Video and Sound - Lecture 5

Lecture 5Video and SoundSummary of PreviousWe have learnt,Reasons why some computer users prefer alternative methods of input over a standard keyboard or mouse.Input data by touchGame controllersInput data by lightOther input types, e.g. audio, video etc.When to use which input device?PracticalToday’s TopicsMonitorsMonitors and Video CardsVideo CardsErgonomics and MonitorsData ProjectorsSound SystemsMultimediaThe word ‘multimedia’ comes from the Latin word multus means ‘numerous’ and media which means ‘middle’ or Centre.Multimedia consists a large number of visual media like graphics, image, animation etcVisual Display DevicesPrimary user hardware for displaying visual media such as graphics, text, images.Consists of components such as Monitor, Video adapter card, video adapter cable.Various such devices are CRT, color CRT, DVST, Flat Panel Displays (LCD & Plasma), LED monitors, etc.MonitorIt is a most common output deviceA monitor or display (also called screen or visual display unit) is an electronic visual display for computers.Originally, computer monitors were used for data processing while television receivers were used for entertainment. MonitorMonitorQuality of picture we see on monitor depends upon,Monitor quality itselfVideo controller.From the 1980s onwards, computers (and their monitors) have been used for both data processing and entertainment.TechnologiesDifferent image technique have been used for computer monitors. Until the 21st century most monitors were CRT but they have been phased out for LCD monitors.They are categorized by color output.Monitors connects to the video card of a computer system.10Monitors TypesDifferent types of monitors exists, which are;MonochromeGrayscaleColorMonochrome MonitorA monochrome monitor is a type of CRT computer display which was very common in the early days of computing. From the 1960s through the 1980s, before color monitors became popular.They are still widely used in applications such as computerized cash register systems. Green screen was the common name for a monochrome monitor.They are abandoned in early-to-mid 1980’s.Monochrome MonitorGrayscale MonitorsA special type of monochrome monitor capable of displaying different shades of gray.They are also known as black-and-white, are composed exclusively of shades of gray, varying from black at the weakest intensity to white at the strongest.Early grayscale monitors can only show up to sixteen different shades Grayscale MonitorColor MonitorsA display monitor capable of displaying many colors. Color Monitors works like a monochrome one, except that there are three electron beams instead of one.The three guns represent additive colors (red, green and blue) although the beam they emit are colorless. Each pixel includes three phosphors, red, green and blue, arranged in a triangle.When the beam of each of these guns are combined and focused on a pixel, the phosphors light up.Color MonitorsThe monitors can display different colors by combining various intensities of three beams.Mixing of ColorsThe most popular display today remains Color monitors CRT. It has been available for more than 70 years.CRT is used.Cost less than LCD monitors. What is being used today?History of the Cathode Ray1855- Heinrich Geissler creates the mercury pump, the first good vacuum tubes. Sir William Crookes uses these to produce the first cathode rays.1858- Julius Plücker bends cathode rays using a magnet1869- J.W. Hittorf establishes that the “rays” travel in straight lines1883- Heinrich Hertz concludes incorrectly that cathode rays are not made up of particles because they are not deflected by electrically charged metal plates1895- Jean-Baptiste Perrin shows that cathode rays are particles because they deposit a negative charge where they impact1897- J.J. Thomson discovers electrons using cathode raysHow Monitor Works?Most use a cathode-ray tube as a display device. CRT: Glass tube that is narrow at one end and opens to a flat screen at the other end. Electrons travel through a vacuum sealed container from the cathode (negative) to the anode (positive).Because the electrons are negatively charged, they are repelled away from the cathode, and move across the tube to the anode.The ray can be affected by a magnet because of its relation to positive and negative chargesHow Monitor Works?Some Anatomy of the CRTAnode- Positively Charged, Ray travels towards thisCathode- Negatively Charged, Ray travels away from thisCathode Ray Tube (CRT) MonitorsA CRT monitor contains millions of tiny red, green, and blue phosphor dots that glow when struck by an electron beam. Electron beam travels across the screen to create a visible image. In a CRT monitor tube, the cathode is a heated filament. The heated filament is in a vacuum created inside a glass tube. The electrons are negative and the screen gives a positive charge so the screen glows.Basic Cathode Ray Tube Electrons excite phosphor to glow Electrons fired from the back Phosphor is arranged in dots called pixels Dot mask ensures proper pixel is litPhosphoreIt is a semi-conducteur material which emits visible radiation in response to the impact of electrons. (i.e. when it absorbs energy from some source such as an electron beam, it releases a portion of this energy in the form of light).In response to a sudden change in the electron beam(from on to off), the light emission does not fall instantaneously, there is a gradual reduction challed ‘fluorescence’ .Scanning Pattern of CRT Electron GunThe electron gun scans from left to right andFrom top to bottom.Refreshing every phosphor dot in a zig-zag pattern.Advantages of CRTThe cathode rayed tube can easily increase the monitor’s brightness by reflecting the light.They produce more coloursThe Cathode Ray Tube monitors have lower price rate than the LCD display or Plasma display.The quality of the image displayed on a Cathode Ray Tube is superior to the LCD and Plasma monitors. The contrast features of the cathode ray tube monitor are considered highly excellent.Disadvantages of CRTThey have a big back and take up space on desk.The electromagnetic fields emitted by CRT monitors constitute a health hazard to the functioning of living cells.CRTs emit a small amount of X-ray band radiation which can result in a health hazard.Constant refreshing of CRT monitors can result in headache.CRTs operate at very high voltage which can overheat system or result in an implosion Within a CRT a strong vacuum exists in it and can also result in a implosion They are heavy to pick up and carry aroundCRT MonitorLiquid Crystal Display - MonitorIt is a flat panel display, electronic visual display, or video display that uses the light modulating properties of liquid crystals (LCs). LCs do not emit light directly .LCD HistoryLiquid crystals were first discovered in 1888 by Austrian botanist Friedrich Reinitzer.RCA, an American Laboratory made the first experimental LCD in (1968). Manufacturers have been developing creative variations and improvements since on LCDs. In 1997, manufactures began to offer full size LCD monitors as alternatives to CRT monitors. Until recently, was only used on notebook computers and other portable devices. LCD TechnologyUsed for displays in notebooks, small computers, pagers, phones and other instruments. Uses a combination of fluorescent-based backlight, color filters, transistors, and liquid crystal to create and illuminate images. Until recently, was only used on notebook computers and other portable devices. From CRT to LCDCRTBulky, heavy, use vacuum tube technology.Using technology that was developed in the 19th century. LCDFirst LCD laptop monitors were very small due to manufacturing costs but now are available in a variety of sizes. Light, sleek, energy-efficient, have sharp picture. Liquid Crystal DisplayThere are mainly two categories of LCD.The passive matrix LCDThe Active matrix LCDPassive Matrix LCDMonochrome passive-matrix LCDs were standard in most early laptops.Still being used today for applications less demanding than laptops and TVs. It consisting of a grid of horizontal and vertical wires.At the intersection of each grid is an LCD element which constitutes a single pixel, either letting light through or blocking it. Passive matrix LCDPixels arranged in a gridPixels are activated indirectlyRow and column are activatedAnimation can be blurryPassive Matrix DisplayActive Matrix LCDActive-matrix LCDs depend on thin film transistors (TFT).TFTs are tiny switching transistors and capacitors. They are arranged in a matrix on a glass substrate. Each pixel is activated directlyPixels have 4 transistorsOne each for red, green, blueOne for opaquenessAnimation is crisp and cleanTFT LCD ScreenAdvantages of LCDThe sharpness of a LCD display is at maximum tweak ness.High peak intensity produces very bright images. Best for brightly lit environments. Screens are perfectly flat. Thin, with a small footprint. Consume little electricity and produce little heat The LCD display unit is very light and can be put anywhere or moved anywhere in the house.Lack of flicker and low glare reduce eyestrain.Disadvantages of LCDAfter a while the LCD display the some of the pixels will die you will see a discoloured spot on a black spot on the display.The cost of a LCD is considerably at a high price.The LCD display will have slow response times.The LCD display has a fixed resolution display and cannot be changed.The viewing angle of a LCD display is very limited.Other types of MonitorsPaper-white displaysHigh contrast between fore and backgroundElectro-luminescent displays (ELD)Similar to LCDUses phosphor to produce lightPlasma monitorGas is excited to produce lightPaper White DisplayNASA -Electroluminescent displaysPlasma MonitorsMonitor SpecificationsMonitor Specifications can be judged through,SizeResolutionRefresh rateDot pitchSizeA monitor’s size affect how well we can see images.With a larger monitor, we can make the objects on the screen appear bigger.Monitors are measured diagonally, in inches, across the front of the screen.A 17 inch monitor measures 17 inches from the lower left to the upper right corner. CRT monitors viewing area is smaller than the monitor’s overall size.ResolutionThe images you see on your monitor are made of tiny dots called pixels.The term resolution refers to the sharpness and clarity of an image. A monitor resolution is determined by the number of pixels on the screen. It is expressed as a Matrix.The more pixels a monitor displays, higher will be its resolution. Clearer will be images appear.For example 640 X 480 resolution means that there are 640 pixels horizontally across the screen and 480 pixels vertically down the screen.ResolutionActual resolution is determined by the video controller. Most monitors can operate at several different resolutions. They are640 X 480800 X 6001024 X 7681152 X 8641280 X 1024As the resolution increases, image on the screen gets smaller.Resolution SettingsStandardsThere are various standards for monitor resolution.Video Graphics Array standard is 640 X 480 pixels.Super VGA is 800 x 600 and 1024 x 768.Today, nearly all color monitors can be set to higher resolution.Refresh RateMonitor refresh rate is the number of times per second that the electron guns scan every pixel on the screen. Refresh rate is important because phosphor dots fade quickly after the electron gun charges them with electrons.If the screen is not refreshed, it will appear to flicker.Refresh rate is measured in Hz or Cycles per second.If the monitor refresh rate is 100 Hz, it means that it refreshes its pixels 100 times every second.Refresh RateDot PitchIt is the distance between the same color dotsRanges between .15 mm and .40 mmSmaller creates a finer pictureShould be less than .22Dot PitchVideo CardsInterface between computer and a display device.Unless a computer has graphics capability built into the motherboard, the video card is required. The CPU, working in conjunction with software applications, sends information about the image to the video card. The video card decides how to use the pixels on the screen to create the image. It then sends that information to the monitor through output interface. Evolution of Video CardsIBM introduced first video card in 1981, named Monochrome Display Adapter (MDA).MDA provided text-only displays of green or white text on a black screen.Parts of Video CardHow Video card works?At most common resolution settings, a screen displays over a million pixels, and the computer has to decide what to do with every one in order to create an image.To do this it needs something to take binary data from the CPU and turn it into a picture you can see.Unless a computer has graphics capability built into the motherboard, that translation takes place on the graphics card. The CPU, working in conjunction with software applications, sends information about the image to the graphics card.The graphics card decides how to use the pixels on the screen to create the image.It then sends that information to the monitor through a cable.It is capable of rendering 3D images.How Video card works?Video Card - GPUSimilar to CPU but designed specifically to perform complex mathematical and geometric calculations necessary for graphics rendering.Less congestion on the system busReduction in the workload of CPUGraphics GPUVideo Card - GPUOperations: bitmap transfers, painting, window resizing and repositioning, line drawing, font scaling and polygon drawing etc.Some GPUs have image enhancement algorithms built-in.Video Card - GPUSome of the latest GPUs have more transistors than average CPU and produce a lot of heat. Heat-sinking and fan cooling are requiredVideo Card - MemoryWhen a video card is connected within the motherboard, it will use the computers random access memory (RAM). If it is not connected to the motherboard though, the video card often has its own memory known as Video RAM (VRAM). The capacity of VRAM in modern video cards ranges from 125 to almost 800 MB. Video Card MemoryIn 2006, DDR technology was the base of the VRAM.The clock rate of the memory was between 300 MHz and 1.7 GHz. The Z-buffer is an important part of the video memory. It takes care of the depth coordinates in 3D graphicsModern cards have up to 512 MB RAMErgonomics and MonitorsEyestrainIt is the fatigue of the eyesSteps to avoidChoose a good monitorPlace the monitor 2 – 3 feet awayCenter of screen below eye levelAvoid reflected lightErgonomics and MonitorsElectronic magnetic fields (EMF)Generated by all electronic devicesEMF may be detrimental to healthSteps to avoidKeep the computer at arms lengthTake frequent breaksUse an LCD monitorData ProjectorsA video projector is an image projector that receives a video signal and projects the corresponding image on a projection screen using a lens system.Data ProjectorsThey replaced overhead and slide projectors.Project image onto wall or screenLCD projectorsMost common type of projectorSmall LCD screenVery bright lightRequire a darkened roomData ProjectorsDigital Light ProjectorsA series of mirrors control the displayMay be used in a lighted roomExample is Cinema ProjectorsSound SystemsIt is an integral part of the computer experienceCapable of recording and playbackSound SystemsSound card are the,Device between the CPU and speakersConverts digital sounds to analogCan be connected to several devicesModern cards support Dolby Surround SoundSound CardSound SystemsHeadphones and headsetsReplacement for speakers and microphonesOffer privacyDoes not annoy other peopleOutside noise is not a factorHeadsets have speakers and a microphonePracticalGoal for your display settingsScreen resolution – 1024 x 768Dots Per Inch – “Large Size” (120 DPI)Base Fonts - “Large Fonts”Changing your computer’s display settingsThen, click here to open the Control PanelClick Start buttonOpening “Display” windowDouble-click on “Display”Re-setting ResolutionNext, move slider-bar to adjust resolution to 1024 by 768 pixelsFirst, click “Settings” tabGetting to “Dots Per Inch”Then, click the “Advanced” button to set Dots Per InchResetting Dots Per Inch (DPI)Change DPI setting to “Large Size” (120 DPI)How does everything look now?At this point, close the Display settings window and see how your desktop screens look. If nothing has changed, try rebooting.If you find that everything, including desktop icons and text, is now very, very tiny, you may also need to reset your base font size. Resetting base font sizeClick the “Appearance” tabSet to “Large Fonts”SummaryWe have learntDifferent types of monitors and their usesCathode Ray Tube Video CardsSound CardsPracticalTHE END