CCTV Digital Basics Training Workbook

8/10/2019 CCTV Digital Basics Training Workbook

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CCTV DigitalBasics

Training Workbook

Security Systems

April 2005


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Bosch Security Systems

CCTV Digital Basics Training 3

Table of ContentsAbout this course ..........................................................................5

Course Prerequisites....................................................................5Course Map ....................................................................................6

Course Objectives .........................................................................7

How to use this book.....................................................................9

Welcome!......................................................................................10

Unit 1: Defining Digital ................................................................11

Digital vs. Analog .......................................................................12What is Digital? ..........................................................................14Video Imagery............................................................................15

Digitizing.................................................................................15Sample rate ............................................................................16Pixel size ................................................................................16Pixel bit depth.........................................................................16Bits and Bytes.........................................................................18

Image File Size ..........................................................................19

Review.........................................................................20Unit 2: Video Compression.........................................................21

Defining Compression................................................................22Benefits of video compression................................................22

Managing Video File Sizes.........................................................24Non-compression techniques .................................................24Video compression techniques...............................................25Video compression standards ................................................27 Review.........................................................................29

Unit 3: Networks ..........................................................................31

Defining Networks......................................................................32The CCTV market...................................................................32

Network basics...........................................................................33Network building blocks..........................................................33Basic network types................................................................34Half-duplex vs. Full-duplex communications ..........................34Bandwidth...............................................................................35Converting Bytes to bits..........................................................36Bandwidth for digital video......................................................36

Network Communications ..........................................................37Protocol interactions ...............................................................37

Communications handshake ..................................................37Network protocols ......................................................................38

Ethernet..................................................................................38TCP/IP....................................................................................38UDP........................................................................................39ISDN.......................................................................................39DSL ........................................................................................39


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4 CCTV Digital Basics Training


Network devices.........................................................................40Hubs and Switches.................................................................40Routers...................................................................................41Gateways ...............................................................................41Modems..................................................................................42

Review.........................................................................43Unit 4 Network Addresses .......................................................47

What are Mac and IP addresses?..............................................48

IP address standards..............................................................49Subnets ..................................................................................50

Domain Naming System (DNS)..................................................51Multicasting................................................................................51Firewalls.....................................................................................52 Review.........................................................................53

Unit 5 Network Transmission Medium....................................55Network Connections .................................................................56Cabling Specifications................................................................56

Network cabling terminology...................................................56

Categories of twisted pair cabling...........................................58

Fiber Optic..............................................................................58Network Interface Card ..............................................................59Repeaters ..................................................................................59

Review.........................................................................60Unit 6 Network Pitfalls..............................................................63

Digital CCTV Networks ..............................................................64Possibilities and Problems......................................................64

Factors for CCTV Network Integration ....................................65Bandwidth and storage requirements.....................................65Connectivity............................................................................66

Connectivity Tests ..................................................................66Firewalls.....................................................................................68

Communicating with IT...............................................................68Appendix ......................................................................................69


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About this course

The CCTV Digital Basics Trainingcourse will provide you with a foundation to concepts of digital signals andnetwork systems, with a focus on CCTV. Included is terminology used within networking environments, and howdata streams are moved and impacted by transmission medium and file size.

Course Prerequisites

This is a foundation course and assumes you are familiar with basic analog video technology. The Bosch SecuritySystems provides a CCTV Analog Basics Trainingcourse that is recommended as a prerequisite to this CCTVDigital Basics course.

The material and instructions in this document have been carefully checked for accuracy and are presumed to bereliable. However, Bosch Security Systems assumes no responsibility for inaccuracies and reserves the right tomodify and revise this document.


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Course Map

In this course, you will complete six (6) units. The recommendation is to progress

through each unit in sequential order. There is flexibility in the training order for units 3,4 and 5, but unit 6 requires all previous units be completed before starting this finalsection. It is preferred that you complete each unit before moving on to the remainingones. However, your instructor may elect to deliver sections in a different sequence toaccommodate the needs of the students or facilities.


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Course ObjectivesThe following are the course objectives for each unit of training.

Unit 1: Defining Digital

After completing this unit, you will be able to:

Describe the components of digital imagery.

Describe two factors that can impact pixel resolution

Define a bit and how it is used in digital video

Define a byte and how it is used in digital video

Identify the differences between digital and analog signals.

Describe at least three advantages of digital vs. analog related to CCTV.

Unit 2: Video Compression


Define video compression.

Identify the benefits of video compression.

Identify and describe different video compression techniques.

Describe the different video file formats and their intended uses.

Determine the relationships between image capture, compression type, file size andrecord time.

Determine the image capture and compression options for a given need, using areference table.

Unit 3: Network Configurations


Define the elements of network traffic.

Describe how network traffic is controlled and checked.

Define Bits and Bytes, and their interrelationship.

Convert Bytes to Bits.

Describe bandwidth and how it impacts network traffic.

Calculate network bandwidth requirements.

Identify and describe the functions of different network components.


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Unit 4: Network Addresses

After completing this module, you will be able to:

Define the different types of network addresses.

Describe how IP addresses are defined and grouped for usage.

Describe subnets and their function

Define DNS and its function

Describe multicasting and how it can be used for CCTV.

Describe the function of firewalls.

Unit 5: Network Transmission Media


Identify the different network transmission medium options.

Describe the characteristics of the different transmission methods.

Identify transmission limits for different media.

Unit 6: Network Pitfalls

After completing this module, you will be able to:

Identify at least 3 potential factors that can impact CCTV connectivity to networks.

Identify at least 3 factors that can impact CCTV bandwidth requirements.

Identify and describe how different network components can limit networkcommunications.

Identify and describe 3 computer based tests for network connectivity.


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How to use this bookYou can use this book as a learning guide, a review tool, and a reference.

As a learning guide

Each module covers several related topics. Topics are arranged to build uponprevious prerequisite experiences or previous topics. For this reason, you should workthrough the topics in sequence. We organized each topic into explanatory concepts.

As a review tool

Any method of instruction is only as effective as the time and effort you are willing toinvest in it. For this reason, we encourage you to spend time reviewing the referencematerial.

As a reference

Be sure to return to this book as needed to refresh your skills and to locate point-of-need information in the field.

Icons and at-a-glance information

Throughout this book you will find icons that represent certain types of information.Usually, this information is represented as a small, easy to process segment thathighlights or summarizes a training topic. Sometimes, these icons help you quicklyidentify point-of-need information. You can review each type of at-a-glance icon in theright hand column of this page.

Margin locatorsThroughout this book you will find in the page margins numbers that correspond to theprojected PowerPointused by your instructor (such as U3-10). These numbers referto PowerPoint slide number that show in the lower right corner of each slide. Usethese markers as your guide to help synchronize the proper workbook page to theprojected visual aid.

Check your skills:Fill in the blankquestions or completethe activity to reinforceyour understanding.

Learn more:

Circle the items in thelist that interest you themost. Ask the instructorto explain them indetail.

Additional Reference:

These notes will directyou to a specificdocumentationresource for moreinformation on a topic.

Demo or Discussion:

Your instructor will leada demonstration or aclassroom discussionthat relates to the topic.Sometimes, you will beasked to complete anexercise that relates tothe topic.


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Welcome!

Your instructor:

_____________________________________________

Your instructors contact Information:

_____________________________________________

_____________________________________________

Class hours:

_____________________________________________

_____________________________________________

Important information about these facilities:

_____________________________________________

_____________________________________________

_____________________________________________

_____________________________________________


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Unit 1: Defining Digital

Objectives


Describe the components of digital imagery.

Describe two factors that can impact pixel resolution

Define a bit and how it is used in digital video

Define a byte and how it is used in digital video

Identify the differences between digital and analog signals.

Describe at least three advantages of digital vs. analog related to CCTV.

Topics covered

Digital signals

Main components of a CCTV system


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Unit 1



U1-5

Digital vs. Analog

Analog CCTV systems have been the backbone for meeting the visual needs ofsecurity for many decades. The CCTV camera has always provided an analog signal,and was usually recorded onto video tape using the analog video signal. CCTV wasoften integrated within other analog security system functions, such as intrusion, firedetection, and access control.

Advances within imaging chip technology, microprocessors, and mass memory have

brought digital benefits to the CCTV markets. Improved image capture quality andcapabilities, increased image manipulation and compression options, higher reliabilityin recording, and faster image retrieval are some of the benefits realized. Up to thispoint, digital technology has made the greatest inroads in the areas of image capture(cameras) and recording/archiving (i.e. DVRs).

Even with such advances in digital CCTV, these systems have remained mostly ananalog signal technology platform. The video standards that CCTV is built upon(NTSC, PAL, SECAM) has confined this visual medium to the analog domain. Theterm digital is often misunderstood and loosely used when relating to CCTVsystems.

In recent years, CCTV systems have begun to transition through a dramatic shifttowards totaldigital integration. This is occurring because the analog signal backbone

standards (NTSC, PAL, SECAM) is being completely bypassed. In their place MPEG,Wavelet, JPEG, or some yet to be discovered new digital standard are replacing theanalog video signals. These signals are not required to be sent to a dedicated andcentralized control center, but are available to one or more PCs - anywhere in theworld.

This new digital signal foundation has dramatic impact on CCTV systems. It isredefining systems as they have been long known: closed dedicated transmissionpaths, with centralized control centers. The new generation of digital CCTV systemsuse open distribution architecture (IP protocols, multicast), with decentralized andmultiple monitoring and/or control points potentially wherever a PC exists. Thesedigital video signals are transmitted over existing computer networks worldwide. Andthe video/audio/control signals remain digital from start to end.

The term IP-CCTVor IP-Surveillancemeans the transmission of digitized videostreams over wired or wireless Internet Protocol (IP) networks. These includecorporate network systems and the internet. The advantages of an IP based CCTVsystem are:

Scalability Easily scaled from one to thousands of camera in any increment ispossible. It offers any frame rate from any camera at any time.

Cost efficient infrastructure The ability to use existing wired networks or wirelesstransmission, opens new areas of access and cost savings for installation. The optionto piggy back onto a preexisting business network system makes expansion easierand provides for new efficiencies in maintaining and managing the infrastructure.

Remote access & control Any video source can be accessed and controlledremotely from anywhere in the world over wire/wireless networks. Intelligence of the

camera functions can be established at the camera location (motion detection, eventhandling, output type, time/date, etc.).

Lower cost An IP CCTV system can easily leverage from existing network systems,business support resources, and storage capabilities.

This training will introduce you to the world of digital CCTV, from two mainperspectives: digital components within an analog world, and as all digital systems.

The following table summarized some the differences and benefits between digitaland analog CCTV. Also included are the benefits of a totaldigital CCTV system.


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Unit 1



Digital Hybrid CCTV Systems

Advantages

Clear, precise and discrete signalvalues, which allows for customizedimage quality options

Ability to manipulate and compressthe signal data for duplication,transmission and storage flexibility

The ability to send signals throughnon-dedicated transmission media

Flexibility in the storage, file transfer,copying and archiving

Simultaneous record and playback

Fast and detailed search capabilities

Non-degradation of recorded videowith use/playback

Digital recording can incorporateencryption

Low maintenance on digital recordcomponents

Disadvantages

Video signal conversion required:analog-digital-analog

Digital components sometimes moreexpensive than analog

System still requires some dedicatedtransmission path

Transmission distance limitations

Video storage limited by hard drivespace

System expansion my be limited bydependent components (i.e. need tobuy more switchers)

More users on system may slow IPSspeed.

May not be real time video

Analog CCTV Systems

Advantages

Uses traditional video cameras,transmission methods, and VCRrecording

Relatively inexpensive to build asystem

Simple and familiar to use

Modular configuration to add/replacecomponents

Provides real time, full videoresolution

Disadvantages

Requires dedicated transmission path

Transmission distance limitations

Time consuming video searches

System expansion my be limited bydependent components

Video tape and recordings wearout/degrade with use

Higher maintenance of VCR

Bulky storage requirements of tapes

Inflexibility in use of recorded video

100% Digital CCTV Systems

Advantages

Digital signal throughout system, andall the benefits of a digital signal

No dedicated cabling required, usesexisting computer networks

Easily scalable system

Non-centralized control centers

Virtual hard disk possible

System redundancy network provides

Disadvantages

Network congestion and bandwidthlimitations

Expense of components (this cost maybe offset by savings in using existingnetwork cabling)

Same security concerns as anycomputer network system

Competing proprietary standards

U1-6

U1-7

U1-8


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Unit 1



U1-9

If we were to digitallycontrolling low voltagewithin a computer, thenOFF (no voltage) wouldbe represented by 0(zero). The normaloperating low voltagesof the computer, say 12volts, would be ON,represented by 1(one). Any voltagevariations would bedigitally rounded to fitwithin the ON or OFF

parameters of 12 voltsor 0 volts.

U1-10

What is Digital?

To put in the simplest terms, Digitalis information represented in discrete valuesofeither ON or OFF bits of information. This on/off format of information is called BinaryCode,and is numerically represented as a 1 or 0 (one or zero). These two valuesrepresent the smallest form of digital information, called a Bit. Thus, a Bit isexpressed as either a value of 1 or 0.

Because of this discrete two state mode of operation, digital systems operate very

precisely. This built-in error detection and correction leads to an inherently higherquality process. The rounding up or down of digital processing screens out slightvariations in information. Variations retained within any process can have anaccumulative effect, resulting in a substantial degrading of the output. Digitalprocessing helps counter this accumulative effect.

Compare this to Analoginformation that is represented as continuousorproportionalvalues. Unlike the discrete values of digital, analog information can contain a widerange of values, along with very small subtle changes. This continuous nature ofanalog information makes it by nature more susceptible to unwanted variations.

Analogs continuousvalue representationof information also

gives it the ability tocapture andreproduce a greatamount of detail. Thiscan also create verylarge files for storingsuch information.

The challenge ofdigital processing is incapturing the level ofdetail required asspecific digital values.

Digital communicationsuse such discreteterms as: Pulse Code Modulation, datacommunications, and video digital signals of Wavelet, AVI, JPEG, and MPEG.

Analog communicationsuse continuousterms such as: AM and FM modulation,high fidelity, and video analog wave signals of Y/C and composite.


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Unit 1



Video Imagery

A digital camera uses the lens to focus the light from a scene onto a Charge CoupledDevice(CCD) within thecamera. The CCD is an imagingsensor that captures the scenelight values, and converts this

information into an analog signalof continuous electrical voltagelevels. This voltage level variesin proportion to the differentlevels of light.

There are different sizesavailable for CCD imagers.Common CCTV imager sizes,called camera formatsare:(inches): 1/3, , ,

2/3and 1. Theformat of the CCD alone doesnot determine the image quality.Other factors need to be taken into account.

Digitizing

Within the CCD, the area of the video image is broken down into small quadrants ingrid-like fashion. Each small grid area is called aPixel. A Pixel is onepicture element,and is a sensor that is the smallest component that captures the video image. Thenumber of pixels (sensors) that are on the CCD surface rates the CCD. A CCD with agreater number of pixels can capture more detailed visual information.

The analog signal that comes from the CCD imager is received by a microprocessorwithin the camera, called a Digital Signal Processor(DSP). This microprocessorconverts the analog signal into a digital signal. This Analog-to-Digital (A/D) signalconversion is called Digitizing.

The quality of the digital image is dependent upon the quality of both the CCD and theDSP analog-to-digital conversion. Image quality is impacted by three factors:

Sample Rate

Pixel Size

Pixel Bit Depth

CCD Resolution isoften measured inmegapixels.Each megapixel = 1million pixels.


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Unit 1



U1-11

Most CCTV Camerashave the following pixelresolution:

Normal active pixels:

510 H x 582 V(NTSC)

500 H x 582 V(PAL)

High Resolution

active pixels:

768 H x 492 V(NTSC)

752 H x 582 V(PAL)

Analog TV resolution isbased upon horizontallines of resolution(TVL)

U1-12

Sample rate

How frequently theanalog signalvalues are looked at(sampled) to obtaina signalmeasurement is the

Sample Rate.The DSPdetermines thesampling rate. Thisdetermines the levelof signal resolution.The higher thesample rates, themore frequent arethe signal capturereadings, which,increases the abilityto capture finer

analog signal changes.

For video signals, sample rates are usually determined at various Hertz frequencylevels. (Professional digital audio sample rate is 48 KHz. Digital video sample ratesare in the range of 5-60 MHz.)

Pixel size

Pixel Size that is on the CCD defines spatial or image resolution. The size of thepixels are usually counted inpixels/inchor mm. The smaller the pixels, the greaterlevel of detail captured.

Pixel bit depth

This defines brightness or chroma resolution. It determines how finely the pixels canbreak down the levels of light it receives, and these fall within a fixed range of values.Each level of scale or depthis called a Bit. This is can be referred to as Pixel BitDepthor Bit Depth. The higher the Bit Depth value, the higher the image resolution isfor brightness or chroma.


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Unit 1



Since digital imagery works on the Binary value system (1 or 0 on or off), each Bitmust record the light as either a 1 or 0 value. For a simple pixel depth of one Bit, theassigned light value can only be a value of either a one or a zero. This digitallytranslates into image values of white or black. This 1 Bit Pixel Depth creates what isoften called a half-tone image. Even using only black and white dots, an image can becreated that appears to have different shades of grey by varying the placement ofthese black or white dots.

For a bit depth of five, the brightness resolution capability becomes 32 different levelsof brightness that can be created. A bit depth of 8 can yield 256 different levels ofbrightness.

To create digital CCTV color, the PrimaryColorsof Red, Green, and Blue arerequired. Each color requires its own Pixel and Pixel Bit Depth. If each color uses fivebits, then you end up with a 15 Bit color system. This digital brightness resolutioncombines to produce 32,768 different possible colors.

U1-13

U1-14


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Unit 1



U1-15

Bandwidth will becovered further inUnit 3 Networks

U1-16

For a 15 Bit color system, a pixel represents one of the primary colors (RGB). Thatpixel can produce one of 32 discrete variations of that color. When one pixel each ofred, green, and blue are next to each other, they create what is perceived as the finalcolor seen in that one image area (one of 32,768 colors possible).

Bits and Bytes

Just as the alphabet is the building blocks of language, bitsrepresent the foundationof digital information, and are the smallest form of digital data. Bit values areexpressed in binary code fashion of 1s or 0s. When transmitting this digitalinformation, it is expressed as bits per second(bps). The slowest component in anetwork system will determine the speed of data transmission. Large file sizes and aslow network component (i.e. modem) can create what we all know as a bottleneck.Video components and medium that transmit this data use bits as their foundation toexpress their carrying capacity (bandwidth):

Modems: 28.8 Kbps, 33.6 Kbps, 56 Kbps

LAN networks: 10 Mbits/sec., 100 Mbits/sec., 1 Gbits/sec.

The next category of digital datais called a Byte. It is typicallymade up of 8 bits. Video imageryand the resulting digital filessizes are expressed in Bytes:

File size: 15 KB, 12 MB

Hard-drive: 40 GB

When Bytes are used forexpressing transmission rates orcapacity, it is stated as Bytes

per second(Bps).


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Unit 1



Image File Size

For digital imagery, the combination of the number of Pixels and Pixel Depth impactnot only image quality, but also the digital file size.

For each video frame captured, a video file is created. That file size is dependentupon the following:

Total number of pixels on CCD based upon its dimension(ie. 768 x 492 = 377856 pixels)

Pixel Bit Depth as determined by the Digital Signal Processor (i.e. 8 bit)

Since CCTV video is motion imaging, full multiple images or image files are produced.The rate of images captured, displayed, or recorded is referred to as Images PerSecond(IPS).

Thus for every second of video captured, digital data is being created at a very highrate. The need to reduce this file size becomes obvious when considering signaltransmission and video file storage requirements.

Reducing digital video signal data file size is called Compression. This is the nexttopic in this training workbook.

U1-17

U1-18


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Unit 1



Fill in the blankquestions or completethe activity to reinforceyour understanding.

ReviewComplete the review questions below. When you are done, review your answers withyour facilitator.

Place either an A(for Analog) or a D(for Digital), before each item below, dependingwhat you think it best represents.

___ 1) Time consuming video searches ___ 11) PAL, NTSC

___ 2) Ability to manipulate & compress signal data ___ 12) DSP

___ 3) Recording can incorporate encryption ___ 13) Bit

___ 4) More users may slow IPS ___ 14) VCR

___ 5) Requires dedicated transmission path ___ 15) DVR

___ 6) May not be real time video ___ 16) Hard drive

___ 7) Provides real time video and quality ___ 17) Mbps

___ 8) Recorded video not degraded with playback ___ 18) JPEG, MPEG

___ 9) Flexible and fast search of recorded video ___ 19) Digitize

___ 10) Continuous values ___ 20) Discrete valuesFill in the blanks.

21. On a Charge Coupled Device, this represents the smallest image producing

element. ____________________________

22. The quality of a digital image produced by a DSP is impacted by these three

factors:

a. ______________________________________

b. ______________________________________

c. ______________________________________

23. The size of the pixels on a CCD determines _____________ resolution.

24. A Byte is usually made up of ____________.

25. The three primary colors of video are: ___________________

26. A 15 bit color camera can produce this many colors: __________

27. Identify the number of binary possibilities for each of the number of bits below:

1 Bit 2 Bits 3 Bits 4 Bits 5 Bits 6 Bits 7 Bits 8 Bits

____ __4__ ___ _16__ __ __ __ __

28. Pixel Bit Depth determines _______________ resolution.

29. How frequently an analog video signal is measured to get a digital value is the

_________________________________.

30. The rate of video image capture is referred to as:

_________________________


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Unit 2: Video Compression

Objectives


Define video compression.

Identify the 2 main benefits of video compression.

Identify and describe different video compression techniques.

Describe the different video file formats and their intended uses.

Determine the relationships between image capture, compression type, file size andrecord time.

Determine the image capture and compression options for a given need, using areference table.

Topics covered

Benefits of compression

Compression types

Determining video storage needs


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Unit 2



U2-3

U2-4

U2-5

Note: Bandwidth will becovered in more detailwithinUnit 3 - Networks.

U2-6

Defining Compression

Understanding the need and method of video compression is an important CCTVsystem design consideration. The compression method chosen impacts how the videois effectively used, stored and transmitted. It also impacts the selection of hardwareand software within the CCTV system. In all compression types, the compromise isbetween data storage requirements and transmission capacity verses image quality.

Since all digital data information is comprised of binary numbers, computer

microprocessors can analyze and manipulate these numerical values in many ways.In CCTV, an important need for digital manipulation is for file compression.

Compressiontakes the digital data and reduces the file size by looking for numericalrepeating patterns or similarities. Compression Enginesare tools used toaccomplish the task of compressing digital files. Just as there are a wide variety ofdigital files, (video, audio, data, text, etc.), there are a wide variety of compressionengines on the market.

Compression engines use mathematical algorithms, which are specially designed forcalculating and solving repetitive mathematical problems. There are many types ofcompression techniques and standards, depending upon the type of files and therequirements for speed, storage, and quality of the output.

The technology that makes this happen is referred to as codec(compress/decompress data). This is the generic term for the hardware and softwarerequired to make compression work across multiple platforms and applications.

Benefits of video compression

Without video file compression, the size and volume of the captured video data couldslow or stop signal transmission, and create excessively large requirements formemory space on storage devices.

A CCTV video signal alone can generate 39,000,000 bytes (39 MB) of image data persecond (at 60 ips). To give you scale to this rate of data creation, a CD (650 MB)would be able to store only about 16 seconds of video. The steady rate of video datacreation would overwhelm most storage and transmission systems. The need forvideo data compression is obvious.

Benefits of video compression are:

Greater storage capabilities provides more image data in less storagespace. This reduces file storage cost.

Faster file transfer rates allows for increased flexibility and speed insharing and transmitting video data. This reduces transmission bandwidthrequirements.

In CCTV, the key challenge of video file compression is in achieving the properbalance between file size compression and image quality.

File compression is expressed as a ratio:

Original file size to New file size

(such as 30:1)Current common CCTV compression ratios are in the range of 15:1 up to 100:1. Thehigher the compression ratio is, the greater the file compression. This usually resultsin lower image quality.


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Unit 2



Table 2.1shows different video file sizes resulting from different levels of file compression and image capturerates. This information is also shows how much recording time is possible based upon these variables and thememory storage size.

Table 2.1 File size and recording times

Hours of recoding by hard drive size:Video FileType

File Size(per image) 30 GB 75 GB 150 GB 240 GB 640 GB

No Compression Color Video (460 TVL) = 650,000 Bytes (65 KB)At 60 IPS

39,000,000(39 MB)

0.21 0.53 1.07 1.71 4.56

At 20 IPS13,000,000

(13 MB)0.64 1.60 3.21 5.13 13.68

At 5 IPS3,250,000(3.2 MB)

2.56 6.41 12.82 20.51 54.70

At 1 IPS650,000(65 KB)

12.82 32.05 64.1 102.56 273.50

Low Ratio Compressed Color Video (High resolution) = 30,000 Bytes (3 KB)

At 60 IPS1,800,000(1.8 MB)

4.63 11.57 23.15 37.04 98.77

At 20 IPS600,000

(60 KB)

13.89 34.72 69.44 111.11 296.30

At 5 IPS150,000(15 KB)

55.56 138.89 277.78 444.44 1,185.19

At 1 IPS30,000(3 KB)

277.78 694.44 1,388.89 2,222.22 5,925.93

Medium Ratio Compressed Color Video (Standard resolution) = 15,000 Bytes (1.5 KB)

At 60 IPS900,000(90 KB)

9.26 23.15 46.30 74.07 197.53

At 20 IPS300,000(30 KB)

27.78 69.44 138.89 222.22 592.59

At 5 IPS75,000

(7.5 KB)111.11 277.78 555.56 888.89 2,370.37

At 1 IPS15,000

(1.5 KB)

555.56 1,388.89 2,777.78 4,444.44 11,851.85

High Ratio Compressed Color Video (Low resolution) = 7,000 Bytes (0.7 KB)

At 60 IPS420,000(42 KB)

19.84 49.60 99.21 158.73 423.28

At 20 IPS140,000(14 KB)

59.52 148.81 297.62 476.19 1,269.84

At 5 IPS35,000

(3.5 KB)238.10 595.24 1,190.48 1,904.76 5,079.37

At 1 IPS7,000

(0.7 KB)1,190.48 2,976.19 5,952.38 9,523.81 25,396.83


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Unit 2



Managing Video File Sizes

Non-compression techniques

A number of techniques can be used to reduce the file sizes created by video. Not allof them involve file compression.

Non-compression techniques to reduce file size include:

Reduce the Frame Sizeof the video frame itself. A 320x240 image is the

digital file size of a 640x480 video image. This requires no file compressionalgorithms.

Reduce the image per second (ips)captured and/or recorded. With 20 ipsyou create 1/3 the digital file size that 60 ips generates. No file compressionalgorithms are used.


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Unit 2



Video compression techniques

To achieve substantial video file size reductions, video compression is required. Thescience of video compression often leverages off our understanding of humanperception.

Normal human perception is more sensitive in discriminating differences in brightnesslevels (luminance), than we are in discriminating color variations (chrominance). Mostcompression engines take advantage of this perception characteristic. This is

accomplished by discarding much of the color information in the picture, and focusingon the subtle changes of brightness variations. In many cases the chrominance bitresolution values can be reduced twice as much as the luminance bit values, with verylittle perceived impact on image quality.

With video imagery, two dimensions of image capture exist:

The image file of each video frame created

The sequence of frames created

Video compression engines can perform file compression tasks in the following ways:

Intra-Frame Compression Compress the individual video frames (singleframe compression). Also known as Full Frame Refresh.

Inter-Frame Compression Compress the differences between frames insuccession (multi-frame compression). Also known as Conditional Refresh.

A variation of both techniques

Intra-Frame Compressionis where the individual video frames are separatelycompressed using an algorithm. These types of compression engines usually work bydiscarding much of the color information, and/or reoccurring, predictable patterns ofpixel data within the file. (Also know as spatialcompression.)

One method is to use blocks of pixel data (i.e. 8x8 pixel groups), which arestatistically analysed for pixel value similarities or redundancies. These pixel data

similarities are then converted to a new digital value for this block area. For sceneswith broad expanses of similar color/detail (i.e. blue sky), great compression resultsare achieved with very little image degrading.

Even in image areas with lots of detail, there are still pixel levels with color orbackground redundancies that can be compressed with little loss of image detail. Ascompression ratios are increased, this repeated blocking together of pixel data foranalysis and compression will eventually negatively impact image quality. This will firstbe notice where contrast edge lines exist, and in areas of fine detail

U2-7

Lossy CompressionData compression

techniques that resultsin some data lossthrough the eliminationof redundant orunnecessaryinformation. Most videocompressiontechnologies use thistype of compression.

LosslessCompression- Data

compression in whichno data is lost. Formost types of data, thistechnique can reducefiles by only 50% (2:1).Lossless compressionis used forcompressing raw dataand computer

programs.

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U2-9

Intra-framecompression has theadvantage of providingeasily retrievable, highquality video frames.


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U2-10

Inter-framecompression can

obtain 100:1compression in minimalmotion scenes, such asin a static warehouse.

U2-11

Inter-Frame Compressionaccounts to the sequence of video frames. For this multi-frame compression to work, the data from previous frames is needed. The algorithmcaptures periodic reference frames (i.e. every 1/2 second) and looks for only thedifferences within successive frames, which are then captured and stored. Thiscompression technique takes advantage of the fact that any given video frame isprobably very similar to the frames around it. (Also known as temporalor conditionalrefreshcompression.)

The above illustration represents a combination, or two stages of video compressiontechniques. Frame 1 is compressed using an Intra-frame algorithm (JPEG). Thesucceeding frames use this same compressed data, and check each succeedingframe to look for image differences. This is the function of the Inter-frame algorithm.Since only the scene differences between frames are accounted to, the compressionalgorithm can produce high compression ratios.

A certain number of frames down the sequence (say 4 frames), a reference frame isperformed to cross check for differences with the previous frames. With this check, itwill estimate the motion and scene to anticipate the compressing of the comingframes using this predicted data. When differences within the scene are detected,the Intra-frame algorithm will only need to compress the scene differences. PeriodicIntra-frame compression is used (~ every 10-20 frames).

Inter-frame compression has the capacity to dramatically reduce bandwidth andstorage requirements of CCTV video. With stationary camera placements, and scenesthat often have little activity, the video sequences captured will exhibit high degrees offrame-to-frame correlation. Even video situations that change regularly due to trafficactivity and/or camera pans, this compression technique can still deliver substantialfile reductions. This is due to most algorithms ability to track and detect repeating

patterns of activity called motion estimation. Thus, Inter-frame compression with itsframe-to-frame conditional refresh characteristics lends itself well to both the CCTVsecurity monitored environments, and the need to store and archive recorded videoinformation.

Inter-Frame compression requires more computer memory and processing powerthan does Intra-Frame compression. This is because it captures and holds in memorymultiple video frames for cross frame comparisons.


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Video compression standards

There are a number of video usage and compression standards. These aresummarized here:

H.320 This lossy standard is intended mainly for video conferencing and isoptimized for transmissions on ISDN (Integrated Services Digital Network, such asLAN and WAN) systems. Since it was developed to address two-way videocommunications, it is a useful standard for real-time video transmission. H.##

standards are set around mostly fixed telecommunication transmission rates. Becauseof this bandwidth constraint, the more users on the system will decrease the imagesper second transmission rate, producing a slide show type of image viewing.

The International Telecommunications Union (ITU-T) created H.320 and its subsetstandards. It sets standards for components and complete transmission systems, inaddition to setting compliance standards for image quality, especially related to signaltransmissions. These standards help maintain compatibility between components ofdifferent manufactures.

H.320 consists of a number of sub-standards:

H.221 Sets standards for multiplexing audio, video, data and controlinformation.

H.261 Describes video coding and decoding methods and file compressiontechniques. Similar to MPEG compression (not compatible), but it varies inthat it trades picture quality against motion. Thus, motion images will havelower quality than static images. This function optimizes bandwidth by havinga constant bit rate encoding (vs. constant quality and variable bit rateencoding.) The compression will always be in multiples of 64 Kbps (for ISDN)

H323 Standards for computer networks (TCP/IP)

H.324 Standards for analog modem connections and lines

JPEG This is an Intra-frame lossy standard, designed for the effective storage ofindividual frame data. Compression ranges of 5:1 to 25:1 will produce little visible lossin image quality. With greater compression rates (up to 40:1) quantization artifactsbecome visible. While JPEG does not include any transmission standards, it is a goodstandard for individual frame compression. It produces a compromise between imagequality and storage requirements. JPEG was created by the Joint Photographic ExpertGroupand is an ISO industry standard.

M-JPEG Also called Motion JPEG, this uses the single frame JPEG compressiontechnique and applies it to the sequence of video frames. M-JEG is widespread in thesecurity industry because of the ability to access individual frames as needed.Because MJPEG does not take into account relationships between multiple frames,the video compression rate is not as great as other standards (i.e. H.320/H.261 andMPEG). M-JPEG is not internationally standardized.

MPEG This term has evolved to represent a family of digital video lossycompression, which uses both the intra-frame and inter-frame algorithms standardsand file formats. This family of standards includes MPEG-1, MPEG-2 and MPEG-4.

MPEGs were created by the Moving Pictures Expert Groupand are ISO industrystandards.

MPEG-1 This was originally created for the storage of video onto CD-ROM media.This standard is slightly below the quality of VHS. MPEG-1 not only defines acompression standard, but also a resolution and transmission standard. Videostandards are a resolution of 352x240 pixels at 30 frames per second (fps), with apreferred data transmission rate of 1.5 Mbits/s. These were selected because they arethe standards for uncompressed audio and popular MP3 audio files. MPEG-1 iscompressed in non-real time and decompressed in real time. Compression rates of30:1 are typical, with compression up to 100:1 for low motion video.

U2-12

CIF CommonIntermediateFormat

This is a part ofH.261 videoconferencingstandards.

CIF formats definethe resolutions:

CIF or Full CIF(FCIF) =360 x 240

2CIF = 720 x 240

4CIF = 720 x 480

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U2-17

MPEG-2 This version was created specifically for digital TV. The compression ofvideo uses both the intra-frame and inter-frame algorithms. MPEG-2 provides anumber of quality options (called profiles and levels), which allows for professionalvideo transmission rates up to 15 Mbits/s. Video resolution standards of 720x480 and1280x720 at 60 fps, along with full CD quality audio are specified. MPEG-2 alsoprovides support for video interlacing, thus meeting standards for broadcast TV,NTSC, HDTV, and DVD-ROMs. Encoding (compressing) video into MPEG-2 datarequires significant computer processing power. Decoding (decompressing) the

MPEG-2 data stream needs only modest computer processing.

MPEG-4 This algorithm of lossy, inter-frame compression standard is Waveletbased. It uses object coding, which identifies motion and isolates this from stationarybackgrounds. It is primarily designed for use with: web streaming media, CDdistribution, video conversation (videophone), and broadcast TV. The compressedfiles are designed to transmit video mixed with graphics, text, 2-D and 3-D animationlayer over a narrow bandwidth, using low bit rates of 4800 bps to 4 Mbps.Compression rates of color images is at 20:1 up to 300:1, with grayscale images at20:1 to 50:1. MPEG-4 is an ISO standard.

Wavelet Wavelet uses whole frame vs. pixel group compression. Wavelets are thesimple pairing up of input values, comparing the differences, and passing the sum ofthe different values (coefficients). The distribution of most image data is concentrated

around a small number of coefficients. This results in efficient compression. BecauseWavelet compression works on filtering the overall image, it provides highercompression ratios than MJPEG, without the blocky artifacts. Compression of colorimages is in the range of 20:1 to 300:1, with grayscale images from 10:1 to 50:1. Thetrade off of this algorithm is speed. It is slower than MJPEG, thus it may not be thebest choice for real-time 30 frames/sec applications. JPEG 2000 is a waveletcompression.

Table 2.2 - Compression Summary

MPEG 1 MPEG-2 MPEG 4 Wavelet M-JPEG H.320/2

CompressionType

Wavelet &Inter-frame

Conditional

Refresh

Lossy


Conditional

Refresh

Lossy


Conditional

Refresh

Lossy

WaveletIntra-frame

Full Frame

Refresh

Lossy

Intra-frame

Full Frame

RefreshLossy

Inter-fram

Conditio

RefreshLossy

TypicalCompression(same quality)

30:1to

100:1

20:1to

100:1

20:1to

300:1

15:1to

300:1

15:1to

25:1

20:1to

100:1

BandwidthRequiremts

1-3 Mbps 5-15 Mbps 0.5-4 Mbps 1-4 Mbps 10-26 Mbps20 kbp2 Mbp

CompressionStrengths

Data storage&

Transmission

Data storage&

Transmission

Webstreaming,

video phone &data storage

Image quality&

Image retrieval

Image quality&

Image retrieval

Data stor&

Transmis

ProductsHiQ

(MPEG-2)VideoJet

VideoJet,DiBos 8

NetCam2,Divar

Eazeo,VideoJet,

DiBos(JPEG)


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Fill-in the blanks for the following statements:

1. The process of taking digital file data and reducing the file size is called:

______________________________________________________________ .

2. __________________________ are used to perform numerical calculations that

solve repetitive mathematical problems.

3. A wide variety of computer software tools exist on the market designed to reduce

the amount of data within files. These are generically called:

______________________________________________________________ .

4. The type of compression most frequently used in video compression, which

results in the loss of some original data is called _______________________ .

5. This is the term used to describe video compression performed on single videoframes only. It is also known as full frame refresh:

_____________________________________________________________ .

6. Identify two methods of reducing digital video file sizes that do not use

compression techniques:

a) ____________________________________________________________

b) ____________________________________________________________

7. The term that describes a conditional refreshvideo compression techniques is

called: ________________________________________________________

8. With any video compression technique, there is always a trade off or compromise

between achieving reduced _______________________________________ ,

and maintaining an acceptable level of _______________________________ .

9. Video compression is expressed in terms of a before and after ____________ .

10. Identify two main benefits of using video compression.

a) ____________________________________________________________

b) ____________________________________________________________

Refer to the Table 2.1 on page 23 for the following questions:

11. If the video is not compressed and capturing at 20 ips, how much video can bestored on a 150 GB hard drive? ____________________________________

12. The file size created every second at 20 ips and at medium compression is:_____________________________________________________________ .

13. If you have a 150 GB hard drive and 3 video cameras. You need to capture andretain at least 40 hours (1 work week) of information. At medium compressionwhat is the fastest IPS the cameras can equally capture at?: ______________ .



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Match the following video compression standards to the descriptions below. Write theterms in the blank spaces provided.

Video CompressionStandards

JPEG MPEG H.320

M-JPEG MPEG-1 H.261

WAVELET MPEG-2 MPEG-4

14. _______

A video conferencing standard that is optimized for transmissionon ISDN and telecommunication lines. There are a number ofsub-standards associated with this that define such issues asmodem connections, interfacing with computer networks, andvideo compression techniques. It uses inter-fame algorithms forvideo compression.

15. ______

Both an inter-frame and wavelet compression technique, whichaccounts to both the single frame and mult-frame data. Thisstandard also defines a transmission standard of 352x240 pixels

at 30 fps with a preferred data transfer rate of 1.5 Mbps (rangeof 1-3 Mbps). It was originally developed for storing video ontoCD-ROM media with image quality close to VHS.

16. _______

This is an inter-frame standard designed to effectively compressframe data, which can easily be retrieved and viewed asindividual frames. As compression rates increase, visiblequantization become noticeable as blocky artifacts.

17. _______

A technique the accounts to the whole image frame and not justgroups of pixels for compression. It uses coefficient values thatrepresent digital differences within the image and compressesthis data. It can provide higher compression ratios without theblocky pixel effects.

18. _______

An inter-frame (single-frame) compression that is appliedrepeatedly to each individual frame of video. It does not accountto any relationships between frames for compression purposes.It is a popular CCTV compression format because individualvideo frames can be easily retrieved and used. At the lowercompression rates, quality is very good for content identification.

19. _______

The inter-frame compression is wavelet based and is designedto meet the needs of web streaming media, CD production, andthe transmission of video mixed with graphics, test, 2-D and 3-Danimation layers. It uses object coding to separate motion frombackground information. It is a newer compression tool.

20. _______

This was designed specifically for digital TV and supports video

interlacing. Standards are specified for video resolution and fps.It uses both intra-frame and inter-frame compressiontechniques. This compression requires high computing power.


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Bosch SecuritySystems provides atotal integrated product:Business IntegrationSystem(BIS)

U3-3

Defining Networks

The CCTV market

In the marketplace of security, CCTV video is rarely the only protection componentwithin the system. The CCTV camera often supplements other security and safetyfunctions such as: access control, intrusion detection, fire protection, and intercomcommunications. For security/safety management and cost control reasons, most ofthese diverse signals are sent to centralized monitoring and control centers.

The great diversity of safety devices and their signals transmitted often createsobstacles to streamlined, cost effective system integration. Proprietary designs andthe lack of a single standard of such diverse systems usually results in parallel datatransmission links, each with their own receiving components. Customer demand andcompetition has also expanded this safety net function to include building energymanagement tasks, such as HVAC and lighting. IT network infrastructures arebecoming more important in achieving a single integrated, low cost, system that canincorporate visual and access security, fire safety, and building managementfunctions.

Digital technologies and computer networked system standards represents the mostlogical solution to such system diversity. The potential to not only integrate signaldata, but to also decentralize the collection and monitoring locations opens new

opportunities in creating system designs. The impact of digital networkedsecurity/safety/building systems effects component designs, system connectivity,communications, and even the business model for staffing and managing suchfunctions.

For CCTV to be a part of this industry evolution towards a computer networkedinfrastructure, a digital video signal is required. As reviewed in Unit 2, compression ofthat video signal is necessary for efficient and practical signal transmission, datastorage, and archiving purposes. This also requires a fundamental understanding ofnetwork systems and their communication protocols.

The evolution of enterprise class security systems allows for interconnection ofmultiple facilities worldwide. Video transmission is now possible through telephonelines (telco), a wide variety of corporate IT network systems, and the internet.

A number of factors are to be considered when integrating digital CCTV into anynetwork system. These include:

The size of the security network

The nature of the security system functions that are to be networked

The design and capacity of the existing network

The opportunities of digital CCTV network systems are tremendous. Createdeveryday are systems that offer greater flexibility, with new levels usability and safety.This also requires new skill sets and knowledge of the infrastructure and terminologyassociated with these existing IT network environments. Your participation in thiscourse is a start on that journey.


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Network basics

Networks are designed for sharing. With the wide variety of network systems thatexist, some fundamental guidelines must be observed in order to effectively shareinformation, devices and resources.

Most analog CCTV systems are Closed Circuit, having their own dedicated networksystem. One way of going beyond this dedicated closed circuit video network designis to integrate it into an existing network system. Digital CCTV systems can make use

of a variety of network systems. These are some basic systems that might be used.

Plain Old Telephone System(POTS) Analog telephone networks,accessed with modem.

Integrated Services Digital Network (ISDN) A digital circuit-switchednetwork using copper lines. It provides voice/data, analog-to-digitaltransitions, and often LAN-to-LAN connectivity. Transmission rate is 128Kbps.

Asymmetrical Digital Subscriber Line (ADSL) A high speed modulationsystem using copper lines that can transmit at 1500Kbps downstream(receiving) and 640 Kbps upstream (sending).

Local Area Network(LAN) Computer systems that may be at single office

site. LANs can have different designs and configurations. Wide Area Network(WAN) Computer systems, which can encompass

multiple buildings or campus type of sites. WANs can have different designsand configurations.

Internet(www) The ultimate and virtual worldwide computer networksystem. This is actually a collection of many networks.

Network building blocks

You can design networks in a variety of ways, depending upon the requirementsexpected of the system, the scale of operation, the volume of data sharing, and costconstraints. All networks require some basic building block components to operatewith. These include:

Network Operating System This consists of a family of software programs thatrun the networked computers. They provide the ability for the computers to shareresources, such as files, printers, and memory space. Serversare computersconfigured to share their own resources. This can be the hard drive or their abilityto connect to other network systems. Clientsare computers configured to usethe resources of server computers.

Network Interface Card (NIC) This circuit board inside computers is designedfor network communications. The digital signals generated by computers are toolow of a voltage for transmitting. The NIC card boosts these signals and properlypackages this data for transmission through the network. It also acts as agatekeeper to control access to the network cables.

Network Peripherals A term that describes devices that are a part of the

network, but are not computers or servers. These can include printers, modems,memory storage devices, and signal control components. These componentshave a special processor that allows them to interface with all serves (orsometimes clients) on a system. Thus a Macintosh and a PC can both use thesame device.

Network Cabling The component that connects everything together forcommunications and data transmission. Digital data can be sent in a number offorms. Transmission can be electrical pulses over cables, light pulses over fiberoptics or through the air, or as radio frequencies to receiving dishes. A singlenetwork may include all of these methods of data transmission.

Topology Theschematic descriptionof a network design.

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U3-5

A server can be set upas both a client and aserver. As a client, itwill have the ability touse other computer

resources.

U3-6

Basic network types

There are three primary types of network models that define the type of computer-network interactions.

Client/Servernetwork Certain computers (or application software runningon a computer) are designated as Servers. These units are configured toshare resources such as files, printers and memory space. They do this byopening their hard drive for file storage/sharing and by their ability to connect

to other network systems. Clientsare computers configured to use theresources of server computers.

Peer-to-Peernetwork Every computer is an equal and can function as aclient and a server. This allows each computer to share its resources with thenetwork, and access the shared resources of other computers on the network.Peer-to-peer networks are generally limited to 10-15 computers or less on asingle LAN system.

Point-to-pointnetwork The mostbasic type of networkdesign that has adirect connection

between twocomputers only.These are basicsystems, inexpensiveto install, and providefull cable capacity.

Half-duplex vs. Full-duplex communications

When communications between computers travels in only one direction at a time, thisis called half-duplexcommunications. Many LAN systems use this mode. A singlecoaxial cable has only one conductor and ground, so only half-duplex communicationsis possible.

Network systems that allow communications in both directions at the same time isoperating in full-duplexmode. A separate channel link is required for traffic to flow intwo directions at the same time. Twisted pair or fiber optic cable allows for full-duplexcommunications.


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Bandwidth

Bandwidth can have two different meanings within the CCTV environment. Thisdepends upon if you are referring to the bandwidth or carrying capacity of a digitalnetwork medium, or the frequency of an analogelectronic signal (analog video/audio).

Bandwidth for digital networks This

refers to the throughput of digital data acrossa network medium. This throughput(bandwidth) refers to the amount of data thatcan be carried from one point to anotherwithin a given time period (i.e. a second).Bits per second(bps) is the term usuallyused to express this capacity.

A cable that has the bandwidth of 120 Kbps(120,000 bps) has four times the capacity ofa cable with 30 Kbps (30,000 bps).

Factors that can impact either bandwidth capabilities or performance are: networkcabling type, network layout design, hardware and peripheral devices (i.e. modems),

software configurations, and network traffic.

Bandwidth for analog signals This measures the differencebetween the highestand lowest wavelength frequency of an analogelectronic signal. Hertzis themeasurement used.

A typical analog TV broadcast video signal has a bandwidth of 6 MHz. A cable systembandwidth occupies 50 to 300 MHz.

U3-7

Transmission Rateor

Throughputare termsused most often by theIT world, instead ofbandwidth.

Frequency thenumber of cyclechanges per second.This is measured inHertz. An analog term.


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U3-8

U3-9

Bandwidth will be

covered further inUnit 5 NetworkTransmission Medium

U3-10

Converting Bytes to bits

Since most data files sizes are expressed in bytes, and transmission capabilities of anetwork are expressed in bits, a conversion is needed to identify the impact data fileshave in network transmission.

There are 8 bits in every Byte, so multiply the Byte file size by 8.

15,000 Bytes x 8 = 120,000 bits (120K)

Bandwidth for digital videoTo determine bandwidth (digital network type) requirements for a video signal, youneed to include the number of images per second (ips) into your bits calculation.

Example: To calculate a video signal compressed to 15 KB digital file size, and the

scene is captured at 30 images per second, the network bandwidth requirements forthis signal is:

15,000 x 8 x 30 = 3,600,000 bits/sec (3.6 Mbps)

Normal network communication traffic will consume some of the available bandwidthcapabilities of a system. Network managers design in a buffer to account for thisongoing traffic. Approximately 65% of a network specified bandwidth is usuallyavailable for data traffic, such as video transmission.

Use the camera(s) bps value(s) to determine how many CCTV connections can beput into a given bandwidth of a video onlynetwork.

Example using 3.6 Mbps in video output per camera:

100 Mbps network connection x 65% available = 65 Mbps (bandwidth)

(100,000,000 x 0.65 = 65,000,000 bps)

Network bandwidth / camera bit output65,000,000 / 3,600,000 = 18 camera connections


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Network Communications

If networks are designed to share, then there must be guidelines for operation.Network standardsare rules that describe how things should be. Usually these areminimum technical requirements that relate to such things as cable specifications,transmission requirements, hardware component design, interface requirements, filestructure, and software performance.

Protocol interactions

Protocolsare sets of rules or standards that controls or enables the connection,communication, and data transfer between two computing destinations. How a widevariety of different computers on a network can communicate with each other requiresthat they use a common network language. Computers must follow specificcommunication protocolsto assure this takes place.

Networks use specific communications techniques to share information. There iscontinuous communications on networks for the purpose of diagnosing the status andhealth of connections, traffic volume, and availability of devices. Much of the invisibleactivity of network communications has very little to do with task of moving data fromone point to another, but with the status check of the system.

Whenever data is transmitted through a network, it needs to be reduced into signalsthat are native to the language of that network. The computer sending data uses anetwork interface to convert its binary data into the language code of that network (i.e.Ethernet). The data is broken up into packetsfor sending. The computer(s) on thereceiving end of this transmission must decode and reassemble the received packets,putting it back into the correct binary code order that is used by its own operatingsystem (i.e. Window NT).

Communications handshake

Much of the communications traffic that goes across a network is not the actual databeing shared or passed on. The task of the network operating system software is tocontinuously inform other applications and users about network status, routinginformation and system availability. This is the general network traffic that systemadministrators have reserve about 35% of the network bandwidth.

When communications is initiated on the network between two computers, an initialhandshakeis required. This communications handshake orpackage headeris sharingthis type of information:

Network Handshake Handshake Response

Who are you? (addressing)I am 161.88.162.12 IP address(nickname training room)

What type of device are you?(functionality)

I am a client PC

Were are you located? (routing)I am in a subnet of network161.88.160.10

Do you speak my language (protocols) I can communicate in TCP/IP

Are you allowed to talk to me?Am I allowed to talk to you? (security)

What is your password?Password recognized, access allowed

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U3-13

Extranet A networksystem that uses both

private and publicnetworks. There are

parts that are open tothe public, and othernetwork components

that are secure,encrypted, and

password protected.Web banking servicesare on Extranetsystems.

Network protocols

As you learned earlier, protocols are sets of rules or standards that controls orenables the connection, communication and data transfer between two computingdestinations. Since there are a wide variety of network types, there also is a widevariety of network communication and design protocols. Some of the more commonnetwork protocols are described below:

Ethernet

This network suite of protocols is one of the most widely installed LAN technologystandards. Ethernetstandards apply to the hardware connectivity, software interfaceoperating system, and transport medium. It is baseband signalling and usually usesthe star network or tree topology.

The transport medium often used is coaxial cable, or specified grades of twisted pairwire. Wireless LAN systems can also use Ethernet. Devices compete for networkaccess, sending a frame (like a packet) of data at a time. It uses a collision detectionprotocol, which detects when frames collide on the network. When this occurs, newreplacement frames of data are re-sent on a random access time setting.

Ethernet bandwidth is specified at 10 Mbps (called 10BASE-T). A Fast Ethernetstandard exists specified at 1000 Mbps (1000BASE-T) otherwise known as Gigabitnetwork/Ethernet. This is typically used for the network backbone.

TCP/IP

This suite of communications protocols is the most widely used in the world. It is thecommunications basis not only for the internet, but also many private corporatenetworks and in Extranetsystems.

TCP/IP(Transmission Control Protocol/Internet Protocol) is a two layeredprogram. The TCPlayer of this protocol manages the assembly of a message intosmall packets for transmission. The TCP layer on the receiving side will then open thepackets and reassemble the data into its original form, using a complimentarycompatible process. It will also re-request lost data, thus providing a reliable datatransfer process between computers.

The IPlayer is responsible for addressing each packet for transmission. Eachcomputer on the internet has a unique IP address.

When data is sent with TCP/IP, it is first broken up into small packets. Each packetgets the senders IP address and the receivers IP address attached to it. The packetis first sent to a gateway computer. This computer only sees a small part of theinternet, reads the IP address and starts routing it to other gateway computers thathave some of the same address code. Eventually, the packets reach the gatewayserver computer that supports the client computer that is to receive the data. This isthe local domain. The packets may take different routes to get to the samedestination, and they most likely will not be arriving in the proper order. It is thefunction of the TCP protocol to gather and reassemble these packets of information.

TCP/IP uses a client/server model of communications. The computer user (client)request and is provided services by other computers (servers). It is also a baseband,

connectionless protocol. Note that the TCP/IP suite of protocols does not specify anytransmission speeds.


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UDP

UDP(User Datagram Protocol) is a communications protocol that uses IP and is anoption to the TCP protocol. It offers a limited amount of service in that it does notdivide the message into packets and reassemble it at the other end (called datagramsin UDP). Separate computer programs that use UDP must take on the function ofchecking that all the data has been received and is in the right order. Since UDP hasless communication rules to follow (no checking of transmissions), it reduces the

network communications traffic, thus reducing network bandwidth requirements. UDPis good when communicating very small data packets (like alarm codes).

ISDN

ISDN(Integrated Services Digital Network) is a protocol for digital transmissionover the telephone network, often referred to as POTS (Plan Old Telephone Systems)It uses the existing telephone lines and required no additional wiring to be run. Voiceand data packets are integrated on the lines using different frequencies to transmitinformation simultaneously. An adaptor is required on both ends of the transmissionline, and if on a shared network, an ISDN router is needed. The ISDN configurationcan deliver between 128 Kbps to 384 Kbps. (vs. 56 Kbps modem rate). ISDN areusually used on WAN telephone networks.

ISDN is distance sensitive, a factor that impacts transmission rates. The network

range is up to 18,000 ft or 3 miles (5.5 km) without a repeater in use. Since it is a dialup service, cost of usage will depend upon connection time. ISDN is good for remoteaccess use: were ever transmission of circuit data or switching data is needed; orbacking up dedicated private lines or LAN-to-LAN connections in case they fail.

Multiple channels (B & D) are setup for transmission. Two B channels at 64 Kbpseach can be segmented (2 to 30), which are used for data, voice and other services.The single 16 Kbps D-channel carries the control signal information. This protocol isloosing popularity where higher speed cable modem and DSL network options exists.

DSL

The DSL(Digital Subscription Line) is similar to ISDN service in that it providesvoice, video and data packets in a digital connection over POTS networks. Where itdiffers from ISDN is that it is an always on service and has higher transmissionrates. There are two basic types available, depending upon the provider: SymmetricDSL (SDSL) and Asymmetric DSL (ADSL). The SDSL uses upstream anddownstream capacity to carry data in both directions. ADSL delivers higher speeddownstream and slower speed upstream. For video downloading, ADSL will providefaster transfer rates. These transmission rates range from 128 Kbps (upstream) to1.54 8 Mbpsdownstream. Thiscan enablecontinuous videotransmission. DSLis distance sensitive(18,000 ft or 3 miles

5.5 km, without a

repeater). This canalso be extended byintegrating this localloop with a fiberoptic networkconnection.

Since the service isalways on, theusage cost will befixed.

UDPis thecommunications

protocol use in theBosch BusinessIntegration Systems(BIS) product.

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U3-15

U3-16

Network devices

Computer network systems are connected and expanded by using a number ofhardware devices that are used to help control network traffic and route it to theproper destination(s). These are defined here:

Hubs and Switches

A Hubhas a number of ports thatprovides connecting points for anumber of nodes on a LANnetwork. A Hub will copy and sendthe data packet to all the othernodes connected to that hub.Passivehubs act as only a conduitfor the data. Intelligenthubs includeadditional features that allow formanagement and monitoring of thenetwork traffic.

A Switch, like a hub routes data to different nodes. But it does so by reading thespecific IP addresses. The Switch has the capability to read the packet destination IPaddress and forward that data only to the correct port(s). The destination IP addressneeds to be within the same network group or domain.

Both hubs and switches support any type of packet protocol.


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Routers

These are devices that forward data packet to differentnetworks by reading thedestination IP addresses (header) of the packet. Routers are connections between atleast two different network systems (i.e. LANs, WANs, internet) and are located withgateways the network connection points.

The router uses the header data and programmed tables to identify the best path toforward the data packet to its destination. They use communication protocols (i.e.

ICMP) to communicate with each other and for configuring the best transmission routebetween two hosts. Routers do very little filtering.

Gateways

These function as nodes on network and act as an entrance point to other networks.On large enterprise network systems, the gateway often acts as a proxy server and afirewall. They also allow different network protocols to interface with each other.Gateways route the traffic from its own network system to the outside network (i.e.internet). For home computers, the Internet Service Provider (ISP) performs thegateway function.

The gateway is associated with both a router, which forwards the data packetaccording to header data and forwarding tables, and the switch, which provides theactual path for the packet in and out of the gateway.

U3-17

U3-18


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Modems

Modem is short for modulator/demodulator. They perform the conversion of analogsignals to digital data and digital data to analog signals. Modems can be an internalboard in a computer, or an external component. If external, it often uses a RS232connector.

At lower data transfer rates, the modem communication protocol to format the dataalmost universal. This allows most modems to communicate with each other. At high

transmission rates, more proprietary protocols may exist.

Modems have characteristics that can allow for some configuring options. Acommunications software package usually comes with the modem to setup thefollowing functions:

Bps This is the data transfer rate. At very slow rates, modems are measured inbaud rates (i.e. 300 baud = ~25cps). At higher rates, they use the bps term. Commontransmission rates are 2.4 Kbps, 2.8 Kbps, 56 Kbps up to about 128 Kbps. The datatransfer rate between modems is only as fast as the slowest modem.

Data compression Some modems perform compression techniques to increasedata transfer rates. The modem on the receiving end needs to be able to decompressthe data packet using the same compression technique.

Flash memory This allows for updating the communications protocols. If it doesnthave flash memory, then it will be using conventional ROM, which can not bemodified.


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Match the network type provided below to the proper description for the following 7questions. Write the word in the blank provided.

Internet ISDN LAN

Client/Server Peer-to-Peer Point-to-Point

WAN POTS ASAP

1. ____________________ A network that consists of two computers connected

directly to each other through a single cross-over cable. This is the most basic

form of computer networking.

2. ____________________ A variety of worldwide computer network systems

interconnected together.

3. ____________________ Computers connected together and each can share

its capabilities with the others, acting as either a client or a server. These are

generally small network systems.

4. ____________________ Computer systems that are usually within a single

office site. There can be a wide variety of network designs used to meet this

need.

5. ____________________ This network system can cover multiple sites and

building locations, but is usually associated with one organization.

6. ____________________ A network designed with a designated maincomputer(s) that function as a resource and connection point for the other

computers on the network. The peripheral computers can communicate to each

other through this main computer and use its other resources.

Calculate the following:

7. An 8 bit digital processor produces a digital file that is 30 Kbytes in size. How

many bits is that?

_____________________________________________.

8. A digital camera is capturing images at 20 ips. The 8 bit processor produces a

10 Kbyte file. What is the video bandwidth for this camera?

____________

9. The previous camera bandwidth is connected to a digital network system that has

a total bandwidth of 10 Mbps. Assuming 65% network speed availability. How

many total CCTV cameras can be connected to this network? ______________



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Match the terms provided below to the proper description. Write the word in the blankprovided.

Ethernet Handshake Half-duplex

ISDN Hub Full-duplex

UDP Gateway Frequency

TCP/IP Switch Bandwidth

DSL Router Analog

Protocols Modem Digital

bps ips packets

10. When signal transmission between two computers can travel in only one direction

at a time is called: __________________________ communications.

11. The data that is packaged into small units for network transmission is referred to

as data __________________________________________.

12. Digital bandwidth in measured in _________________________________.

13. The number of cycle changes per second and is measured in Hertz refers to the

_______________________ of an analog signal.

14. The ______________________ bandwidth is determined by the difference

between the highest frequency and lowest frequency of a signal.

15. ____________________ Sets of standards for network design, connectivity,

and communications.

Documents

CCTV Digital Basics Training Workbook