Lecture 5 Video and Sound

Summary of Previous We have learnt, Reasons why some computer users prefer alternative methods of input over a standard keyboard or mouse. Input data by touch Game controllers Input data by light Other input types, e.g. audio, video etc. When to use which input device? Practical

Today’s Topics Monitors Monitors and Video Cards Video Cards Ergonomics and Monitors Data Projectors Sound Systems

Multimedia The 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 etc

Visual Display Devices Primary 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.

Monitor It is a most common output device A 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.

Monitor

Monitor Quality of picture we see on monitor depends upon, Monitor quality itself Video controller. From the 1980s onwards, computers (and their monitors) have been used for both data processing and entertainment.

Technologies Different 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.

Monitors Types Different types of monitors exists, which are; Monochrome Grayscale Color

Monochrome Monitor A 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 Monitor

Grayscale Monitors A 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 Monitor

Color Monitors A 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 Monitors The monitors can display different colors by combining various intensities of three beams.

Mixing of Colors

What is being used today? The 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.

History of the Cathode Ray 1855- 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 magnet 1869- J.W. Hittorf establishes that the “rays” travel in straight lines 1883- Heinrich Hertz concludes incorrectly that cathode rays are not made up of particles because they are not deflected by electrically charged metal plates 1895- Jean-Baptiste Perrin shows that cathode rays are particles because they deposit a negative charge where they impact 1897- J.J. Thomson discovers electrons using cathode rays

How 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.

How Monitor Works? 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 charges

Some Anatomy of the CRT Anode- Positively Charged, Ray travels towards this Cathode- Negatively Charged, Ray travels away from this

Cathode Ray Tube (CRT) Monitors A 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. The cathode ray tube (CRT) is a vacuum tube containing an electron gun (a source of electrons) and a fluorescent screen used to view images. It has a means to accelerate and deflect the electron beam onto the fluorescent screen to create the images. The image may represent electrical waveforms (oscilloscope), pictures (television, computer monitor), radar targets and others. CRTs have also been used as memory devices, in which case the visible light emitted from the fluoresecent material (if any) is not intended to have significant meaning to a visual observer (though the visible pattern on the tube face may cryptically represent the stored data). The CRT uses an evacuated glass envelope which is large, deep (i.e. long from front screen face to rear end), fairly heavy, and relatively fragile. As a matter of safety, the face is typically made of thick lead glass so as to be highly shatter-resistant and to block most X-ray emissions, particularly if the CRT is used in a consumer product. CRTs have largely been superseded by more modern display technologies such as LCD, Plasma, LED and OLED, which offer lower manufacturing and distribution costs. A cathode ray tube is a vacuum tube which consists of one or more electron guns, possibly internal electrostatic deflection plates, and a phosphor target. In television sets and computer monitors, the entire front area of the tube is scanned repetitively and systematically in a fixed pattern called a raster. An image is produced by controlling the intensity of each of the three electron beams, one for each additive primary color (red, green, and blue) with a video signal as a reference. In all modern CRT monitors and televisions, the beams are bent by magnetic deflection, a varying magnetic field generated by coils and driven by electronic circuits around the neck of the tube, although electrostatic deflection is commonly used in oscilloscopes, a type of diagnostic instrument.

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 lit

Phosphore It 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 Gun The electron gun scans from left to right and From top to bottom. Refreshing every phosphor dot in a zig-zag pattern.

Advantages of CRT The cathode rayed tube can easily increase the monitor’s brightness by reflecting the light. They produce more colours The 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 CRT They 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 around

CRT Monitor

Liquid Crystal Display - Monitor It 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 History Liquid 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. 31

LCD Technology Used 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. 32

From CRT to LCD CRT Bulky, heavy, use vacuum tube technology. Using technology that was developed in the 19th century. LCD First 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. 33

Liquid Crystal Display There are mainly two categories of LCD. The passive matrix LCD The Active matrix LCD

Passive Matrix LCD Monochrome 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 LCD Pixels arranged in a grid Pixels are activated indirectly Row and column are activated Animation can be blurry

Passive Matrix Display

Active Matrix LCD Active-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 directly Pixels have 4 transistors One each for red, green, blue One for opaqueness Animation is crisp and clean

TFT LCD Screen

Advantages of LCD The 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 LCD After 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 Monitors Paper-white displays High contrast between fore and background Electro-luminescent displays (ELD) Similar to LCD Uses phosphor to produce light Plasma monitor Gas is excited to produce light

Paper White Display

NASA -Electroluminescent displays

Plasma Monitors

Monitor Specifications Monitor Specifications can be judged through, Size Resolution Refresh rate Dot pitch

Size A 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.

Resolution The 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.

Resolution Actual resolution is determined by the video controller. Most monitors can operate at several different resolutions. They are 640 X 480 800 X 600 1024 X 768 1152 X 864 1280 X 1024 As the resolution increases, image on the screen gets smaller.

Resolution Settings

Standards There 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 Rate Monitor 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 Rate

Dot Pitch It is the distance between the same color dots Ranges between .15 mm and .40 mm Smaller creates a finer picture Should be less than .22

Dot Pitch

Video Cards Interface 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 Cards IBM 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 Card

How 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.

How Video card works? 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.

Video Card - GPU Similar to CPU but designed specifically to perform complex mathematical and geometric calculations necessary for graphics rendering. Less congestion on the system bus Reduction in the workload of CPU

Graphics GPU

Video Card - GPU Operations: 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 - GPU Some of the latest GPUs have more transistors than average CPU and produce a lot of heat. Heat-sinking and fan cooling are required

Video Card - Memory When 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 Memory In 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 graphics Modern cards have up to 512 MB RAM

Ergonomics and Monitors Eyestrain It is the fatigue of the eyes Steps to avoid Choose a good monitor Place the monitor 2 – 3 feet away Center of screen below eye level Avoid reflected light

Ergonomics and Monitors Electronic magnetic fields (EMF) Generated by all electronic devices EMF may be detrimental to health Steps to avoid Keep the computer at arms length Take frequent breaks Use an LCD monitor

Data Projectors A 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 Projectors They replaced overhead and slide projectors. Project image onto wall or screen LCD projectors Most common type of projector Small LCD screen Very bright light Require a darkened room

Data Projectors Digital Light Projectors A series of mirrors control the display May be used in a lighted room Example is Cinema Projectors Insider information A projector is rated in lumens. This is a measure of how bright the projector is. Higher lumens ratings result in a brighter projector. For a guide to lumens ratings, see http://www.projectorpeople.com/tutorials/lumen-guide.asp.

Sound Systems It is an integral part of the computer experience Capable of recording and playback

Sound Systems Sound card are the, Device between the CPU and speakers Converts digital sounds to analog Can be connected to several devices Modern cards support Dolby Surround Sound

Sound Card

Sound Systems Headphones and headsets Replacement for speakers and microphones Offer privacy Does not annoy other people Outside noise is not a factor Headsets have speakers and a microphone Insider information The PS2 game SOCOM II Navy Seals includes a USB headset to allow verbal communication with other team members.

Practical

Goal for your display settings Screen resolution – 1024 x 768 Dots Per Inch – “Large Size” (120 DPI) Base Fonts - “Large Fonts”

Changing your computer’s display settings Then, click here to open the Control Panel Click Start button

Opening “Display” window Double-click on “Display”

Re-setting Resolution First, click “Settings” tab Next, move slider-bar to adjust resolution to 1024 by 768 pixels

Getting to “Dots Per Inch” Then, click the “Advanced” button to set Dots Per Inch

Resetting 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 size Click the “Appearance” tab Set to “Large Fonts”

Summary We have learnt Different types of monitors and their uses Cathode Ray Tube Video Cards Sound Cards Practical

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