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Understanding IP Video for

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www.securitysales.com MARCH 2007A2

Part 1of 4

elcome to the latest of Security Sales & Integrations acclaimed

D.U.M.I.E.S. series: Understanding IP Video for D.U.M.I.E.S. Broughtto you by Pelco, this four-part series has been designed to educate read-

ers about networked video the next phase of surveillance technology following the

quantum leap from analog to digital CCTV systems. D.U.M.I.E.S. stands for dealers, users,

managers, installers, engineers and salespeople.

There has been much debate recently about the direction CCTV video is heading. Many

individuals believe analog video and some of its theories will become obsolete as Internet

protocol (IP)-based surveillance becomes dominant within the industry.

This belief begs the question: Why then is fundamental CCTV theory a necessity when

everything is headed toward digital? The following points can easily answer this question:

The output quality of any IP circuit is only as good as the input

How an image is captured has not changed through the years

Lighting, image detail and image quality are still a top proprietyThere is a saying that rings true: Images one sees, such as colors created by a sunset, are

still analog. With this in mind, lets review the basics of solid CCTV system design and ana-

lyze how those elements can be transitioned into todays emerging IP-based systems.

Networked video surveillance

systems are at the forefront of

the convergence of IT and

physical security.However, no

matter what the delivery

method,the proven,time-tested

principles of CCTV system

design remain vital. Applying

these theories to IP-based

systems can help overcome

some inherent shortcomings.

Using Camera Specs toSolve IP Application Issues

By Bob Wimmer

Principal

Video Security Consultants

[email protected]

AT A GLANCE

Although IP video represents an

exciting new age,the principlesof proper CCTV system design

still apply

Whether IP or not,understand-

ing camera specifications and

terms such as lux, IRE and AGC

are essential to obtaining desir-

able results from a video system

installation

IP cameras tend to be trickier to

deploy in outside applications

due to lighting factors

Paying close attention to f-stop

ratings and signal-to-noise ratios

(SNR) are key to achieving opti-

mal images from IP cameras

W

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IP Cameras Designed 2 Ways

At their source, all IP cameras are

analog.

It is a proven fact that any digital

system, whether it is an IP camera,

digital multiplexer or digital recorder,

relies on the overall quality of the

video input for success. Understand-

ing camera specifications and how

they can affect video quality in an IP

system is a challenge. There are cam-

era parameters and features that can

contribute to success or failure.

To help reduce confusion and elim-

inate other pitfalls, we first must re-

view basic IP camera system designs.

In the first design, an integrated op-

tics package (IOP) and an IP interface(encoder) are combined into a single

equipment housing. This design adds

to the overall size and power require-

ment of the camera package, as well

as some cable distance issues that will

be discussed later in this series. How-

ever, some of the advantages com-

pared to other system designs include

single installation requirements,

equipment location management and

ease of wiring, just to mention a few.

The second design involves incorpo-rating two separate units, one consisting

of the camera and optics, while the other

includes the encoder, which converts

the analog signal into a networked-

based format. Although this formation

requires two separate units, it is pre-

ferred in some outdoor applications due

to cable distance requirements.

Whichever method you select, there

is one thing common to both: The

conversion from an optical image to a

format that can be applied to the en-

coding section of the camera system.

Effects of Lighting on IP Cameras

Understanding camera specifica-

tions can be very useful to any surveil-

lance application. This holds true for

both IP and non-IP camera systems.

Lets compare two typical published

IP camera specifications:

Camera 1:

Pan/tilt/zoom (p/t/z) MPEG4/JPEG

network IP camera

26x optical zoom, pan range of

340 and tilt range of 115

Day/night function to provide

optimized sensitivity

Minimum illumination color:

2.2 lux (50 IRE, F1.6, AGC on);

black-and-white: 0.3 lux (50 IRE,

F1.6, AGC on)

Camera 2: Fully configurable MPEG4 com-

pression engine

Optimal synchronization of audio

and video

Motorized pan and tilt capability

with click-to-move on image

64/128-bit WEP encryption

Built-in intelligent motion de-

tection

Now, which one of these IP cameras

is rated for indoor use only? The an-

swer is Camera 2. The reasoning be-

hind this selection is simple. Most IP

cameras (about 80 percent) are de-

signed for indoor applications in

which there is usually an abundance

of available light to produce a quality

image (50 lux or greater), while out-

door applications can encounter

available light levels as low as .1 lux.

External syncinputs

CCD

Analog

A/D convertersample/hold

A/Dconverter

D/Aconverter

Video outEncoderdigital

Micro computerdigital BLC

AGCgamma correction

CCD drivedigital

Sync generatordigital

CCD Camera Block Diagram

At their source, all IP cameras are analog. It is a proven fact that any digital system,

whether it is an IP camera, digital multiplexer or digital recorder, relies on the overall

quality of the video input for success.

IP camera

Lens

Imager

Imagedrivers

Video

processing

Encoder

board

Ethernetboard

I/O

board

Ethernet output RJ-45

AC input

Analog video output BNC

IP camera

Lens

Imager

Imagedrivers

Video

processing

Encoder

board

Ethernetboard

I/O

board

Ethernet output RJ-45

AC input

Analog video output BNC

Integrated IP Camera Block Diagram

In this camera design, an integrated optics package (IOP) and an IP interface (encoder) are

combined into a single equipment housing. Some of the advantages of this design include

single installation requirements, equipment location management and ease of wiring.

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clear as to why no concern for light lev-

els is declared. Especially since all qual-

ity cameras can produce great video at

the 10 foot-candle or 10.7-lux level.

Outdoor applications require more

information in order to select the prop-

er IP camera or to ensure quality video

images. According to the Outdoor

Light Levels chart, it is now necessary

to list the camera sensitivity, especially

when the overall light levels fall below

1 foot-candle or 10-lux levels.

Using our sample cameras color

specification, it becomes apparent this

camera was designed for low-light ap-

plication. But how low? Again, refer-

ring the Outdoor Light Levels chart,

it appears this camera should produce

a video image during light levels equal

to a deep twilight condition. The ques-

tion now arises: Will the quality of the

image be acceptable? Lets find out.

Indoor Light Levels

The illumination levels cameras haveto work with indoors is shown in foot-

candles (FC) and lux across a half-

dozen environments.


Whether the camera is comprised

of a single unit or two combined as-

semblies, when considering any IP

camera for a low-light/outdoor appli-

cation, the camera sensitivity param-

eter must be comprehended.

Lets take a close look at the sensitivity

specifications of Camera 1. The color vs.

black-and-white should be no mystery,

but what about the rest of the informa-

tion? Divide and conquer is always a

good rule to follow when trying to un-

derstand multilayered specifications.

Lets begin with the value of 2.2 lux.

Lux is a light unit for measuring illu-

mination. It is defined as the illumina-

tion of a surface when the luminous

flux of 1 lumen falls on an area of 1m 2.

It is also known as lumen per square

meter, or meter-candelas.

Some camera specifications also

list illumination in foot-candles. A

foot-candle is the light intensity (illu-mination) of a surface at a distance of

1 foot from a source of 1 candela. It is

equal to 1 lumen per square foot (1FC

= 1 lm ft2. A quick conversion follows:

1 foot-candle equals 10.7 lux.

Indoor Vs. Outdoor Applications

For the most part, IP cameras have

been designed for indoor or high light

level applications. Camera 2s specifi-

cations easily confirm this fact by not

including any information on theamount of light required to produce a

video image. Referring to the Indoor

Light Level chart, it becomes very

There is an old saying applicable

here that goes something like this:

The big print gives and the smallprint takes away. The data sheet pro-

vides the amount of light required,

but how was that number calculated?

Mystery of the IRE Unit Explained

An IRE unit is a measurement de-

signed by the Institute of Radio Engi-

neers, now called IEEE or the Institute of

Electrical and Electronic Engineers. The

measurement indicates the amount of

signal strength generated by a camera,

or in the case of an IP camera, the outputof the IOP (integrated optics package).

Typically, there are 140 IRE units asso-

ciated with a 1V peak-to-peak (p-p) full-

strength video signal (1 IRE = .00714V).

The introduction of the IRE unit makes

luminance level values much easier to

understand and communicate.

A video signal is divided into two

sections. The first section is the vertical

and horizontal synchronization sig-

nals. This unit is used in the ITU-R

BT.470, which defines PAL, NTSC and

SECAM EIA-170A standards and is

used to lock up the video equipment in

order to produce a stable image. The

standard level, which supports a true

signal, is listed as 40 IRE units.


CCD camera

I/O

Board

Video

processing

Imagedrivers

Imager

LensAC input

OutIn

Analog video

Ethernetboard

Encoder

board

Encoder

Ethernet Output RJ-45

Camera With IP Encoder Block Diagram

This camera design involves incorporating two separate units, one consisting of the

camera and optics, while the other includes the encoder, which converts the analog sig-

nal into a networked-based format. Although this formation requires two separate units,

it is preferred in some outdoor applications due to cable distance requirements.

Outdoor Light Levels

Light levels in outdoor environments

encompass a much higher degree ofvariance than those indoors. Some ap-

plications demand cameras designed

for extremely low-level lighting.

Condition Illumination

FC LUX

Sunlight 10,000 107,527

Full daylight 1,000 10,752.7

Overcast day 100 1,075.3

Very dark day 10 107.53

Twilight 1 10.75

Deep twilight 0.1 1.08

Full moon 0.01 0.108

Quarter moon 0.001 0.0108

Starlight 0.0001 0.0011

Overcast night 0.00001 0.0001

Condition Illumination

FC LUX

Warehouse 13.9 150

Manufacturing 18.5-93 200-100

Retail stores 69.7 750

Office work 46.4 500

Banks 18.5-46.4 200-500

Detail work 139.4-185.8 1,500-2,000

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The second section of the meas-

urement is the actual video signal

strength from the camera. The reason

IRE is a relative measurement is be-

cause a video signal may be any am-

plitude. A value of 100 IRE is defined

as the range from black to white in a

video signal to produce a high-quali-

ty, full video signal. A value of 0 IRE

corresponds to the zero voltage value

during the blanking period.

With all of that stated, the simple fact

is since the video strength measured in

IRE units is linear, the greater the IRE

level the stronger the video signal.

Returning to our camera example

with a rating of 2.2 lux @50 IRE (see

Camera Output Comparison), we

can see the difference of 100 IRE out-

put vs. 50 IRE. In order to produce thehigher quality image, more than 4.4

lux of light would be required.

Some at this point might say, So

what? The video image is still accept-

able, so what is all of the concern?

The answer is it isnt just the reduced

quality of the video but also what this

loss of IRE units will do the overall

scheme of things.

First, for the IP system that incor-

porates individual encoders, each en-

coder must convert the analog videosignal into digital. This is accom-

plished via an A/D (analog-to-digital)

encoder. Each encoder has a set of

input parameters and many of them

require a minimum of 50 IRE units in

order to function properly.Secondly, in the case of an integrat-

ed IP camera, the encoder board may

try to amplify the video signal up to

the 100-IRE levels, which can cause a

grainy, or noisy, image file and thus

increase the bits per second transfer

rate on a network.

F-Stop Determines Performance

Throughout a given day, the amount

of illumination reaching a scene de-

pends on the time of day and atmos-pheric conditions. Direct sunlight pro-

duces the highest contrast scene,

allowing maximum identification of

objects. On a cloudy or overcast day,

the objects in the scene receive less

light, resulting in less contrast.

To produce an optimum camera pic-

ture under the wide variation in light

levels (such as occurs when the sun is

obscured by clouds), an automatic-iris

camera system is required. Typically,

scene illumination measured in foot-

candles or lux can vary over a range of

10,000 to 1 (or more), which exceeds the

operating range of most cameras for

producing good quality video images.

To overcome this situation, lenses

with auto iris are incorporated. Howev-

er, all lenses have a rating to specify

their ability to pass light at low-light

levels, as well as handle extreme light-

ing conditions. The term indicating the

lens performance is known as the f-

stop rating of the lens. The camera spec-

ification sheet lists the minimum f-stoprating of the test lens used in producing

the camera performance specifications.

The f-stop deals with the iris of a lens

and how well the lens can pass light. To

better understand how this works lets

make a comparison to the human eye.

As light becomes brighter, the iris of your

eyes closes to allow only the proper

amount of light to reach your retina and

produce a quality image. It is the same

with the lenses used in IP cameras.

A growing concern in lens selectionis the minimum f-stop rating of the

lens, or how well it operates at low

light levels. With the increased use of

IP cameras for outdoor usage this

concern has become a very real issue.

Even with advancing technology, IP

color cameras require more light to

produce the same quality picture as a

black-and-white surveillance camera.

The f-stop rating of any lens is given

by the ratio of the focal length of the

lens divided by the actual mechanical

diameter of the iris opening of that

lens as follows:

F-stop rating = F (focal length in mm)

D (iris opening in mm)

The lower the f-stop rating of the

lens, the faster, or greater, the light-

gathering capability of the lens. The

1V peak to peak or 140 IRE units

Make-up of a Video Signal

A video signal is divided into two sec-

tions: the vertical and horizontal syn-

chronization signals; and the actual

video signal strength from the camera.

Typically, there are 140 IRE units asso-ciated with a 1V peak-to-peak, full-

strength video signal.

Camera Output Comparison

Here we see the difference in image quality when 100 IRE unit output is compared to 50

IRE unit output. Even though the image on the right might still seem acceptable, it will

likely suffer degradation during video processing.

100 IRE output 50 IRE output

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normal minimum f-stop rating of a

typical lens is between f1.0 to f1.8.

Since every camera requires a lens

to produce an image, the specifica-

tion will list the type of lens used in

the testing phase of the camera. In

this case, the lens selected was a fixed

lens with an f-stop rating of f1.6.

If an integrator has the ability to se-

lect different lenses, he or she must

ensure that the rating of the lenses is

equal to or less than whats shown in

the data sheet. If not, again the video

output strength from the camera will

suffer. The end results could mean no

video images or excessive image file

sizes for both storage and transmis-

sion of the video signal.

As a helpful hint, the f-stop rating

of lenses is logarithmic, which means

every single f-stop increase in a lenswill decrease the amount of light

passed through that lens by 50 percent.

Common f-stops are listed as f1.0;

f1.4; f2.0; f2.8; f4.0; f5.6. This fact also

will hold true when installing any

zoom lens on an IPO camera. The rat-

ing of a zoom lens is always the best

rating. As one zooms in on an object,

the amount of light will decrease on

that cameras sensing device, causing

lower video output levels.

How AGC Impacts IP Cameras

Many people are already familiar

with automatic gain control (AGC).

However, what does AGC have in com-

mon with IP cameras? First, for those

who are unfamiliar with the function

of AGC, a quick primer is in order.

The purpose of AGC is to increase

the sensitivity of the camera during

low-light level applications. This fea-

ture is a compromise because it will

amplify the video signal to improve

image strength, but at the same time

it also amplifies the random noise

generated by the circuitry within the

camera. This amplification of noise

causes a grainy image that randomly

moves about the scene.

So, how can AGC affect the per-

formance of an IP camera? IT person-

nel probably already know the an-

swer, but non-IT types may require

an explanation.

MPEG4 compression uses what iscalled temporal reduction as one of its

compression methods. This is the cor-

relation between adjacent frames in a

sequence. This information is the

basis for MPEG as well as the H.26*

series of compression standards.

In temporal reduction, two types of

image arrangements are analyzed.

The first one is a full representation of

the viewed image. This is known as

the I-frameand is encoded as a single

image, with no reference to any pastor future images. In some circles, it is

also referred to as the Key-frame. The

logic for temporal asks, if there is no

movement, why bother saving the in-

formation? Conversely, any move-

ment will be detected and the com-pression process will begin.

Many people refer to IP cameras as

intelligent cameras; and they are up to

a point. But the IP compression en-

gine cannot tell the difference be-

tween actual movement and excessive

AGC noise. Consequently, in many

cases the bit image rates as well digital

storage devices will suffer.

AGC is a compromise. It is incorpo-

rated to improve camera sensitivity at

a price. Without AGC, the camera usedin this example would require more

than 22 lux of light to produce a 50-

IRE signal output.

High SNR Helps Offset AGC Issues

What areas can be improved to help

the AGC situation?

The enemy of picture clarity and

compression engine is noise; this elec-

tronic noise is present to some extent in

all video signals. Noise manifests itself

as snow or graininess over the whole

picture on the monitor. Signal-to-noise

ratio (SNR) compares the amount of

noise generated within the camera to

that of the video signal strength. The

higher the number (measured in dB),

the better the noise characteristics

and the less grainy the picture will be,

especially at low light levels.


Videosignal

Full video

Video quality

0 20 50 100 IRE

Usablevid

eo

IRE Output Level Vs. Lighting

Video image quality improves as the level of IRE units increases. IP systems that con-

vert analog video into digital use encoders that may require a minimum of 50 IRE units

in order to function properly. In the case of an integrated IP camera, the encoder board

may amplify the video signal up to the 100-IRE level, which can cause a grainy image.

Light loss10lux

5lux

2.5lux

1.25lux

f1.0 f1.4 f2.0 f2.8 f4.0

Lens F-Stops

The f-stop rating of lenses is logarith-

mic, which means every single f-stopincrease in a lens will decrease the

amount of light passed through that

lens by 50 percent.

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Note that every time a video signal

is processed in any way, noise is intro-

duced. This noise cannot be reducedby correction equipment; it is intro-

duced at the source. A common source

of noise: when AGC is introduced at a

camera in very low lighting conditions.

What is the reason for all of these

concerns for a little-understood data

sheet parameter? The answer is sim-

ple: as more and more dealers turn to

IP systems and digital motion detec-

tion, the SNR becomes very important.

This is because to IP cameras with

built-in activity detection, noise isviewed as motion. If not properly un-

derstood, IP networks, as well as mass-

storage devices, can soon reach their

maximum transmission and storage

limits with very little actual useful in-

formation. Cameras with a SNR greater

than 50dB are highly recommended

when used in networking situations.

What Specifications Dont Tell You

While some of todays manufactur-

ers publish the exact procedures and

criteria they used in order to provide

you with their cameras sensitivity,

other manufacturers assume everyone

is already knowledgeable on how spec-

ifications are determined. Well, there is

a little-known fact about camera speci-

fication that holds a big punch.

Camera manufacturers list the di-

rect amount of light that the camera

requires to produce an image. Many

give you the f-stop rating of the lens

that is used, the output signal strength

(measured in IRE units) and whether

the AGC is incorporated to produce

the numbers listed in the data sheet.

However, one test item is missing:

What was the reflectance factorof the

test pattern used in the procedure?

Reflected light in the real world set

of parameters, especially in the sur-

veillance arena, varies from 5 percent

to 95 percent depending on the type

of scene.The test percentage used by most is

referenced as either 75 percent or 89.9

percent and is determined by the

test pattern incorporated when testing

the cameras sensitivity. After review-

ing the reflectance chart, it does not

take long before most can realize that

real-world surveillance operates with

a great deal less reflectance than that

offered by the cameras specifications.

This difference between the actual

and data-sheet reflectance indicatesthat the minimum sensitivity printed

on the data sheet will require much

more lighting when used in these areas.

As an example, lets use the camera

specifications that we have been ap-

plying throughout this article. This

specification was based on an 89.9-

percent reflective test pattern. If this

camera was located in an outdoor as-

phalt parking lot (5 percent to 10 per-

cent), it would require at least 9 to 10

lux of light to perform within the lim-

its set by the data sheet.

Image Enhancement Is on Deck

All of the items discussed in this ar-

ticle will control the output quality of

any IP solutions surveillance systems

to some extent.

For the most part, indoor or high

light level areas seem to suit IP cam-eras well and do not pose too many

concerns. However, as the IP revolu-

tion advances to outdoor or low-light

applications, broader background

knowledge will be necessary.

The next installment of this

D.U.M.I.E.S. series will discuss fea-

tures that will enhance IP camera

image quality, as well as address basic

system layouts.

Robert (Bob) Wimmer is president of Video SecurityConsultants and has more than 35 years of experi-ence in CCTV. His consulting firm is noted for tech-nical training, system design,technical support andoverall system troubleshooting.

Foot-candlesorlux

F-stop

Reflectance

IREouput

Typical Testing Setup for Camera Sensitivity

In their specifications, camera manufacturers list the directamount of light that the camera requires to produce an

image. Many give you the f-stop rating of the lens that is

used, the output signal strength (measured in IRE units) and

whether the AGC is incorporated to produce the numbers

listed in the data sheet.

Reflectance Factor Chart

Manufacturers usually fail to disclose

the reflectance factor of the test pat-

tern used to derive camera specifica-

tions. This is important because reflect-ed light in the real world varies from 5

percent to 95 percent depending on the

type of scene.

Empty asphalt parking lot 5%

Parkland, trees, grass 20%

Red brick 35%

Unpainted concrete 40%

Parking lot with cars 40%

Aluminum building 65%

Glass windows and hallways 70%

Snow cover landscape 85%

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