape. The cost difference in the systems was
staggering. Drive sizes and processor speeds continued to double every year, or so while
DVR development continued to improve. The record duration issues soon faded away
and the ability to connect to the DVR remotely via Ethernet highlighted the leap in value
provided by digital and networked devices.
Larger disk drive sizes increased storage capacity while record speeds of DVRs
continued to rise. The initial 30ips units recorded continuously for about two hours on a
two gig drive. Today’s 480ips units will record continuously for about 32 hours on a
single 500GB drive. Multiple drives per unit and manually reduced record speeds remove
record duration as an issue. Export of video clips to DVDs reduces the need for archived
video although many high profile applications still use VCRs for long term backup.
Are DVRs getting better everyday? The fast answer is yes. There are trade offs
involved. At first glance, faster record speeds are obviously better. A closer look reveals
that faster record speeds result in shorter record durations because the available drive
space is filled more rapidly. There is also the question of record quality. The higher the
quality (lower compression) the larger the file sizes and shorter record durations result.
CIF size is another variable. Most DVRs operated in 2CIF (field mode) until recently.
4CIF (using both fields to generate frames) requires twice the storage space for recording
and slows the record rate in most units.
With so many combinations of hardware and software to compare, the only way to tell
which result is best is to see them side by side. Each manufacturer has a tendency to
quote the quality measurements and numbers that make their product sound best. Your
“perceived image quality” is the best answer for you. Once you have made that decision
you will have to contend with the realities of cost, record duration and a number of other
issues before making the best business decision for purchase of products.
NVR (Network Video Recorder): NVRs are network based digital video recorders. The
video from IP cameras can be recorded anywhere through the Internet. The idea of an
NVR is to go end to end digital. Use an IP camera to serve video into the network via
Ethernet. A browser based connection can be made with the camera from anywhere. You
can also record the video anywhere through the Internet.
The flaw in this scenario is the preponderance of old technology already in place. One
option is to convert traditional analog cameras to digital using a video server that will
convert the NTSC/PAL camera format to TCP/IP. This provides a partial solution with
some interesting challenges to overcome.
It would be nice as a sales type to concentrate efforts on all new installations to avoid the
pitfalls of existing infrastructure. This is sometimes possible with new locations. Even a
new location with an existing business may require the same type of equipment to be
installed as in their other locations. Regardless of the new, the customer typically wants
compatibility with the old.
Is the latest and greatest always the best?
The natural tendency is to think that new development in technology is a continuous
chain of improvements. This is not necessarily true. When you successfully apply a new
approach to solving an old problem you often find that by the time the product is ready
for release the basic premise of improvement is achieved and something dramatic is
improved. You may also find that the original products had some convenient and widely
used features that were either forgotten or unable to be addressed in the new design. Sales
objections will immediately concentrate on these issues. After a period of time, the
“needed” additional features will find their way into the newer products, or fade to the
folklore of times past.
Cases in point: Tube cameras had really good video quality (compared to the initial CCD
cameras) and really short operating lives. So the big objection to the initial CCD cameras
was “low quality images.” Since tube cameras were pretty much unusable after a year or
two in operation and many of the original CCD cameras are still in use twenty years later,
the objections soon faded. Incremental improvements in CCD cameras made them what
they are today. Nobody is saying “Gee, I wish I could find some of those old tube
cameras to install in a big casino deal.”
Each new device is a trade off. They have advantages and disadvantages. Many devices
considered bonanza products today started out as a disappointment. There is no more
classic example than the DVR. Digital Video Recorders were a marriage of technologies.
A product driven by the security industry, a hand full of pioneering CCTV manufacturers
invested in developing a DVR based on the standard Personal Computer. PC capabilities
were improving at a rapid pace. This provided a double blessing for development of
security devices. Each security company could develop their software and a few
proprietary hardware components, while the PC industry moved on. DVR engineers
improved their own contributions while PC processor speeds and disk drive capacities
doubled every six months to a year.
The first DVRs showed up in the US about the end of 1995. They were a bit premature as
the anticipated PC drive capacities were a little behind schedule. The first DVR I was
involved with had a standard model with a two gigabyte storage drive and a premium
model with six GB (three 2GB). Since the video storage capacity of a 2GB hard drive is
approximately equal to a T120 VHS tape, the initial DVRs were no more practical than a
multiplexer coupled with a time-lapse VCR. The price difference was staggering and
there was no way to archive the data when the drive filled. The major objection was, “But
I just press a button on my VCR and it hands me an archive copy.”
You might think that such an expensive new product would harm the vision of this new
technology. Quite the contrary, people were enamored with the prospect of “Digital
Recording.” Complaints and complements ran side by side for a while, but eventually the
tide turned toward the digital world. DAT tapes soon were incorporated as archive
devices (difficult, complex, yet possible). Drive sizes increased with no help from the
security developers. Doubling the drive size doubled the record duration and further
complicated archiving to tape. Big drives and small tapes made for a labor intensive
backup process. Eventually drive capacity reached the size where most users could retain
data longer than they needed it. Archiving to DAT pretty much disappeared in video
applications. RAID systems are often used in the most critical applications to address safe
Probably the single biggest eye opener for DVRs is the Internet. Based on PC and
network technology, remote software allowed operators to view live and recorded video
from anywhere. (Take that VCR!) Many CCTV manufacturers, unaware of the value add
of software, provided the remote viewing software free of charge. They felt they had to
because everyone else was giving it away. Even those who do charge for their full
featured remote software provide a free browser version with limited features.
Notable Transitions in CCTV:
What How When
CCD cameras replace tube Fast transition. CCD versions were more Late 1980s
cameras. reliable and tubes wore out quickly. This
is a true technology takeover.
Multiplexers are born. Quickly adapted into CCTV applications. 1993
Disadvantage of less than real-time
updates was overshadowed by the ability
to view and record 16 cameras through a
single box. A “killer app.”
Digital Video Recorders A good idea at first glance, but the 1995 - ?
replace Multiplexers. practicalities and lower cost of the
Mux/VCR combo live on. DVRs had a
slow start due to storage issues. DVRs are
now the top dog on the high end and lower
DVR prices are edging out multiplexers in
all but the low end. DVRs are easily the
slowest implemented “killer app.”
Speed Domes overtake The Speed Dome all in one replacement 1992 - ?
traditional PTZ products. for the traditional PTZ assembly was an
immediate success in most applications.
PTZ units still have their place in selected
applications (they can look up as well as
down). Still, Speed domes are another
LCD monitors overtake Smaller size and capable of composite and 2000 - ?
tube monitors VGA display are big advantages. Higher
cost and compatibility (display update and
quality) issues will keep the traditional
monitors around for some time.
NVRs replacing DVRs “All digital” solutions are looking more 2005 - ?
attractive. There is much traditional CCTV
product in place and in production that
will keep NVRs in the hybrid mode for
IP cameras replacing CCD Traditional cameras still have a strong 2005 - ?
cameras. advantage in video quality and sales
familiarity. A video server in every camera
makes the IP camera the one to bet on in
the long term.
Progressive scan cameras The CCTV industry is built on the ???
overtaking 2:1 interlace NTSC/PAL standards (interlaced fields).
cameras. Much has to change in all areas before
progressive scan cameras can be used to
advantage. Most are used with the selector
switch in the 2:1 position.
Some technology changes happen quickly. Others take much longer because they are
partial solutions. Traditional features are still needed and users of the products need a
solution, not just a new technology.
So what happens to the older technology products? From the sales side, it would be great
if all the old products were like tube cameras that became obsolete almost immediately.
Once a tube camera expired, it was replaced with a CCD version. Replacement was
mandatory and there was no down side to replacing with the newer technology. A CCD
camera and a multiplexer installed fifteen years ago are probably still working today. In
order to replace this with newer products you have to discard the older versions. They are
as good as they ever were. The new technology has to show a significant improvement,
or wait for the older solutions to fail before replacement.
The once high margins obtained with the older technology products have long since
diminished. The original manufactures may have gotten out of the business and
abandoned the market to newcomers who are willing to work with lower margins. The
newcomers may even have copied the original designs. Conventional wisdom is that
there is no money in the older products. Another thought on this is that the older
technology with lower cost is more attractive to a customer base that was priced out of
the market the first time around. This expanded low end market is expanding the overall
CCTV market. One thing is for sure, the older products won’t see a lot of development
effort thrown their way. Development dollars will go to the new products.
Why bother using alarms to increase record rates. Why not
record all cameras as fast a possible all the time?
There are several things to know before understanding the answer to this question.
- Record speeds were not always as fast as they are with today’s units. Alarms and
other indicators were used to increase the record rate of alarmed (or all) cameras
for the duration of the alarm condition.
- People are used to altering record speeds with alarm conditions and typically want
to see these features included for other reasons beyond update speed.
- Now that record speeds are generally faster (with 30ips from each camera
achievable) and with 4CIF recording, people noticed that their drive space
couldn’t retain the duration required for their application.
In the beginning, DVR (and multiplexer) record speeds were slow. Connect 16 cameras
at 30ips total and it will take over two seconds to see a new update of each camera. You
might even slow this rate down to allow your record duration to match the total record
time needed for the application. So what you were getting is an occasional update from
each camera. If something important happened on one camera, the demand was to
increase the image update to as close to real-time as possible while the important event
was occurring. Typical solutions included temporarily increasing the record speed of all
cameras and/or interleaving the active cameras at a faster sequence. Some units allow
exclusive recording of the alarmed camera. Of course you are not recording the other
cameras in this mode.
Whichever method employed, the additional updates of one camera come at the expense
of the others. The good news is that you get more updates of the camera you want and
bad news includes fewer recorded images of the other cameras and shorter overall record
duration due to increased storage demand.
Alarms are important for many reasons other than increasing the record rate. Current
version DVRs have an impressive array of features tied to alarms in addition to speed
changes. For instance: Alarms generate an alarm list for easy review, forward alarm
notification to remote software users, send emails to selected addresses and trigger
positioning of other dome cameras to better watch the action. So alarms are here to stay
and users are asking for additional feature to be added to products.
Many of today’s products can record all cameras in real-time, or close to it. Image quality
improvements have increased the average file sizes of images. Each new feature seems to
take a toll on storage requirements. Once past the euphoria of knowing how fast and how
clearly images can be recorded, the realities of the wallet begin to sink in. Maximum
speeds are still scaled back to increase record duration and alarms are still used to make
changes as needed.
If the unit can record as long as needed at full speed, that’s the way to go. Even then,
alarms will still be valuable for sending local and remote alerts and optimizing camera
Addendum #1: VCR101 and VCR102 are old documents that will provide
some insight into the types of VCRs used in security and the applications for each.
VCR is an acronym for Video Cassette Recorder. All VCRs are based on the one you have at
home. Millions of VCRs are produced every year for home use. This is a convenient way to view
and record movies, or, anything else shown on TV. Security is a specialty (vertical) market for
the major VCR manufacturers. Compared to the home market, a relatively small number of time-
lapse VCRs are sold.
The basic concept: In the VCR, video images are recorded on magnetic media, the video tape,
which consists of a Mylar substrate material with a metal oxide coating. A magnetic recording
head, in the VCR mechanism, rearranges the metal oxide “magnets” to form a pattern which
represents a picture. Images are recorded, one after another, for as long as tape is available.
Types of video cassettes: VCR tapes are identified by a letter/number designation. T120, for
instance means, T for time and 120 for 120 minutes of record time. This two hour tape records for
two hours in a standard recorder, using the standard recording format. A T160 tape, would then
last for 160 minutes. The standard recording method produces the highest quality images possible
from that VCR. Overall recorder quality will vary from model to model depending on the quality
of the design. Like anything else, you get what you pay for.
What do you do if what you want to record is more than 120 minutes? Most home VCRs have
other record modes which use a thinner head, allowing more images to be recorded on the same
length of tape. The long play (LP) mode will record for four hours on T120 tape. The extended
play (EP) mode will record for six hours on T120 tape. Why don’t we just use the extended play
mode all the time and get the longer record time? The smaller heads produce less video
information and the result is a lower quality picture. The ratio between SP, LP and EP is 1, 2, 3.
EP records three times as long as SP, so, the T120 tape lasts for six hours. A T160 tape will last
for 8 hours. Is the picture quality a reverse three to one ratio with EP being one third as good as
SP? This is subjective and you will have to judge for yourself. There is a considerable quality
difference however the longer record time has a big advantage.
How many images are actually recorded? The NTSC (National Television Standards Committee,)
video standard is 60 fields per second. From a single video source, 30 frames result from display
of consecutive odd and even fields (2:1 interlace).
Images per second: Total Images T120: Total Images T160:
SP (2 hr. mode) 60 432,000 (2hr) 576,000 (2.6hr)
LP (4 hr. mode) 60 864,000 (4hr) 1,152,000 (5.3hr)
EP (6 hr. mode) 60 1,296,000 (6hr) 1,728,000 (8hr)
When a recorded tape is played back in a VCR, the device will automatically switch to the
appropriate playback mode. The same head type must be used for record and playback. This is
sometimes an issue when tapes are recorded on one VCR and played back on another.
What have we learned so far?
1. Cassette tapes come in different lengths, which affect the length of record time.
2. VCRs can record in different modes, which affect the length of record time and the picture
Commandments of understanding VCRs:
I. All types of VCRs are based on the home VCR.
II. Tradeoffs are made between record duration and image quality.
III. Tradeoffs are made between record duration and image update rate.
IV. There are four general types of VCRs.
1. Home VCR.
2. Time-lapse VCR.
3. 24 hour “real-time” VCR.
4. High density VCR.
Commercial VCR (home style): This is the VCR you have at home. It is designed to play and
record movies in conjunction with a television. It can range in complexity from record only with
no additional functions to a variety of features including pause/still, single step and multiple event
recording. They all have one thing in common, they are to difficult for humans to figure out,
unless you are a VCR savant. There are typically two, or, three record speeds (they are called
speeds, even though they are actually lengths of time.) SP is standard play (2 hour.) LP is long
play (4 hour.) EP is extended play (6 hour.) These times are relavant with T120 tape (T = time,
120 = 120 minutes.) The longer record settings use thinner record heads so that more images can
be recorded on the same length of tape. Quality suffers as record time increases because the
smaller heads provide less video information.
Advantage: Least expensive VCR option. Always records at a “real-time” rate.
Disadvantage: Limited record time (2hrs - 6hrs with T120 tape. Up to 8hrs with T160 tape
Where used: Every home. Any low end application. Used as an additional recorder in some
installations. Sometimes used to record multiplexer playback from the monitor loop out connector
so that a tape can be played back in another location with no multiplexer.
Time-lapse VCR: Time-lapse VCRs typically have several record speeds (again, they are
actually elapsed times.) In 2 hour mode, they record and play back just like the home VCR. Six
hour mode is like EP. Longer time settings are time-lapse, which means that they do not record
all the available images. They skip images so that the capacity of the tape can accommodate a
longer period of time. Want the tape to last longer? Just use a longer time-lapse mode. The
individual images are just as good, however, they are further apart (in time).
Time-lapse VCRs were designed with the security industry in mind. Even though the price is
much higher than a standard VCR, the benefits for long term recording make this an economical
device for solving problems typically encountered in security. System operation requires that the
tape is changed at a routine interval. The attendant can change the tape at the same time every
day, during the normal work week and then switch to a longer time record mode to accommodate
Advantage: A single VCR tape can last for a specified length of time (typically; 2, 6, 12, 24, 48,
72, 168, 480, 960 hours) depending on the VCR selected. Provides good quality pictures because
the SP head is used for all time settings with the exception of the 6 hour mode, which uses the EP
Disadvantage: Fewer images are recorded as time-lapse time increases. You run the risk of
missing the detailed action you want.
Where used: Good fit in any application where a long time span is required. The ability to switch
from 24 hour mode and 72 hour mode, makes this a natural for Monday through Friday
businesses. Set it to 24 hours Monday through Thursday and change the tape every morning.
Change it to 72 hours on Friday morning, allowing the tape to last until returning after the
24 Hour “Real-time” VCR: This is a compromise between a real-time and a time-lapse VCR. It
will record at one third the realtime rate for a period of 24 hours (if you use T160 tape.) There are
trade-offs to endure. T160 tape is thinner (to fit on the same reels as T120,) and it will stretch
(doesn’t have to stretch far. The head is only 15 microns wide). You need to replace it more often
than T120 tape. A thinner record head is used. This allows more images to be recorded in the
same space. The resolution of the image is not a good as with the normal width head.
The 24 hour “real-time” recorder was designed with multiplexers in mind. At the time it was
released, there were only two players in the multiplexer business (Robot and Dedicated Micros.)
At the time, the maximum switching rate of both entries was 20 images per second. The recorder
was designed to record 20 images per second (every third field,) taking advantage of the
multiplexer maximum switch rate and continuing at that speed for a 24 hour period using T160
Advantage: Records for 24 hours with T160 tape. Records at a rate of 20 images per second
(NTSC.) Good comprimise between update rate, elapsed time of recording and usable image
Disadvantage: Not quite real-time. No longer record time to accommodate weekends. Lower
quality picture than produced by standard time-lapse VCRs. Many current multiplexers have a
maximum switch rate of 30, or per second. These multiplexers must be set to the slower 20
update rate to work properly with this recorder.
Where used: This is the darling of the retail market. Retail stores are typically open seven days a
week. There is always someone there to change the tape. The higher update rate and 24 hour
cycle time make this a natural for daily operations.
High Density VCR: High density recorders record at three times the rate of the traditional time-
lapse recorder. This is done by using the EP head instead of the SP head used with traditional
time-lapse. Although there is no standard for update rate with time-lapse VCRs, many currently
available devices record 5 images per second in 24 hour mode. The high density entries record,
15 images, with a lower picture quality, using the EP head. This three to one ratio holds true for
all time lapse modes.
Advantages: Three times the update rate of traditional time-lapse VCRs. Longer time lapse modes
available to accommodate weekends and longer time periods.
Disadvantages: Lower image quality than traditional time-lapse VCRs due to the use of EP head.
Where used: Can be used anywhere time-lapse recorders are appropriate. Good trade off between
24 hour real-time and time-lapse recorders. Records for 24 hours at 75% the update rate of real-
time recorders and still has longer time lapse modes available for weekends.
Comparing 24 hour modes:
Images per second: Images per hour: Images per 24 hours:
Time-Lapse VCR: 5 18,000 432,000 576,000 (32hr)
High Density VCR: 15 54,000 1,296,000 1,728,000(32hr)
24 Hour Real-Time: 20 72,000 1,318,500 (18hr) 1,728,000 (24hr)
Multi-mode VCRs: Wouldn’t you know that someone would try to cram all the functionality of
the four types of VCRs into a single unit? And if you are willing to pay the price, you will have
all these record modes at your finger tips. You could record in 24 hour “real-time” mode Monday
through Thursday, then switch to high density time-lapse for the weekend. These recorders could
be used as playback stations for tapes recorded on a variety of VCRs.
Advantages: All functionality in a single box (can be used to review tapes recorded on any of the
other VCR types). You get a feeling of power, knowing that you can do it all. They’re great for
demos. With prerecorded tapes, you can show the difference in quality produced with different
Disadvantages: Highest price. You could probably buy a 24 hour real-time and a time-lapse VCR
for the same price. They can be confusing to operate.
Where used: This can fit into any application due to the “all in one” versatility of the unit. The
price scares away the low end customer. The complexity may scare those with specific, simple
needs. As price comes down on these units, they may become the “Universal VCR.”
VCR 101 described the different types of VCRs. This document discusses typical applications for
these VCRs. VCR applications vary, just like with any other piece of equipment, based on the
needs of the user. The ideal situation would be to record at the maximum rate, all the time, and
never have to change a tape. Since this appears to be impossible, users make trade offs between
image update rate and record time. With a little imagination and an appropriate budget, virtually
all applications can be accommodated. Could you record at maximum speed and never change a
tape? If you never wanted to see anything more than 2 hours old, you could set the recorder to
rewind and record at end of tape. The tape continually records over and over, each two hours, or
six hours (or eight hours with T160 tape, or 24 hours in a 24 hour “real-time” recorder).
How can a VCR fit the needs of a variety of users? The paragraph above indicates how you can
keep recording over and over on the same tape, however, most applications require archiving of
information. Typical applications are as follows:
1. Record everything all the time, with as fast an update rate as possible.
2. Record everything all the time. As long as I have a few images of each camera each minute,
3. Record everything, all the time. Time-lapse mode is OK for most situations; however, I need
the fastest possible update rate when certain events happen.
4. I don’t want to wade through unneeded recorded information. I just want to record when
1. Record everything all the time with as fast an update rate as possible: If this is the goal
and you are ready and willing to change tapes as often as required, you can use the commercial
(home) VCR in the two hour mode for the highest quality picture, or, six hour mode (or 8 hour
with T160 tape,) if the lower quality picture is acceptable. Many users modify their record rate
requirement when they realize how often they must change a tape. The 24 hour “real-time”
recorder starts looking very attractive. Want to record at that “real-time” rate over the weekend?
You could use three recorders, using the tape end output of one to trigger recording on the next.
2. Record everything all the time/slow update rate is OK: Many applications do not require
motion video, or, anything close to it. Just knowing if anyone was in the room or, around the
building is all that the application requires. An appropriate time-lapse setting and no alarm inputs
will provide the update speed required to fulfill this requirement. The traditional time-lapse
recorder is the answer for this application.
3. Record all in time-lapse, record faster on alarm: This is similar to number two for normal
operation, however, when an event is taking place in certain areas, the maximum update rate is
required to see as much activity as possible. The traditional time-lapse VCR is appropriate for this
situation. It is set to the appropriate hours setting for normal operation and triggered by an alarm
input to the two hour mode when a critical event takes place.
4. Event Recording: Any VCR which can be triggered into the record mode by an external alarm
may be used in an event record application. The VCR records nothing in normal operation. When
an alarm is encountered, the recorder will spring into action, capturing the event for later review.
In this way, only alarm related images are recorded on the tape. This is the ideal result; however,
this mode is never perfect.
This requires some explaining. What people think of as an “event recorder” is a stripped down
version of a time-lapse recorder. Many current time-lapse recorders have an event record mode,
which probably was the evolutionary push that erased the event recorder from the landscape.
In the standard time-lapse transition, the alarm input changes the recorder from a time-lapse mode
to a faster, usually real-time, mode. The recorder could be sitting idle, not recording anything,
then triggered to the fast record mode by the alarm. There is a flaw in this operation as the
recorder takes several seconds to reach proper operating speed. It takes about a second to engage
the heads and another three, or, four seconds to reach full speed and provide proper color. You
will notice this yourself with any recorder. The initial picture produced at start up is black and
white, with the color showing up a few seconds later. You may see a vortex of color in the center
of the screen as the tape is gaining speed. If the application will tolerate this delay, almost any
VCR will fit the bill. Often this is not the case. The first few seconds of the event may be the
If the heads are kept engaged all the time, the start up time after an alarm trigger is almost
instantaneous. This is, of course, preferable to the delay mentioned before. The problem is that
the engaged head causes heat which would damage the tape after a period of time. Because of
this, the tape must be moved to prevent damage. Although the movement takes place at
infrequent increments, there are still unwanted images on the tape. Time-lapse recorders with an
event record mode (like the RV2496) will record a field each minute or so. (The RV2496 records
two fields each minute in L01 mode, two in three minutes in L03 mode.) In the L01 mode, with
no alarms present, the tape will fill up in 150 days. A TLVCR in 960 hour mode will fill the tape
in 40 days. The defacto event record mode is to set the TLVCR to its longest record mode and
trigger to two hour mode on alarm. This allows alarm recording without recording much of
anything under normal circumstances.
Application: You can get a tape of only alarm images using a multiplexer. Never discourage
anyone from recording all images all the time from the designated VCR record output of the
multiplexer. Using a second VCR, you can record from the loop out of the call monitor. The VCR
sits idle until triggered by the multiplexer alarm output. The alarmed camera switches to the call
monitor. Viola, the VCR records the alarmed camera. You can set the record duration in the
multiplexer menu. Multiple alarms sequence to the call monitor and the VCR while standard
recording continues on the normal VCR output.
Application: Are you worried about someone triggering a continuous alarm which will run the
VCR out of tape in less than two hours, rather than the 24 hour time-lapse duration? You can
have the tape end alarm of the VCR trigger a second VCR into record. Another approach is to use
a 24 hour “real-time” recorder as the primary VCR. This VCR is already recording at top speed.
General applications guidelines:
24 hour “real-time” recorder: If someone is available on a daily basis to change the tape and
you can get by with the lower quality of image, this is the recorder for you. This is even more
attractive when recording a multiplexer output as image updates are already spaced out by the
Time-Lapse VCR: This recorder typically provides better quality images. It is a natural where
longer record times are required to accommodate weekends. The delay between images is more
palatable with single source inputs (single camera, quad, monitor outputs.)
Combination VCRs: These provide the best of both worlds, allowing ‘real-time” and time-lapse
in the same device.
Addendum #2: Pixels, record speed and CIF: This document, Pixels,
Record Speeds and CIF, provides some interesting input on the dark side of some recent
features. Be careful with how you use this information. Although it is factually true (at
least until a series of product advances are made,) it can be politically incorrect. No one
wants to hear that a smaller number can be better than a larger one.
Pixels and Record Speed and CIF (Oh my!):
There is a lot of misinformation out there on the subjects of pixel count, CIF sizes and
record speeds. This paper is an attempt to provide some of the answers.
Horizontal Pixel Count: The number of pixels per horizontal line varies from
manufacturer to manufacturer. You will hear numbers like 640 (us,) 704 and 720. Logic
dictates that the bigger numbers are better, right? I submit that the quality is the same.
The pixel sample rate is controlled by hardware. 720 are the maximum number of pixels
that can be sampled on a horizontal line with hardware typically used in multi-channel
DVRs. The 720 pixels start at the beginning of the line and end at the other end. Since the
ends of the line are less stable than the middle, the first eight pixels and the last eight
pixels of each line are black.
Since the black pixels are irrelevant, some manufacturers don’t use them, claiming only
the remaining 704 usable pixels (720 minus 16). With years of experience doing this and
extending the theory that the ends of the line are less stable, some manufacturers ignore
the first forty pixels and the last forty pixels on each line, using the 640 pixels in the
centralized stable area.
There are advantages to the 640 per line approach:
- When you think about it, the area covered by the 640 samples is the very same
area covered by the center 640 pixels in the 704 and 720 formats.
- The pixel count and quality in that area is the same.
- Since there are fewer pixels, the storage requirement is smaller.
- The 4x4 display using 640 pixels allows all individual cameos to be the same size.
Larger formats often run the image off the ends of the viewing area making the
cameos at the edge appear smaller than those in the middle.
Vertical Pixel Count: The vertical pixel count is fixed based on the video standard used.
Each field has 240 scan lines available in NTSC. Field based pixel formats always end in
240 (like 640x240, 720x240). Frame based formats use both the odd and even interlaced
fields from the same camera. Frame based formats will end in 480 in NTSC (like
640x480, 720x480). PAL single field will end in 288 and frame will end in 576.
Pixel format review: Pixel sample rates are the same, although some manufacturers
sample the entire line, some don’t. Full size images require all the pixels to display. If
you capture one field, you have to artificially generate the second field to view a full size
image. If you capture frames (two consecutive interlaced fields) you will have all the
original information for a full image (at a higher quality), but you will have a larger file
to record (with shorter record duration) and fast moving objects will probably be
distorted due to the time difference between field captures (1/60th of a second in NTSC).
Also with frames, you have to wait to capture two fields, so the record rate is slower.
CIF Formats: CIF (Common Intermediate Format) refers to the size of an image.
- CIF (or 1CIF) is a quad size image (one quarter the size of a full size image). In
some applications, the image is viewed at this size. Some applications expand CIF
images to full size by artificially generating every other pixel both horizontally
and vertically. The result is lower in perceived quality than a recorded full image.
Pluses: Small recorded file size, longer record duration and fastest transfer speed.
Minuses: Low image quality when expanded to full screen. Less detail than a full
- 2CIF is a full width, single field image. 2CIF images are usually recorded in this
format. The second field is internally generated for viewing by artificially
generating every other vertical pixel. The result is better than a one CIF expanded
image, not as good as a recorded full image.
Pluses: Good compromise between smaller and larger formats allowing good
quality with reasonable record storage needs and record durations.
Minuses: Not the fastest, not the highest quality. A tradeoff position.
- 4CIF is a full size (both fields from the same camera) image. The quality is as
good as it gets. At least for the still portions of the image.
Pluses: Highest quality image.
Minuses: Distortion of fast moving objects in the image. Won’t be appropriate for
cameras with fast movement. Largest file size. Slowest record rate.
- Quad CIF is a 1/16th size image. This is equivalent to a single pane in a 4x4
image. Not often used due to the lack of detail.
Pluses: Really small image file sizes, but not much to look at. OK for information
if identification is not an issue. Faster transfer speed.
Minuses: Very low quality image.
Typical Pixel Counts for CIF Sizes:
4CIF 2CIF 1CIF Quad-CIF
Full image Full width, Quad size 1/16th size
NTSC 720x480 720x240 360x240 180x120
704x480 704x240 352x240 176x120
640x480 640x240 320x240 160x120
PAL 720x576 720x288 360x288 180x144
704x576 704x288 352x288 176x144
640x576 640x288 320x288 160x144
What CIF size is best? As is often the case, the answer is that it depends. Each method
has advantages and disadvantages. If you capture and record a 1CIF image you have the
advantage of smaller files, longer record durations and smaller size files to transmit to
remote software. The disadvantage is that you have less real information to work with. To
display a 1CIF image as full screen you must internally generate additional pixels in both
directions (every other pixel horizontally and vertically). So the expanded quality is not
going to be as good as a captured 4CIF image displayed in the same area. If you capture a
2CIF image there is less information generated for display (vertical pixels only for full
screen display). 4CIF images are already full images.
A 4CIF image sounds best if the highest quality image is your major concern. Further
review shows that there are drawbacks to frame recording. You have very large file sizes
taking a large amount of disk storage space, reducing record duration and requiring
considerable bandwidth to transfer images to remote locations. The drawback that you
must see to appreciate is the separation of moving objects in the image. Since you are
capturing two consecutive images from the same camera that are separated in time by
1/60th of a second, a fast moving object will show tearing in the image. To visualize this,
imagine that you painted a delivery truck on a closed set of mini-blinds. The slats of the
blinds mimic the interlaced fields of the image. Now move every other slat three inches
to the right. The resultant distorted image is what you might see with 4CIF image
capture. This distortion might show up in the live display as well, depending on how the
live images are processed. You might be able to filter out some of the moving object
distortion, or use a “deinterlacer” (separate and realign the fields), but I haven’t seen
good results yet. Most units that I’ve seen have considerable tearing, especially with a
moving dome. The deinterlacer route stops the tearing, but it discards one of field of
information in the moving area of the image. So you’re back to the 2CIF answer in the
most crucial area of the image.
2CIF is a good compromise between 1CIF and 4CIF. (This is something we learned the
hard way from a previous product that used 4CIF.) Image quality, file size, record
duration and bandwidth requirements are a good tradeoff providing the most workable
solution for CCTV applications.
On Intellex our ACC compression uses 2CIF, although it will work with any format. In
fact, Intellex IP uses ACC in all formats. This proprietary compression scheme greatly
reduces file size by recording only the moving portions of images and employing
sophisticated noise-filtering algorithms. The result is a compression designed for CCTV
providing a smaller average file size with high image quality.
CIF Size: Image Quality: File Size: Record Bandwidth Overall:
1CIF Lowest Smallest Longest Least Best if image
quality is not a
2CIF Middle Middle Middle Middle Best overall.
4CIF Highest Largest Shortest Most Best quality with
Record Speeds: Fast record speeds are now commonplace. Numbers like 480 by 480
seem to roll off the tongue. Just a short time ago, numbers this size referred to the number
of pixels in an image. Now they refer to live update speed and maximum record speed as
well, leading to the resultant confusion. A true 480x480 DVR would produce live update
rates of 480ips and total record rates of 480ips. The result is a real-time 16-channel DVR.
Live update speeds: For a marketer touting a 480x480 DVR, the first number refers to
the total number of live camera updates per second. If you are recording single fields
from a camera, the maximum updates you could have from that camera is 30ips (NTSC,
25ips PAL). The 480-number refers to a 4x4 live display on a 16-channel DVR. Each
individual cameo in the 4x4 display is updating at a rate of 30ips. If the DVR has fewer
than 16-channels, you could only have a maximum of 30ips per camera. So a 9-channel
maximum is 270ips. So make sure you are doing an “apples-to-apples” comparison when
Record speeds: For the same 480x480 DVR mentioned above the second 480 refers to
the maximum number of images that can be recorded each second. For field based
recording the maximum is 30ips per camera. So this 480 refers to 30-recorded images per
second for each of 16-channels.
There are a few units that can actually display and record at these speeds. This is done
using a 1CIF (320x240) image. When 2CIF and 4CIF images are processed the speeds
are reduced. The best competitive units are getting better all the time. Today’s numbers
look like this:
- 1CIF record max is 30ips per camera.
- 2CIF record max is 7 – 15ips per camera.
- 4CIF record max is 5 – 7.5ips per camera.
One unit in particular will allow you to configure the record rate per camera (1-30ips at
1CIF, 7ips at 2CIF and 5ips at 4CIF). Most are either/or for all cameras. Some allow up
to four cameras at 4CIF and all others at 1CIF. Some say they do things that don’t really
happen. Many say 480 but actually do less with inconsistent updates that are not evenly
spaced. Rest assured that all are getting better. Whatever lies are told today seem to come
true the following year.
Even the best I’ve seen won’t play back a 4x4 multi-screen in real time. Individual
cameras record and play at 30ips, but multi-screen takes a few seconds to playback one
second’s worth of video. All the images are there when you single step through them, but
the multi-screen display doesn’t have the processing horsepower to keep current. Wait till
This is the story as of today. The future will provide rapid improvements.
Addendum #3: “Picture Quality” is a very old document that can shed
some light on the different quality measurements mentioned by various manufacturers.
Picture Quality: A Pixel is worth a thousand words…
And it could take a thousand words to explain the various terms used to describe the
quality of a CCTV image. There is a lot of confusion out there. You hear terms like; Scan
Lines, TV Lines, Lines of Resolution, Digital Images, Analog Images and Pixels. What
does it all mean?
CCTV is an industry in need of standards. Manufacturers of different equipment used in
the same CCTV system often use differing terms to describe the quality of the image they
produce. The “box processing” people, Multiplexers and DVRs, stick to Pixels, as do
manufacturers of computer equipment. VCR and Monitor manufacturers use Lines of
Resolution. Camera manufacturers use both Pixels and Lines of Resolution.
One standard that we do have in the US is NTSC (National Television Standards
Committee). This is the agreed upon configuration of transmitted video used in television
broadcast. This standard (minus the carrier frequencies and additional data used in
broadcast TV,) is the way that all video in coax cable is formatted. This is often referred
to as composite video, or, base band video. It contains video, horizontal and vertical
synchronization pulses and other things necessary to give CCTV manufacturers a starting
point from which to begin design of their contributions to the CCTV industry. This
standard has been around and has remained relatively unchanged since the big
depression, long before the advent of the digital electronics age. Some of today’s
confusion stems from the different measurements used in digital electronics.
Before digital electronics, manufacturers of cameras, monitors and VCRs, measured the
end quality of their products by viewing a test pattern. The test pattern is a series of
converging lines with a circle in the center. Smaller patterns of black and white lines are
scattered about the image. All the line sets are calibrated to a known number. If a line set
were extended across three quarters of the width of the screen, it would take the indicated
number of lines to fill that area of the picture (200, 400, etc.). Why three quarters and not
the full width of the screen? The ratio of the standard TV image is three high to four wide
(a rectangle). By using three fourths of the width, lines of resolution could be compared
horizontally and vertically. If you are old enough, or, if you find a TV station that shuts
down for some period of the day, you will have seen a similar test pattern on the TV
screen. It is usually accompanied by an audible tone. (It used to wake up us old timers
when the TV stations shut down in the wee hours of the morning.)
To do the test, you looked at the converging sets of lines and estimate where on the
pattern the formerly black and white lines turn into a mass of gray. Is this extremely
accurate? Hardly: However, you eventually reach a consensus among technical and
marketing people and a number of “Lines of Resolution” is placed on the spec sheet.
“Lines of Resolution” is an after the fact visual appraisal of the video picture based on the
ability to distinguish between alternating black and white lines as they become smaller
and closer together.
If you have grasped this concept, then you already know what “TV Lines” are. They are
the same as lines of resolution. The terms are used interchangeably. TV Lines have
nothing to do with Scan Lines.
“Scan Lines” are the individual electron beam tracings on a television, or, monitor. There
are a total of 525 lines in the NTSC format consisting of odd and even fields at a rate of
60 fields per second (30 frames in a 2:1 interlaced format).
Up until now, we have been referring to “analog” pictures. By that I mean pictures
produced in the traditional television format. Tube cameras, VCRs and TV monitors all
did it this way. Contemporary CCD cameras and computer monitors use digital pixels.
VCR technology and TV monitors are still analog.
Enter digital electronics into the picture…
There is only so much you can do with an analog picture. Would you like to see two
pictures on the same monitor? You can use a switcher to alternate two images, one at a
time. You can use an analog splitter to overlay one image on another. This produces
either two tall thin images, or, two short wide images. In order to get four symmetrical
images on one monitor we need to perform some digital wizardry.
With digital electronics, we sample a scan line some number of times. We continue to
sample additional scan lines. This provides us with a matrix of the make-up of the
original picture in digital format. We can then discard some of the pixels both
horizontally and vertically, perform some color changing magic to compensate for lost
pixels, convert the image back into NTSC format and then place four, nine, or, sixteen
images on the same monitor. Do you lose some picture quality with each transition from
one form to another? Yes you do. These are basics of how resizing is done. The
particulars of how this is done make all the difference in the end result. So, what is a
A “pixel” is a picture element. This is the smallest portion of a digitized picture which
can be changed. If you have ever taken a close look at one of those spectacular mosaic
tile murals in a nice Mexican, or, Italian restaurant, you noticed that the detail is
composed of small tile pieces which have been artfully arranged to provide the beautiful
picture. Pixels are something like the tile pieces. Pixels are typically expressed as a
matrix, like, 256x256, or, 512x464. This refers to the number of individual pixels,
horizontally first, then vertically.
If one person is speaking in lines of resolution and another is preaching pixels, is there
any hope? You can convert pixels to Lines of Resolution by multiplying pixels by .75.
This seems to be the generally accepted conversion factor. Where did this come from?
Pixels are the total number of individual elements across the picture (or top to bottom).
Remember that Lines of Resolution are measured across three quarters of the horizontal
picture (75% of the total distance). The theory is that each pixel can display an alternate
What is the best combination of equipment to comprise a CCTV system? This could be a
long debate. Each manufacturer will say that their equipment is the right fit for the right
application. Is the end user willing to pay any price to get the very best equipment on the
market today? Don’t count on it. Sometimes doubling the price will only get you a small
increase in quality. The real test of how good the final picture looks is to do side by side
comparisons. Big numbers for lines of resolution and large numbers of pixels don’t count
for much if the final result is a fuzzy picture. The quality of the image produced by any
individual component in a CCTV system is directly related to the quality of the image
provided by the proceeding component in the system. All components are important. The
overall image quality is most limited by the weakest component in the system. Let’s
discuss each component in a small CCTV system one at a time. For this discussion, we
have cameras, a multiplexer, a VCR and a monitor.
Cameras: As we now know, almost all cameras produced for CCTV today are of the
CCD type. This means that they are digital devices, meaning that the camera captures
images in a pixel format and then converts it to NTSC (composite video). Since camera
manufacturers are used to rating their devices in lines of resolution, they still do that and
also rate them in pixels. If you use your calculator and compare the lines of resolution
and the pixels, you will see that lines of resolution are nearly equal to 75% of the
horizontal pixels. If not, somebody is obfuscating the numbers.
Lenses: Don’t forget lenses. If the image is not presented to the CCD pick up device of
the camera accurately, everything else will suffer. Know what you will be looking at.
Constant indoor lighting can provide good images from an inexpensive camera. Once you
venture outside, a low lux level is required to provide adequate images in low light
situations. The general rule is, auto iris in varying light conditions and fixed lenses in
constant light (indoors).
Multiplexers/DVRs: By nature, multiplexing devices digitize images from a number of
cameras, resize them and then display them on a single monitor. The information
recorded on tape and hard drive is usually not as detailed as the live display.
Consequently, the replayed video is at a lower quality than the live display. Recording
devices are typically the weakest link in the chain (VCRs because of the tape conversion
and disk drives due to the video compression methods).
Cables: Don’t forget cables. Each time the NTSC image is moved from one device to
another, it typically is transported through coax cable. Each cable has a connector at each
end. If you have made one of these connections yourself, you know why bad cables are
the number one cause of failures in the CCTV industry. The quality of the cable, the
cable distance and the connections can greatly affect the quality of the final image.
Even in the relatively simple system in our discussion, the video image has undergone
several separate transitions. Which is the most important component in the system? The
real answer is that they are all interdependent. Due to the technology used, the recording
device is usually the most limiting factor.
So, what have we learned? There are different methods used to express the quality of a
video image. “Pixels” are used with digital devices. “Lines of Resolution” are used with
analog devices. “TV lines” are the same as lines of resolution. You can convert from
“Pixels” to “Lines of Resolution” by multiplying Pixels by .75. (If you run into someone
who wants to express their output in Megahertz of bandwidth, you can guestimate that by
dividing “Lines of Resolution” by 80. Ex. 200/80 = 2.5Mhz). If someone points to a
monitor image and asks if that is an analog, or, a digital image, the answer is that all
standard monitor images are analog. The image may have been digitized (in fact several
times) prior to display on the monitor. Typically, all modern camera images start out
digitized. Multiplexers and DVRs digitize the multi-screen images. VCRs are usually the
weakest link in the image chain due to the conversion to and from magnetic tape, with
color suffering more than B&W. Digital recording on a hard drive is better but can still
be a lower quality than the live display. Several image conversions take place, even in a
small CCTV system. The overall image quality is limited to the quality of the weakest
link in the system. All system components are interdependent quality wise. Each
produces a picture based from the information provided to it.
There is much information in these few pages which should provide more than is needed
to make any customer feel that they are dealing with an industry expert. This information
is rarely found in a single document. If you were to ask everyone you know in the CCTV
industry, you might find a handful who could explain all this off the top of their head.