Doordarshan summer Training report


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Doordarshan summer Training report

  1. 1. Doordarshan Lucknow Summer Training Report Year 2012Under the guidance of: Submitted by: Sushant Shankar Mr.R.Naithani B.Tech.4thYear(ECE)
  2. 2. DeclarationI hereby declare that work entitled “summer training report”, submitted towardscompletion of summer training after 3rd year of B.Tech(ECE) at Institute ofEngineering and Technology, Dr. Ram Manohar Lohiya Avadh UniversityFaizabad, comprises of my original work pursued under the guidance ofMr. R.Naithani. The results embodied in this report have not been submitted to any otherInstitute or University for any award. Sushant Shankar B.Tech. 4th year Branch-E.C.E.
  3. 3. CERTIFICATEThis is to certify that Mr. Sushant Shankar,a candidate of B.Tech. from Instituteof Engineering and Technology, Dr. Ram Manohar Lohiya AvadhUniversity,Faizabad completed 4 week vocational summer training programat Doordarshan lucknow, under my guidance and direction. Signature of the Guide Mr. R.Naithani
  4. 4. Acknowledgement“It is not possible to prepare a summer training report without the assistance &encouragement of other people. This one is certainly no exception.”On the very outset of this report, I would like to extend my sincere & heartfeltobligation towards all the personages who have helped me in this endeavor.Without their active guidance, help, cooperation & encouragement, I would not havemade headway in the project.First and foremost, I would like to express my sincere gratitude to my project guide,Mr. R.NaithaniI was privileged to experience a sustained enthusiastic and involved interest fromhis side. This fuelled my enthusiasm even further and encouraged me to boldly stepinto what was a totally dark and unexplored expanse before me. He always fuelledmy thoughts to think broad and out of the box.I would also like to thank Mr.P.K.Tripathi who, instead of his busy schedule, alwaysguided me in right direction.I would like to thank Mr. V.B.Patel (head of vocational training) to given me a chanceto do this training and all the staff member for motivation guidance and supportthroughout the training.Thanking YouSushant Shankar
  5. 5. Table of Contents1) Preface 12) Introduction of Doordarshan Lucknow 23) Fundamentals of monochromes and Colour TV System 34) Colour Composite Video Signal (CCVS) 55) TV camera 66) TV Lightning 117) Microphone 158) Principle of video tape recording 169) Vision Mixing 2710) 3 –D GRAPHICS 3111) Television Transmission 3312) TV Transmitter Antenna System 3513) OB van 3714) Earth station 3815) DTH (Direct-To-Home) 43
  6. 6. PrefaceTraining is important phase of student life. During this period student gets both theoreticalas well as practical knowledge of the subject. Training also impresses a student overallapproaches to life and impress his personality and confidence. Our training was in Doordarshan Kendra lucknow. This report contains a detailedstudy of Doordarshan Kendra lucknow. There are 3 division here :-  1) Studio  2)Transmitter  3)Earth Station1) Studio - Doordarshan is a leading broadcasting service provider in india. DD Lucknow is full-flathead broadcast set up. Many serials &program are being made here like "BIBI NATIYON WALI", "NEEM KA PED" and "HATIM TAI" etc. recorded in studio.2) Transmitter- Here the transmission of both audio and video has been made. The transmission sectiondoes the function of modulation of signal. Power amplification of the signal & mixing of audio andvideo signal is done here.3) Earth Station – The main function of earth station is to make contact with satellite or communicatewith it. The signals from other transmitter are down linked here.Also the signals here are uplinked to send it to larger distance. 1
  7. 7. Introduction of Doordarshan lucknow Lucknow Doordarshan started functioning on 27th Nov. 1975 with an interim setup at 22, Ashok Marg, Lucknow. The colour transmission service of National Channel (only with Transmitter) started from 15-8-82. While the regular colour transmission service from studio was started in 1984 with ENG gadgets. During Reliance Cup, OB Van came to Kendra for outdoor telecast having 4 colour camera chain, recording equipments, portable microwave link. In March 1989 new studio complex started functioning. EFP Van came to DDK Lucknow in 1989 with compliment of 3 colour camera chain and recording setup for outdoor telecast. The entire recording of studio/van have been replaced to Beta format High Band edit VCR and still in use as the old recording are on H.B. UP Regional Service telecast with up linking facility from studio (DDK, Lucknow) started in January 1998 on INSAT-2B. This service was changed to INSAT-2D (T) ARAB SAT. on 14-7-98. The news feeds are up-linked to Delhi occasionally from Lucknow Earth Station.Studio program is transmitted from 10 KW-TV transmitter installed at Hardoi Road through StudioTransmitter Microwave Link. Besides this, one 16 feet PDA is being installed at TV Transmitter site toreceive the down link signal of Regional Service telecast from studio via ARAB SAT. on INSAT-2D (T). Site of 22 Ashok Marg, Lucknow is being utilized by Doordarshan Training Institute (for staff training) having one studio (12m x 6m) and colour camera chain. The DTI Lucknow was inaugurated in September 1995. In the beginning, only the development programmes were telecast but later on to enlighten the viewers as per their needs, expectations, many more informative, educative and entertaining programmes have been introduced from time to time. Lucknow Doordarshan produced some of the best programmes in the country as "BIBI NATIYON WALI", "NEEM KA PED" and "HATIM TAI" etc. To entertain cross-section of the society. 2
  8. 8. FUNDAMENTALS OF MONOCHROME AND COLOUR TV SYSTEMPicture formationA picture can be considered to contain a number of small elementary areas of light or shadewhich are called PICTURE ELEMENTS. The elements thus contain the visual image of thescene. In the case of a TV camera the scene is focused on the photosensitive surface of pickup device and a optical image is formed. The photoelectric properties of the pick up deviceconvert the optical image to a electric charge image depending on the light and shade of thescene (picture elements). Now it is necessary to pick up this information and transmit it.For this purpose scanning is employed. Electron beam scans the charge image andproduces optical image. The electron beam scans the image line by line and field by field toprovide signal variations in a successive order. The scanning is both in horizontal andvertical direction simultaneously. The horizontal scanning frequency is 15,625 Hertz. Thevertical scanning frequency is 50 Hz. The frame is divided in two fields. Odd lines arescanned first and then the even lines. The odd and even lines are interlaced. Since the frameis divided into 2 fields the flicker reduces. The field rate is 50 Hertz. The frame rate is 25 Hert.Number of TV Lines per Frame - If the number of TV lines is high largerbandwidth of video and hence larger R.F. channel width is required. If we go for larger RF channelwidth the number of channels in the R.F. spectrum will be reduced. However, with more no. of TVlines on the screen the clarity of the picture i.e. resolution improves. With lesser number of TV linesper frame the clarity (quality) is poor. 3
  9. 9. Resolution -The capability of the system to resolve maximum number of picture elementsalong scanning lines determines the horizontal resolution. It means how many alternate black andwhite elements can be there in a line. The vertical resolution depends on the number of scanninglines and the resolution factor (also known as Kell factor)Grey Scale- In black and white (monochrome) TV system all the colours appear as gray on a10-step gray scale chart. TV white corresponds to a reflectance of 60% and TV black 3 % giving riseto a Contrast Ratio of 20:1 (Film can handle more than 30:1 and eye‟s capability is much more).Brightness - Brightness reveals the average illumination of the reproduced image on the TVscreen. Brightness control in a TV set adjusts the voltage between grid and cathode of the picturetube (Bias voltage).ContrastContrast is the relative difference between black and white parts of the reproduced picture. In a TVset the contrast control adjusts the level of video signal fed to the picture tube.Viewing DistanceOptimum viewing distance from TV set is about 4 to 8 times the height of the TV screen. Whileviewing TV screen one has to ensure that no direct light falls on the TV screen. 4
  10. 10. Colour Composite Video Signal (CCVS)  What is video signal ? Video is nothing but a sequence of picture .The image we see is maintained in our eye for a 1/16 sec so if we see image at the rate more then 16 picture per sec our eyes can not recognize the difference and we see the continuous motion. In Tv cameras image is converted in electrical signal using photo sensitive material. Whole image is divided into many micro particle known as Pixels. These pixels small enough so that our eyes cannot recognize pixel and we see continuous image ,thus at any instant there are almost an infinite no. of pixel that needs to be converted in electrical signal simultaneously for transmitting picture details. However this is not practicable because it is no feasible to provide a separate path for each pixel in practice this problem is solved by scanning method in which information is converted in one by one pixel line by line and frame by frame .Colour Composite Video Signal is formed with Video, sync and blanking signals. The level isstandardized to 1.0 V peak to peak (0.7 volts of Video and 0.3 volts of sync pulse). TheColour Composite Video Signal (CCVS) has been shown in figure.Frequency Content of TV SignalThe TV signals have varying frequency content. The lowest frequency is zero. (when we aretransmitting a white window in the entire active period of 52 micro seconds the frequency is Zero).In CCIR system B the highest frequency that can be transmitted is 5 MHz even though the TV signalcan contain much higher frequency components. (In film the reproduction of frequencies is muchhigher than 5 MHz and hence clarity is superior to TV system.) long shots carry higher frequencycomponents than mid close ups and close ups. Hence in TV productions long shots are kept to aminimum. In fact TV is a medium of close ups and mid close ups. 5
  11. 11. DC Component of video signal and DC restorationA TV signal is a continuously varying amplitude signal as the picture elements give rise to varying levelwhich depends on how much of incident light the picture elements can reflect and transmit the lightsignal to the TV camera. Hence the video signal has an average value i.e. a DC component correspondingto the average brightness of the scene to scene. RF Transmission of Vision and Sound Signals TV Transmission takes place in VHF Bands I and III and UHF Bands IV and V. Picture is amplitude modulated and sound is frequency modulated on different carriers separated by 5.5 MHz. Also for video amplitude modulation negative modulation is employed because of the following main advantages. Pictures contain more information towards white than black and hence the average power is lower resulting in energy saving. (Bright picture points correspond to a low carrier amplitude and sync pulse to maximum carrier amplitude). Interference such as car ignition interfering signals appear as black which is less objectionable. Picture information is in linear portion of modulation characteristic and hence does not suffer compression. Any compression that may take place is confined to sync pulse only. The design of AGC circuit for TV Receiver is simpler. AM produces double side bands. The information is the same in both side bands. It is enough to transmit single side band only. Carrier also need not be transmitted in full and a pilot carrier can help. However, suppressing the carrier and one complete side band and transmitting a pilot carrier leads to costly TV sets. A compromise to save RF channel capacity is to resort to vestigial side band system in which one side band in full, carrier and a part of other side band are transmitted. Sound Signal Transmission In CCIR system B sound carrier is 5.5 MHz above the vision carrier and is frequency modulated. The maximum frequency deviation is 50 KHz. Also the ratio of vision and sound carriers is 10:1 (20:1 is also employed in some countries) If we assume maximum audio signal is 15 KHz the band width is 130 KHz. According to Carson‟s Rule the bandwidth is 2 x (Maximum frequency deviation + highest modulating frequency). However, calculated value(using Bessel‟s function) of Bandwidth is 150 KHz i.e. 75 KHz on either side of sound carrier. In CCIR system picture IF is 38.9 MHz and sound. IF is 33.4 MHz. At the receiver end it is necessary to ensure that signal frequencies in the region of the vestigial side band do not appear with double amplitude after detection. For this purpose the IF curve employs NYQUIIST slope. 6
  12. 12. The Colour Television It is possible to obtain any desired colour by mixing three primary colours i.e. Red, Blue and greenin a suitable proportion. The retina of human eye consists of very large number of light- sensitivecells. These are of two types, rods and cones. Rods are sensitive only to the intensity of the incidentlight and cones are responsible for normal colour vision. The small range of frequencies to whichthe human eye is responsive is known as visible spectrum. This visible spectrum is from 780 mm(Red) to 380 mm(Violet).Additive Colour MixingThe figure shows the effect of projecting red, green, blue beams of light so that they overlapon screen. Y= 0.3 Red + 0.59 Green + 0.11 Blue Fig. 10 Additive Colour Mixing 7
  13. 13. TV CameraINTRODUCTION:A TV Camera consists of three sections.a) A Camera lens & Optics: To form optical image on the face plate of a pick up deviceb) A transducer or pick up device: To convert optical image into a electrical signalc) Electronics: To process output of a transducer to get a CCVS signalTYPES OF PICK - UP DEVICESThere are three types of pick up devices based on :a) Photo emissive material: These material emits electrons when the light falls on them.Amount of emitted electrons depends on the light . Monochrome cameras used in Doordarshanwere based on this material. These cameras were called Image Orticon Cameras. These cameraswere bulky and needed lot of light. These are no longer in use at present.b) Photo conductive material: The conductivity of these material changes with amount oflight falling on them. Such material with variable conductivity is made part of a electrical circuit.Voltage developed across this material is thus recovered as electrical signal. Earlier cameras basedon this principle were Videocon Cameras. Such cameras were often used in the monochrometelevise chain . These cameras had serious Lag & other problems relating to dark currents.Improvement in these cameras lead to the development of Plumb icon and Sat icon cameras.c) Charge coupled devices: These are semiconductor devices which convert light into a chargeimage which is then collected at a high speed to form a signal.Most of the TV Studios are now using CCD cameras instead of Tube cameras. Tube cameras havebecome obsolete & are not in use .Camera sensors – CCD basicsThe CCD is a solid-state device using special integrated circuitry technology, hence it is oftenreferred to as a chip camera. The complete CCD sensor or chip has at least 450 000 pictureelements or pixels, each pixel being basically an isolated (insulated) photodiode. The action of thelight on each pixel is to cause electrons to be released which are held by the action of a positivevoltage. 8
  14. 14. The Charge held under electrode can be moved to electrode by changing the potential on thesecond electrodes. The electrons (negative charges) follow the most positive attraction. A repeat ofthis process would move the charges to next electrode, hence charge-coupled device. A system oftransfer clock pulses is used to move the charges in CCDs to achieve scanning.There are three types of CCD device:frame transfer (FT).interline transfer(IT).frame interline transfer (FIT).Size of the chip used for broadcast cameras varies from ½ inch to 2/3inchFrame transfer (FT)Frame transfer was the first of the CCDs to be developed and it consists of two identical areas, animaging area and a storage area. The imaging area is the image plane for the focused optical image,the storage area is masked from any light. The electrical charge image is built up during one fieldperiod, and during field blanking this charge is moved rapidly into the storage area. A mechanicalshutter is used during field blanking to avoid contamination of the electrical charges during theirtransfer to the storage area. The storage area is „emptied‟ line by line into a read- out registerwhere, during line –time, one line of pixel information is „clocked‟ through the register to producethe video signal.Interline transfer (IT)Interline transfer CCDs were developed to avoid the need for a mechanical shutter The storage cellis placed adjacent to the pick-up pixel; during field blanking the charge generated by the pixel isshifted sideways into the storage cell. The read-out process is similar to the frame transfer device,with the storage elements being „clocked‟ through the vertical shift register at field rate into thehorizontal shift register, then the charges read out at line rate. Earlier forms of IT devices sufferedfrom severe vertical smear, which produced a vertical line running through a highlight. This wascaused by excessive highlights penetrating deeply into the semiconductor material, leaking directlyinto the vertical shift register. Later IT devices have improved the technology to make this a muchless objectionable effect.Frame interline transfer (FIT)Frame interline transfer CCDs are a further development of the interline transfer device toovercome the problem of vertical smear. As its name suggests, it is a combination of both types .The FIT sensor has a short-term storage element adjacent to each pixel (as IT) and a duplicatedstorage area (as FT). During field blanking the charges are moved from the pixels into the adjacentshort-term storage element and then moved at 60 times field frequency into the storage area. Thisrapid moving of the charge away from the vulnerable imaging area overcomes the vertical smearproblem.Development in CCD technology has seen the introduction of:  The hole accumulated Diode (HAD) sensor which enabled up to 750 pixels/line, with increased sensitivity and a reduction in vertical smear;  The hyper HAD sensor, which included a microlens on each pixel to collect the light more efficiently (this gave a one stop increase in sensitivity over the HAD sensor);  The power HAD sensor with improved signal-to- noise ratio which has resulted in at least half an ƒ-stop gain in sensitivity; in some cases a full ƒ-stop of extra sensitivity has been realized. 9
  15. 15. Optical block for Video CamerasCCD CAMERAS (Charge coupled devices)—A typical three tube camera chain is described in the block diagram. The built in sync pulsegenerator provides all the pulses required for the encoder and colour bar generator of the camera.The signal system is described below: The signal system in most of the cameras consists of processing of the signal from red, blueand green CCD respectively. The processing of red and blue channel is exactly similar. Greenchannel which also called a reference channel has slightly different electronic concerning aperturecorrection. So if we understand a particular channel, the other channels can be followed easily. Solet us trace a particular channel. The signal picked up from the respective CCD is amplified in astage called pre-pre amplifier. It is then passed to a pre amplifier board with a provision to insertsexternal test signal. Most of the cameras also provide gain setting of 6 dB, 9dB and 18dB at the preamplifier. Shading compensator provides H and V shading adjustments in static mode and dynamicmode by readjusting the gain. After this correction the signal is passed through a variable gainamplifier which provides adjustment for auto white balance, black balance and aperture correction.Gama correction amplifier provides suitable gain to maintain a gamma of 0.45 for each channel.Further signal processing includes mixing of blanking level, black clip, white clip and adjustment forflare correction. The same processing take place for blue and red channels. Green channel as anadditional electronic which provides aperture correction to red and blue channels. Aperturecorrection provide corrections to improve the resolution or high frequency lost because of the finitesize of the electron beam . Green channel has fixed gain amplifier instead of variable gain amplifierin the red and blue channels. All the three signals namely R, G and B are then fed to the encoder section of the camera viaa colour bar/camera switch. This switch can select R, G and B from the camera or from the R, G, BSignal from colour bar generator. In the encoder section these R, G, B signals are modulated with SCto get V and U signals. These signals are then mixed with luminance, sync, burst, & blanking etc. toprovide colour composite video signal (CCVS Signal). Power supply board provides regulatedvoltages to various sections. 10
  16. 16. TV LIGHTINGGENERAL PRINCIPLES: Lighting for television is very exciting and needs creative talent. There is always atremendous scope for doing experiments to achieve the required effect. Light is a kind ofelectromagnetic radiation with a visible spectrum from red to violet i.e., wave length from 700nm to 380 nm respectively. However to effectively use the hardware and software connectedwith lighting it is important to know more about this energy.Light Source: Any light source has a Luminance intensity (I) which is measured inCandelas. One Candela is equivalent to an intensity released by standard one candle source oflight.Luminance flux (F): It is a radiant energy weighted by the photonic curve and ismeasured inLumens. One Lumen is the luminous flux emitted by a point source of 1 Candela.Illumination (E): It is a Luminous Flux incident onto a surface. It is measured inLUMENS/m2, which is also called as LUX. A point source of 1 candela at a uniform distance of 1meter from a surface of 1 square meter gives illumination of 1 LUX.Luminance (L): It is a measure of the reflected light from a surface. Measured in Apostilbs. A surface which reflects a total flux of 1 lumen/m2 has a luminance of 1 Aposilbs .Elementary theory of light also says that:Colour temperature:One may wonder, how the light is associated with colour . Consider a black body being heated;you may observe the change in colour radiated by this body as the temperature is increased.The colour radiated by this body changes from reddish to blue and then to white as thetemperature is further increased. This is how the concept of relating colour with temperaturebecame popular. Colour temperature is measured in degree Kelvin i.e., 0C +273) . The tablebelow gives idea about the kind of radiation from different kinds of lamps in terms of colourtemperature.a) Standard candle 19300Kb) Fluorescent Lamps range 3000-6500oKc) HMI lamp 5600+- 400oK(H=Hg, M=Medium arc, I=Metal Iodide}d) CSI (Compact Source Iodide) 4000+- 400oKe) CID (Compact Iodide Daylight) 5500+- 400o Colour TV Display,white 6500oKf) Monochrome TV 9300oKg) Blue sky 12000 – 18000oKh) Tungsten Halogen 3200oKi) Average summer sunlight (10am –3pm) 5500oKIt can be noted that as the temperature is increased, the following things happen:1) Increase in maximum energy released2) Shift in peak radiation to shorter wavelengths (Blue)3) Colour of radiation is a function of temperature 11
  17. 17. Hence by measuring the energy content of the source over narrow bands at the red and blueends of the spectrum ,the approximate colour temperature can be determined. All the colortemperature meter are based on this principle.COLOUR FILTERS AND THEIR USE:Colour filters are used to modify the colour temperature of lights and to match colourtemperature for cameras while shooting with different colour temperature. These filterschange the colour temperature at the cost of reduction in light transmission. Colourtemperature filters are also introduced in the optical path of cameras to facilitate cameraelectronics to do the white balance without loading the amplifier chain. Cameras electronics isgenerally optimized for a colour temperature of 3200K, hence it uses reddish filter whileshooting at higher colour temperatures.Generally it is normal to correct daylight to produce tungsten quality light, because it is usuallyeasier to do and saves lot of power, otherwise blue filters are going to reduce lot of light thusrequiring the use of higher wattage lamps.. However, when the amount of tungsten to becorrected is small it may be more practical to convert it to daylight, but with a considerablyreduced light output form the luminaries. There are two basic types of filter :-i) One which is orange in colour and converts Daylight to Tungsten Light.ii) One which is blue in colour and converts Tungsten to Daylight.Day Light: The sun does not changes its colour temperature during the day it is only its appearance froma fixed point on earth. It is because the sunlight gets scattered because of the medium , shorterwavelengths like blue gets more effected. Certain situations like, sunrise and sunset causes thelight to be more yellow than midday, because the light has to travel the long distance so acareful note should be made of the Transmission factor of each of the filters. Often acompromise has to be reached in terms of correction and light loss.NEUTRAL DENSITY FILTERSIn addition to colour temperature correction sometimes it may be necessary to reduce theintensity of daylight at an interior location. Neutral density filters available to attenuate thelight are of:0.3 Density which has a transmission of 50%= 6dB=1 f stop0.6 Density which has a transmission of 25%= 9dB=2 f stop0.9 Density which has a transmission of 13%= 12dB=3f stopCOMBINATION OF CTC FILTERS AND NEUTRAL DENSITYFILTERS:Single filters exist which are a combination of full colour temperature orange and neutraldensity as follows:-Full Orange + 0.3 N.D. with a transmission of 50%Full Orange + 0.6 N.D. with a transmission of 38%The HMI light source has a colour temperature of about 60000K and can be used with exteriordaylight without the need for a colour temperature correction filter.DIFFERENT LIGHTING TECHNIQUES:- Eye light, Low intensity light on camera itself to get extra sparkle to an actors eye-Rim light, to highlight actors outline, it is an extra back on entire body at camera level 12
  18. 18. - Kickkar light, Extra light on shadow side of the face at an angle behind and to the side of theactor- Limbo Lighting, Only subject is visible, no back ground light- Sillhoutt lighting, No light on subject, BG is highly litLIGHTING CONSOLEIn a television production, each scene will require its own lighting plan to give the desiredeffect. In order to assist in setting up a particular lighting plon, a console should provide :-a) One man operation and a centralised control desk with ability to switch any circuit.b) Facilities to obtain good balance with flexibility to have dimming on any circuit.c) With all controls for power at low voltage and current.Modern lighting consoles also provide file & memory to enable the console operator to storeand recall the appropriate luminaries used for a particular lighting plot. These console alsoprovide Mimic panels to show which channels are in use and which memories or files havebeen recalled.DIMMERSThree basic methods for dimming are :-1. ResistanceThis is the simplest and cheapest form of dimmer. It consists of a wire wound resistor with awiper .It is used in series with the load.2. Saturable Reactor (System SR)The basic principle of the saturable reactor is to connect an iron cored choke in series with thelamp.LIGHTING THE SET FOR DRAMA:--Openings such as windows within a set should behighlighted without overstating them. Where the walls having such feature should be lit toreveal these features but care must be taken to ensure that there is only one shadow. The top ofthe set should be darkened off by using the barndoors, this puts a "ceiling" on the set by givingthe feeling of a roof. If more than the top of the set is darkened, that gives enclosed feeling.Indoor day time:1. If there is a choice in the direction of the sun(Key) take the shortest route inside the set to awall, and if possible throw the shadow of window bars onto a door - it usually is in shot.2. A patch of light on the floor inside the set, backlight from outside using a soft source at steepelevation adds realism.3. When a set does not have a window, a window pattern can be projected onto a wall toproduce a suitable window effect.4. Roof and Ceiling Pieces - if they make lighting impossible, check if they can be removed at theplanning state. Light any ceiling pieces from outside, use a soft source at ground level. If theceiling has plaster moulding or ornamentation, a hard source may be used. Indoor night time:- The outside of the window should be dark, except for a possible dim skyline if the room is wellabove adjacent streets, or lit by an outside practical lamp i.e. street lighting.- The wall with the window in it should be lit at night to be brighter than for the day condition.Subjectively the walls appear brighter at night than at daytime. .- Often a completely different feel to the set can be obtained by reversing he direction oflighting in the set compared to that used for day. 13
  19. 19. - General for night effects it is not a good plan to just simply dim the set lighting when changingfrom day to night. This is because the excessive change in colour temperature of the lightsource and the apparent increase in saturation of surfaces at low luminance.Outdoor daylight and Moonlight:The direction of the light is dictated by the position of the sun or moon. As a general principle oneshould remember that sunlight (hard source) is accompanied by the reflected "skylight" (soft source)whereas moonlight is a single hard source. One of the biggest problems when lighting exteriors is themaintenance of “single shadow" philosophy - double shadows on a long shot will quickly destroy theapparent realism created in the set. Very large area filler light is ideal for exterior daylight scenes.This can be achieved by using a suspended white screen 12 x 8 where the filler would be positionedthen lighting it with hard light.The exact lighting treatment will depend on the situation but as a general rule, moonlight effects arenormally achieved by back lighting to give a more softer, romantic mood than would be achievedthan a frontal key.In colour, to obtain a night effect, blue cinemoid is used over the luminaries. This gives a stylisedeffect. An alternative is to use much more localised lighting than for daylight and light only theartists and odd parts of the set. 14
  20. 20. MICROPHONESIntroduction Microphone plays a very important role in the art of sound broadcasting. It is a device whichconverts accoustical energy into electrical energy. In the professional broadcasting fieldmicrophones have primarily to be capable of giving the highest fidality of reproduction over audiobandwidth.Microphone ClassificationDepending on the relationship between the output voltage from a microphone and the soundpressure on it, the microphones can be divided into two basic groups.Pressure Operated TypeIn such microphones only one side of the diaphragm is exposed to the sound wave. The outputvoltage is proportional to the sound pressure on the exposed face of the diaphragm with respect tothe constant pressure on the other face. Moving coil, carbon, crystal and condenser microphonesare mostly of this type. In their basic forms, the pressure operated microphones are omni-directional.Velocity or Pressure Gradiant TypeIn these microphones both sides of the diaphragm are exposed to the sound wave. Thus the outputvoltage is proportional to the instantaneous difference in pressure on the two sides of thediaphragm. Ribbon microphone belongs to this category and its polar diagram is figure of eight.Types of MicrophonesThere are many types of microphones. But only the most common types used in broadcasting havebeen described here.Dynamic or Moving Coil MicrophoneThis is common broadcast quality microphone which is rugged and can be carried to outsidebroadcast/recording etc. It consists of a strong permanent magnet whose pole extensions form aradial field within a round narrow gap. A moving coil is supported within this gap and a domeshaped diaphragm usually of aluminium foil is attached to the coil. The coil is connected to amicrophone transformer whose secondary has sometimes tapings to select proper impedance formatching. With sound pressure changes, the diaphragm and coil move in the magnetic field,therefore, emf is induced in the speech coil, which is proportional to the incoming sound. Theprimary impedance of the matching transformer is generally high (5 to 6 times of the speech coilimpedance so that low frequencies are not lost and rising impedance frequency characteristic isavoided as best as possible. The resonant frequency is generally damped with special arrangementsof absorption in acoustic cavity, Bass/boost arrangements are provided by an equalising tubeconnecting the rear side of diaphragm i.e. inside of microphone with the atmosphere. The diameterand length of the tube is critically adjusted for achieving good frequency response. 15
  21. 21. Dynamic Microphone (Moving Coil)Ribbon/ Velocity MicrophoneCorrugated aluminium foil about 0.1 mm thick forms a ribbon which is suspended within twoinsulated supports. The ribbon is placed within the extended poles of a strong horse shoe magnet.The ribbon moves due to the difference in pressure (at right angles to its surface) i.e. from the frontor rear of the mike. There exists the maximum pressure difference between the front and rear ofribbon because of maximum path difference. The sound does not develop any pressure gradientwhen it comes from the sides of the microphones because there is no path difference. It reaches thefront and rear of ribbon at the same time, hence no movement of ribbon. Thus, this microphone isbi-directional and follows figure of eight directivity pattern with no pick up from sides. Such amicrophone has a clarity filter. This is a series resonant circuit at low frequencies across theprimary of microphone transformer. When switched to the “Talk” or “Voice” position, the responseis modified cutting down low frequencies by about 8 dB at 50 Hz. This filter should therefore not bein circuit during music performances. All the other types of microphones are pressure operatedwhereas ribbon mike operates on pressure gradient which results in the change in velocity of theribbon. Thus it is also called the „Velocity‟ microphone. This microphone is very good for balancingof programmes. In case of Orchestra, instruments with strong output are positioned towards thedead side and week voices or instruments are arranged on the front and rear of the mike. Thedistance and location with respect to microphone are considered against loudness of voice ormusical instrument during balancing. Ribbon Microphone Output Magnets Corrugated ribbonTransformer N SElectrostatic or Condenser MicrophoneThis consists of a thick metallic plate insulated from the body of the microphone and connected topolarising voltage through a resistance. Another thin foil is fitted close to the above plate forming acondenser. The sound pressure variations on the foil, change the capacitance due to increase anddecrease of distance between foil and the plate. With fixed DC voltages across the two, the quantityof charge changes due to the variation of capacity. The changes in electrical charge form the soundsignals and are picked up through a coupling capacitor. 16
  22. 22. This microphone delivers – 80 dBv with a very good frequency response. The output impedance ofthis microphone is high. The popular method of providing d.c. voltage to the condenser is known as„Phantom Powering‟. Variable directivity capacitor microphones are becoming popular these days.Fig. 3 Condenser Microphone Output Phantom power Head Amplifier Output Transformer Veryhigh resistance Insulator Phantom power DC blocking capacitor Earthed back-plate DiaphragmElectret ‘Microphone’It is a modified form of condenser microphone in which the polarising voltage is avoided. In fact aplastic polymer containing metallic dust keeps the metal particles permanently charged withinthe plastic insulation and such a polymer within the diaphragm foil or fixed plate delivers theelectrical signal on the principle of the condenser mike. The hissing noise gets avoided since there isno external polarising resistor as a load. The microphone has high impedance and is generallyhaving FET pre-amplifier. The microphone costs very little but developes excellent quality designsin many forms. 17
  23. 23. PRINCIPLES OF VIDEO TAPE RECORDINGIntroductionVideo tape recorder is a most complex piece of studio equipment with analog and digitalprocessing servo system, microprocessors, memories, logic circuits and mechanical devicesetc. Also these recorders have been the main limitation so for as the quality output fromstudio is concerned. Right from fifties, continuous efforts are being made to improve itsperformance so as to reproduce cameras faithfully by improving S/N ratio and resolution.Designer for video tape recorders had to consider the following differences in the video andaudio signals:Magnetic PrincipleMagnetic field intensity H = NI / LMagnetic flux density B = HMagnetic Flux Ø= BA( is of the order of 100 to few 10,000 for ferromagnetic materials)Property of the ferromagnetic materials to retain magnetism even after the current or the H isremoved is called retentivity and is used for recording electrical signals in magnetic form onmagnetic tapes. This relationship can also be represented by a curve called BH curve. Magnetictapes are made of ferromagnetic materials with broader BH curve than the material used for videoheads as the heads are not required to retain information. 18
  24. 24. WRITING SPEED AND FREQUENCY RESPONSERecording ProcessWith reference to figure 1(d) when a tape is passed over the magnetic flux bubble, the electricsignal in the coil will cause the electric lines of force from the head gap to pass through themagnetic material of the tape producing small magnets depending upon the strength of the current.Polarity of the magnetic field which causes these bar magnets depends on the change of current.Decreasing current will cause NS magnet and vice versa. Power of these magnets is as per BH curve.Thus the magnetic flux strengthens the unarranged magnetic particles as per the signal and theystay in that condition after the tape has already passed the magnetic head (fig. 2). Length of themagnet thus formed is directly proportional to writing speed of the head v, and inverselyproportional to the frequency of the signal to be recorded, i.e.Recorded wavelength for one cycle of signal = speed x timeOr Wave length of the magnetic signal tape = v / f Recording Processthe problem to be solved in the development of VTRs was how to provide higher speed to recordvery high frequenciesThe other limitation of recording medium is the range, during when the extracted signal is morethan noise. This range is only 10 octaves. Thus the system can no longer be used forrecording/reproduction after this dynamic range of 60 db, because of 6 dB/octave playbackresponse characteristics. Beyond this range the low frequencies becomes inaudible and the higherfrequencies become distorted.During the initial stages it was tried to record video signal with stationary video heads andlongitudinal tracks using tape speed of the order of 9 m/s which was very difficult to controlbesides very high tape consumption i.e, miles of tape for 3 to 4 minutes of recording and this wascoupled with breaking of video signal frequencies into 10 parts recorded by 10 different videoheads and then switched during playback to retrieve the signal. The quality of the reproducedsignal was also compromised up to the resolution of 1.7 MHz or so. Around 1956 the „AMPEX‟company of USA then came out with Quadruplex machines having two revolutionary ideas whichlaid the foundation of present day VTRs/VCRs.These ideas were:1. Rotating Video Heads and2. Frequency Modulation before recording 19
  25. 25. Increase in writing speed by rotating headWhen a video head mounted on a rotating head wheel writes on a tape moving across it, will lay atrack of length which will depend not only on the speed of the tape but also on the rotating speed ofthe head. Single head with diameter d number of rotation per sec as r and full omega wrap or twoheads in ½ omega wrap i.e. little over 180 degree, which most of the present day VCR are using, willhave a writing speed of dr minus or plus the linear tape speed (which is negligible as compared tothe rotating speed). This avoids the requirements of miles of tape for few minutes of recording in astationary head type of recorders tried earlier.Monitoring During RecordingMost of the video tape recorders provide Electronics to Electronics monitoring (EE Mode) at thetime of recording. The video signal is monitored after routing it through all the signal systemelectronics of the recorders excluding the video heads and preamplifiers etc. Some of the recordersalso provide simultaneous playback for the off tape monitoring by using additional heads duringrecording called confidence heads.Thus the VTRs could achieve wider frequency range with:a) Faster writing speedb) Smaller gap, andc) Octave band compression with frequency modulation.Also achieving accurate speed for motors with servo system reduces the timing errors.Play back processDuring play back when the recorded tape is passed over the head gap at the same speed at which itwas recorded, flux lines emerging from the tape on crossing the head gap induce voltage in the coilproportional to the rate of change of flux, i.e. d /dt and this in turn depends on the frequency of therecorded signal. Doubling of frequency causes voltage to increase by 6 dB. This accounts for thewell known 6 dB/octave playback characteristics of the recording medium. This holds good only upto a certain limit thereafter at very high frequencies, lot of losses take place during playback andrecording process causing noise to be more than the signal itself. It may be noted that when the gapbecomes equal to the wavelength of the recorded signal, two adjoining bar magnets may produceopposite current during playback and the output becomes zero. Similar thing happens when thegap equals 2, 3 …n. times the wavelength. First extinction frequency occurs when gap becomesequal to wavelength. For getting maximum output, head gap has to be one half of wavelength.Frequency at which zero output occurs is called extinction frequency (Fig. 3). Thus the maximumusable frequency becomes half of the extinction frequency. These parameters are related by: 20
  26. 26. Playback ProcessSo in order to record the higher frequencies we must increase the writing speed for a minimumvalue of wave length recorded on tape i.e. tape. This minimum value of tape is again restricted bythe minimum practically possible head gap.Now the ratio of video and audio frequencies is approximately 300, so we must increase the writingspeed or reduce the gap by the same factor of 300 to get the desired results. Perhaps a speed of 60mph will be required to cope with the higher video frequencies.VIDEO TAPE FORMATS-INTRODUCTIONFormat of Video tape recorder defines the arrangement of magnetic information on the tape. Itspecifies:1. The width of tape,2. Number of tracks for Video, Audio, Control, time code and cue,3. Width of tracks,4. Their electrical characteristics and orientation.All machines conforming to one format have similar parameters to enable compatibility orinterchange i.e. the tape recorded on one machine is faithfully reproduced on the other.There are a number of formats in Video tape recording and the number further gets multiplied dueto different TV. Standards prevailing in various countries e.g. PAL, SECAM, NTSC and PAL-M.CLASSIFICATION OF FORMAT:A) Analog Formats:VTRs using composite Video for professional Broadcast use were , Quadruplex 2” , 1" format and C (All reel/Spool Type) which were then replaced by U- matic cassette recorders followed by bestquality analog format with separate luminance & chrominance recording called componentAnalog formats. These were Betacam SP from SONY & M-II from Panasonic.a) Quadruplex Format (Segmented)This was the first professional broadcast video tape recorder introduced by AMPEX in 1956 and hassince been replaced by 1" recorders of type B and type C formats. 21
  27. 27. This format uses spool of 2" wide tape, 4 heads on transversely mounted drum, with a very highwriting speed of about 41m/s. These machines had higher operational cost and required constantengineering efforts to keep them running. These machines have since been phased out except fortransfer/archival purpose.b) Type B Format (Segmented helical)This format was developed by BOSCH/BTS using helical scan with 1" tape as BCN series of VideoTape recorders. It uses a scanner with head wheel carrying two video heads around which tape iswrapped in about 190o. Each television field is recorded on six tracks with each head scanning a 52line segment. The scanner diameter is 50mm and rotates at 150 rev/sec. The tape moves at24cms/sec. The 80 mm long tracks are recorded at an angle of 14.3o. There are four longitudinaltracks out of which two are full quality audio tracks, third for the time code and the fourth for thecontrol track. Video writing speed is 24m/s. The flying erase head mounted on the same head-wheel and the associated electronics allows for roll free electronic editing. The addition of digitalframe store unit provides freeze frame and slow motion. The portable version in the same formathas also been marketed by the manufacturers for studio use.c) Type C Format (field per scan helical) This is the combined format of AMPEX and SONY using 1" tape with a full omega wraparound a helical scanner running at 50 rps. Main head mounted on a 135 mm dia drum records onefield i.e.B). DIGITAL FORMATSModern television post production demands multi-layer special effects with several manipulationshaving first generation quality. This requires multi-generation playback & a transparent recordingsfrom Video cassette players./recorders. which can be met only by the digital formats without loss inpicture quality..Digital Composite/Component FormatsA) D1 format was the first DVTR not to compromise on the technical quality in any way. It isbased on 4:2:2 sampling structure of CCIR-601, completely transparent in quality but veryexpensive and bulky. Still it is considered as reference machine for digital formats and known asfather of all digital formats.It uses 3/4" tape & has a writing speed of about 30m/s.Its drum is running at 150 rps withsegmented tracks. Digital coding is in 8-bit words with a raw picture data rate of 216 Mbps.b) D2 format was the first economical DVTR based on CCIR - 601, 4 fsc sampling on compositevideo. It offered easy interface to a composite world at a reasonable cost. It was soon overshadowedby the then forthcoming D 3 format.c) D3: D3 was developed by NHK and Panasonic using composite system, 1/2" metal particle VHSsized cassette thus saving cost. It records 8 bit digital video at a sampling rate of 4 fsc (17.73MHz)in 8 tracks per field. Data rate is similar to D2.d) D4: 4 is perhaps an unlucky number in Japan as there is no D4.e) D5: Panasonics new component system D5 is a successor to D3. It is digital component usingsame cassettes as D3 but running at double speed. In addition to all the usual facilities, D5 canplayback existing D3 tapes. It gives just 2 hours from a long size cassette. Coding is 10-bit withluminance sampling at 13.5 MHz. D5 can handle 4:3 or 16:9 aspect ratio with full restoration. 22
  28. 28. For 16:9, sampling rate is 18 MHz with 8-bit coding Based on CCIR 601. It is without any datacompression.Digital Betacam:It is based on CCIR 601, and allows 16:9 upgrades. To reduce data rate it uses Bit Rate reduction(BRR).Bit rate reduction is in the ratio of 2:1. This has been made possible because of theconversion of data from time domain to frequency domain and removing the redundancy from thedigital video data. Equivalent system without BRR would have required more tape speed, extra thintape, and extra narrow tracks and would have also needed double the number of heads on drum ordouble the drum speed. It is compatible with Betacam SP and is having 4 PCM Digital Audio Track.Scanner for this machine is larger then that of Betacam SP but the helix is such that when rotated atframe rate ,track angle of analog Betacam is traced .This gives a time compressed replay is which isthen expanded in TBC. For digital Betacam, to handle large data the scanner speed is increased to 3times. One field is recorded in one and half revolution in 6 tracks of 26 Micrometers each.BETACAM VIDEO CASSETTE RECORDERS-INTRODUCTION:Betacam series of VCRs are based on analog component system. These VCRs had become popularbecause of their low initial and running costs in comparison to B and C Format machines. Thequality of reproduction of Betacam SP was near to these analog formats. Betacam format wasintroduced in 1982 followed by Betacam SP in 1987.Popular Betacam SP VCRs which are being replaced with digital VCRs in doordarshan are:-BVW 75P - SP Recorder cum player, with DT head (Slow motion heads for dynamic tracking) & PVW2800P PRO SERIES besides camcorder and portable version of this format.Head drum: Head drum for BVW 75P carries as many as 10 video heads, two heads forLuminance Ya, Yb, two heads for chrominance Ca, Cb, two heads for Dynamic tracking Luminance DTYa,DTYb, two heads for Dynamic tracking chrominance DT Ca, DT Cb, and finally two heads for Eraser REa & REb(Rotary erase). In some of the models where slow motion is not available DT heads and associated electronicsis not required. This makes those models cheaper to BVW 75P. 23
  29. 29. VIDEO SYSTEMVideo system is based on component analog system. Composite video is decoded into itscomponent, Luminance Y and colours as R-Y & B-Y. You may note that these colour signal are baseband signal and have nothing to do with 4.43MHz subcarrier frequency. Y is recorded directly afterFM on one of the video tracks by Ya & Yb head. Chrominance signals are first compressed as CTDMsignal (Compressed time division multiplexing) and then frequency modulated. This FM chroma isthen mixed with AFM audio channel 3 & 4 before it is recorded along with chrominanceinformation. TAPE TRANSPORT FOR PVW SERIES OF BETACAM SP 24
  30. 30. DIGITAL VIDEO CASSETTE RECORDER PROFESSIONAL (DVCPRO)-INTRODUCTIONWith the advent of digital signals, breakthrough came in the field of recording from analogrecording to digital recording around the year 1990. In the series of development of digital taperecording systems, it is felt to have a system which should be handy for the purpose of fieldrecording along with capability of long duration recording. A recording format is developed by aconsortium of ten companies as a consumer digital video recording format called “DV”. DV (alsocalled ”mini DV” in its smallest tape form) is known as DVC (Digital Video cassette).DVCAM is a professional variant of the DV, developed by Sony and DVCPRO on the other hand is aprofessional variant of the DV, developed by Panasonic. These two formats differ from the DVformat in terms of track width, tape speed and tape type. Before the digitized video signal hits thetape, it is the same in all three formats.What is DV?DV is a consumer video recording format, developed by a consortium of 10 companies and later onby 60 companies including Sony, Panasonic, JVC, Phillips etc., was launched in 1996. in this format,video is encoded into tape in digital format with intra frame DCT compression using 4:1:1 chromasubsampling for NTSC (or 4:2:0 for PAL). 25
  31. 31. This makes it straightforward to transfer the video onto computer for editing due to its intra framecompression technique. DV tapes come in two formats: MiniDV size (66mm x 48mm x 12.2mm) andDV, the standard full size (125mm x 78mm x 14.6mm). They record digital compressed video by aDCT method at 25 Megabit per second. In terms of video quality, it is a step up from consumeranalog formats, such as 8mm, VHS-C and Hi-8.What is DVCPRO?DVCPRO is a professional variant of the DV, developed by Panasonic. In DVCPRO, the basebandvideo signal is converted to 4:1:1 sampled data sequence from the originally sampled 4:2:2 signalby the method of subsampling and the resulted data are converted into blocks which are shuffledbefore passing through compression circuitry and again reshuffled back to their original positionafter compression. It is to mention here that still pictures containing little or no movement arecompressed using intra frame compression whereas the pictures with large amounts of movementsare coded and compressed in intra field form. Error correction code is added to the compressed andreshuffled data sequence by using Reed Solomon product code before it is sent to recordingmodulation method. The modulated data sequence generated by 24-25 coding method usingscrambled NRZI is recorded onto the tape via video head. Recording process for audio signalWithin the DV(Digital Video) format, audio can be recorded in either 2 channel (1 left and 1right) or 4 channel mode (2 stereo pairs). In the DVCPRO format the audio is 2 channelrecord mode only, though provision is made to replay 4 channel type DV tapes. It is tomention here that audio data is recorded un-compressed.2 Channel Audio Record ModeThe audio signal is digitized by sampling the analog audio signal with 48 kHz samplingfrequency and quantized the samples by 16-bit linear quantizer. In PAL (625/50 Hz)DVCPRO system, one frame of video occupies 12 tracks on the tape. One frame correspondsto 40 milliseconds(25 frames/sec implies 1 frame/40 msec). So 40 milliseconds of audiodata (per channel) is recorded into 12 track frame period.At 48kHz sampling frequency, 1920 samples are generated in 40 msec(40 x 48 = 1920)which have to be accommodated in 6 tracks. DVCPRO format fix the first six tracks for databelonging to the channel 1 input and the second six tracks for data belonging to channel 2.Each track contains 1920/6 = 320 samples(320 x 16 bits = 640 bytes) which can bememorized in 9 x 72 matrix in processing module. 26
  32. 32. VISION MIXINGIntroductionVision mixing is a process of creating composite pictures from various sources. Visionmixing involves basically three types of switching or transitions between various sources.These are mixing, wiping and keying. These transitions can also be accompanied by specialeffects in some of the vision mixers.MixingTwo input sources are mixed in proportion in a summing amplifier as decided by theposition of control fader. Two extreme position of the fader gives either of the sources atthe output. Middle of the fader gives mixed output of the two sources; control to thesumming amplifier is derived from the fader.WipeIn this case the control for the two input sources is generated by the wipe patterngenerator (WPG), which can either be saw tooth or parabola at H, V or both H & V rate.Unlike in MIX, during WIPE, one source is present in one side of the wipe and the secondsource on other side of the wipe. A very simple to very complex wipe patterns can begenerated from the WPG.KeyIn the Key position between two sources i.e. foreground (FG) and background (BG) thecontrol derived from one of the source itself (overlay), or by the third source (externalkey). This keying signal can be generated either by the luminance, Hue or chrominance ofthe source input. The keyed portion can be filled with the same or with matte or externalsource. Matte means internally generated BG with choice of colors from the vision mixeritself. 27
  33. 33. NON LINEAR EDITING & 3-D GRAPHICS-INTRODUCTIONFundamentally editing is a process where one places Audio video clips in an appropriate sequenceand mainly used in video post production. Linear editing is tape based and is sequential in nature. Ithas various problems like long hours spent on rewinding of tapes in search of material, potentialrisk of damage to original footage, difficult to insert a new shot in an edit, difficult to experimentwith variations, quality loss is more, limited composting effects and color correction capability.Non-linear editing (NLE) is a video editing in digital format with standard computer basedtechnology. NLE can also be extended to film editing. Computer technology is harnessed in Randomaccess, computational and manipulation capability, multiple copies, multiple versions intelligentsearch, sophisticated project and media management tools, standard interfaces and powerfuldisplay.ADVANTAGES OF NLENLE has various advantages over tape based (linear) editing.Flexibility in all editing functions.Easy to do changes, undo, copy, duplicate and multiple versionEasy operation for cut, dissolve, wipes and other transition effects.Multi-layering of video is easy.Powerful integration of video and graphics, tools for filtering, color correction, key framing andspecial 2D/3D effects.Equally powerful audio effects and mixing.Possible to trim ; compress or expand the length of the clip.Intelligent and powerful 3D video effect can be created and customized.Efficient and intelligent storage . Standard NLE System 28
  34. 34. BREAKOUT BOX-Various video sources like VTR, CD player, camera and other playback/recording devicesare connected to NLE machine through breakout box. The NLE machine takes input fromvarious video sources for editing and gives output for monitoring and recording throughbreak out box.INPUTSVideo InputsThere are three analog inputs (1) Component Video (2) S-Video (3) Composite videoAudio InputsTo capture synchronized audio with your video, you must connect audio out from the VTRor other play back device to the audio inputs. You can also connect audio only devices forsound track production etc. the dps reality board (NLE hardware) has three analog audiooptions ; balanced, unbalanced and Aux. 29
  35. 35. Time CodeTime code is simply a series of labels attached to a recording at timed intervals, generallyfractions of sounds. Each label contains a time of recording. Time code is used for editing;in order to be able to return repeatedly to a selected time, and for synchronization amongaudio and video recorders and players. The two versions of time code that are availablewith dpsOUTPUTSVideo OutputComponent (CAV) Video has three connectors, labeled Y, B-Y, R-Y. A cable connects each of thesethree outputs to your video monitor or VTR.Audio OutputChoose what type of video to output based on whether your VTR and other video and audioequipment can receive balance or unbalance audio. Audio out is connected to speakers for playbackor to a VTR or other audio recording device during recording. 30
  36. 36. 3 –D GRAPHICSTHE FIVE MODULES OF SOFTIMAGESoftimage 3 D Extreme has given different modules that correspond to different phases of theworkflow process you use to create animation. Each of the modules replaces some of the menu cellson the left and right menu columns, while leaving other menu cells that are applicable in allmodules. The modules are listed along the top right corner of the screen: Model, Motion, Actor,Matter, and Tools. You can enter these modules either by clicking the text labels in the top rightcorner, or by pressing the supra keys that represent them: F1 for Model, F2 for Motion, F3 for Actor,F4 for Matter, and F5 for Tools.MODELYou start your workflow in the Model module, where you construct all your scene elements.Model‟s tools enable you to create objects from primitive shapes, draw curves, and developsurfaces from those curves.MOTIONYou then move to animate some parts of your scene, using the animation tools found in the Motionmodule. The Motion module allows you to set animation keyframes for objects, assign objects topaths, and to see and edit the resulting animation on screen. After you have refined your animationusing the F Curve tools, you move to the next module, Actor.ACTORThe Actor module contains the special Softimage tools for setting up virtual actors, assigninginverse kinematic skeletons, assigning skin, adjusting skeletons deformations, and weighting theskin to the IK skeletons. Actor also contains the controls for physical-based animation – Dynamics,Collisions, and Qstretch – which is an automatic squash-and-stretch features.MATTERWhen your modeling, animation, and acting are complete, you move to the fourth module: Matter.In the Matter module, you assign color and material values to the objects in your scene, determininghow they will look in the final render. 31
  37. 37. At any time in the first four modules, you can create lights and adjust their effect on the scene. TheMatter module is also where you perform the last step in the workflow process, rendering.TOOLSTools contains a variety of utility programs for viewing, editing and exporting your work. You mayview individual images, sequences of images, and line tests. You may bring in images created inother programmes as image maps or import objects created in other programs as geometry. Youcan composite sequences of images together, reduce colours in sequences of images for reducedcolour games systems, and move your finished work to video disk recorders and film recorders. The four view windows 32
  38. 38. TELEVISION TRANSMISSIONVESTIGIAL SIDE BAND TRANSMISSION - If normal amplitude modulation technique is used forpicture transmission, the minimum transmission channel bandwidth should be around 11 MHztaking into account the space for sound carrier and a small guard band of around 0.25 MHz. Usingsuch large transmission BW will limit the number of channels in the spectrum allotted for TVtransmission. To accommodate large number of channels in the allotted spectrum, reduction intransmission BW was considered necessary. The transmission BW could be reduced to around 5.75MHz by using single side band (SSB) AM technique, because in principle one side band of the doubleside band (DSB) AM could be suppressed, since the two side bands have the same signal content.DesignAll the TV transmitters have the same basic design. They consist of an exciter followed by poweramplifiers which boost the exciter power to the required level.ExciterThe exciter stage determines the quality of a transmitter. It contains pre-corrector units both atbase band as well as at IF stage, so that after passing through all subsequent transmitter stages, anacceptable signal is available. Since the number and type of amplifier stages, may differ according tothe required output power, the characteristics of the pre-correction circuits can be varied over awide range. Block Diagram of TV Exciter (Mark-II)Vision and Sound Signal AmplificationIn HPTs the vision and sound carriers can be generated, modulated and amplified separately andthen combined in the diplexer at the transmitter output.In LPTs, on the other hand, sound and vision are modulated separately but amplified jointly. This iscommon vision and aural amplification.A special group delay equalization circuit is needed in the first case because of errors caused by TVdiplexer. In the second case the intermodulation products are more prominent and special filtersfor suppressing them is required.As it is difficult to meet the intermodulation requirements particularly at higher power ratings,separate amplification is used in HPTs though combined amplification requires fewer amplifierstages. 33
  39. 39. IF ModulationIt has following advantages  Ease of correcting distortions  Ease in Vestigial side band shaping  IF modulation is available easily and economically Power Amplifier StagesIn BEL mark I & II transmitters three valve stages (BEL 450 CX, BEL 4500 CX and BEL 15000 CX)are used in vision transmitter chain and two valves (BEL 450 CX and BEL 4500 CX) in auraltransmitter chain. In BEL mark III transmitter only two valve stages (BEL 4500 CX and BEL 15000CX) are used in vision transmitter chain. Aural transmitter chain is fully solid state in Mark IIItransmitter.Constant Impedance Notch Diplexer (CIND)Vision and Aural transmitters outputs are combined in CIN diplexer. Combined power is fed to mainfeeder lines through a T-transformer.BEL 10 kW TV TRANSMITTER (MARK-II) Block Diagram of BEL 10kW TV Transmitter (Mark-II)TRANSMITTER CONTROL SYSTEMThe transmitter control unit performs the task of transmitter interlocking and control. Also itsupports operation from control console. The XTR control unit (TCU) has two independent systemviz.1. Main control system. (MCS)2. Back-up Control System (BCS) 34
  40. 40. Functions performed by MCS (Main Control System)- XTR control- Interlocking- RF monitoring- Supporting operation from control console- Three second logic for protection against sudden fluctuation.- Thermal protection for 1 kW and 10 kW vision PAs- Thermal protection for 130 Watt vision PA and Aural XTRa- Mimic diagramFunctions performed by BCS (Backup control system)- Transmitting control- InterlockingThe block diagram of the TCU (Transmitter control unit) indicates the connectivity of TCU withcontrol console and the control elements of the transmitter. Commands are inputs through the keyboard. The control elements are controlled in accordance with the programme fused in theEPROMS.Only while operating from the MCS (Main Control System), the interaction with TCU is supportedthrough a LCD display unit. The LED bar display board showing the status information, is used byboth the MCS and BCS (Back up Control Unit).Main Control System (MCS)The MCS consists of the following :1. Mother Board with the following PCBs.CPUBIT I/OInterlock Interface Board (IIB).Analog I/O Board (AIO)Control Interface Board (CIB)Analog Receiver Board (An Rx)Rectifier and Regulator Board (RRB mcs)2. Key Board3. LED Bar Display Board4. Relay Board5. LCD Display Unit6. Transformers T1 and T2.7. + 5V/3A. Power Supply Unit. 35
  41. 41. TV TRANSMITTER ANTENNA SYSTEMAntenna System is that part of the Broadcasting Network which accepts RF Energy fromtransmitter and launches electromagnetic waves in space. The polarization of the radiation asadopted by Doordarshan is linear horizontal. The system is installed on a supporting tower andconsists of antenna panels, power dividers, baluns, branch feeder cable, junction boxes and mainfeeder cables. Dipole antenna elements, in one or the other form are common at VHF frequencieswhere as slot antennae are mostly used at UHF frequencies. Omni directional radiation pattern isobtained by arranging the dipoles in the form of turnstile and exciting the same in quadraturephase. Desired gain is obtained by stacking the dipoles in vertical plane. As a result of stacking,most of the RF energy is directed in the horizontal plane. Radiation in vertical plane is minimized.The installedantenna system should fulfil the following requirements :a) It should have required gain and provide desired field strength at the point of reception.b) It should have desired horizontal radiation pattern and directivity for serving the planned area ofinterest. The radiation pattern should be omni directional if the location of the transmitting stationis at the center of the service area and directional one, if the location is otherwise.c) It should offer proper impedance to the main feeder cable and thereby to the transmitter so thatoptimum RF energy is transferred into space. Impedance mismatch results into reflection of powerand formation of standing waves. The standard RF impedance at VHF/UHF is 50 ohms. 36
  42. 42. Outdoor Broadcasting vanO B Van (Outdoor Broadcasting van )- OB van is used for live broadcasting like anymatch or any event. It consist all the equipments that is present in the studio for telecasting. It alsoreferring as mini studio . It has mainly 3 parts :1)Power supply unit2)Production control unit3)Audio console and VTR Inner View of OB van Inner View of OB van 37
  43. 43. Earth StationSATELLITE COMMUNICATIONSatellite Communication is the outcome of the desire of man to achieve the concept of global village.Penetration of frequencies beyond 30 Mega Hertz through ionosphere force people to think that ifan object (Reflector) could be placed in the space above ionosphere then it could be possible to usecomplete spectrum for communication purpose.Intelsat-I (nick named as Early Bird) was launched on 2 April 1965. This was parked ingeosynchronous orbit in Atlantic ocean and provided telecommunication or television servicebetween USA and Europe. It had capacity for 240 one way telephone channels or one televisionchannel. Subsequently Intelsat-II generation satellites were launched and parked in Atlantic oceanand Pacific Ocean. During Intelsat III generation, not only Atlantic and Pacific ocean got satellitesbut also Indian Ocean got satellite for the first time. Now Arthur C.Clarke‟s vision of providingglobal communication using three Satellites with about 120 degrees apart became a reality. So farIntelsat has launched 7 generations of geosynchronous satellites in all the three regions namelyAtlantic Ocean, Pacific Ocean and Indian Ocean.For national as well as neighbouring countries coverage, some of the following satellites are used:ANIK : Canadian satellite system INSAT : Indian SatellitesAUSSAT : Australian SatellitesBRAZILSAT : Brazilian SatellitesFRENCH TELECOM : French SatellitesITALSAT : Italian SatellitesCHINASAT : Chinese SatellitesSTATSIONAR, GORIZONT, Russian SatellitesArchitecture of a Satellite Communication SystemThe Space SegmentThe space segment contains the Satellite and all terrestrial facilities for the control and monitoringof the Satellite. This includes the tracking, telemetry and command stations (TT&C) together withthe Satellite control centre where all the operations associated with station-keeping and checkingthe vital functions of the satellite are performed. In our case it is Master Control Facility (MCF) atHassan.The radio waves transmitted by the earth stations are received by the satellite ; this is called the uplink. The satellite in turn transmits to the receiving earth stations ; this is the down link. The qualityof a radio link is specified by its carrier-to-noise ratio. The important factor is the quality of the totallink, from station to station, and this is determined by the quality of the up link and that of the downlink. The quality of the total link determines the quality of the signals delivered to the end user inaccordance with the type of modulation and coding used. 38
  44. 44. The Ground SegmentThe ground segment consists of all the earth stations ; these are most often connected to the end-user‟s equipment by a terrestrial network or, in the case of small stations (Very Small ApertureTerminal, VSAT), directly connected to the end-user‟s equipment. Stations are distinguished bytheir size which varies according to the volume of traffic to be carried on the space link and the typeof traffic (telephone, television or data). The largest are equipped with antenna of 30 m diameter(Standard A of the INTELSAT network). The smallest have 0.6 m antenna (direct televisionreceiving stations). Fixed, transportable and mobile stations can also be distinguished. Somestations are both transmitters and receivers.Space GeometryTypes of Orbit The orbit is the trajectory followed by the satellite in equilibrium between two opposing forces.These are the force of attraction, due to the earth‟s gravitation, directed towards the centre of theearth and the centrifugal force associated with the curvature of the satellite‟s trajectory. Thetrajectory is within a plane and shaped as an ellipse with a maximum extension at the apogee and aminimum at the perigee. The satellite moves more slowly in its trajectory as the distance from theearth increases .Most favourable OrbitsElliptical orbits inclined at an angle of 64o with respect to the equatorial plane. This orbit enablesthe satellite to cover regions of high latitude for a large fraction of the orbital period as it passes tothe apogee. This type of orbit has been adopted by the USSR for the satellites of the MOLNYAsystem with a period of 12 hours. Please note that the satellite remains above the regions locatedunder the apogee for a period of the order of 8 hours. Continuous coverage can be ensured withthree phased satellites on different orbits. 39
  45. 45. Circular inclined orbits : The altitude of the satellite is constant and equal to several hundreds of kilometers. The period is ofthe order of one and a half hours. With near 90% inclination this type of orbit guarantees that thesatellite will pass over every region of the earth. Several systems with world wide coverage usingconstellations of satellite carries in low altitude circular orbits are for e.g. IRIDIUM, GLOBAL STAR,ODYSSEY, ARIES, LEOSAT, STARNET, etc.Circular orbitswith zero inclination (Equatorial orbits). The most popular is the geo stationary satellite orbits ; thesatellite orbits around the earth at an altitude of 35786 km, and in the same direction as the earth.The period is equal to that of the rotation of the earth and in the same direction. The satellite thusappears as a point fixed in the sky and ensures continuous operation as a radio relay in real time forthe area of visibility of the satellite (43% of the earth‟s surface).Factors deciding the selection of Orbit The choice of orbit depends on the nature of the mission, the acceptable interference and theperformance of the launchers :The extent and latitude of the area to be covered.The elevation angle of earth stations.Transmission duration and delay.InterferenceThe performance of launchers TVRO SystemPresently Doordarshan is up linking its national, metro and regional services to INSAT-2A (74oC)and INSAT-2B (93.5oE) and INSAT 2E (83o C). Down link frequency bands being used are C-Band(3.7-4.2 GHz) and Ex-C Band (4.5-4.8 GHz). Satellite Earth Station Uplink / Downlink ChainTransmission of base band to SatelliteThe base band signal consists of video (5 MHz), two audio subcarriers (5.5 MHz & 5.75 MHz) andenergy dispersal signal (25 Hz). After modulation (70 MHz) and upconversion (6 GHz) the carrier isamplified and uplinked through Solid Parabolic Dish Antenna (PDA). Down link signal can bereceived through same PDA using Trans-Receive Filter (TRF) and Low Noise Amplifier (LNA). Afterdown conversion to 70 MHz, it is demodulated to get audio and video. 40
  46. 46. Satellite TransponderAs shown in fig, the uplinked signal (6 GHz) at satellite is received, amplified and down converted to4 GHz band and sent back through filter and power amplifier (TWT). The local oscillator frequencyof down converter is 2225 MHz for C band and Ex-C band transponders. Block diagram of Satellite TransponderReceiving Satellite SignalFor receiving a satellite signal we need following equipment :1. Satellite receiving antenna (PDA).2. Feed with low noise block converter (LNBC).3. Indoor unit consisting of satellite system unit and a Synthesised satellite receiver. Parallels of Latitudes Latitude as angular distanceAzimuth and ElevationFor receiving a satisfactory signal from the satellite the dish antenna should be pointed towards thesatellite accurately. For that we need to know the azimuth and elevation of a particular satellitefrom our place. The azimuth and elevation are angles which specify the direction of a satellite froma point on the earths surface. In layman terms the azimuth is the east west movement and theelevation can be defined as the north south movement of the dish. Both the azimuth and elevationof a dish can be affected by three factors for geo-stationary satellites. 41
  47. 47. They are1. The longitude of the satellite.2. The latitude of the place.3. The longitude of the place.Calculation of Angle of ElevationWhere r = Radius of the earth (6367 kms) R = Radius of Synchronous orbit (42,165 kms). = Latitude ofthe earth station D = difference in longitude of the earth station and the satellite. ( r - s) 2 1 CosCalculation of AzimuthIndoor UnitsThe indoor unit contains two units.They are :1. System unit2. Satellite Receiver UnitSystem unit The system unit contains a passive power divider and power supply for the LNBC. The powerdivider divides the IF into two equal parts to be applied to the two receivers. The power supply isfed through same cable to the LNBC. Satellite Receiver Unit The satellite receiver contains thedown converter, video/audio demodulators and processing circuits. Finally we get two video/audiooutputs. A synthesised receiver accepts signal in the range of 900 to 1700 MHz. The block diagramof a typical EC receiver is shown in figure 9. The IF is applied to a four-stage low noise amplifier foramplification. The overall gain of the amplifier is around 22 dB. This signal is then applied to FETmixer where a LO frequency of 1500 to 2300 MHz is mixed so that an IF of 600 MHz is produced.The local oscillator consists of two similar VCOs (voltage controlled oscillator) one operating in therange of 1500 - 1749 MHz and the other in the range of 1750 to 2300 MHz. They are controlled by asynthesiser IC. A sample of the LO frequency is taken and phase compared with a stable referencecrystal frequency of 4 MHz and error if any, is then applied to the VCO for frequency correctionthrough a low pass filter. Thus the VCO works in a phase locked loop mode. 42
  48. 48. Direct-to-Home Satellite Broadcasting (DTH)INTRODUCTIONThere was always a persistent quest to increase the coverage area of broadcasting. Before theadvent of the satellite broadcasting, the terrestrial broadcasting, which is basically localized, wasmainly providing audio and video services. The terrestrial broadcasting has a major disadvantage ofbeing localized and requires a large number of transmitters to cover a big country like India. It is agigantic task and expensive affair to run and maintain the large number of transmitters. Satellitebroadcasting, came into existence in mid sixties, was thought to provide the one-third globalcoverage simply by up-link and down-link set-ups. In the beginning of the satellite broadcasting,up-linking stations (or Earth Stations) and satellite receiving centers could had only been affordedby the Governments organizations. The main physical constraint was the enormous size of thetransmitting and receiving parabolic dish antennas (PDA). In the late eighties the satellitebroadcasting technology had undergone a fair improvements resulting in the birth of cable TV.Cable TV operators set up their cable networks to provide the services to individual homes in localareas. It rapidly grew in an unregulated manner and posed a threat to terrestrial broadcasting.People are now mainly depending on cable TV operators. Since cable TV services are unregulatedand unreliable in countries like India now, the satellite broadcasting technology has ripened to alevel where an individual can think of having direct access to the satellite services, giving theopportunity to viewers to get rid of cable TV. Direct-to-Home satellite broadcasting (DTH) or DirectSatellite Broadcasting (DBS) is the distribution of television signals from high powered geo-stationary satellites to a small dish antenna and satellite receivers in homes across the country. Thecost of DTH receiving equipments is now gradually declining and can be afforded by common man.Since DTH services are fully digital, it can offer value added services, video-on-demand, Internet, e-mail and lot more in addition to entertainment. DTH reception requires a small dish antenna (Dia60 cm), easily be mounted on the roof top, feed along with Low Noise Block Converter (LNBC), Set-up Box (Integrated Receiver Decoder, IRD) with CAS (Conditional Access System). A bouquet of 40to 50 video programs can simultaneously be received in DTH mode.UPLINK CHAINDTH broadcasting is basically satellite broadcasting in Ku-Band (14/12 GHz). The main advantageof Ku-Band satellite broadcasting is that it requires physically manageable smaller size of dishantenna compared to that of C-Band satellite broadcasting. C-Band broadcasting requires about 3.6m dia PDA (41dB gain at 4 GHz) while Ku-Band requires 0.6 m dia PDA (35dB gain at 12 GHz). Theshortfall of this 6 dB is compensated using Forward Error Correction (FEC), which can offer 8 to 9dB coding gain in the digital broadcasting. Requirement of transmitter power (about 25 to 50Watts) is less than that of analog C-band broadcasting. The major drawback of Ku-Bandtransmission is that the RF signals typically suffer 8 to 9dB rain attenuation under heavy rainfallwhile rain attenuation is very low at C-Band. Fading due to rain can hamper the connectivity ofsatellite and therefore rain margin has to be kept for reliable connectivity. Rain margin is providedby operating transmitter at higher powers and by using larger size of the dish antenna (7.2m PDA).Fig.1 shows schematic of uplink chain proposed to broadcast bouquet of 30 video programs inDoordarshan, Prasar Bharati, India. 30 video programs may either be down-linked from satellitesor taken from other sources like video tape recorders, 43
  49. 49. video cameras etc. in digital format. These sources are fed to Router whose outputs are divided inthree groups A, B and C. Each group contains 10 video sources multiplexed in a Multiplexer. Thesethree multiplexed streams are digitally (QPSK modulation) modulated individually at 70 MHzIntermediate Frequency (IF). Each group is further doubly up-converted, first conversion at L-Band(950-1450 MHz) and second conversion at Ku-Band (12-14 GHz).DOWN-LINK CHAINDown-Link or receiving chain of DTH signal is depicted in Fig.2. There are mainly three sizes ofreceiving antenna, 0.6m, 0.9m, and 1.2m. Any of the sizes can easily be mounted on rooftop of abuilding or house. RF waves (12.534GHz, 12.647GHz, 12.729 GHz) from satellite are picked up by afeed converting it into electrical signal. The electrical signal is amplified and further downconverted to L-Band (950-1450) signal. Feed and LNBC are now combined in single unit calledLNBF. The L-Band signal goes to indoor unit, consisting a set-top box and television through coaxialcable. The set-top box or Integrated Receiver Decoder (IRD) down converts the L-Band first IFsignal to 70 MHz second IF signal, perform digital demodulation, de-multiplexing, decoding andfinally gives audio/video output to TV for viewing.