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.

10
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

 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.
What is being used today?

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.

 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
How Monitor Works?

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.

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.

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.

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.

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.

 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 - 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

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

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

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

THE END