unit 13 broadcast media radio and television · unit 13 broadcast media : radio and television...

UNIT 13 BROADCAST MEDIA : RADIO AND TELEVISION

Structure

Introduclion

Objectives

Broadcasting : Historical Genesis

Radio Broadcasting

13.3.1 Techn~cal description

13.3.2 AM and FM radio

13.3 3 Ham Radio

How Television Works

13 1.1 TV Transn~ission Techn!quc\

Emerging Trends in Broadcastlllg

Summary

Unit End Activities

Referencec and Suggested Reading

13.9 Clues to Check Your Progress

13.0 INTRODUCTIION In the earlier blocks uf this course, we have discussed the nature of communication in general, with specific reference to the communication proce5s in the context of education and training. The role played by technology in the field of education and training have also been clarified. This block deals with the role of audio and video media in educational conimunication. Within the spectrum of audio and video media. broadcast media in particular have special role in the field of educational technology and this for~nh the subject matter for the present unit.

Broadcasting can be detined as instant dissemination of information through wireless means to the public at large. Radio and TV are the twin broadcast media, which have established themselves all over the world, the former as a means of transmission of

i sound and the latter as a means of transmission of moving pictures and soiund. In the recent past, the word broadcasting has acquired a broader connotation to include data broadcasting. (transmission of computerized data thkough wiredlwireless means), Internet broadcasting, etc. For the purpose of this wi t howevcr, we contine ourselves to broadcasting in the traditional sense, namely radio ahd television.

Lct us bear in mind that the technologies of radio and TV are specialized areas of studies in themselves. However, for students of educational lechnology an understanding of these technologies from a user's poiat of view is important rathcr than from the view point of broadcast engineering. design and development. Thcrefore. we shall concentrate on the common technological features ,of the two technologies as well as their individual features but leave out intricate details concerning specific equipments and systems. I

13.1 OBJECTIVES After studying this unit, you should be able to :

describe, briefly, the historical development of hrvadcast media: c

Audio and Video Media explain the principles of working of radio as well as television;

enumerate the basic hardware features of a broadcast setup (radio as well as television);

discuss the different models of transmission and reception of RadiojTV signals:

visualize some on-going and future developments in the world of broadcasting.

13.2 BROADCASTING: HISTORICAL GENESIS Broadcasting developed as a result of early experiments in wireless communications conducted towards the last decade of the 19Ih century. Although Marconi is usually credited as the inventor of wireless, parallel inventions by several other pioneers working independently in other countries, including India, have contributed to the birth of wireless and its offspring, the broadcast media - Radio and Television.

Radio

Broadcasting in India was started in 1927 by a company called the Indian Broadcasting Company (IBC), through radio stations established at Bombay and, later at Calcutta. In 1930, this company was taken over by the government and the two radio stations were continued under the banner 'Indian Broadcasting Service'. In 1936, the Delhi radio station went on the air, and soon the name 'All India Radio'(A1R) was given to the Indian Broadcasting Service. It became popular as Akashvani.

AIR has steadily grown over the years both in terms of its reach and variety" in its programme content and has since become a household name across the country. After independence, successive five year plans havt: helped radio broadcasting to emerge as unique mass medium with the mandate to infonn, educate and entertain people.

The spread of portable transistor radio sets during the later half of 1960's is a major landmark in the history of radio. As the transistor sets operated on batteries, were highly portable and available at affordable prices, radio became a byword as the common person's medium. Today the reach of radio is almost cent percent (99.37%) with almost every family in the country owning at least one radio set.

Even though entertainment programmes form the bulk of day-to-day broadcasts and commanded maximum listenership, educational programmes have always been a compulsory factor in the fixed-point charts of all the radio stations. Usually you find a typical radio station airing school broadcasts, for schools, universities and distance education learners, which are broadcast from different AIR stations both on medium wave and short-wave. Since 1993, programmes meant for IGNOU students are being broadcast from select AIR stations regularly. Unfortunately, the listenership of educational broadcasts is rather marginal in many cases because of several factors like the timings not being suitable to the target audience, non-availability of radio reception facility at the schools, programmes not sufficiently exciting, lack of enthusiasm on the part of teachers in programme production and the domineering presence of Television. The National Education Policy document of 1986 and also the Programme of Action, 1992 underpinned the need for harnessing radio for educational purposes. The real breakthrough in this regard came in the year 1999, when the Ministry of Information and Broadcasting took a policy decision to throw open FM Radio to private broadcasters at 40 select places in the country. While unveiling the scheme, one frequency at each of the 40 places was kept reserved for educational broadcasting and passed them on to the Ministry of Human Resource Development for establishing the FM radio stations. The Indira Gandhi ~ a t i o n a l Open University was chosen as the nodal agency to implement the project within a time frame of 3 years starting from the year 2001-02. These stations were established under the banner 'Gyan Vani': Allahabad, Banglore, Coimbatore, Lucknow. Mumbai, Vishakhapatnam and Bhopal. With daily transmission ranging from 8 hours to 12 hours and a coverage area of about 60 km radius each.

The Gyan Vani network of 26 stations aims to address the educational and development needs of the local communities. Each Gyan Vani station operates in an alltonornous manner with the collaboration of local educational institutions and NGO's in the day- to-day management and running of the station. Live educational lessons with phone-in interactions from the target audience are the noteworthy features of Gyan Vani broadcasts at all the places. The medium is usually English or Hindi or the local language At present there is transmission of educational and enrichment audio programmes through FM Radio network of the Gyan Vani Statims located at different places of the country. There is also transmission of live Interactive Radio Counseling (IRC) sessions for IGNOU students through AIR Stations (http://www.ignou.ac.in)

Table 1 : Radio Broadcasting Milestones

Television

Early experiments in wireless communication by Alaksander S Popov of Russia, Guglielmo Marconi in England and Jagdish Chandra Bose in India. Radio Amateurs pick up SOS sent out by Titanic. Broadcasting on a regular scale starts in USA, followed by U.K. The Indian Broadcasting company starts from Bombay. Birth of All India Radio. The transistor revolution results in rapid expansion of radio sets. FM Broadcasting takes roots in different countries, including India. Over powering popularity of TV causes set back to radio listening, especially in urban areas. Digital Audio Broadcasting(DAB) starts in advanced countries. FM radio expansion in India. - IGNOU's 'Gyan Vani' Educational FM radio; first Gyan Vani station starts at Allahabad.

DTH Service of Prasar Bharati launched.

Television came into our country as late as in September, 1959, apd that too only in Delhi. By that time the advanced countries were having colour television. To begin with, it was an experimental venture and viewership was confined to 180 odd community sets located in 'tele-clubs' formed in and around Delhi under a grant-in-aid by UNESCO. / The transmission timings were just about 20 minutes, twice a week. School television (STV) was started in 1961 and entertainment programmes in 1965, by which time

I i daily transmissions too were introduced.

/ After long years of lull, TV expansion made a quantum leap with Bombay TV coming

i on the air in October 1972. A year later, Srinagar and Amritsar stations were inaugurated. Calcutta, Madras and Lucknow stations were added in 1975.An important milestone in the history of Indian television is the Satellite Instructional Television Experiment (SITE) conducted during 1975-76 with the help of an American Satellite ATS-6. Educational and developmental programmes were beamed to 2400 villages across the country which received them through Direct Reception Sets (DRS). The success of this unique experiment has paved the way for satellite television in our country through our own Satellite system INSAT, at later stage. Television as a separate entity from All India Radio was announced id 1976 and was christened as Doordarshan on April 6 that year.

The 1980s saw major strides in television expansion. Natiional programme was initiated in 1982.Colour television was also introduced in the eve of the Asian Games in 1982. Close on its heels followed satellite television through the INSAT system. In 1984 the University Grants Commission (UGC) telecasts (later called 'country wide classroom') were introduced. The second channel of Doordarshan from Delhi was also commenced that year. The VCR (Video Cassette Recorder) revolution too made its beginning in the 80's, and soon made inroads into the nooks and comers of the country. Theatrical viewing of feature films, which till then had been the most popular pastime of the masses, suffered a setback as the 'video boom' readily offered everyone the more

Broadcast Media: Radio and Television

Audio and Video Media convenient and cheaper alternative of domestic vlewing through VHS (Video Horrle System) cassettes.

The television scene in the 1990s was marked by initiatives like development oC tsans- national TV channels through satellites and the spread of cable. The hitherto unchallenged dominancc of Doordarshan gave way to do7,ens of foreign as well as domestic TV channels, which competed fiercely with one another for viewership and advertisement revenues. While most of these channels are entertainment-oriented, there are notable exceptions like the 'Discovery Channel' and the 'National Geographic' which are dedicated to exploration and adventure docun~entaries.

IGNOU telecasts on Doordarshan made a modest start in 1991 with half hour slots on alternate days. In due course. they were extended to all days of the wcck. A separate educational TV channel. 'Gyan Darshan' was started on 26"' Jan. 2000. Gyandarshan is a satellite-based channel airing programmes contributed by major educational bodies in the country such as IGNOU, UGC-CEC, NCERT-CIET, National Institute of Open Schooling, etc. Another significant development is the birth of the technology channel 'Ekalavya' which started on 26'h Jan, 2003, as part of the Gyari Da-shan bouquct, to cater to engineering students. Gyan Darshan (GD), a fully digital 23 hour exclusive Educational TV Channel, is a digital bouquet of 4 channels. The transmission of GD channels is almost completely automated through the installation of the video server (http.11 www.ignou.ac.in1).

While these are undoubtedly ma-jor developments on the educational TV scene, the limitation at the moment is the apathy of the cable operators who, in most cases, shy away from including the educational channels on ib*;. -~;~.vorks. SO most of the homes in the country do not in practice receive them. Although satellite television is becoming common but the companies offering these services too did not include these channels till at the initial stage. However, developments like DTH services (Direct-to-I-Iorne TV of which you will study in detail in Unit 3 of this Block) and Conditional Access Syctem (It is a system introduced by the Union of India under the provisionh of Cable Television Networks (Regulation) Amendment Act, 2002 to regulate the functioning of cable services in India and to give consumers a choice to view and pay for channels of their choice, are taking care of this problem to some extent.

The world 1925 1930-35

1935

1954

1967

1968

1974 1988

1990's 1995 onwards India 1959 1965

1975-76 1982

Table 2: Television Milestones .-

Mechanical Television invented by J.L. Baird in UK.

Electronic television by Baird in UK, Gaborisky In Russia, Takayenagi in Japan, Jenkins and Zworkyin in USA. First regular TV services in the world, from Berlin. Colour TV starts in USAiNTSC system) Birth of PAL and SECAM colour TV systems in UK and France respectively

Birth of Satellite lelevision(USA & Europe) First Video Cassette Recorder(VCR) by Japan High Definition TV Broadcasting starts in Japan World-wide boom in Satellite and Cable networks DTH (Direct-to-Home) makes inroads in developed countries

Experimental TV service(from Delhi) starts Regular TV service(from Delhi) starts Satellite Instructional Television Experiment(S1TE)

Colour Television and satellite relays start on the eve of Asian Garnes

Teletext service from Delhi Gyan Darshan(1ndia's first educational TV channels) starts

Eklavya Technology Channel starts.

Since 2005, DD Bharati channel carries a special slot called Gyan Sarita offering Broadcast illecria: Radio and Television enrichment programme in science, technology, etc. produced by IGNOU.

13.3 RADIO BROADCASTING

In the foregoing section, we have seen how the twin media of Radio and Television have evolved and grown over the years. Having understood the prominent place the two media have come to occupy in the personal and community life of the people, let us now take up Radio and discuss its technical building blocks and how exactly radio broadcasts take place.

Radio Broadcasting sub-systems: Any radio broadcasting system can be understood as consisting of the following major sub-systems:

The studio center

Studio-to-Transmitter Link (STL)

The transmitting center

Radio propagation path

Reception system (radio set).

13.3.1 Technical Description

Studio

The studio center is the place where the programmes are recorded, edited, produced, and played back at the time of transmission. This is the place where all recordings, editing, dubbing, mixing, live broadcast and announcements during transmissions take place. In the case of live broadcasts, the studio center again is thc place of origin of the programmes with the concerned artistslperformersl announcerslnews readers operating from one or the other studio of the studio center. Even in the case of OP's(outside broadcast), the events being broadcast from the OB spot are invariably routed through the studio center for convenience of switching and other technical reasons. Thus the studio center becomes the eventual outlet for the programmes in all cases.

A studio center may have just one or more studios designed for recording different kinds of programmes. Apart from Studio(s) . the ccnter will also have facilities such as editing rooms, control room and other related technical facilities. Broadcast organizations like the All India Radio earmark their studio for specific purposes e.g. talks, music, drama and transmission (playback). This is because, ideally, different kinds of programmes require to be recorded in difftirent acoustic conditions. This aspect is taken care of while designing the studio structure and its acoustics. Acoustics of the studio is done in such a manner that the studios are insulated from outside noises and generate sounds with the clarity and the requjred reverberation.

Multi-purpose Studio

Smaller production houses cannot afford to create separate studios for individual purposes like talks, drama, music, etc. In this case. a single multi-purpose studio is the answer. The acoustics of a multi-purpose studio can be designed essentially for talks. When it has to be used for music or drama, reverberation can be added electronically (such electronic devices are available and are commorh as a part of the control room set up) in the right magnitude.

Transmission Studio

This is for the purpose of playing back pre-recorded tapes interspersed by live announcements etc. in a pre-determined sequence. The number of transmission studios

Audio and Video Media (also called playback studios) would d e p e n ~ upon he number of broadcast channels that the station handles. All India Radio's Broadcasting House (BH) in Delhi, for example, contains 36 studios - some of them for production, and the rest for transmission.

Announcer Boot11

An announcer bdoth is attached with each of the production studios. While the actual programme (talk/ discu,sion/ clrama/ music concert1 etc.) takes place ins ~e the studio, the Announcer Booth serves various related works like ~ e e p i v ? continuity with programr 3s fro111 otlier studios, linkitlg announcements, playing filler music and pre- recorded material, playback of pre-recorded music into the studio, etc.

Microphones

The primary source of audio in any broadcast studio is the microphone. It is an indispensabln device for auclio recording, whether inside the studio or outside. At this stage the folloTving particulars may be noted fc.- a preliminary understanding of the subject.

Microphone (mike for short) is a device which converts sounds into electrical signals. These electr':al signalb are fi~rther amplified and processed in succeeding stages of the broadcast chain. There are different kinds of inicrophones to suit different occassions places and purposes. From a programmer's standpoint, there are two broad cat~yories of microphones:

Omni-directions- microphone: These are mikes which can pick up sounds from any direction equally well. When such a mike is placed at the center of a table with the persons seated all around. .11 the voices will be picked up by it without any discrimination. In studios, omni-directional mikes can be used for group di@cussions and multi-way interviews, as a .ingle mike would suffice the purpobe and provides operational convenience.

Uni-directional microphones: Tb ,tee are mikes which can pick up sounds very well only in one direction rnd hardly from other dilections. In other words, uni-directional mikes are like a sensitive ear in the direction in which they are pointed, whereas they are deaf to sounds coming from all other directions. These mikes are much more sensitive than omni-directional ones in the particular direction in which they are pointed; so they can be used to pick up of sounds from a distance e.g. in outdoor locations for sports events. In the studios, unidirectional mikes can be used for announcerslnews reader and in radio plays.

In between tt-cse two omni and unidirectional mikes there are mikes with directional patterns like bi-directional, cardioid (can p ~ c k up sound from the front but reje ts sounds to the side and rear).

Audio Mixer

Audio mixer is the generic term for the announcer console (a device for combining, routing, and changing the level. tone, andlor dynaillics of audio signals. From an operational staiid point, an auulo mixer can be understood as an equi;ment to which all the sources in the studio and announcer booth (micr gho~,zs, t Ge decks. CD player, etc) are coilnected dnd fro111 which the selected source(s) at any time can be passed on to the succeeding stages of the broadcast chain, or for other puq ases like monitoring, recording, editing etc. Like so many other electronic gadgetry, audio mixers too are avajlable in a wide range of models, facilities and technical features.

A minimum of eighl ch'tnnels (iight different sources) can be kept connected to the mixer: say, 3 or 4 microphone chan .els and the rest of tape drck, CD player. cassette player, etc. Bigger recording studios meant for western orchestn, use many more

microphones simultaneously and therefore the channel capacity of the mixer too needs Broadcast Media:

to be larger in their case. While the features may diffnt in details, but in all cases it is Radio and Television

the audio mixer, wnich combines the programme sources of a studio and gives out the composite programme from the announcer booth to the control room.

Control Room

The control room is the focal area at which all the technical activities in a studio center con erge. Engineers in control room have overall responsibility for the technical operations in the studio set up, for switching of broadcitst feeds to the transmitting center and incoming feeds from extp-nal sources. In particular, the following functions are carried out in the cor ,rrol room:

To receive programmes online from each studio (through the respective announcer booth), and fror. external sources like the ,adio-networking terminal, outside broadcast spot, etc.

To &ibute the programmes to respecti ~e transmitters, other radio stations that may be forming a network for programme exchange, satellite up-link facility or to any other destination.

Thus, the control room set-up is primarily an electronic switching syctem These switching operations are performed by using a 'control conso':'. The control con\ole has provision for continuous monitoring of the ongoing programmes either through headphones or loudspeakers to control their audio levels. The audio levels are carefully controlled, as too high a level will cause distortion and also overload the transmitter. On the contrary. too 10- a level will cause poor signal-tobnoise ratio and. ultimately. poor reception in the radio sets.

Studio-to-Transmitter Link (STL)

The pr3grainmes emanating from the studio center are transported electronically to the transmitting center througl~ thc STL. This is because. in most cases, broadcact tr; ~smitters are located several kilometers away from the studiu center, usually in the outskirts of the city. This fact necessitates some form of electronic link between the studio and transmitter. In the few cases where a transmitter ic co-located as they require a large area for the aerial field with the studio, this link can be a harrl-wired connection between the two. In practice, STL can be any one of the seieral technical options available: telephone lines, coaxial cables, microwave link. FM radio lin,,, etc.

Telephonic Lines

Dedicated leased telephone lines are the most popular form of STL. Normal telephone lines have a narrow frequency response which is good enough for telephonic

' conversation but not as a transparent medium for broadcast ya l i ty audio. Hence the telephone lines used for STL are specially 'loaded' for improved frequency response

: and carefully maintained to prevent breakdown$ or loss of quality.

I Coaxial Cable

I Coaxia: cable connection is generally ,nore robust than a telephone line in its physical construction and performance. Coaxial cables are relatively less prone to loss during

j signal transmission and protect the signals from cross-talk and other interferences. For longer STL routes, coaxial cables are preferred nver telephone lines.

Microwave link, FH Radio l Satellite

I Microwave. FM radio and satellite linka offer wireless solutions for STL. In all these cases the transmitting equipment (Microwave transmitter1FM transmitterlsatellite uplink) is installed as part of the studio center and corresponding receiving system at the radio transmitter site.

Audio and Video Media STLs of either kind (wired and wireless) have their own advantages and disadvantages. For example, a dedicated telephone line link is simple and easy to maintain but is prone to failures during rainy season and road repair works. Coaxial cable links are costly to install and maintain, but they can offer better quality over long haul routes. Microwave and FM links can provide reliable service over short distances, provided that there are no natural or man-made obstructions such as big trees or buildings. There is a need for line-of-sight (free of physical obstructions) between the studio and transmitting stations. A satellite link requires a costly ground installation at the studio end which becomes costly to maintain as well, apart from the expenses involved for use of satellite itself. But if a number of transmitters spread across the country have to be fed from the same studio center, the satellite link becomes very convenient and economical.

We can appreciate that the STL is a crucial link and even a temporary failure of it causes disruption in the broadcast schedule. Hence, in most cases redundancy is ensured by, say, providing one telephone line link and a back-up FM link for the same STL.

Transmitting Center The transmitting center is the place which houses the radio transmitter and the antenna system with the help of which the programmes are transformed into 'radio' frequencies and radiated in the form of 'electromagnetic' waves. A separate radio transmitter is needed for each broadcast channel. In the case of a radio station broadcasting many channels, the transmitting center houses that many individual transmitters and contains an elaborate technical infrastructure and a sprawling aerial field, with masts of different heights and shapes towering over the surrounding landscape.

I

In the case of radio stations broadcasting multiple channels, (say, Delhi 'A'. Delhi 'B', etc.) the transmitting center may house all the concerned transmitters (and the antennas) in the same place. Alternatively, a transmitting center may contain just one transmitter, to cater to a single-channel station. In either case, a separate transmitter with a distinct 'carrier frequency' is essential for each broadcast channel. For example, Delhi 'A' channel is broadcast through a transmitter which operates at a carrier frequency of 809 Hz(medium wave). while Delhi 'B' is broadcast through another transmitter operating at a carrier frequency of 1020 KHz (again in the medium wave). The transmitter generates the allocated RF (radio frequency) 'carrier', and it is this frequency that distinguishes the particular broadcast channel. Broadcast stations invariably announce this frequency in their opening announcements as so many 'kilo hertz' or so many 'meters'(of wavelength). The incoming audio signals 'modulate' the carrier in such a manner that either the amplitude (the 5trength) or the frequency of the carrier is continuously varied in accordance with the amplitude variations of the audio signals. This modulated RF contains the on-going programme either in the form of its amplitude variations (called amplitude modulation) or frequency variations (frequency modulation). The radio transmitter also amplifies the modulated RF power to a sufficient level (the power output of a transmitter is as so many kilowatts) for delivering to the transmitting aerial.

The audio signals (programmes) delivered from the studio center through STL are '~nodulated' onto the carriers generated by the respective transmitter and then 'the modulated RF (radio frequency) power is fed from the transmitter to the antenna. Froin the antenna, the RF power gets radiated outwards in the form of electromagnetic waves also called radio (waves). The nature of radio waves is such that their propagation follows different paths depending on the carrier frequency of transmission. Frequencies in the Medium wave range (roughly between 300 KHz to 3 MHz) travel skyward, get reflected by the electric charges in the upper atmosphere and reach places several hundred kilometers away.

In general, MW (medium wave ) broadcasts are limited to a radius of around 500 Km, while SWs (short waves) can reach (under favorable conditions) as far as 4000 Km.

-- -

FM (frequency modulation) radio, on the contrary, can provide only line-of-sight Broadcast Media: Radio and Television coverage that is, typically, about 50 to 60 kms.

Radio receiver technology has undergone a sea change with the invention of transistor. Before that. the radio sets were, like the present day TV sets, heavy and bulky, consuming a lot of batterylelectric power and requiring a long outdoor aerial wire to pick up the broadcasts. Since 1960's, the transistor radios have made rapid inroads into people's homes, as they became increasingly portable, trouble-free and economical on power consumption. Nowadays, pocket sized single-band radios are the most popular among listeners. The radio owes its universal reach largely to these tiny devices which form the last link in the broadcast chain.

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Check Your Progress 1

I Answer the following questions briefly:

1 . What would be the role of studio in case of outside broadcast?

...............................................................................................................

2. Recapitulate the major categories of microphone.

...............................................................................................................

3. Explain the functions of STL.

Radio Receivers

The universal popularity of radio broadcasting particularly in the rural and remote areas is mainly on account of its simple reception mechanism- the radio set. Rapid technological advances have transformed the radio reception system from the heavy and bulky sets of the past (which adorned the rich and middle class homes till the 1970's) to the highly portable. virtually trouble-free transistor radios which have since become the common possession of the poor. In fact, the transformation is so complete that today the name 'radio set' hardly exists in common parlance; instead, we just refer to them as 'transistor sets' or simply as 'transistor'? There are innumerable tapes and models of these 'transistor sets' to suit different applications, tastes, and pockets.

' Irrespective of the type or model, all radio sets receive the broadcasts in the same way: the basic receptor is the receiving aerial. Communication receivers use externally installed aerials of different shapes and lengths especially for HF reception (i.e. SW

I Band). In all other receiver sets, it is the in-built telescopic rod aerial whose length and orientation are adjustable for best reception of the particular HF broadcast. MW

I Broadcast are picked up by a ferrite rod aerial mounted inside the set. For best reception, the orientation of this has to be adjusted in the horizontal plane and, for this purpose, the set itself will have to be rotated.

) The radiation picked up by the aerial is too weak and needs amplification. The electronics inside the set firstly selects the particular broadcast station's frequency, (by the act of

13

Audio and Video Medin band heleclion and tuning) amplifies this particular radio frequency, down-converts it to a lower order called intermediate frequency, "detects" .he audio frequency(AF) signal by stripping off its 'carri,r', amplifies the AF still further and f' lally delivers it the loudspeakers(s) or headphones. The end transducer is the loudspeaker/ht.idphone which converts the AF (which is an electrical signal) back into sound enzrgy, which alone can be heard by us.

In a nut shell, we can say that a broadcast from the studio is sent through to the the transinitter (an electronic device which through an antenna sends the audio signal ). Fro111 here the signal travels to the tower (typically, tall structures designed to support antennas also known as aerials and then to the people. Or it may come through a communications satellite,. Networks of stations may simultaneously broadcast thc same progrlunme at the same time through microwave link or by satellite. At the end it is recei-led by an antenna and the reciever of the radio set. Through the Internet too radio services may be available.

13.3.2 AM and FM Radio Waves

AM (Amplitude m dulation) was used extensively for radio broadcast in the last century and is done even now. It involves the transmission of messages via a radio canier wave, which is a waveform that happens to be modulated. AM moderates the strength of the 'I. ,lnsn~itted signal according to the information being sent and the amplitude of the transmitted signal is made proportional to the sound amplitude captured by the microphone but there is no change in the transmission frequency. Where as in frequency modulation (FM) it is the frequency that is varied. Beca~lse of the susceptibility of AM broadcast to atmospheric disturbances like ionospeneric refractions, and relatively louzr quality transmission, the shift is towards FM radio. However in FM broadacst, the radio waves do not bend but go straight and hence, need line of sight i.e, thev are hindered by physical obstacles and need antennas palced very high.

13.3.3 Ham radio

It is also known as aniateufradio. The bperators use personal communication equipi. .ents like transmitters and receivers to communicate with other such ham radio operators. There can be a network of such ham radios. They are useful for conversation as they allow two way flow of inforration. Ham radio is useful for broadcasting local news, entertainment prograirimes and warnlngs about disasters and accidents to the conlmunity.

F o u r Progress 2 1 i Answer the following questions briefly:

i I . Differntiate between AM and FM waves.

...............................................................................................................

2. Explain an amateur rad;.) service

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t 13.4 HOW TELEVISION WORICS Broadcast Medla:

Radio and Televisiolt

It is said that 90% of all the knowledge that we get froan the external world is through our eyes. The nower of the television medium springs from this basic fact: it is a visual medium with the unique ability to make us 'see' events ~alking place in distant parts of the globe, recorded or live. Obviously, the technology involved in television ib highly complex one. Rut, for our purposes, it is possible to understand the basic principles of its working, without going too deep into the intriclbte ~cientific ,--engineering aspects.

The basic device that converts the real world scents into TV signals is the video camera. A process called 'scanning' that takes place inside the camer, does this. The light from the real world sc,ne enters the video camera through its lens system in the front and converges inside the camera, where it forms a tiny optical .mage of the real scene. This optical image is a true replica of the real world scene- with all its detail, the motion and colours exactly reproduced th. ein. [A beam of electrons inside the camera 'scans' this optic 1 image point-by-point, line-lby-line, and from top to bottom, much as we read the page of this unit: each line word-by-word, and from top to bottom. as we go along. it scans, the optical info8mation contained at each point (brightness and colour) is translated as a 'video signal'.

I

When the electron beam comes to the last point at thebottom of the optical image (in other words, when the scanning of the iinage is cowdleted). the electronic syctem in the calnera makes the beam to quickly bounce back to' the top to repeat the process of scanning all over again. Technically, one cycle of Tadning is called a 'frame' and the process takes place so rapidly that as many as 25 frames are scanned within just one second.

The video signals thus generated go through a complex chain of equipment, met transmitted and finally reach your TV set. Inside t h ~ TV set, the same process of scanning takes place in exact synchronization with the one inside the camera. The electron beam in the picture tube ( that is, TV screen) 'writes' the image point-by- point and line-by-line, theyeby recreating the total optical image, as it was formed inside the camera. In other words, the TV system generates discreet still images of the real scene from instant, but they are generated at a rapid rate of 25 frames per second. The human eye suffers froin a limitation called 'Persistence of Vision' (in this context, it is to be seen as an advantage), because of which it cannot distinguish such rapid changes: instead, it perceives the image as a single m e with motion contained in it. This property, coupled with the fact that TV signals titavel as fast as light, makes the television broadcasting possible.

Please bear in mind that what we described above is a gross over simplificatioi~ of what goes on in the numerous and complex machinery that form the TV broadcast chain, with the camera and the TV set at the two ends of it. While a detailed technical description is not required for our purposes a broad understanding of the hardware setup of a typical television station would be very much in our scope. In the following section let us dwell on these aspects. Since we have already studied the features of a radio static-n in earlier sections of this unit, we will concentrate now on the additional features that a TV station is composed of.

I TV Studio

The studio is the place where action takes place and the same is shot with the help of video cameras (usually more than one simultaneously). The floor area of a TV studio ranges from that sf a typical living room (- 25 square meter) to as inuch as 400 square meter or even more. Bigger studios are necessary if drama sequences employing elaborate sets and lighting arran2~ments are to be provided. For other purposes, e.g. news reading, interviews, educational lectures etc., small studios are preferred, because of economic reasons and also because modern technology permits space-saving by

Audio and Video Rledia way of 'virtual' sets. portable equipment, etc. Most studios in the educational sector and private TV channels adopt this trend.

The interiors of a TV studio, as in a radio studio, are acoustically treated for noise-free environment, and contain soundproof double doors. A separate soundproof entry for sets, and a lighting grid which is suspended from the ceiling, are some of the additional features of a TV studio.

Production Control Roon~ (PCR)

Every TV studio is invariably associated with a Production Control Room, which houses all the electronic equipment and operational controls to conduct the 'show'. It . is usually located adjacent to the studio, with an observation glass window between the two. From the PCR, the producer (sometimes called Dircctor) of the programme calls the shots, while other technical personnel are engaged in their assigned tasks like camera control. audio control. lights, vision mixing, insertion of external feeds, and recording the programme on a video tape.

The cameramen in the studio handle their individual TV cameras to compose the shots from different angles. in accordance with the 'commands' of the producer. Inter-communication between the producer in the PCR and the cameramen in the studio happens through the headsets, which the cameramen constantly wear during the shooting.

Editinoost Production Suites

The terms postproduction refers collectively to ali th- yr,~cesses that follow in making the final TV programme, after thc basic material is shot either within the studios or outdoors. These processes may include putting the wanted shots in the desired sequence, adding the opening and closing shots, laying the commentary track, music mixing, graphicslanimation sequences and other inserts, and producin, the final master tape. The amount of editing and postproduction work depends on the format of the programme. As for instance, drama and documentary programmes involve extensive post production work that may run into several days, while current affairs programmes, educational talks, simple demonstrations, etc. require less postproduction work. Live programmes like news. of course, cannot have any postproduction. However, in their case, editing of news clips, visuals: etc. happens beforehand and they are played back as part of the programmc during the telecast.

I Conlputer Graphics and Animation This is an indispensable facility for educational programmes in particular. Successive advancements in computer technology have resulted in a variety of user-friendly software for graphics and animation which can run on computers. This kind of 'open

H architecture' has the added advantage of easy upgradeability and networked operation within a studio complex.

Set Design

Traditionally, sets in a TV studio are constructed by assembling aft. X 4 Ft. plywood cutouts in the required shape. Modular set-design containing sub-assemblies, which can easily be dismantled and re-used for different shapes and sizes. is preferred now a days for reasons of economy and easy storage. 'Virtual sets' are those which are created electronically on the TV screen against the background of performers in the studio, with the help of computer-generated imagery. This concept is gaining currency as it can obviate the tedium and the cost involved in traditional set design and construction. In this case, nothing actually exists in the studio, except a blue screen, as the backdrop for the performers. The set is 'created' on the final image by electronically replacing the blue background by the artwork generated with the help of computers.

16

Broadcast Media: Radio and Te.evision

C'

I

The computer software also provides for perspective changes of the virtual set. as per changes in camera angles, as if in a realistic situation.

Outdoor Coverage Facilities

All TV production houses, particularly those involved in news and current affairs programmes, need these facilities in an adequate measure. At the simplest, they consist of a hand-held or shoulder mounted camcorder (portable audiolvideo recorder) with a built-in microphone and a single person crew. This may be good enough for a quick coverage of a natural disaster, an accident site, etc. for a pre-planned event or documentary pror'uction. Otherwise things like popable lighting equipment, tripod- mounted camcor,.:r, wheels and trolley for jerk-free movement of the camera, different kinds of microphones, etc. are used. The size of the crew too may have to be bigger as a producer, a production assistant, cameraman, sound recordist, an electrician, and

l

a helper are needed .

For live coverage of outdoor events, an OB Van (Outdoor Broadcast Van) is used. The technical system in the Van will be similar to that found in the TV studio and control room to facilitate production in real time by a multi-camera set up. In other words. an OB Van can be described as a multi camera set up on wheels.

':idea Tape Formats

Even though the ongoing digital revolution bas brought in its wake tape less recording systems for video, at the present juncture however tppe is still the most widely used medium for professional applications. There are a number of technical formats in vogue for recording and reproduction of video, the more prominent of which are described below.

VHS (Video Home System)

This is a widely used domestic video format. The recording is done on VHS cassettes containing half-an-inch wide tape which can hold up to 4 hours of programme. With the growing popularity of VCDs (Video Compact Disc) and DVDs (Digital Versatile Disc), the VHS tapes are likely to become a thing of the past in a few years from now.

U-matic: This was very popular as a professional tape format during the 1980's and it uses a 34 inch wide tape. U-matic 'High Band' and U-matic 'SP' were later versions of the format with superior features. The U-matic format is now largely overtaken by later inventions like the Betacam etc.

Betacam: It is a family of half-inch professional videotape products. It is meant for analogue recording of video. Betacam cassettes contain half inch wide tape like the VHS, but the similarity between the two ends there. While VHS is only a domestic format, Betacam is a profess~onal grade forniat meant for institutional use and broadcast. Among the analogue formats, Betacam is the most dominant format in the broadcast world as on date.

Digital formats: In recent years a number of formats for digital recording of video on tape have gained currency, the chief among which are tlhe DVC pro format for recording very high quality digital video and Digital Betacam, which is superior to betacams and also ensures better quality.

As a rule, all analogue (glossary) tape formats suffer from generation losses i.e. degradation in technical quality when a programme is transferred from one tape to another. Such transfers are essential especially during post production. Digital (glossary) formats, on the contrary, are immune to generation losses; so the final master tape can be technically as good as the raw stock on which the original recording is done. Digital formats also offer other advantages like better shelf life of recorded tapes, easier post production, convenience in transfer of tape content through computer networks, broadcast automation, etc.

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.iudio and Video Media 13.4.1 TV Transmission Techniques

So far, we have discussed about things related to TV studios and television production. That, of course, is only part of the story. Now let us understand how television transmission takes place and how exactly the many TV channels reach your TV set even though they originate at different places, in different countries.

Basically, the three most popular means of distribution of TV signals to homes are:

Broadcasting through terrestrial(ground-based) transmitters

Satellite and cable distribution

Direct-to-Home(DTH) Television via satellite

Terrestrial Transmitters

. As in the case of a radio transmitter, a TV transmitter 'modulates the incoming TV signals on to a higher frequency carrier, amplifies the power of the modulated waves and sends them to the aerial system for radiation into space in the form of electromagnetic waves. Since a TV signal is in practice two distinct signals one for the picture and the other for the sound - a TV transmitter is in effect a two-in-one transmitter, which deals with the picture as well as sound transmission in an integrated fashion. Again, while radio transmission takes place in medium wave, shortwave, VHF (glossary) and UHF (glossary) bands, for compelling technical reasons international regulations restrict terrestrial TV to VHF and UHF bands only. Please recall that wave propagation in these bands follows a straight path, which, means that TV signals, like FM radio, travel over line-of-sight (glossary) distances. To maximize the coverage area of a TV station, therefore, the transmitting aerials are located on the top of tall masts. The typical coverage area of a 10 KW TV transmitter with a 200 meter high mast is about 60 Km radius. In metro cities with many skyscrapers, you need much taller towers to satisfy the line-of-sight requirements within the coverage area. So is the case in hilly areas with many ups and downs. Short towers will do if the area is a flat, rural landscape. For example, in Mumbai, the Doordarshan tower is 300 meters tall. Also, wherever possible, TV towers are located on hill tops, to gain maximum vicibility (and therefore coverage) for the transmitting aerial. This is the case in Pune where the TV tower is located on the Sinhagarh hill.

Terrestrial transmissions can be received by TV homes by means of simple 'Yagi' aerial which can be erected on a roof top or a balcony. A typical Yagi aerial contain 3 aluminum rods of specific lengths (to suit the wave length of transmission). Out of these, the middle one is folded inwards and is known as a folded di-pole. The transmissions picked up by the folded dipole are carried to the TV set inside the house through a flat cable called feeder line.

The rod in front of the folded dipole is called 'director' and the one behind is called 'reflector'. Together, they help in maximizing the 'gain' of the aerial in the wanted direction.

Till a decade ago, urban areas in our country were replete with these aerials, sprouting from the rooftops of numerous households, as TV reception would have been impossible without them. Terrestrial transmission of Television is now largely overtaken by satellite and cable because of the phenomenal growth in cable networks in the recent past. For non-cable TV household$, however, terrestrial TV continued to be the only lifeline. Therefore, Doordarshan maintains a large fleet of terrestrial transmitters across the country to ensure TV coverage to remote rural communities at affordable cost.

Satellite and cable Distribution

A chief limitation ot3{eikstrial TV, you will agree, is its limited range. further limited by line-of-sight propagation. This limited range can be improved to some extent by erecting taller towers and increasing the power of transmitters, but obviously there

18 --- . .- - - . -


are limits and terrestrial transmissions cannot be expected to go beyond 100 km even in favourable circumstances. The only way of expanding 'errestrial TV coverage across longer distances is by setting up 'repeater' stations, i.e. pickup the signals at the fringe of the coverage area of the original transmitter and re-transmit them through a second transmitter, and so on. While this is practicable and is being adopted in maw cases, it is a very costly proposition as tens of thousands of such repeater would be needed for a country of our size.

It is here that satellite communications come in, as an eccnomical alternative to terrestrial repeaters. Communication satellites are man made devices placed at an altitude of about 36,000 km up above the equator, so that they revolve around the earth, much like the moon( earth's natural satellite) revolves around the earth. However, because of the particular altitude of their orbit, communications satellites take exactly 24 hours to complete one revolution, the same time that earth takes to rotate around itself. Any satellite at a lower orbit revolves much faster, while those at higher orbits revolve slower. The time period of 24 hours is unique to this particular orbit which is known by the name 'geo-stationary orbit', because the satellites in this orbit appear stationary as seen from the earth. Communications satellites receive the signals sent towards them from the ground and, dfter necessary frequency conversion and amplification, retransmit them back earth% .l, so that they can be received by a suitably equipped dish antenna located within the 'foot print' (that is, coverage area) of the satellite. Since a single satellite can 'see' as much as one-third of the earth's surface. a compliment of just three satellites can provide global coverage of television, cutting across national boundaries and continents.

The transmission side of a typical satcom system consists of an 'earth station' to which the programmes generated by the studio center are sent. The earth station contains necessary electronic equipment to 'uplink' (that is, transmit upwards to the satellite) the signals in the desired frequency band, with the help of a large dish antenna which is accurately kept directed to the satellite in the sky. Once adjusted, the dish remains pointed towards the satellite all the time. So ilt does not need to be disturbed except for very occasional perturbations. Presently, maximum number of satellite TV channels the world over operates in the so called 'C' band (4 to 6 GHz range). However, as this band is already crowded, 'Ku' band (12 to 18 GHz) is the new frequency band which is rapidly gaining currency for upcoming TV channels, as well as for DTH.

The receiving system is known by the acronym DRS (Direct Reception System) which consists of a dish antenna (typical size 8 to 12 ft. diameter) fitted with a feed- horn and LNBC (Low Noise Block Converter) at its focus. When the earthward transmission from the satellite falls on the dish, the elects-omagnetic waves get reflected to converge at its focus. A 'feed-horn' mounted at this point collects the energy and feeds the LNBC.

The LNBC performs the dual t ~ s k of amplification and conversion of high frequencies, to similar signals carried at a much lower frequency. These lower frequencies travel through cables and is then fed to a satellite receiver. It is the job of the satellite receiver to process the received signals into a form which can be handled by the domestic TV set, which is kept connected to the output of the satellite receiver.

Most satellite TV channels as of now adopt digital transmission techniques to economize on the satellite transponder space. Therefore the satellite receiver employed in the DRS should be a digital one. Such receivers are known by the technical term Integrated Receiver Decoder (IRD). Digital satellite TV channels also often employ 'scrambling' techniques, so that only authorized IRD are activated for de-scrambling the signals. For example, most of the private TV channels like DD (Doordarshan) and Gyandarshan are free-to-air, without any scrambling.

We have noted above that C band DRS employ dishes which are typically 8 to 12 ft in diameter. Moreover, as different TV channels are seat through different satellites,

Audio and Video hfedia you need so many dishes, each pointing towards one or the other satellite, to receive all the channels on your TV set. This is clearly a cumbersome proposition; hence the need for a cable operator as a necessary middle man in the process. A cable operator receives all the channels through a cluster or DRS systems (called cable head-end) and distributes them to individual homes through cables. The equipment used at the head-end permits the same cable to carry all the channels without getting mixed up. The tail-end of the cable is wired into your home and connected to your TV set.

From the above description, you will appreciate that cable iietworks are a necessary adjunct to satellite television. Direct-to-Home TV services operating in Ku-band, however. are an exception to this rule. About DTH and related matters, you will study separately in another unit of this Block.


Answer the following questions briefly:

1. Explain the main function of production control room.

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2. Explain some advantages of satellite TV vis-h-vis terrestrial distribution.

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3. Why are hill tops or high altitude locations needed for TV towers?

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13.5 EMERGING TRENDS IN BROADCASTING

Recent technological advancements have brought in their wake many epoch-making changes in the way broadcasting is carried out, some of them altering the very nature of broadcasting as it was understood so far. Let us take a brief look at some of the current and emerging trends.

Digital Audio Broadcasting(DAB) through Satellites

Digital Audio Rroadcasting (DAB) through satellites enables global coverage and also CD like quality for audio broadcast.. Thus, DAB is an efficient solution for the problems of quality as well as quantity at one stroke. However, the disadvantage is that ordinary radio sets cannot work for DAB; you need special sets which are quite expensive for the common man. The 'Worldspace' radio is an example of satellite based DAB. With a fleet of three satellites, Worldspace aims to provide high fidelity programmes to global audiences. In the context of education, DAB can have interesting applications for distance education institutions that wish to offer their programmes for learners dispersed across continents.

Campus Radio

At the other end of the scale, the concept of highly localized broadcasting with a coverage area of no more than 5 hm radius. is also gaining currency. Educational

2 0 - -. .. - - -- - -.

'institutions can set up th-ir own radio station at minimal cost to serve their respective Broadcast Media: Radio and Television

campuses and neighborhood. Campus Radio can be used to promote cornrnunity life. student welfare activities, supplementary educational iessons beyond classroom hours, counse'ling through distance mode, career guidance, cultural activities etc.

Briefcase radio

A briefcase radio is a radio station thal is so simply de~ig,~;d and compact that it can fit into a briefcase. It is being used in some places as a community radio to share the local news, knowledge and problems. The com~nunity is active in the production and broadcast of such programmes. The programme shave a limited reach but serve the purposes of the community quite well. It has been successfully used in some places like Gujrat, Karnataka, Andhra Pradesh., etc. You may visit the websites such as h t t ~ : l l w w w . c o m m u n i t v r a d i o n e t w o r k . o r ~ / t o ~ 2 O r a d i o to know more about briefcase radio.

Digital Terrestrial Television (DTT)

While the traditional TV trdrrsmission is terrestrial analogue, DTT is digital. To receive DTT, you need a set top box before your TV set. Doordarshan has DTT mode in the four metro cities already. Apart from superior picture and sound quality, the real advantage of DTT lies in the value-added services it can offer to the viewers: video- on-demand, tele-shopping, program-related services, etc.

Webcasting

The universal reach of the internet and World Wide Web has enabled broadcasters to adopt this medium tc reach out specific audiences irrespective of geographical boundaries and, in the process, take advantage of the value-added features that only the web casting mode can offer. Unlike conventional broadcasts, webcasting enables viewers/listeners to access their chosen programmes at a time of their convenience on their computer sets and repeatedly if desired. Access can be restricted by the broadcaster as per their marketing strategy: say pay-per-view, as per monthlylyearly subscription etc.

Many leading sound broadcasters around the world (ificluding All India Radb) have their web casting channels. But television channels on the web are still not so prolific because of technical reasons like non-availability of sufficient bandwidth at many places. In the absence of adequate bandwidth, web cast pictures tend to lack definition and be jerky, unclear and go into freeze every now and then.

f

i 13.6 SUMMARY Broadcasting as you know now is the instant communication of messages to the masses through electronic but wireless mode. In this unit we have discussed about the two most popular technologies for broadcasting -radio and television. Due to factors like economy and greater accessibility these two technologies are still very popular and are of special use for educational purposes. From a humble beginning, radio has become economic, portable and above all accessible to almost every one. Hence, it is a valued technology for educational broadcast. Facilities for interactiviry had added to its value Television has although arrived much later but its appeal is greater as it provides visuals along with audio. Educational programmes are being telecast today through Indian channels as well as foreign ones.

I Radio broadcasting comprises the functioning of several subsystems such as studio, which is the prime location for recording and is the first step from which audio transmission initiates. It has several eruipments like microphones, audio mixers, etc. The audio signals are carried from the studio by STL to transmitting centers, through

-- - -- 2 1

Audio and Video Media wired or wireless means. From these centcrs radio signals received are converted into radio frequencies and radiated as electromagnetic waves. The radio receivers finally pick up these waves and play it to us. FM radio is today inore popular than AM radio as frequency modulation leads to transmission . not prone to atmospheric disturbances.

In television the video camera is the basic device needed for capturing the audio and visuals and translate them into video that are transmitted to television sets which deliver the sound and pictures to us. Television studio is the venue for indoor shooting. Television signals can be distributed through several modes like satellite and cable distribution and DTH via satellite. AT the end of this unit we have discussed about the new trends that are emerging today in broadcasting such as DAB, campus radio, etc.

13.7 UNIT END ACTIVITIES

1. Visit the web site of IGNOU and read about the Electronic Media Production Center.

2. Visit your nearest TV/Radio station and look around the studio and other technical areas. Make your own notes of the facilities you have observed and relate them to what you have read in this unit. Broadcast stations are usually restricted areas. So you may require prior permission from the station authorities for your visit, although such permission may not be difficult to obtain if have your student Identity card and explain the purpose of your visit.

13.8 REFERENCES AND SUGGESTED READING

You may visit websites on topics discussed in this unit, like the following:

http://www.indiatogether.or~/medialarticles/air75.htm retrieved on29.5.07

http://en. v~ikipedia.or~lwikilAll India Radio retrieved on 29.5.07

http://plannin~commission.nic.in/reports/peoreport/cmpdmpeo/volume2/erosi.pdf retrieved on 29.5.07

httu://en.wikipedia.ordwiki/Broadcastin retrieved on 29.5.07

http://en.wikipedia.or~/wiki/Mixing console retrieved on 3 1 S.07

httD://www.answers.com/topic/broadcastln retrieved on 3 1.5.07

http://en.wikipedia.org/wikj/Radio retrieved on 3 1 S.07

http://www.cybercollege.com/frtv/frtv0 17.htm retrieved on 3 1.5.07

http://www.adamwilt.com/DV.html retrieved on 1.6.07

httu://www.webopedia.com/TERM/A/analog.html retrieved on 1.6.07

http://www.answers.com/line%200f%20sight retrieved on 1.6.07

http://telecom.hellodirect.com/docs~Tutorials/AnalogVsDi~ital. 1.05 1501 .asp retrieved on 1.6.07

Glossary

AM: Amplitude Modulation. A system of modulation which is adopted for transmission of radio broadcasting in the medium wave and short wave bonds. AM is also used for transmission of video signals in terrestrial TV transmissions.

AeriaYAntenna: A Metal wire/rod/dish-shaped structure which radiatesfreceives electromagnetic waves. The physical dimensions of the antenna elements are designed to be a simple fraction or multiple of the 'wavelength' of radiation.


Conditional Access System (CAS): A system of cable distribution which enables the viewers to selectively subscribe for their preferred channels. A 'set top box' at the subscriber end can be made to receive only the subscribed channels and block the

C-Band: Frequencies in the range 4 to 6 GHz. C band is popular for satellite TV uplinks and downlinks.

DTH: Direct to Home Television: A system of satellite TV which enables direct reception at homes through small, individual dishes, rather than through cable distribution. DTH services are broadcast on Ku band and still higher frequency bands.

FM: Frequency Modulation. A system of modulation which is adopted for transmission of radio broadcasting in the VHF(Very Hjgh Frequency) and UHF(U1tra High Frequency) bands. FM is also used for transmission of sound signals in terrestrial TV, and satellite communications.

Ku Band: Frequencies in the range 12 to 18 GHz. which are used in satellite communication mostly for DTH services.

MW: Medium Wave: Frequencies in the range 300 KHz to 3000 KHz(3 MHz). MW broadcasts have a typical coverage area range upto 500 Kms radius.

Modulation: The process by which the audiolvideo information is embedded on to a higher frequency 'carrier' for the purpose of transmission. Such as Amplitude Modulation (AM); Frequency Modulation (FM).

Persistence of Vision: Property of human eye, because of which we perceive rapidly changing(but discreet) still frames as a single frame containing motion. Cinema and Television make use of this property to give us the illusion of moving pictures, while in reality, what they present is a series of still frames which follow each other in rapid succession.

RF: Radio Frequency: The portion of electromagnetic spectrum used for transmission " of radio and TV broadcasts.

SW: Short Wave: Frequencies in the range 3 MHz to 30 MHz. SW broadcasts can reach distances of 2000 Kms or more. due to reflections from ionosphere.

Studio to lkansmitter Link (STL): The means of connecting studio to the transmitter for sending audiolvideo programs. The link can be either a hard-wire one (e.g. non- exchange line, ISDN, Coaxial cable) or wireless (e.g. microwave, FM, satcom).

lkansponder: A Satellite-borne electronic device meant for receiving and transmitting the broadcasts.

UHF: Ultra High Frequencies: Frequencies in the range 300 MHz to 3000 MHz are known as UHF.

VHF: Very High Frequency: Frequencies in the range 30 MHz to 300 MHz are known as VHF.

Analog and digital form: analog is the process of taking an audio or video signal and translating it into electronic pulses as for instance by ordinary telephones or radio. Digital on the other hand is breaking the signal into a binary format where the data is represented by a series of "1"s and "0"s as for example by computers.

Line of sight: An unobstructed view from transmitter to receiver. Satellite, infrared (IR) and microwave transmissions require line of sight between nodes, whereas portable phones, cell phones and wireless LANs (Wi-Fi) do not. (httv://www.answers.com/ line%20of%20sight

23

$ i ~ . l i o and Video hledia 13.9 CLUES TO CHECK YOUR PROGRESS


1 Even outside broadcast routed through it.

2. Unidimentional . omnidimensional. cardioid, etc.

3. Audio from htudio transported to transmitter through STL


1. AM modulates the strength of the trammitted signal according to the information being sent.; FM- frequency is varied.

2. Ham radio


I . It houses all the electronic equipments and operational controls and the producer and the technical per~onnel qerform their jobs.

2. Terrestrial distribution suffers from line of sight limitation

3. Fur line of sight transmission

24

UNIT 14 . NON-BROADCAST MEDIA: AUDIO AND VIDEO (PART 11)

Structure

14.6 Introduction

14.7 Objectives

14.8 Video and Education

14.8.1 Distinguishing Features

14.8.2 Video Studio

14.8.3 Main Equipments in Video Studio

14.8.4 Videotape Recording Formats 14.8.5 Video Programme: Presentation Formats 14.8.6 Video Programme Production Stages

14.8.7 Storage and Archival Considerations

14.9 Strengths and Limitation of Non-Broadcast Media

14.10 Summary

14.11 Unit End Activities

14.12 References and Suggested Reading


14.6 INTRODUCTION

In the first part of this unit you have studied about audio as non broadcast medium. We have discussed its advantages over the broadcast mode. In this part we shall continue with non broadcast media and discuss video as the non broadcast medium. You know that visuals have their own importance and a thing seen is better retained than something heard. Hence, learning demands not only audio but also visual inputs. We shall bring forth to you in this unit a discussion on the importance of recorded video programmes in the fieid of education. You will also study about the different video formats, their utility, equipments necessary in a video recording studio and other such aspects.

14.7 OBJECTIVES

After studying this unit, you should be able to:

discuss the important features of video as educational medium;

expiain the different video formats for teaching -learning;

describe the various programme production processes in the video medium;

identify and discuss various types of the equiprnents used in video production centers.

14.8 VIDEO AND EDUCATION Video can complement the classroom instruction as well as distance mode of teaching in a variety of ways. It can make the invisible world visible, for example, undersea photography, deep space photography/photographs of distant places, microscopic things, etc. It can enable students to derive visual experience of phenomena not commonly seen in everybody life. It can also explain complex processes in a condensed manner, provide concrete illustrations for abstract concepts and thus facilitate better comprehension and retention. Video has proved its effectiveness/supremacy in teaching

certain subjects such as agriculture, science, geography, oceanogra~hy, astronomy, Non-broadcast Media: Audio and Video (Part 11)

medicine, etc. For other disciplines too visuals always help in learning.

Video promotes learning by making it more enjoyable and also understandable. It can increase the effectiveness of instruction and cut down dropout rates. Video programs if well plannedlc~~ganized and presented, may provide situations that are better than classroom situations that provide instructions without using videos. At times the student can learn through video through his or her own effort. even without much intervention from the teacher. The photographic memory of human beings enables retention of larger quantities of information and speeds up the learning process. It plays an invaluable role in accelerating the learning process in children as well as adults. With video it is possible to combine narration with pictures that depict the subject and this makes the learning process faster as it involve\ both the senses of sight and sound.

Though video in the classrooms is comparatively new and is yet to become popular in teaching-learning process, the video in the non-broadcast mode is considered as a more effective medium than the television broadcast due to its certain advantages over the television. St dents have full control over the pace, time and place of learning. The replay facility makes it more suitable for individualized learning. Educational videos are therefol-e gaining popularity. IGNOU producles videos fro supplementing the print medjun. .a various disciplines. TV channels of UGC, NCERT, IGNOU and even private channels provide instructions through video.

14.8.1 Distinguishing Features

Human beings are blessed with several faculties and one of them is the faculty of sight. The ability to memorize visual and aural information, recall and express it lnakes human beings superior to other forms of life on this planet. Primitive man used visual forms of communications by drawing on stone; cave walls and even using sculpture to communicate his experiences to his fellow human beings through visuals thus made. As human beings developed they used leaves, paper, wood as medium for visual communications.

Human beings learn from experience. Apoint to note is that much of this is visual. We learn to read by visually identifying alphabets and attl'jbuting sounds to them. We experience visual phenomena, like rain, lighting, fire, etc. and learn from these visual experiences to take appropriate action. We are able to learn from watching others and emulating them. Video can record these events and play them back to us repeatedly. However, it has been found that such retention and internalization of information and its recall is much better when a thing is seen than when it is only heard or only read. Hence, video is of great help in the field of education . It can enhance the effectiveness of a classroom lecture in many ways besides facilitating distance education. The invention of Video has enabled man to transmit, store and reproduce visual information for use on demand.

With the invention of video recording techniques, its potential as tool for learning was realized. Video now plays a vital part in the education process, bringing experiences from all around the world through television programmes, video cassettes, digital video discs (DVD) and Compact Discs (CD) , Internet, cell phones. etc. This medium has a vast impact in that it can be transmitted across great distances making the same material available to a much larger section of people.

Video recording technology has enabled human beings to capture and store visuals and aural experiences and deliver it to the masses thus making the range of experiences larger and richer. Through television we can experience events live as well as recorded even if they are at remote places. Video along with the audio medium is enabling teachers to teach in a more effective way in classrooms and also in teaching in the virtual classrooms. As mentioned for audio, video recordings too can be accessed by the learners at the time and place of their choice ur,;ike telecasts at fixed hours. They

37

Audio and Video Media can also be stopped, skipped and started at will and this happens to be an advantage over the ones telecast.

Today portable handy cams and even the cell phone are used for capturing, storing. editing, and exchanging visuals and data in other forms. Also, the process is easy and even a lay man can perform all these activities. In view of the importance of educational videos for educational purposes and entertainment, today there are courses on videography, digital still photography, non-linear editing, sound recording, etc.

14.8.2 Video Studio

The video studio is used for both the broadcast as well as for the non-broadcast mode. In the broadcast mode the productions are transmitted from the studio. On the other hand video programmes can also be recorded and then edited to make the master program. These master programmes can also be transmitted in the broadcast mode. In the non-broadcast mode the master program after the final preview is mass duplicated into the analog or the digital video format. These recordings are then sent to the students, who Can play them back at thew home1 workplace or can access them at study centers with audio-video library. In this section you will come to know about the video studio used for the recording. The video studio is divided into the following two

Studio floor: The video studio floor is the main activity centre for the video program. Depending upon the format of the program sets, microphone., lights, and camera etc. are placed in the studio floor.

Control rooms: The control room has various equipments installed such as those for vision mixing, audio mixing, lighting control. video recorderslplayback, camera control units, video type writer, caption scanner, computer, video monitors. waveform monitors (used to measure and display the level. of a video signal with respect to time. amplifiers, ' speakers, etc.

The size of the studio depends upon several factors such as the equipments used, the number of the cameras to be used and also depends upon the format of the program it is expected to handle. In major television organizations, video studio$ of requisite sizes are earmarked for specific programri.,ing needs. The video studio sizes in the range of 75 to 200 sq. m floor areas are suitable for educational program production. Studios of still larger sizes would find more utility for the public television and entertainment programming.

A rectangular shape for the studio floor rather than exact square is preferred in order that the floor area may be best utilized for camera movement and set erection. A square shape tends to give rise to unfavorable acoustics. The ceiling height is a critical requirement for the video studios. The miilimum height required is governed by the considerations like vertical space needed for air conditioning ducts, proper angles for studio lighting in the vertical plane, etc.



1. List two advantages which video cassettes have over television broadcast.

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2 Ex~lain any two video tape recording formats.

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14.8.3 Main Equipments in Video Studio Non-broadcast Media: Audio and Video (Part 11)

There are several types of equipments used for a multi camera video production , some of the major ones are discussed below:

Video Camera: Video cameras meant for use in studio or outdoor functions contain CCD (Charge couple device) chips to convert light into electrical signal. It stores and displays the data for an image in such a way that each pixel in the image is converted into an electrical charge. With suitable changes in accessories, it is possible to use the same video camera in studio and for outdoor shooting. Nowadays the camcorder (Camera plus recorder in a cingle casing or as a removable attachment) has become the preferred system for outdoor shooting. Its advantage is that a single person crew may carry out the shooting, which may also include audio as narration, music, etc.

Production switcher (Vision Mixer): It is the cbntrol to any video studio set up and most of the post production situation. It is a device used to select among different video sources and in some cases mix them and Add special effects. A significant special effect that professional grade production switchers provide is the "Chroma Key", with the help of which the plain background of a person (usually blue colored background) can be electronically replaced by any other video content-live or pre-

Digital Video Effect (DVE): Digital video effect equipment can be used either as a stand alone unit or in conjunction with the production switches, although the latter method is preferred in most production houses The common terms to describe this class of effects are: compression, expansion, split screen, freeze, perspective, rotation, reversal, posterization, page turn, roll and slide.

The consideration that can be kept in view while choosing digital effects equipment are - the range of effects that it can provide, whether the effects are easy to set up and repeat at will, whether the picture edges and movements are sufficiently smooth, resolution and other specification determining picture quality.

In general it is desirable to locate DVE facliities at the postproduction btage rather than at the studio. as to operate the required effects in live situations would be rather difficult. Also, beware of the fact that any overuse of these effects in educational programming can be visually distract~ng and counter productive.

Video cassette recorder (VCR): VCR provides facilities for recording and playback of removable video tape cassettes containing magnetic tape !sed for recording audio

Lighting: Lighting plays a very important role in television. It illuminates the camera 'to see' and 'record' a subject or scene clearly and distinctly. It also helps to provide an illusion of depth, giving a three-dimensional effect to otherwise two-dimensional images. For complex production?, several lights of varied intensity may be required.

14.8.4 Videotape Recording Formats

The invention of magnetic tape developed the ability to store audio and video. Technology further advanced and now we have economically priced machines :hat could easily record video and audio at low cost.

Video Home System (VHS): It is used for recording and playing analogue video cassettes. It is quite popular in homes as well as educational institutions. Educationists began producing programs on VHS and distributing them to learners Government bodies have also used video and audio tape recarders to impart education to villagers and disadvantages group of society on issues like hygiene, sanitation, cooking, caring for children, treatment of diseases, advanced farming methods, cottage industry and many other issues.

Audio and Video Media VCD: New technology has resulted in the Video Compact Disk (VCD) and the (IIVD). VCD is a standard digital format for storing video on a cornpact disc (CD) and are played through dedicated VCD players, computers, etc. VCD is cheaper, compared with the DVD. It displays Video quality similar to VHS but is more robust. The VCD being a non-contact medium minimizes damage caused by dirt, dust, etc. It also allows for interactivity between the viewer and the program unlike the VHS with little or no scope for interaction. Interaction kith the program gives the viev :r opportunity to get involved with the subject and enhances the learning process.

DVD: This is an extension of the VCD format. DVD stands for Digital Versatile Disc or digital video disc. DVD can be used to record video, audio, store data. keep records and be used for any purpose that requires the storage of data or information in digital for~nat. DVDs have higher recording densities up to many times more than VCD and the newer ones have several times more storage capacity. DVD's produce higher quality pictures, they can handle multiple sound tracks making it suitable for education across many languages. DVDs are also interactive and can combine text graphic and video information. DVD will soon become the choice of educationists due to the rapid fall in its price and the fact that it is less prone to damages.

CDs and DVDs for educational purposes are today readily available. Even teachers are being trained to use certain softwares like macromedia to prepare (author ) educational programmes with content in multi media such as text , which may be hyperlinked for providing a lot of information, visuals that are still and animated to explain processes, voice and scope for simulation. Assessment is also possible through quizzes. Scope for navigation is also inbuilt.

Tape as a medium of play out and storage, has certain disadvantages over the modern disk technology and these are presented in the following tabulated comparison form (Table I ).

Table 1 - -

Tape Disk --

Larger in size Smaller

Cost of tape mo 3 than DVD DVC disk cheaper than video tape

Reasonable quality of video and audio Excellent quality of video and audio

Tape is a contact medium and hence DVD and VCD being non contact medium have prone to tape damage, which is an a longer life irreversible phenomena

Significant time taken to fast forward No time taken as random access possible and rewind tape

Multilingual capabilities are limited Multilingual capabilities are excellent

Interactive programs are not suitable Interactive programs are highly suitable for DVD for video tape due to its linear play and VCD due to its non-linear play out out characteristic characteristic

Storage requirements are large Storage requirements are small

Indexing and searching of content Indexing and searching of content is very easy is difficult as the content can be labeled

14.8.5 Video Programme: Presentation Formats

There are various presentation formats of the video programme. Some of them are:

i) Talk shows: A single person may talk~lecture. There can be also be those who express their 'dissent' to the speakers with two or more speakers and one who anchors. For instance, debates among people holding conflicting views, @anel discussions where each panelists presents hisfher views, etc.

ii) Discussion: It covers all talk shows like interviews, panel discussions, etc. and even the audience may participate in such discussions.

iii) Demonstrations: These can be used to show a process, actions and reactions. For example how to provide first aid to an accident victim, or a show that teaches horticultural skills. Videotaping has the advantage that the 'perfect' version is recorded and shown and ensures a convincing and controlled demonstration. You can even present action in a speeded-up or slowed-down form, or stop it in a "freeze-frame" to study a particular feature.

iv) Interview: A wide variety of situations can be termed interviews. Personality chat, formal round-the-table discussions, explanatory discussions, reminiscences, etc. may be presented through interviews. Famous TV interview programme like the question time, hard talk are the typical examples.

v) Illustrated talk: In addition to the talk thdre are visuals illustrating it as for example, a person working in a laboratory, museum , etc.

vi) Game shows: Competitions that could be academic as quizzes or those involving physical strength and stamina, etc. comprise game shows.

Non-broadcast Media: Audio and Video (Part 11)

Besides these there are many other formats like drama, musical programmes, etc.

14.8.6 Video Programme Production Stages

Now let us study the different stages involved in the production of videos. There are three stages- preproduction . production and post production stage.

Preproduction Stage: The preproduction stage deals with the preparation of the program proposal, academic note, idea, premises, synopses, treatments, script development, script breakdowns, production schedule, and storyboard. The program proposal is generated after research and extensive discussion with the producer and the academic experts. The proposals should contain the title, the target audience, the justification, the program objectives and an outline of the content and the treatment.

Research is undertaken at the initial stages of the program proposal and a synopsis, which briefly describes the basic story lineltheme is prepared. The treatments are longer descriptions with summaries accompanied with pictures depicting a premise.

TV Script: A script is then written for the video program. It relates words (which may be a simple summary or a detailed script of the commentary and/or the presenter's words) to the storyboard. It should contain carefully researched material and should be complete as far as possible to prevent tedious time consuming editing at a later stage. The TV scripts \differs from the audio script in the fact that it contains comments for video and audios as well. This is normally divided into two halves. Left side of the sheet for video related descriptions and the right Side for audio.

In the preparation of the script and its associated documents, various individual styles are used. The following are the typical example that are most commonly used in script preparation:

Synopsis: This is general outline of the program idea. In a drama, it may accompany the script to give a rapid summary of the plot, action, character, etc.

Break down shot/ show format: It lists the items or program segments in a show in the order they are to be shot. It may show duration of the participation, shot numbers, etc. The program may start with the opening titles and music for few seconds. It will then show the program introduction followed by the detailed program and in the end it will show the end titles.

Story board: The storyboard is presented on specially designed paper with areas representing a TV screen and a place below the screen for Video and Audio cues. The areas appearing like TV screens will contain rough drawings of the camera shot

41

Audio and Video Media as planned and how the frame would look to the viewer. The storyboard will also contain issues like backgrounds used, characters, lighting descriptions, dialogue. etc.

A storyboard helps put your ideas across. before undertaking the shooting of the program. It helps the whole team visualize the complete production. Another use of the storyboard is that it gives all the personnel involved with the production, a clear understanding of the events that are to take place and the sequence of 'the shoot. Cameramen understand what angles they have to position their cameras, whether they need to take a close-up shot or a medium shot or a long shot. Lighting people understand the lighting needs according to the kind of shot. Character generator personnel also come to know about the capr Ions to prepare, etc.

Scouting talent, guests, planning for sets, etc. are also undertaken. Locations will need to be identified, permission for shooting in these locations will have to be obtained from the local municipal or governing bodies, sets and furniture will have to planned and manufactured, TV recording studios or equipment will have to be checked up and booked to ensure that they have the right kind of equipment for the recording of the program. Floor plan may have to be made and it involves drawing out the whole floor if the production is shot in a studio giving a bird's eye view of the placement of furniture and other things. Planning for lighting, graphics, audio specification, boom microphones, etc. are also done at this stage.

Production Stage: At this stage all the planning processes and the pre-production tasks converge and the functioning of full production team comes into play. The producer holds the production meeting before the actual recording of the programme. It is attended by the production assistants, cameraman, lighting supervisor, technical director, sound engineer, vision mixer operator, VTR operator, property designer, etc. The producer discusses the production script and the floor plan prepared by the set designer, which is then distributed among all the members. The detailed camera cards are also circulated to the cameraman. All the technical issues (lighting and the selection and the placement of the microphone etc.) are discussed with the technical director and the other technical operations staff and finalized with the producer.

Before the actual recording the producer should supervise the following aspects:

Set has been properly erected and placing of all the things, like furniture, decorative pieces, etc. as required for sets are completed.

The lighting in the studio are done as per the requirement.

Cameras have been aligned properly with the help of CCU and are positioned in the studio floor. Camera cards have been fixed on each of the cameras.

All the necessary AudioNideo tapes used for the playback and recording are being handed over to the VTR engineer.

Microphone and the other technical equipment checked by the technical director are put in the proper places.

The credits (name of script writer, editor, producer, etc. ) have been entered in the Video type writer (VTW) or computer.

The production and the technical crew members have taken up their respective tasks and positions.

Reading and rehearsal: This stage involves the reading of the script, tinling the length of the program, correcting for pronunciation, articulation, language and experimenting with camera angles. Rehearsals are important as they save valuable TV production time by identifying possible errors and correcting them. The producer will concurrently assesses his production, guides cameras into the shots he is seeking, and works out substitute treatment where necessary. A proper reading and rehearsal is rewarding as it minimizes studio costs.

42

Video recording: Once the program has been thoroughly read and rehearsed it can be recorded. This involves the producer, production assistant, cameraman, floor manager, vision mixing engineer, sound engineer, microphones, video recorders, etc. Recording is carried out under the direction of the producer who is ably assisted by the production assistant and the floor manager. The video production is shot as a sequence of takes with a crew member logging good and no good takes using time code as a reference. This will be used in the editing process.

Post-production: Postproduction begins after the audio and the videos have been recorded in the tape. It now requires proper editidg to make the master program.

Editing: Once the recording process is over the video and audio recording material is moved into an editing room. Editing rooms can comprise of linear type editing suites or the more modern Non linear editing workstations depending on the availability and costs. Here mistakes, improper takes, unwanted visuals and sounds that were recorded in the recording process are cleaned up. Additional elements like graphic elements that could not be added at the time of the shoot are inserted here. Video could be acquired from a multi location shoot and these are then pieced together using the storyboard as a reference. Sound effects and music as needed by the program are added and mixed to form the composite audio track.

Preview: At the end of editing the final program a preview is held to evaluate the program and carry out changes if found necessary. If there are changes necessary the program will go back for editing. The master tape now ready is used for broadcast, duplication or is stored in a suitable library.

14.8.7 Storage and Archival Considerations

Storage: Proper storage of audio video material,^ produced is important. Proper environmental conditions should be ensured in the place where they are stored. Humidity, high temperature, dust, textile particles, harsh chemicals, strong magnetic fields, direct sunlight, lights of certain frequencies, can be harmful. It is better to put the tapes and CDs, DVDs, etc. in their cases to prevent mechanical damages, especially scratches. Dropping them or shaking them can also damage them. Tapes are especially delicate and should not be meddled with. Rewinding them should be done carefully. Misalignments and careless fitting while playing them could damage them severely. Finger prints from touching them leads to sticky patches that attract dust. It is important to ensure that the storage space is fireproof, thermally insulated and is not vulnerable to water and dampness. The storage araa should be air conditioned. Nowadays the racks and vaults used for storage are metallic and not wooden. The cassettes and discs should be stored upright. The master-copies should not be easily accessible to one and all but should be in the custody of trained people. The replay equipments should be properly maintained. However, in spite of all precautions, data carriers could be damaged. Even digitally stored data may be lost. Replay instruments could also damage the data carrier. Even normal replaying on repeated occasions may damage them. Hence, it is always better to maintain backup copies. It is also important that replay machine and the recorded formats are compatible with each other. With obsolesce of replay machines, the new machines may not be able to read the data stored in the older formats which then become uselesk. Let us discuss a simple example. New models of computers may not be able to read the data we had stored in floppies. Hence it is necessary to keep pace with obsolescence and transfer data in a format that the new machines will replay.

Archiving: Archiving audiolvideo means they would be stored for a long time. We see some old films that have now poor audio and video quality. But good films, audios, videos have to be stored properly for future generations. The data may be stored in analog or digital form. Unless storage is done properly the archived materials may lose quality. Nowadays computers help in the processes related to the preservation of

Non-broadcast Media: Audio and Video (Part 11)

Audio and Video Media data i.e. archiving. To ensure the retention of quality and allow subsequent replay, the data (audio /video ) is digitized, compressed and then stored in an intermediate archive format (IAF). Indexing and cataloguing are also required for subesequent searching of the audiolvideo content. This is because as the archive grows in size, searching the data becomes difficult. Indexing helps us to create path to the data stored. Conventionally, creating a few key words for annotating the data is done. But today more advanced techniques that make retrieval of the data stored easier are available.Cata1oguing as is done in libraries for printed materials, is the process of sytematically listing the items available. It includes preparing a formal description of the audio-video tapes and titles. This could include a title, a brief description of the content , the location of recording, etc. These information help in easily locating a particular audiolvideo from those stored.



1 . Briefly explain the role of the scriptwriter.

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2. Explain the importance of floor planning in video production.

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3. Briefly explain the editing process.

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STRENGTHS AND LIMITATIONS OF NON- BROADCAST MEDIA

In the two parts of this unit we have been discussing about non-broadcast media. In this section we shall discuss the strengths and limitations of these media (both audio and video) :

Strengths of Non-broadcast Media

i Non-broadcast media can overcome many of the limitations of radio and television broadcasts. It provides considerable freedom to the learners who can use it any time and place at their convenience. Also the pace of delivery can be controlled. The viewer can review the program many times and take their own time to understand the subject.

The cassette player is comparatively inexpensive, simple to operate, flexible and portable.

It is a flexible medium. Sufficient time can be allocated to a topic that can be taken up in details.

Video is effective for course materials which need demonstrationlvisual illustrations which cannot be taught effectively through radio and audio cassettes.

To hold attention and motivate the students, the content can be presented in NO^-broadcast Media: Audio and Video (Part 11)

interesting formats, which can help the student retain and recall information presented through the programs.

Programs of a sensitive nature can be used effectively with targeted students through the non-broadcast mode by virtue of the fact that the non-broadcast

Educational broadcast is not accorded priority in the radioltelevision set up. The technical staffs concerned with the planning and production of radio programmes often lack adequate knowledge of the relevant pedagogical needs of the learners and their characteristics. The subject expert at times may not have any deep acquaintance with the complexities of programme production. Hence good quality videos can be assets for learners.

Limitations of the non-broadcast media: The following are the main limitations of non-broadcast media.

With the increasing use of phone-in methodology used in today's broadcast, interaction with the student is easy. The student can clarify the doubts on the

I

r spot. With live interactions the-program becomes more interesting. Whereas in I the non-broadcast mode response is via letters or phone calls or emails asking i for clarifications.

It provides fixed rate of presentation of information. Hence ~t 15 very difficult to update the programme once the audiolvideo cassettes are dispatched to the students.

Due to the availability of the variety of format (AnaloglDigital) and systems, which are essentially incompatible, the choice of any particular format to record

f the audiolvideo programme is very difficult, thereby increasing the complexity of the inventory that has to be maintained for ardy program.

It can be expensive if the audiolvideo cassettes are sent to very large number of I students. The logistics of the distribution system is cumbersome. There is also no

surety if the materials reached the students on time.

Audiolvideo cassettes require costly recording and presentation equipment. I For an educational programme, they are better as part of an integrated package

with print, and other modes of delivering instrhctions rather than being sufficient I in themselves.

A wide range of media is now being applied in the field of education and distance education is revolutionized by the use of their use. Non broadcast media have become popular because they help us overcome some of the weakness of the radio and television broadcast-like the availability of broadcasts only during the scheduled times. Videocassettes enable students to view the material at a time of their own choosing with as many pauses and as many replays as necessary. This increases learner control over the technology.

activities involved in production such as designing the camera script, developing production and technical plans, booking the studio, organizing various production tasks and activities and co-ordination with a host of oolleagues for studio preparation, rehearsals and dry run and final recording of the programs. This also includes taking

Audio and Video Media Non broadcast media (video) can be of many types like talk shows, interviews, discussions, game shows, drama, etc. The modern CD and DVDs are today replacing the video cassettes because of the many advantages they have such as they are more sturdy, economic and light in weight. Teachers are today trained to prepare multimedia CD and VCDs and amateurs can also preparing educational videos through handy cams.


1. Go for a virtual trip to a radio and TV studio. For this you may use:

Google images. Download a few images related to this unit and prepare notes on them.

For radio, visit Websites like : htt~://www.heritage.or~/Press/radiostudio.cfm

h t t p : / / r a d i o . a b o u t . c o m / o d ~ f u n r a d i o t h i n ~ 6.htm

For TV , visit Websites like: http://en.wikipedia.org/wikifTelevision studio

http:/lwww.bbc.co.uWnorfoI~senseof~lace/forum tour.shtm1

Remember websites are prone to be changed or withdrawn.



htt~://en.wiki~edia.ora/wiki/Camera control unit retrieved on 1 1.6.07.

http://en.wikipedia.orp;/wiki/Lavalier microphone retrieved on 11.6.07.

http://en.wiki~edia.org/wiki/Microvhone retrieved on 1 1.6.07

htt~://en.wiki~edia.org/wiki/loudspeaker retrieved on 1 1.6.07

http://en.wikipedia.orrr/wiki/Waveform monitor accessed on 13.6.07

httv:Nsearchstora~e.techtarget.com/sDefiO,.sid5 rrci295633.00.html accessed on 13.'6.07

htt~://~~w.sc~hoto.com/html/studiolight.hml accessed on 13.6.07

http://en.wikivedia.org/wiki/Video CD accessed on 13.6.07

14.13 CLUES TO CHECK YOUR PROGRESS


1. Can be accessed at time and place of choice.

2. VHS, DVD, etc.


. 1. The scriptwriter designs the script for the programme, suggests visuals, graphics, music and effects

2. It involves drawing out the whole floor to give a bird's eye view of the placement of furniture and other things.

3. The editing process constitute, selecting and combining the suitable sounds and video after they have been recorded and adding the special effects in the postproduction. In the digital recording editing can take place both in production 9s well as in the postproduction. Editing process enables the producer to physically assemble the audio and video fragments into a coherent message on a master video tape.

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'-w

UNIT 15 TELECONFERENCING ,

15.0 Introduction

15.1 Objectives

15.2 Teleconferencing and Open Distance Education

15.3 Synchronous Communication Technologies 15.3.1 Audio Conferencing Technologies

15.3.2 Video Conferencing Technologies

15.3.3 Computer Conferencing Technologies

15.4 Teleconferencing for Teaching-Learning

15.4.1 Designing Instruction for Teleconferencing

15.4.2 Conducting Teleconferencing Sessons

15.5 Summary

15.6 Unit End Activities

15.7 References and Suggested Reading


15.0 INTRODUCTION Various technologies used in distance learning, as discussed in the earlier units are the broadcast & non-broadcast audio/ video media. These technologies generally lack a two-way communication channel between the teacher and the student. Successful distance education systems ensure active learning that involves interactivity between teacher and students and among students themselves. The quality of educational process depends upon sustained, two-way communication. Teleconferencing has great potential for providing this essential two-way communication. The potential of teleconferencing (TC) lies in creating greater opportunity for dialogue, which facilitates more effective learning than studying in isolation.

In this unit, we shall study various types of telecanferencing technologies that are available and their advantages, disadvantages and applications in distance learning / teaching. It is necessary to understand the limitations and potential of this technology to evaluate its use in distance education. Teleconferencing is a function which can be hosted on a variety of technologies i.e. telephone, saaellite, Internet and can be applied to wide range of situations like live video lecturing to a large audience, from point to point, individual desktop, PC Chats. The success of the teleconferencing may well depend on factors other than the technology. These factors range from institutional issues, to cost, to student and tutor attitude to technolbgy. It is also highly dependent on the teaching methods adopted. In view of its use teleconferencing may become the most used technology in distance education in near future.

15.1 OBJECTIVES After studying this unit, you should be able to:

explain the role of teleconferencing in distance; learning;

describe various types of teleconferencing;

explain the advantages and limitation of audio, video and computer conferencing;

understand and describe how to make best use of teleconference technology in distance education.

47

Audio and Video Media 15.2 TELECONFERENCING AND OPEN DISTANCE

EDUCATION

Students who study at a distance are separated both from their tutor and their peers. Social interactions, sharing of ideas. joy of learning and discovering together, sharing successes and failures and general social support are all to a certain extent, missing form distance learning environment. Students may therefore feel isolated, lose motivation. experience frustration and a host of unwelcome emotions.

The task of distance educator is therefore to obviate these problems as much as possible by using appropriate technologies, maintain a stimulating environment and create opportunities for students to communicate with teachers and with each other on a regular basis. This is where the teleconferencing technologies comes handy and offer opportunity to provide interactivity needed to offset some of the demotivating aspects of studying alone. Therefore, let us study about teleconferencing and understand how to make use of this technology in distance teaching1 learning.

A two way comn~unication using electronic equipment between students who are located at separate locations and teacher in a studio can be called "teleconference". Such communication is facilitated by a combination of electronic equipment and communication channels. The communication channels can be simple telephone networks to satellite links. Interaction between teacher and student is achieved by different type of technologies. These technologies are divided as synchronous and asynchronous depending on the nature of communication either live or recorded. Synchronous communication are real time conversations between all participants in the conference. For instance. a radio broadcast received simultaneously by all the listeners, teleconference telecast from IGNOU headquarters to students at study centers via satellite. etc. are examples of this type of communication. In asynchronous communication messages delivered are not accessed at the same time but at different times by different receivers. For instance. email and voice mail. In this mode each recipient will read the messages at hislher convenience. Success of using teleconferencing technologies in distance teaching depends on technologies available with the institution and trained man power for developing the courseware suitable for the medium used.

Conferencing helps in the following manners:

0 provides equitable access to resources to learners especially to those in rural and remote places .

0 facilitates rapid access to information.

0 makes learning interactive, participatory and dialogue based.

facilitates collaborative learning through exchange of information , sharing of resources, team work .

a provides a virtual learning environmeilt when access to real experiences is not feasible.

SYNCHRONOUS COMMUNICATION TECHNOLOGIES

Synchronous communication in education ineans that teacher and the students interact with each other in "real time" as in teleconferencing. It is a live situation where recorded instructions are not played but live interactions are there. The ongoing conversation is made possible electronically. For example two-way videoconferencing allows students to interact with instructor. Less complex technologies, such as telephone conversations are also synchronous, Synchronous technologies can be classified as shown in the following figure (Figure 1).

48

I ~ u b i o Conferencing Technologies

Synchronous communication technologies

video

Conferencing Technologies

Teleconferencing

cornbuter

Conferencing Technologies

Fig. 1

15.3.1 Audio Conferencing Technologies

Let us now study about Audio conferencing technologies These technologies can be further classified depending on medium used as audio, audio graphic and phone-in radio as shown in the figure 2.

Audio conferencing technologies

r --1 ---

Audio conferencing Audio graphic conferencing Phone-in radio

Fig. 2 r

Audio conferencing

,- Simple conversation on telephone by more than two persons may be treated as 'Audio Conferencing'. Nowadays many telephone networks and modem hand sets can offer this facility. While conversation between two people is a point to point communication, by using conferencing facility a telephone network can be used for multipoint communication. Such conference facilities can be used in distance teaching easily as they are simple to set up. They can be setup by dialing the number designated for conference by each students. However as the number of students connected to the system increases the quality of the sound may reduce. To overcome this situation a special equipment known as 'Audio Bridge' is developed.

Audio Bridge is designed to co1,nect number of telephones so that people from different places can converse simultaneously. This bridge electronically mixes the audio signals from the connected telephone line from various locations. The circuitry in the bridge balance the signals level and also isolatelreduce the telephone line noise to provide quality audio. The conference can be set up using bridge either by students dialing the number designated for conference or an operator at conference nodal location connecting to the students required to participate in the audio conference.

In case of student calling into the conference bridge, a telephone number (allotted to special bridge) can be published or sent along with the time schedule of the conference. The telephone number can be toll free number (see glossary) to encourage participation. In this type of conference each student has to dial in as per the schedule. In case of an operator connecting, each and every participating student located at different location will be dialed from the bridge equipment. The limitation in such a system could be that a list of the numbers of the students is requ~led and a student has to be present

v at the same location during conferencing. While standard telephone set can be used for participating audio conference, better d ~ . , . : speaker phone can be used for hand free conversation. It is also good idea to install amplifier in the hall where more

c students are assembled, at a given center. The center can have acoustically treated hall for better audio quality.

Audio Graphic Conferencing

Audio conferencing can be improved by value addition by way of sending picture1 data along with voice communication. The picture1 data information can be sent in advance for use at the time of audio conferencing or it can be sent over a telephone

49

. \udio and Video Media line itself. This mode of conferencing is called audio graphic conferencing. Graphic scanner, electronic white board/ electronic tablets with appropriate software can be used to transmit graphics, sketches, etc. Audio Graphic conferencing is also some times referred to as enhance audio or audio plus.

Audio Graphic conferencing is advantageous than mere audio conference as it also transmits visual information. Even though simple static graphic are received by the students, they are of great help in understanding the topic under discussion. These visuals bring clarity in explanation of the subject. Sometimes we may be required to use separate lines to transmit the voice and visuals for better interaction.

The advantages of audio conferencing and video conferencing can be used in this conferencing mode with limited expenses. Some of the visual requirements can be met through this graphic conference.

Phone in Radio

Phone-in radio is very popular nowadays. Every one in the vicinity of FRI broadcast might have heard one or the other phone-in programs. In phone in radio, the communication is point to multipoint by radio broadcast to the learners and the interaction is through a simple telephone line. Teachers at the studio of the broadcasting station teach and answer the queries raised by learners, who dial into the studio telephone numbers using ordinary telephone. To encourage students to interact freely, these numbers can be toll free i.e. students need not pay for the calls made. Voice of the students on telephone is also mixed and broadcast therefore everybody listening to the programme is also benefited by the discussion. Phone in radio virtually creates a classroom spread over large area covered by the radio broadcast. For example IGNOU conducts interactive radio counseling program with the help of All India Radio national network, which can be heard through out the country. Government of India is encouraging universities to install FM radio stations for campus broadcasts. These low power stations can boost Phone-in radio use in education sector. Equipment needed by the student to participate in Radio Phone in program is only radio receiver and Telephone. Fax machines may also be used to communicate during such programmes to send text and sketches if required.

The advantages of phone in radio are obvious as the reach and availability of radio is widespread and it is also easily affordable. Limitations of the phone-in radio are that interaction is with teacher only as the students are linked to the teacher. Students can only listen to the other students participating in the program, but cannot interact directly with them. As this kind of program is synchronous in nature it needs scheduling so that many can benefit from it.

1 Merits and Demerits of Audio Technologies

I Let us summarize the merits and demerits of audio conferencing :

Merits

Equipment required to setup audio conference is simple and less expensive.

Options for selecting Telephone or speaker phones and a telephone networks are many.

Audio conference can be easily recorded by the students themselves for reference.

Students can participate in the conference from anywhere.

Demerits

Difficult to explain abstract concepts on audio conference due to lack of visual information.

It is difficult to learn through audio information only.

Teleconferencing Scheduling is necessary and needs coordination between teacher availability and student convenience.

Since eye contact is not possible it is difficult to retain attention of students.

Integrating Audio Technologies

The following points may be kept in mind while using audio technologies for delivering lecture / discussing topics in conference mode:

Since students can not see each other in audio conference, addressing each of them by their names is desirable to give a personal touch..

It is better to encourage interaction and let everyone participate in the discussion.

Relevant text, pictures, sketches relevant to the topic under discussion can be sent in advance.

The conference can be recorded and suitably edited for the benefit of other students who missed the conference or want to review the contents.

It is important to take every care in selecting equipment for good quality audio communications.

We also have to remember that in audio confdrence the voice/audio quality is of primary importance, therefore the equipment, environment and content design are to be carefully selected and planned.

15.3.2 Video Conferencing Technologies

Video conferencing, also called video teleconferencing is setup using both audio and video equipments for transmission as well as reception from separate locations. This set up allows student to see the teacher and histher presentation and interact with himher. Unlike audio graphic conferencing, in video conferencing video cameras are used for transmitting moving pictures. Video aonferencing is set up either between point to point through a telephone network and equipments for compressing and decompressi~g the audio video signals or it cah be point to multi point by using broadcasting equipments.

Video conferencing systems can be divided broadly into two types as shown in

conferencing

(Usually through satellite, cable) (Microwave, Desk top Video)

One-way video and two way audioconferencing: In this type of conference, as the name indicates video is seen only one-way. Students (participants) at multiple sites can see the teacher, but the teacher can not see them except those physically present in the location (studio). Satellite transmission is used in India for one way video and two way audio type of teleconferences. Such teleconferences are used when instructions are to be provided at multiple locations across a wide geographical area. Distance learning through this kind of conference needs a teaching end studio equipped with video cameras, microphones and other mixing equipment. Final studio signals are transmitted to satellite for broadcast or to a cable network system.

The receiving sites/ learning centers will have down linking equipment to receive the satellite signals through a small dish or directly from cable and displayed in class rooms/study centers by standard TV sets. Audio interaction with teacher is provided

5 1

Audio and Video Media by the use of :in audio bridge at the teaching end and telephone lines at remote classroon~s.

Two-way audio video conferencing: In this type of conference audio and video signals are exchanged between teaching studio and receiving center. Thc two way conference can be point to point 01- between multiple locations. The receiving center can receive pictures and audio from other centers. All centers are equipped to send and receive video and audio viz. cameras, microphones and monitors.

Satellite based conferencing: Satellite transmission is best suited for point to multi point communication. Normally a large size dish with satellite transmitting equipment (up-link facility ) is installed for sending audio video signals to satellite at the teaching centre. At the receiving centers relatively simple receiving equipment with small size dish is installed.

Many educational institutions may not be in a position to set up up-link and down link equipment on their own. However, these institutions may use facilities set up by the government at certain locations. One example of an educational system that makes use of satellite communication in India is training and development comn~unication channel (TDCC) coordinated by ISRO and IGNOU. Such conferences are being organized on Gyan Darshan, the educational television channel of India. The return audio channel is usually through telephone network and it is also possible via sateilite with additional equipment.

You may have notiied similarity with the phone - in radio service and satellite-based conference as both or' them use broadcast media to send the educational program. Even though the broadcast is at a scheduled time, students can tape the programme and play it back at a convenient time.

Cable Network Based Conference

Cable networks are set up to bring entertainment satellite channels to homes. This type of cable connection can be used to transmit one-way video and one-way audio transmission to the community at large or between specific locations/receive centers. Cable network based conference will be effective in local area or small townships. In one school 1 collage, the teacher would teach while in the others, the students can access the televised program.

Cable companies will soon be able to use the technology of digital video to offer hundreds of channels to each home and school. Although many of these channels will be used for commercial entertaintnent purpose, it is expected that a couple of channels will become available for education.

Two-way audio video conferencing (Microwave, desktop conferencing facilities)

For two-way audio video conferencing both teaching and learning ends should have similar equipment to send and receive audio as well as video. Usually microwave TV conferencing are point-to-point cc~mmunications whereas desk top conferencing can be used for multi point communications.

Microwave Television Conferencing : While, Satellites are popular for enabling video communications over long distances. microwave translnissions provide a cost- effective method for videoconferencing within more localized areas. Microwave systems are designed to transmit good quality video signals to areas that are not more than 40 km apart. They provide in line of sight (without physical obstacles to block the signals) point-to-point communications. Microwave stations operate at a lower power, require comparatively relatively less expensive equipment. One problem of microwave communication is the availability of limited number of channels in the spectrum in any one area. Microwave communjcations are not popular for providing education in India.

52

Digital (Desktop) Videoconferencing

'I'his tech~ology involves the capturing, manipulation and storage of video in digital brmats. Desktop videoconferencing uses a computer along with a camera and ~nicrophone at one site to transmit video and audio to a computer at another site or ?ires. The computers involved in digital videoconferencing, require a videoconferencing board (codec board) with the ability to compress and decompress the digitized video. This technique is less expensive than satellite or microwave systems. The disadvantages are that visuals of rapid movements may be of lower quality and that fast transmission lines as Integrated Services Digital Network (ISDN) are required. Slower transmission lines can affect quality of transmission. They are also not very suitable for large groups with many participants.

Advantage /Disadvantages of Video Technologies

Advantagesldisadvantages of the video conferencing are summarized as follows:

Advantages

Allow both audio and video communications. Hence it is suitable for teaching that involves demonstrations. Video medium supports visuals related to lab experiments and animations and thus explain abstract topics.

Encourage interactive learning.

Disadvantages

It is expensive and the infrastructure at each site may be unaffordable for many institutions.

Requires teachers trained to teach through this technology, and requires a crew with camera men and other technical experts. Effective programmes require rehearsals with teachers and technical team . The programmes are scheduled and learners need to be present at the time of transmission.



1 . Explain the need for interactivity in distance education.

...............................................................................................................

2. What is essential other than equipment and communication channel for teleconferencing?

Teleconferencing

............................................................................................................... 3. How do you overcome lack of visual information in using audio conferencing?

Audio and Video Media 15.3.3 Computer Conferencing Technologies

In computer conferencing. computers are connected by local area network (LAN) or internet. Access to computer conferencing is not limited by time and space, thus offering greater access to student in learning from distance. Computer conferencing allows learners to access information from the teacher and at the same time enables them to interact among themselves. Unlike the audio and videoconferences, computer conferences are mostly text based such as chat rooms and shared white boards. Following are two types of computer conferencing:

Internet videoconferencing

Internet Chat (Text only)

Internet Videoconferencing

In order to set up an internet video conference we need to have digital video camera, microphone. digitizing card for audio & video, speakers, network card and conference software installed in the computers at both sides. I lnternet video conferencing usually results in a small image and quality of video depends on the band width availability i.e. speed of the internet connection. In most cases, a regular modem is far too slow to transmit effective video. With improvements in technology, it is possible to get better pictures and sound across internet that can be viewed full screen with better lip-sync i.e. synchronization between lips and sound.

Internet Chat

Internet Chat is a two-way, interactive exchanpe over the Internet in text mode. Tn chat mode, two or more people at remote computers connect to the same chat "room" and type messages. Typed messages can be seen by all participants on a shared screen. Online chat allows students and teachers to communicate in "real-time." In internet chat, student feels free to communicate in the absence of cameras/microphones but helshe may have to concentrate hard to express in text mode. Shared white boards can be used to communicate t/u-ouglz text a ~ d graphics with appropriate sqftware tools. Advanced software even allows users at remote sites to share applications. The student and teacher will both be able to provide inputs and analyze the results. The advantages of online collaboration through chat or shared whiteboards are that the communications are synchronous and the feedback for the students is immediate. Need for similar software at both sites can be a disadvantage. Number of participants may be limited for simultaneous collaboration.

Advantages1 Disadvantages of Computer Technologies

Advantages and disadvantages of computer technologies are summarized as follows

Advantages

Computers allow students to learn at their own pace and review as often as they

With the use of multimedia, learning can be made interesting and interactive

In computer conferencing usage of text make student more attentive and make them feel free without camera fear.

The Internet gives world wide access with minimum cost .Teaching is possible internationally in true sense.

I Disadvantages Teleconferencing

I Availability of regular power supply is one of the main problems in some areas besides access to computer hardware and desired software.

Even though the speed of network connectivity is improving day by day, it is still not fully sufficient to meet video conferencing dem~nds. Therefore communication is still mainly by text.

Tackling computer viruses is not easy.

I In spite of great developments in computer technology there could be some uncertainty in connectivity or availability of the servers in some places.

15.4 TELECONFERENCING FOR TEACHING-LEARNING

I In this section we shall discuss the use of TC for teaching and learning.

m 15.4.1 Designing Instruction for Teleconferencing

I As we have discussed various types of conferencing technologies, let us now discuss the instructional designs specific to these technologies. In designing instruction for teleconferencing, focus needs to be on how to present it in audio-visual way.

When designing material to be delivered through teleconferencing, one should incorporate different activities involving students at the various sites to retain their attention. Such as discussions, student presentations, sharing of experiences, etc. Changing instruction methods periodically during the session will also sustain students' interest. While teaching material viz. pictures, diagrams, maps, graphs. tables, and charts may be conceptually similar to those used in conventional class room teaching, but they should be designed so that they are formatted to suit the medium being used. For example, graphicslcharts should be prepared with big font size and good colour contrast to show up clearly on the receiving side monitors. information presented should be adequately summarized for retention and recall.

In fact, the ability to show movement in video can be effectively used to demonstrate experiments to show the processes and operation of the equipment and tools. Animations, slow motions can help in analysis of the actions over a period of time. Simulations and three dimensional models simplify understanding of complex three- dimensional qualities of an object or structure. Historical topics may be supported by the photos or film clips to add authenticity to the subject and to take students to

15.4.2 Conducting Teleconferencing Sessions

Once basic teaching me1 hods are finalized, the following three-step strategy may be adopted.to ensure good rapport between students and teacher.

Preparation Before Conference

It generally takes more time to deliver instruction through technology than in a traditional face-to-face setting. Therefore lessons are to be planned accordingly. Practicing with equipments and a few target students if possible, enables smooth teleconference sessions later. Ensure that students received necessary background materials to make the best use of the conference. Discussion topics or questions may be defined clearly in advance so that students can prepare for interaction. Possible study questions may be created to help in focusing on discus3ions.

Audio and Video Meclia During the teleconferencing Session

Eye contact is very important in video conference. Facial expressions, tone of voice. body movements are also important to enhance communication and attention of the student. Raising questions, involving students, and praising student contributions are also to be parts of the discussions. Presentation may be in short spells interspersed with discussions. Instruction and interaction can be alternately used. Avoid reading from the prepared text and maintain a moderate speaking pace. Concepts discussed in the program may be reviewed and focused questions should be asked as all student5 may not feel free to express doubts in conference mode. Acthitie\ may be integrated to reinforce the content V ~ L . quizzes, worksheets, role-playing, and experiments. Topics or questions may be displayed on the screen as reinforcement. Student-to-student interaction may be encouraged.

After the Session

Recordings of the presentation may be reviewed for improving presentation, style, and delivery methods. Student feedback may be obtained on the strengths and weaknesses of the instructional materials and the teaching strategies used. Since the technology is the only link between teacher and student one should be open to latest technologies and new ideas.



1 What is the major difference in computer conferencing and other conferencing methods and what are its advantages?

...............................................................................................................

2. How can we keep distance student actively involved in teleconferencing'?

15.5 SUMMARY

Students who study at a distance are separated from their teacher and their fellow students. Distance education system must provide for interactivity between students and teacher and among students themselves using appropriate interacti-ve communication technologies. Synchronous interactive technologies are commonly referred to as "teleconferencing" irrespective of the communication medium being utili~ed. Each audio, video and computer conferencing have their advantages and disadvantages' depending on their respective media formats. (See table-1 below). Designing instructional material for teleconferencing is challenging as it requires careful planning in many ways. Scheduling and appropriately allowing interactivity among students participating in the conference distributed across networks is very important for successful teleconferencing.

Teleconferencing Table 1 --

Technology Advantages Disadvantages

Audio conference Inexpensive No visual support Easy to set up

Phone- in-radio Easily accessible bera~~ with teacher Wide coverage only; Scheduling required

Cable Network

Must be scheduled

Microwave Videoconference May be interactive Must be scheduled

1 Relatively inexpensive Limited coverage Line-of-sight transmission

Instant -feedback Requires Web access


1. Visit your study center and participate in a teleconferencing programme meant for the PGDET programme. Recount your experience as a report.

2. Listen to the Interactive Radio programme of IGNOU and interact with the resource persons. Recount your experience as a report.



http://web.mit.edu/is/isnews/v18/n03/180309.html Retrieved on 15.6.07

http:llen.wikipedia.org/wikiNideoconferencing Retrieved on 19 .6.07

http://www.webopedia.com/TERM/V/videoconfe~ncing.html

Retrieved on 19 .6.07

http://picture~hone.com/productsAearn tvpes of systems.htm Retrieved on

http://fcit.usf.edu/distance/chap9.htm Retrieved on 20 .6.07

Audio conferencing: Voice-only communications linking two or more sites. In most cases, standard telephone lines and speakerphone~s are employed.

Audio graphic conferencing: Voice communications supplemented with the transmission of still images. Pictures, graph3, or sketches can be transmitted during

can be used.

Bookmarks: A list of sites that can be saved by browser software. The hot list enables user to access favorite sites without retyping the URL.

5 7

Audio and Video Media Bandwidth: The transmission capacity of a telecomnlunications system. The greater the bandwidth, the greater the amount of digital information that can be transmittec' per second.

Bridge: A device, often leased through a telephone company that links three or more telephone lines together for audio teleconferencing.

Codec (Compression-Decompression): An electronic device that converts standard television signals into compressed digital signals for transmission. The same device can converl incoming compressed digital signals back into viewable television signals. A codec allows motion images to be transmitted through special telephone lines.

Desktop videoconference: Multimedia microcomputers are used to display live video images that are transmitted w.er LANs or digital data lines.

Internet: An Internet is a network. The term Internet usually refers to a collection of' networks interconnected with routers.

ISDN (Integrated Services Digital Network) : A modem telephone system that allows rapid digital transmission of sound, data, and images.

ISRO: Indian Space Research Organization

LAN (local-area network) : A computer network limited to a building or area of a building.

Microwave: A high-frequency transmission that can be used for television signals or computer data. Microwave transmissions are said to be line of sight, which means that they cannot pass through tall buildings or mountains.

T1 line: A special type of telephone line that transmits digital information at a high rate. These lines are much more expensive than regular telephone lines.

Teleconferencing: Electronic techniques that are used to allow three or more people at two or more locations to communicate.

Toll free number: Toll free number is a telephone number: calls made to this number are billed to the receiving party (Organisation). In other words, caller need not pay for the calls made to this telephone number.

Check Your Progress-1

1. For breaking isolation, motivation

2. Resources - physical equipments, financial. attitude of teachers, etc.

3. Through audio graphics - fax, computers, etc., visuals can be sent

Check Your Progress-2

1. Major part of interaction in computer conferencing is by text mode and help student express freely with out any fear of camera and microphone. Text based interaction makes learners attentive.

2. Student interest in teleconference can be ensured by:

Defining discussion topics in advance and allowing students to prepare for interaction

May assign discussion questions before teleconference

Encouraging students to answer some of the questions or express their opinion, ideas and experiences etc.

Alternating between instruction and interaction frequently. 58 --

UNIT 16 DIGITAL AUDIO AND DTH Structure

Introduction

Objectives

Basic Concepts

Digital Audio Formats

Storage Devices

Digital Audio Broadcasting (DAB)

Digital Video, DTV and DTH

Upcoming Audio-Video Delivery Technologies

Summary

Unit End Activities

References and Suggested Reading

16.1 1 Clues to Check Your Progress

16.0 INTRODUCTION

Sound is a part of everyday sensory experience for most of us. Just as eyes detect light and color, similarly ears are for the detection of sound. But we seldom ponder over the characteristics and behaviour of sound and the mechanisms by which sound

I

1 is produced, propagated and detected. The basis for such an understanding requires I

some knowledge of sound. Sound is a wavc which is dreated by vibrating objects and I propagates through a medium from one location to another. In this unit, we shall first I briefly discuss the nature, properties and behaviour of sound so that we can have an

insight into the realm of digital audio, its applications and the strategy for selecting appropriate storage devices for it.

The enormous growth in the entertainment industry over the last few decades has been due to the revolution in the field of audio and video technology. The advent of digital technology has as such revolutionized the field of communication, be it in the

I field of entertainment or education and this is a15 J going to fuel future growth in the 1 education sector. We shall discuss some of the most commonly used terms associated with audio recording and also discuss the audio-video delivery technologies.

16.1 OBJECTIVES

After studying this unit, you should be able to:

differentiate analog audio from digital audio;

discuss advantages of digital audio;

explain different digital audio file formats;

discuss variozs storage and delivery options for digital audio; I

describe digital audio broadcast technology, satellite television and DTH;

discuss latest trends in digital audio-video technology.

Audic~ ant1 I'ideu Media 16.2 BASIC CONCEPTS

Digital audio receives sound frdm the acoustic world, converts it into electrical sig11,); transforms into digital domain (0 & 1 ), then there is storage, retrieval and processin;; . data in digital domain and finally it is transfomled back into wund for the acousrr world. All this may appear confusing to some of you. Obviously. to understand digi:; audio technology you must familiarize yourself with the nature of sound in the acousti, world. In the following sub-sections, wc shall study the nature of sound and why an,! how it is transformed into digital audio.

The Nature of Sound

In a classroom, most of the communication that takes place between the teacher and the student is through speech, a form of sound. Every day we hear different types of sounds around us. Sound forms one of the most important aspect of our life. Let us make an attempt to understand how sound is generated.

A vibrating object generates sound by agitating air around it. The vibrating object could be any thing sucli as - the vocal chord of a person, the membrane of a "tabla" or the vibrating diaphragm of a loudspeaker. The sound generated so, propagates in the form of waves through air. We may describe wave as a disturbance in the air that travels from one location to another 1c:ation. These sound waves on reaching our ears cause sensation of hearing. Similarly, a microphone, picks up these sounds and converts them into electrical signals analogous (similar) to the sound waves falling on it. A typical sound wave is depicted in Figure 1.

Fig. 1: A typical sound wave

'The vibrations of the sound generating object are carried by the sound waves. These vibrations in a sound wave when measured as number of cycles (vibrations) per second , are known ds frequency of the sound. The unit vf measurement of frequency is hertz (hz) where one hertz means one cycle per second. Similarly 300hz means 300 cycles per second. As we measure weights in grams, kilograms and Quintals, frequencies are expressed in hertz, Kilohertz (khz.) and Megahertz (rnhz.) where 'k' means one thousand and 'm' signifies one lakh (100000).

Do you think we humans are capable of hearing all sort of sounds? The answer 1s a big 'No'. Our hcaring is limited to sounds ranging from 20hz to 20khz only. All the \ounds beyond this range can not be perceived by us but by certain animals such as bats, dogs etc. Sounds below 20 hz are termed as subsonic while those above 20khz are called ultrasounds. Waving hand in air however does not produce any sound, even though it is a vibrating object. Do you know . why? We can't wave our hands more than 20 times ner second. This implies, waving hand produces sound of frequency less than 20Hz

The Analog Audio A microphone picks up sound and converts it into an electrical signal known as audio signal. In practice, the term "sound" is used with reference to the sound we hear

while "audio" denotes sound in the form of electrical signal. A typical audio recording Digital Audio and DT

process involves amplification of the electrical signal received from microphone for strengthening the signal and finally writing it on a magnetic tape. During playback, the recorded signal is picked up from the tape and fed to a loudspeaker, after required amplification, to reproduce the original sound. The peculiarity of the analog audio process is that during the complete process of recording and play back, the waveform (shape & form of the signal) of the audio signal does not change. Though every effort is made to maintain the wave shape of audio during recording and playback process, but due to technical and economical constraints some changes in the wave shape of the signal do occur. The undesirable change in the signal wave shape is known as distortion. Noise is another factor which affects an audio. It is the undesirable signals, which generate within audio devices and gets mixed with audio signal. Though efforts are made to keep these two i.e. distortion and noise, at bare minimum but the cost of the technology involved becomes the major constraint.

Digital Audio

Most of the data available to us including sound is analog in nature rather than digital. The term 'digital audio' refers to an audio in the form of mathematical digits viz. 0, 1, etc. All mathematical computations can be done using only two digits, 0 and 1. In mathematics that we have learnt at school, all the mathematical numbers are written using ten digits from 0 to 9. It is known as decimal number systems since it employs ten digits (from 0 to 9) for creating any number. But all the numbers of our decimal number system can also be represented using only two digits -0 and 1 in various combinations. This is called binary number system that employs only two digits, 0 and I . How these computations are done is beyond the scope of this unit. The great advantage of using only two digits 0 and 1 is that these digits can be easily represented electrically. While the presence of a voltage signifies '1' the absence of a voltage represents '0'. It is just like a switch 'ON' and switch 'OFF' condition.

The process of creating digital audio begins with collecting information from analog audio signal by sampling it at regular intervals and converting the samples so obtained into binary numbers. A little bit of technical explanation of this aspect has been included as it will be helpful for understanding this unit and technology integration skills.

Let us get back to the process of digitisation. The process commences with capturing analog audio signal e.g. using a microphone. The output of a microphone is analog signal, which is carried with the help of a cable to the recording equipment, where it is converted into digital audio signal. The process of converting analog audio signal into an equivalent digital audio signal is known as analog to digital conversion. (AID conversion in short). For AID conversion, firstly the audio signal is sampled thousands of times per second. Here, sampling means periodically collecting electrical information about analog audio. The number of samples taken per second is known as the sampling ratelfrequency. Most of digital audio recording equipment offers you a choice of selecting sampling rate for recording. This is governed by factors such as desired audio quality and compatibility with other audio systems. Higher the sampling rate you choose better is the quality of digital audio and greater storage space. But a given digital audio machine may not be able to playback recordings done at a pahicular

C

sampling frequency. Therefore, while choosing the sampling frequency for a recording you have to keep in mind the capability of the machine on which it is expected to be

I played later. i-

Once sampling is performed, each sample is converted into binary form i.e. a number I comprising digits, 0 and 1 only. A single digit, either 0 or 1, is called a bit and a set of I eight bits is called a byte. One bit is a datum and many bits are data. How many bits

are being used to represent each sample is called resolution of the audio. With lower I resolutions there will not be adequate information in the digital signal to represent the

Audio ~ q d Video Media frequency, h-gher the resolution higher shall be the audio quality of a record~~ig.

The thumb rules: Audio quality = sampling rate Audic luality = resolution



1 . What is the sampling frequency?

...............................................................................................................

............................................................................................................ ...............................................................................................................

2. How is audio quality related to sampling frequency?

...............................................................................................................

...............................................................................................................

...............................................................................................................

Why Digital Audio? Analog audio has been there for a very lo lg time. While it still continues in certain applic,.iions but in recent times the digital audio is taking over because of its several *

ad van tag:^ over analog audio. Improved audio quality is the major advantage of digital audio but it also has several other advantages over analogue technology. For ~xample, audio effects such as echo, reverberation, etc. can now be performed on a digital audio workstation without requiring complex and expensive analog audio equipment. The quality of audio depends upon several factors. Let us see how digital audio proves better on some of these fronts.

Low noise level: You know that any unwanted sound is known as noise. The magnetic ' :pe used for audio recording has an inherent noise known as tape hiss, which definitely introduces some noise in audio recordings. Though very low noise tapes have been developed but tape noise could not be eliminated completely. Once noise creeps into an audio recording, it can't be removed easily and completely. As compared to analog audio, the digital audio is less susceptible to tape noise because of its different composition ( a sequence of 0 and 1).

Generation loss: When you perform an audio recording using a microphone, the recorded material is known as 'first generation' recording. When a 'copy' of the original recording is made by tape to tape transfer, the copy is known as second generation recording. If once again, a new copy is made from the 'second generation' tape, it is known as third generation recording and so on. During each copying process some noise and distortion gets added in the copied version thereb. degrading the recorded audio quality. This degradation of audio quality due to copying process is known as generation loss. As a result, the audio quality suffers on account of reduced frequency response and higher noise. While in analog audio this phenomenon is quite ' significant but neg1ig:ble generation loss occilrs during copying of digital audio recordings.

Sustainable quality: During tape storage over long perious, the au 'io signal recorded on magnetic tape gets weakened. The loss of signal strength results in degradation of audio quality. In case of analog audio, the audio quality suffers a lot due to this phenomenon but digital audio is quite less susceptible to it.

In addition to improved sound quality of digital audio due to the fa~tors discussed so far, there are several other benefits associated with digital audio which have contribute+ to its great success. Some of these factors are:

62

Storage and processing: Storage and manipulation of digital audio is much easier as Digital Audio and I)'!

compared to its analogue counterpart. This has led to availability of ,ilany new recording devices and post-producfion equipment with varied features. Audio work station is one of such systems which makes use of computer based devices for storage and processing of audio in digital format. The analog audio is input to the workstation, which digitizes and then stores digital audio on a hard disk. Editing and effects can ,: performed on the stored digital audio on the work station itself without requiring anv additional equipment.

Reduced storage space requirements: Digital audio recording devices like audio CD, DAT (Digital Audio Tape), MOD (Magneto Optical Disk) etc. require much less space than the analogue magnetic tape for the same duration of an audio. The DAT cassette is even smaller than domestic audiocassette. Similarly, CD and MOD are much smaller in size but have greater capacity to carry digital audio than old days vinyl records used for storing analog audio.

Commercial advantage. The cost of digital equipment have become quite comparable to its analogue counterparts. Much of digital equipment costs even less and is continuously on the decline. Due to increasing convergence between digital audio and the information technology, the digital audio devices are becoming more

i

economic.

Though digital audio gives an overall better quality than analog audio, but it suffers from the problem of dropout. It is the moment; j lrss of audio signal due to the loss of magnetic coating on the tape. Dropouts occur due to wear and tear of the tape as it rubs against the record/playback/erase heads ,,nd other tape guiding mechanical systems in a tape recorder. In analog audio recordings dropouts go unnoticed since our ears tend to fill in the gaps but in digital audio it may lead to absence of a digit thereby changing the meaning of the recorded information which results in prnducing an altogether different sound i.e. distortion. However, digital error correction methods have been developed reducing this problem to nearly negligible.

16.3 DIGITAL AUDIO FORMATS

The digital audio signal is put through a process of encoding prior to writing onto a recording medium for better signal recovery at the time of playback. Encoding and decoding may also involve compression which is a complex process of deleting redundant informz"on from the digital audio at the time of recording thereby reducing the size o, the information required to be stored. During playback, original audio is rebuilt thro~dh a decoding process. This process is similar to short hand writing, where the information, e.g. an English dictation, is encoded first using short hand symbols or codes and is thereafter decoded to the ,ymbols used in English. With the arrival of CDs and-computers in digital audio recording business, many new recording formats have been developed, based on different encoding techniques. The digital audio is recorded on CDs, hard disk of the computers etc. in the form of a file identified by its unique name given by the user. Let us understand, what is an audio Ale.

Take an example of a typical audio CD carrying 10 songs on it. All the ten songs on it are given unique names viz. Track01 .cda, Track02.cda, Track03.cda, ... ... TracklO.cda. Here, each song named as a track number is called a file. You might have observed that each track name has a dot (.) in between. The part preceding the dot is called file name whereas the part after dot is known as the extension. The extension always comprises three digits and it signifies the format of the file. It is the file format which tells a b o ~ . the type of encoding ehproyed while r :ording audib. A variety of file formats for recording (storing) digital audio are in vogue.

Audio and Video Media The standard file format for storing information on an audio CD is CDA format ( .cda) while major audio file formats developed for computers are Wave file format (.wav ) and AIFF file format ( .aif ) respectively. The listener may not be able to differentiate between same piece of audio recorded in different file formats. In the following sections we shall discuss one of the file format which is a popular audio file format.

MP3 format : The term MP3 is short for "MPEG Audio Layer 3" where MPEG is an acronym for Moving Picture Experts Group. In addition to being a file format ( .mp3), MP3 also refers to a standard for compressing audio files to reduce their size. As we have learnt earlier, compression is the technique of reducing the file size by deleting the redundant data but in case of MP3, at higher compression schemes, even some of the useful information from original audio is deleted leading to reduced audio quality. Sound files can be reduced by as much as a factor of 10 while retaining high level of audio quality. Though, it is not CD quality but it is quite close. On an audio CD, the size of audio data is quite large, which is fine for CD players. But if you want to move it across the Internet, it is too large (details available under title " The Streaming Audio" at the end of this unit.). This reason makes compression more important than ever. To overcome the problem of large size of audio files, MP3 format was developed. It also allows you to put an entire audio content (.cda format) of 10 audio CDs on to one CD recorded in MP3 format. On an average, a MP3 audio CD can hold more than hundred movie songs. The incredibly small file size of MP3, combined with high quality audio, has virtually led to an explosion of music on the Web (Internet).

A special MP3 player is required to playback MP3 files. There are many, but some of the more popular software based players for computers include 'Winamp' and 'Windows Media Player'. Away from the computers. several Walkman-style portable MP3 players have appeared in the market. These players allow you to load MP3 files into their temporary memory (storage) from computer and carry your music with you. You can always load new music on these players while deleting the previous one. Most of recent audio CD players have built in capability to play MP3 audio CDs also.

There are many other digital audio formats such as the WMA (Windows Media ~ u d i o ) from Microsoft that offers good quality audio and also helps in protecting copyrighted songs from free distribution, WAV (Waveform audio format), Audio Interchange file format(AIFF), OGG, etc. We shall not go into the details regarding these formats.

16.4 STORGE DEVICES

Today there are a variety of audio data storage devices that have evolved over time. They are used for recording ( storing) data in analogue or digital form. We shall discuss some of them in this section. With the invention of phonograph, the evolution of recording and reproduction techniques for audio signals started in year 1877. Since then, the technological developments in the recording industry have focused on recording and reproducing audio faithfully i.e. without introducing distortion and noise in audio. In 1960s, the introduction of open reel tape recorders brought revolution in the entertainment and broadcast sector. However, the professional tape recorders being quite bulky and expensive could not enter into consumer market. With the development of cassette recorders in 1963, the music industry witnessed an enormous growth as the cassette recorder became indispensable for the music lovers. Similar to cassette tape recorder, the development of compact disk, called CD in brief, introduced most people to digital audio. Disc format evolved further to give rise to Mini Disc (MD), whose development was targeted at producing a disc smaller than CD, with recording capability and were easy to use. Most of the digital audio recordinglstorage devices can be classified into two categories namely, magnetic storage devices and the optical storage devices depending upon the medium used for the recording. You might have

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already used one of the magnetic storage devices, the audio cassette record&. These recorders use a nlagnetic tape housed in a cassette for storage of audio. It is simple to record and reproduce through this technology.

Among the optical storage devices, Compact Disk Digital Audio (CD-DA) also called Audio CD is popular. They offer far superior audo quality compared to the gramophone disc (LP). In addition. audio CD players offer better functionality and CD life is much more than that of the gramophone disc. Audio CD has now been adopted throughout the world. Use of audio CD is so common that the gramophone disc is already on the verge of extinction. Audio CD contains recording in digital form. The system is immune to scratches on the disc surface and external vibrations to a good extent. Though, audio CD is immune to light scratches on the disc surface, however, it requires careful handling. Some tips for audio CD care are:

Always handle the disc by its edge.

Avoid touching the side without label.

Avoid sticking paper or tape on CD.

Write on the labeled side with a felt pen only.

Protect disc from excessive heat.

Store CD in a box with CD on its edge (vertically).

Don't use warped CD, which can damage the laser head of the CD player

Clean disc surface with soft clean cloth only. Never use solvents like thinner1 head cleaner etc. for CD cleaning.

Recordable CD (CD-R) resembles in shape and size an audio CD. In addition to being a rccordable rnedium, it has all the advantages of a conventional CD. Using standard software packages for CD writing, the CD-R can be written (recorded) easily with the help of a computer fitted with a CD writer and audio card. CD-R can be recorded in the studio itself and is immediately available for playback. The shortcoming of CD- R disc is that, unlike tape, it cannot be erased. CD-R can, therefore, be used only to record material of permanent nature and can be a very useful medium for archival recordings. However, there are now rewritable CDS (RWCD), although they are not as popular as CD-R.

Mini Disc (MD) is a smaller size CD. Recording of same duration as of audio CD is possible in MD that is only 80 mm in diameter. Both studio verbion and consumer grade portable MD recorders (similar to Walkman) are available from a number of manufacturers. Due to operational advantages, low cost and better technical quality compared to analogue cassette recorders, portable MD recorders together with their studio version are getting quite popular especially for field recordings.

More recently portable digital audio recorders using removable h a d disc or flash card memory have been developed by a number of manufacturers for field use. These machines have conventional operating buttons and can store upto many hours of audio. They also incorporate simple editing features like forwardhackward scrubbing, cut, copy, delete, etc. Transmission of the edited recordiDg to the Radio station through normal telephone line or ISDN (a digital phone line) is also supported. Super audio CD. an optical audio disc format for delivering digital audio , Digital Video Disc audio (DVD -A), a digital format for delivering audio on a DVD, etc. are some of the newer technologies in this area.

16.5 DIGITAL AUDIO BROADCASTING (DAB)

Digital Audio and DTH

Digital audio broadcasting also known as digital radio. is a new technology for broadcasting audio using digital radio transmission. Digital radio is like conventional analog radio but is much better in many aspects as given below.

Audio and Video Media a It offers an i~nproved sound quality. At t1.e listening end, digital radio receivers get sound quality that is significantly better than conventional analog radios, just as audio CD sounds better than earlier Vinyl records (LPs). The crystal clear sound of digital radio is comparable in quality to audio CD.

a No frequencies are to be retrie~nbered which makes tuning of radio easy. With analog radio. you need to tune your radio receiver to the frequency of a radio station e.g. . . .. MHz for "C, an Vani" Delh; uut the digital radi receiver displays the names of the stations for you to make a selection.

a No interference and no re-tuning is required while on move. The digital radio eliminates the noise which plagues the analog audio. Analog radio signals are subject to different kinds of in lference on their way from the transmitter to radio receiver. Mountains, high-rise buildings and weather conditions cause these probl~ms. Digital radio reception is virtually immune LO interferences because it employs a sinart receiver inside wh' h there is a tiny computer. The receiver is capable of re-constntcting a solid usable signal out of distorted transmissions. In contrast, an an log receiver cannot differentiate the usefi ! information from the noise.

a Transmission of text, data and pictures along with audio. These services are still to be fully utilized but some broadcasters are already broadcasting multi-media radio.

For the listener, digital radio will b~ .n intelligent communications de ice that will offer more servic, , and conveniences than that by convcntional analog technology. The possibilities of additional data which can be sent to you through display panel c your digital radio receiver include:

a Song titles, lyrics. artist and album names

a Traffic and weather information, including emergency warnings

a Paging servic s

a Text services, such as stock n~arket rates

a Complementary information about a product being advertised oil-air

Beyond tl.is, there are many other possibilities for digital radio, for instance, personal receivers that could use Global Positioning Satellites to pinpoint your exact location on the earth. Also, due to digital processing. it is possible for digital radio to transmit and receive computer file downloads and fax transmissions. Digital radio has the technical potential to revitalize radio as a cost-effective and powerful medir n. Digital radios aren't cheap at the moment, but rising demands and the mass production benefits shall bring down the prices in future. It is already being used in the field of education for the benefits discussed above. BBC has already launched it and Prasar Bharati is also planning digital audio brc ~dcast for All India Radio (http:Nwww.studio-systems.com/ hotnews/broadcast~~ewslJulyA~~200 119.htm).

16.6 DIGITAL VIDEO, DTV AND DTH

Digital video is a tllpe of video recording system that uses digitalised video signals. It is usually recorded on tape, then distributed on optical discs u ,dally Digital Video Discs.A digital image is not always better than an analog image, and in some cases it can be worse. However, there are several reasons for preferring digital video over analog. Following are the two main reasons for switching to digital video.

a The quality of digital video. independent of the storageldelivery medium, depends mainly upon the applied encoding and compression techniques. Like digital audio, video in digital domain opens trenlendous opportunities, which are denied through the analog video.

Once video is transformed into digital domain, it becomes data, which makes "digital video" L oranch of information technology (IT). The technologies being developed in IT industries can now be used to store, process and transmit video. The benefits of falling prices of IT produc~s can now be reaped by digital video by using these products for storage and processing of video.

The processing power of the modern desk,op computers makes the earlier expensive and complicated video processing easier. Computer based non-linear editing (NLE) systems are replacing the tape based sy-tems, as is done at audio workstations in case of digitr' audio.

1 Digital Television (DTV)

i Television has changed the way we F . e the world and has profoundly affected the world of entertainment a well as education. "he popularization of digital television

i that use digital signals over analogue will further change it. Television in the digital age won't be limited to video and audio, but will become truly interactive, thus facilitating distance education. Digital television is heading toward a convergence with 1 computers. Convergence of information technolog) and digital video has made

' interactive television a possibility. DTV uses digital datn, which is digitally compressed and is decoded by a specially designed television set or a standard receiver with a set top box ( a box placed on top of your digital television ) or a PC with thc necessary equipn,cnts.

Digital television (DTV) can cany additional information (data) in addition to audio and video signals. There is little c o s ~ in sending the interactive data out to every viewer with a digital television. For using this data, the set-top box, has been developed. The set-top box processes the data :ent with the broadcast for storing and executing the applications. Once a computer is used for TV reception, there should ue no difficulty in qhowing both, i.e. video and data, on the computer's monitor. Interactivity is an important element in education, therefore digital television can play a kr j role in disseminating education.

The communication networks like telephone, internet, cellular network etc., which have been devel~ped to handle data, can now easily carry digital video and audio to listant places in a short time without any loss in the quality. Built on the communication technology, the streaming video has openeu new horizons for distributed learr',lg. Also known as computer-mec'iated instruction, distributed learning harnesses powerful technologies such as:

satellite broadcasting

video or audio conferencing

Web-based multimedia formats

Video files can provide a powerful visual medium to enhance education. For example, an instructor may offer all his lectures online, which allows a learner who missed a lecture due to illness, an extra oppclunity to +&e notes and leai-n the material. Other

t' possibilities of streaming video include I Displaying the clippings of historical or live events

On-line demonstrations

visual representations

The clear advantage of this form of distributed learning is that it provides learners with eaF. access to valuable class rnaterial through the internet.

DTH (Direct to Home Television) I Direct to home (DTH) television service, also known as direct broadcast satellite

service, is becoming popular in India. In March 2001, the government allo- led Ku-

Digltal Audio and DTH

Audio and Video Media band direct to home television broadcasting by issuing a notification and laying down the ground rules for companies wanting to enter DTH in India. DTH is the technology that allows people to receive television programmes directly via satellite, using a small dish antenna The user can receive DTH broadcasts without having to depend on cable TV providers. The KU-band DTH service offers greater and direct connectivity to the viewers providing access to 100 channels through a small dish antenna.

The conventional method, like "Doordarshan" transmission. is to send out television programming from terrestrial transmitters, which we receive with roof top antennas. In the close vicinity of television station where the signal received is quite strong, even portable indoor antennas provide good picture quality. With the explosion of satellite- based television services the cable TV era begun. In a satellite-based system, the broadcaster creates and beams his television content to a geo-stationary satellite using a large dish antenna. Most of the artificial satellites actually used for communications or broadcasting aregeo-stationary satellites. The geo-stationary satellite is the artificial satellite that revolves around the earth, but it looks stationary from the ground. The satellite receives the signal and sends the signals back to earth covering a much wider area. The local cable operator receives these channels, using multiple 8 to 12 feet diameter dish antennas and then sends them to individual homes using a coaxial cable, for a monthly subscription.

Now DTH has arrived which is again a satellite based television broadcasting. The primary difference between the normal satellite based television and DTH is the transmission band allocation for these services. The DTH service operates on Ku band, which is different froin the C-band currently employed by the satellite TV broadcasters. The main advantage of the new DTH system is the size of the antenna required to receive the signal, which is much smaller in size. For Ku band, dish of about 35 to 40 centimeters in diameter can he used. The antenna is small and light enough to mount it on the terrace/balcony/bracket of a window and connect it to TV set with a cable. The DTH signal as such is not suitable for feeding directly to a TV receiver and it must be passed through a small receiver (a set top box) before feeding to the television set.

Since, DTH system can acconlmodate over 100 channels. the direct-to-home TV service providers will offer a bouquet of channels. much as the cable operator does now. Like existing pay TV channels, DTH transmission can only be received if the subscriber has paid a fee. The authorization may come in the form of the SIM cards currently being used to sell airtime to mobile phone users. Slipping this "smart card" into the set top box will unlock the service for a given number of hours. When the purchased time is exhausted subscribers shall have to buy another card to renew the service.

While promising enhanced picture quality, DTH also has the scope for interactive television and value-added services like

Movie on demand

Internet access

Home shopping

Banking

In addition to the initial fixed cost, a monthly subscription fee brings more financial consequences and may take time to be popular anlong the masses. Therefore, the installation costs and subsequent subscription of DTH services could be costly propositions for the consumers vis-A-vis the cable TV services. However. competition among the service providers and other factors may bring down the price.

16.7 UPCOMING AUDIO-VIDEO DELIVERY Digital Audio and DTH

TECHNOLOGIES

In this section we shall'disclrss some of the upcoming audio video technologies:

NICAM stereo-Digital sound for terrestrial television

KICAM is an abbreviation for Near Instantaneous Companded Audio Multiplex, a sq\tein developed for delivering high quality stereo sound on television transmissions. The NICAM stereo, as popularly known, is not only used to deliver a better audio, but it can also be used for &ding the data as well. This data could be a picture, text file or any other digitised material.

The television broadcast carries NICAM stereo sound in addition to analog mono sound to maintain the compatibility with the existing television receivers without NICAM feature. The audio and data can be sent in several eombinat~ons. this allows the user to choose a language out of the two languages being broadcast. Another possibility is to download data while continuing to receive audio a s well. The data channel can provide a value added service such as providing supplementary information in the form of text for the video being shown.

Satellite Radio

While on travel suppose you are listening to your favorite radio stations, but when you travel too far away from the source station, you observe the signal breaks and fades. On long trips, when you pass through different cltieS, you might have to change radio stations every hour or so. However, a ~atellite radio station broadcasts its signal from more than 35,000 km anay in the sky and reaches your car radio with complete clarity allowing you to travel through different cities without having to change the radio station. Satellite radio. offers uninterrupted, near CD-quality music beamed to your radio from space. The major adbantages offered by a typical satellite radio station over conventional radio station include the followmg:

As discussed earlier. the digital signal means no fading, noise or intertfKence. The system can deliver near CD quality sound. which remains consistent within the coverage area of the satellite.

The satellite coverage area could be more than 12 million square kilometers without any loss of sound quality

Generally, digital receiver has a data port that can be connected to personal computer. This enables access to multimedia content directly to individual receiver andcornputer using a small satellite antenna without requiring any telephone or Internet connectivity.

Streaming Audio

Internet. popularly called web, is a huge network of computers spread over the globe. The computers dedicated lo provide information for other computers are called 'servers' and the computers that receive information from these servers are known as 'clients'. You can access Internet by connecting your computer through a telephone line or other communication network to the server of an Internet service provider. You can connect to any server on the Internet by logging on (cbnnecting) it through it's unique address e.g. www.ignou.ac.in - the address of IGNOU's web site (server). When you are connected to a server, the information available on the server in the form of text, pictures, audio and video etc. is downloaded (brought) to your computer for display and listening, as per selections made by you. Due to technical limitations of the telephone line commonly used for Internet accesb, the download process may take appreciable time for downloading large sized information.

There are basically two ways to receive audio over the Web. The old way is by downloading audio files. In theory,'audio files, like any other digital data, are sui~able --

69

Audio and Video Media cargo for the Internet. But realistically, because high-quality audio files (e.g. WAV files) are huge in size, moving audio data across Internet takes enormous time. In normal transfer method, the user has to download a complete audio file to his computer and the file can be played only after the download is complete. Conventional downloading over telephone lines is a process that literally takes hours to yield a few minutes of sound.

The new way is by receiving "streamed" audio. Streaming is a technology for playing audio and video directly from a website. The old way involves long delays while the new way delivers instant sound. But like most emerging technologies, streamed audio is still experiencing growing pains.

Streamed audio technology is able to deliver real-time or "live" events over the Internet, called Web casting. Streaming audio being an Internet-based technology, can be accessed from anywhere in the world. Not surprisingly, more and more radio stations worldwide are getting interested in web casting the music, sports and news in a bid to broaden their reach. Streaming technology allows learners to access lengthy pre- recorded audio and video clips. Users can also watch or listen to a live event from a remote location. Streaming technology serves as a valuable means of delivering content for distributed learning programs. Streaming audio can provide a powerful medium for education. An instructor may offer all his lectures online. An online process is what is happening at that moment. These lectures can be stored for off line learning through "audio on demand. In this process the user is presented with an index of material stored on the server, from which s h e may choose a programme for listening. It shall provide an extra opportunity to the student who missed the lecture (on line) and makes it possible for him to take notes and learn the material at the time of his choice. The streaming audio has several possibilities including the following:

On-line lectures, recorded interviews, etc.

Music teaching, for instance, a streaming audio file would be valuable to a music teacher. While going through the textual information, students shall also be able to listen to the related notes, music etc.



1. Are the quality of MP3 audio and CD comparable? Justify your answer.

...............................................................................................................

2. Mention some of the advantages of DAB.

...............................................................................................................

- - - - - - - - - --

In this unit we started by defining sound as a wave produced by the vibrating objects. The electrical signal derived from sound can be stored on a magnetic tape. The electrical representation of a sound called audio signal aims at retaining the wave shape of the original sound and any deviation from it is termed as distortion. The sound quality has touched new heights with negligible distortion and noise in digital audio recordings. The technology for recording sound continues to improve and advent of digital audio technology has brought radical change in means of transmitting, processing and

recording sound. For more faithful storage and retrieval of the audio, the digital Digital Audio and DTH

technology transforms it into mathematical numbers built upon binary number system. A digital audio signal is obtained by sampling an analogue audio signal followed by encoding it. Higher sampling frequencies are used for making Hi-fi audio recordings. To a large extent, the recording of digital audio on magnetic tape is not subject to the degradation in magnetic properties. During playback, digital audio is converted back to analogue sound for listening.

Along with the development of digital audio a plethora of storage and delivery devices including CD and DVD have emerged. Hard disk based networked systems have brought in new concepts of collaborative production and transmission along with new challenges in the area of media management. Digital audio and video being a form of data has brought all the benefits associated with Information Technology to audio- video technology. Due to theifinteractive capabilities, Digital iadio, DTV, DTH, Satellite radio and streaming audio-video (all built on the communication technology) have opened new horizons for distance learning.

16.9 UNIT END ACTIVITIES 1. Find out about the types of audio storage devices commonly available in the

marke't and prepare a note on those useful for distance education.

16.10 REFERENCES AND SUGGESTED READING You may visit websites on topics discussed in this unit, like the following:

1 Retrieved on 2 1.6.07

htt~://~~~.an~wer~.com/topic/analog?cat=health Retrieved on 2 1.6.07

httD://www.mrichter.com/cdr/Drimer/analo Retrieved on 21.6.07

httv://en.wiki~edia.or~/wiki/Analon sound vs. digital sound Retrievedon21.6.07

0 Retrieved on 21.6.07

http://en.wikipedia.org/wiki/Audio file format Retrieved on 5//7/07

httD://www Retrieved on 5//7/07

10 broadcasting#DAB and FM.2FAM compared Retrieved on 5//7/07

http://www.studio-sy-stems.comlhotnews/broadcastnews/J:~1yAu~ 119.htm Retrieved on 5//7/07

h t t p : / / w w w . b b c . c o . u W d i ~ i t a l r a d i o / a b o u t l Retrieved on 5//7/07

http:Nwww.afronets.org/archive/1999 10/msg00073.~hp Retrieved on 51/7/07

I 16.11 CLUES TO CHECK YOUR PROGRESS

i Check Your Progress 1

t 1. Audio signal is sampled thousands of times per second. Here, sampling means t periodically collecting electrical information about analog audio. The number of

samples taken per second is known as the sampling ratelfrequency.

L. 2. Directly related (proportionate)

Check Your Progress 2 1 . No, though quality of MP3 audio CD may be quite close to standard audio CD

but when it comes to Internet for which MP3 format was primarily developed, MP3 audio makes use of heavy compressions leading to inferior audio quality.

2. Better quality, scope for interactivity, etc. - -- 7 1

L

NOTES

.,. ,

Questionnaire

1 1. How many hours did you need for studying the units?

1 2. Please give you reactions to the following items based on your studying the block:

Excellent Very Good Poor Give specific examples, if Good poor/excellent

1 lllustrations Used I (diagrams, tables,

I Mail to: Course Coordinator, MES-032 (PGDET).

I Maidan Garhi, New Delhi- 1 10068 I [email protected]

unit 13 broadcast media radio and television · unit 13 broadcast media : radio and television...

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