basic television ppt.pptx

7/25/2019 Basic Television ppt.pptx

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Basic Television

Broadcasting


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Introduction

The composite video signal generated by camera andassociated circuitry is processed in the control room before

routing it to the transmitter. At transmitter, picture carrier

frequency assigned to the station is generated, amplified and

later amplitude modulated with the incoming video signal. The

sound output associated with the scene is simultaneouslyprocessed and frequency modulated with channel sound carrier

frequency. The two outputs, one from picture signal transmitter

and the other from sound signal transmitter are combined in a

suitable network and then fed to a common antenna network for

transmission. As is obvious, the picture and sound signals,

though generated and processed simultaneously pass through

two independent transmitters at the broadcasting station.


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Basic Television System

The basic television system converts light and sounds into electrical video and audio

signals that are transmitted wirelessly or by cable!

and reconverted by the television receiver and loudspeaker into television pictures and

sound.


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Television Studio

an acoustically treated compact anechoic free from echo!

room

suitably furnished and equipped with flood lights for proper

light effects

uses dimmerstats with flood lights that enables suitable

illumination level of any particular area of the studio

depending on the scene to be televised

several cameras are used to telecast the scene from

different angles

large number of microphones are provided at differentlocations to pick up sound associated with the programme


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Television Studio Technical Aspects

The camera and microphone outputs are fed into the control room by

coa"ial cables

The control room has several monitors to view pictures picked up bydifferent cameras.

#onitors used are T$ receivers that contains no provision for

receiving broadcast signals but operates on adirect input of

unmodulated signal

%eadphones are used to monitor and regulate sound outputreceived from different microphones through audio mi"ers

&or a live studio, video tape recording and telecine machine rooms

are located close to the control room

'rogrammes as enacted in the studio are recorded on a video tape

recorder $T(! through the control room. These are later broadcastwith the $T( output passing through the same control room

All the rooms are interconnected by coa"ial cables and shielded

wires.

In large establishments, there are several such studio units with their

outputs feeding the transmitter through a switcher in the mastercontrol room, which selects one programme at a time


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Television Studio )ayout


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Television #ulticamera Studio System *iagram

The multicamera studio system contains quality controls ++ and audio console!, selectioncontrols switcher and audio console!, and monitors for previewing pictures and sound.


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Television Studio - Sample 'icture

Television studio with lighting system, cameras , monitor, microphone and green background. reen

Background is for chroma keying. +hroma /eyingis the process by which a specific colour element

chroma! is removed from a video scene and replaced keyed! with a different element.


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Television Studio with +hroma /eying

Television studio with chroma keying for Superman.

Television studio with chroma keying for 0eather 1ews.


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Television )ive Show Studio

Television studio with chroma keying for Superman.

The ame Begins 2 ##+ Studio of ermany.


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Television +ameras

Two basic groups of television cameras -

3. Self +ontained +amera

has all the elements necessary to view a scene and generate a

complete television signal. Such units are employed for outdoor

locations and normally have a $T( and baby flood lights as anintegral part of the televising set up

4. Two5unit Systems

employs separate camera heads driven by remote camera

control equipment located in the central apparatus room


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Television +ameras

Self +ontained +amera

Two nit Systems


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Television +ameras - )enses

Television cameras can produce images to different scales

depending on the focal length viewing angle! of the lens employed.

)enses of longer focal length are narrow angle lenses while those

of shorter focal length are wide angle lenses.

1arrow angle lenses below 467! are suitable for close ups of

distant ob8ects because of the magnifying effect due to their longer

focal length.

)enses with angles over 967 are most suited for location shots

which cover large areas.

#edium angle lenses 46 to 967! are called universal lenses and

are used for televising normal scenes.


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Television +ameras - )ense Turret

A rotating device on a camera for bringing any of several lenses

in front of the shutter

An image orthicon turret assembly holds four lenses of focal

lengths :; mm, ;6 mm, 3;6 mm and a


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Television +ameras - >oom )ens

A zoom lens is a mechanical assembly of lens elements for which the focal

length and thus angle of view! can be varied, as opposed to a fi"ed focal length

&&)! lens

A true


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Television +ameras - +amera #ountings Studio cameras are mounted on light weight tripodstands with rubber wheels to

enable the operator to shift the camera as and when required. It is often

necessary to be able to move the camera up and down and around its central a"is

to pick5up different sections of the scene 'an5tilt unitsmay be used which typically provide a :967 rotational capability and

allow tilting action of plus or minus ?67

In many applications,primarily closed circuit systems, where it is desirable to be

able to remotely move the camera both hori


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Television +ameras - $iew &inder @ssentially a monitor which reproduces the scene on a small picture

tube.It receives video signals from the control room stabili


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Television +amera - Studio )ightings It is necessary to illuminate each area of action separately besides

providing an average level of brightness over the entire scene.

)ighting scheme is so designed that shadows are prevented The light fi"tures used include spot lights, broads and flood lights of 6.; /0

to ; /0 ratings

The brightness level in different locations of the studio is controlled by

varying effective current flow through the corresponding lamps. &or a

smooth current control, dimmerstats autotransformers! are used for low

rating lamps are silicon controlled rectifiers S+(s! for higher power lights


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Television +amera - Audio 'ick5up The location and placement of microphones depends on the type of

programme. &or panel discussions, news5reading and musical programmes

the microphones may be visible to the viewer and so can be put on a desk

or mounted on floor stands. %owever, for plays and many other similar

programmes the microphones must be kept out of view. &or such

applications these are either hidden suitably or mounted on booms. A

microphone boom is an ad8ustable e"tended rod from a stand which is

mounted on a movable platform. The booms carry microphones close to

the area of pick5up but keep them high enough to be out of the camerarange. Boom operators manipulate boom arms for distinct sound pick5up

yet keeping the microphones out of camera view.


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'((A##@ +1T() (# The production control roomor studio control roomSCR! is the place

in a television studio in which the composition of the outgoing program

takes place.

It is manned by the programme director, his assistant, a camera control

unit engineer, a video mi"er e"pert, a sound engineer and a lighting

director. The programme director with the help of this staff effects overall

control of the programme while it is telecast live or recorded on a $T(. The

camera and sound outputs from the announcers booth and $I' studios are

also routed through the programme control room.


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+amera +ontrol nit +.+..! The camera control unit has provision to control


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$I*@ S0IT+%@(

A video switcher is a multicontact crossbar switch matri" with

provision for selecting any one or more out of a large number ofinputs and switching them on to outgoing circuits. The input

sources include cameras, $T(s and telecine machine outputs,

besides test signals and special effects generators. Thus at this

point the programme producer with the assistance of video switcher

may select the output of any camera, or mi" the output of two ormore cameras.Similarly various effects such as fades, wipes,

dissolves, supers and so on may be introduce and controlled with a

mi"er.


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$I*@ S0IT+%@( - Three Types of $ideo Switchers

#echanical 'ushbutton Switcher 5 In this type the signals are

terminated on the actual switch contacts. The bank of switches isinterlocked to prevent simultaneous operation. This type of switcher

is used primarily for portable field units or in ++T$ systems

because switching is not frequent and momentary disturbances in

the picture during switching can be tolerated.


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(elay Switcher 5 or relay cross5bar is an electromechanical

switcher. %ere magnetically activated read switch contacts are usedto effect switching. The relays can be operated by remote control

lines. (eed relays have fast operate time around3 ms! and so can

be used to enable switching during the vertical blanking interval.

&igure below shows a : " ; switching matri" employing a reed relay

switcher.


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@lectronic Switcher 5 These are all electronic switchers and use

solid state devices that provide transition times of the order of a fewmicro5seconds. Their si


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$I*@ S0IT+%@( - Types of Switching Transitions

The actual switching transition is either carried out by a lap5

dissolve operation or a fade out5fadein form of switching.


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$I*@ S0IT+%@( - @lectronic Switcher +onfiguration

&igure below is a functional block diagram of very simple broadcast switcher5mi"er. It has five inputs out of which any two may be selected to drive the two buffer

amplifiers. These, in turn feed into a mi"er amplifier.

The mi"er transfers video signals by fade out5fade in method. The potentiometers at

the remote mi"er amplifier can be positioned to select 366 per cent output from

either A or B bus. Assume A and B inputs were at 366 per cent and 6 per cent levels

respectively. If camera 1o. 4 is selected on the A bus, it would appear at the output.

Similarly, if camera 1o. : is selected on the B bus, it will not appear at the mi"er

output. %owever, when the levers that control the potentiometers are moved through

their full travel, the output from the mi"er amplifier would transfer from A bus to B bus

at a relatively slow rate providing a transition from camera 1o. 4 to camera 1o. :.Similarly more comple" switchers can be designed to provide different switching

matrices.


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Special @ffects enerator

A special effects generator 5 normally located along with the

camera control units in the camera apparatus room. It is

programmed to generate video signals for providing special effects.Its output is available at a panel in the production control room. The

special effects signals include curtain moving effects, both

hori


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SC1+%(1I>I1 SCST@#

To generate a meaningful picture on the raster of a monitor or receiver, some means

are needed to synchroni


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*istribution of +amera utputs to #onitors #onitors usually have well designed video amplifiers with bandwidth as large as :6

#%


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#AST@( +1T() (# #+(! Master control 5 the technical hub of a broadcast operation common among most

over the air television stations and television networks. It is distinct from a production

control room in television studios where the activities such as switching from camera to

camera are coordinated. It is also vastly different from the studio where the talent are

located. A transmission control room is usually smaller in si


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T@)@$ISI1 T(A1S#ITT@( - Analog


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T@)@$ISI1 T(A1S#ITT@( - Analog

A simplified functional block diagram of a television transmitter is shown

in the &ig. 1ecessary details of video signal modulation with picture

carrier of allotted channel are shown in picture transmitter section of thediagram. 1ote the inclusion of a dc restorer circuit *+ clamp! before the

modulator. Also note that because of modulation at a relatively low power

level, an amplifier is used after the modulated (& amplifier to raise the

power level. Accordingly this amplifier must be a class5B push5pull linear

(& amplifier. Both the modulator and power amplifier sections of the

transmitter employ specially designed $%& triodes for $%& channels andklystrons in transmitters that operate in %& channels.

The modulated output is fed to a filter designed to filter out part of the

lower sideband frequencies known as vestigial sideband.

The filter output feeds into a combining network where the output from the

sound transmitter is added to it. This network is designed in such away that while combining, either signal does not interfere with the working

of the other transmitter. A coa"ial cable connects the combined output to

the antenna system mounted on a high tower situated close to the

transmitter. A turnstile antenna array is used to radiate equal power in all

directions. The antenna is mounted hori


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A1A) T@)@$ISI1 T(A1S#ISSI1 - 'icture Signal

Transmission

At the production control room video signal amplitude as received fromthe camera is very low and direct coupled amplifiers are used to

preserve dc component of the signal. &urther on, ac coupling is

provided because it is often technically easier and less e"pensive to use

such a coupling. This involves loss of dc component which, however, is

reinserted at the transmitter before modulation. This is carried out by a

dc restorer circuit often called a blanking levelclamp.

In the master control room the composite video signal is raised to

about one volt '5' level before feeding it to the cable that connects

the control room to the transmitter. Though the transmitter is located

close to the studios, often in the same building, matching networksare provided at both ends of the connecting cable to avoid

unnecessary attenuation and frequency distortion.

&or picture transmission, the signal is transmitted by amplitude

modulation transmitter.


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A1A) T@)@$ISI1 T(A1S#ISSI1 - 'SITI$@ A1* 1@ATI$@ A##*)ATI1

0hen the intensity of picture brightness causes increase in amplitude of the

modulated envelope, it is called Epositive modulation. 0hen the polarity of

modulating video signal is so chosen that sync tips lie at the 366 per centlevel of carrier amplitude and increasing brightness produces decrease in

the modulation envelope, it is called Enegative modulation. The two

polarities of modulation are illustrated in &ig. D.34.


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A1A) T@)@$ISI1 T(A1S#ISSI1 - A# Signal


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A1A) T@)@$ISI1 T(A1S#ISSI1 - S1* SI1A)T(A1S#ISSI1

The outputs of all the microphones are terminated in sockets on the sound

panel in the production control room. The audio signal is accorded enoughamplification before feeding it to switchers and mi"ers for selecting and

mi"ing outputs from different microphones. The sound engineer in the

control room does so in consultation with the programme director. Some

prerecorded and special sound effects are also available on tapes and are

mi"ed with sound output from the studio at the discretion of programme

director. All this needs prior planning and a lot of rehearsing otherwise thedesired effects cannot be produced. As in the case of picture transmission,

audio monitors are provided at several stages along the audio channel to

keep a check over the quality and volume of sound.

&or audio transmission, the signal is transmitted by frequency

modulation transmitter.


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A1A) T@)@$ISI1 T(A1S#ISSI1 - &(@F@1+C #*)ATI1


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*IITA) T@)@$ISI1 T(A1S#ISSI1 - *igital IS*B G T

Integrated Services Digital BroadcastingISDB! Transmission

*IITA) T@)@$ISI1 T(A1S#ISSI1 *igital IS*B T


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*IITA) T@)@$ISI1 T(A1S#ISSI1 - *igital IS*B T


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QAMquadrature amplitude modulation!5 the amplitude of two waves, ?67 out5of5phase

with each other in quadrature! are changed modulated or keyed! to represent the data

signal. Amplitude modulating two carriers in quadrature can be equivalently viewed as

both amplitude modulating and phase modulating a single carrier.



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*ifferential Fuadrature 'hase Shift /eying DQPSK! 5 A variation on the F'S/ modulation

technique, DQPSKrelies on the difference between successive phases of a signal rather

than the absolute phase position.



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Ortogonal !requenc"#division multiple$ingO%DM! 5 a method of encoding digital data

on multiple carrier frequencies.



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Thank Cou So #uch

wyn Tumulak Balolong


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Additional (eferrences -

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www.tv5handbook.com

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http-HHwarrensheetsdesign.comHblogHthrough5the5lens5of5a5camera5designing5a5television5studioH

www.wikimedia.org

http-HHskaarho8.comHdesignsHatem5ccu5for5bmd5studio5camerasH

www.ggvideo.comwww.sportsvideo.org

www.pactv.com

www.wikipedia.com

http-HHwww.dibeg.orgHtechpHstructureHstructure.html
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