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Video
Terms and Definitions
Chapter Objectives
After completing this chapter you will:
• Describe the components of the video subsystem.
• Differentiate among monitor types.
• Understand basic monitor theory and terminology.
• Recommend a resolution for a particular monitor size.
• Describe different types of video memory.
• Be able to install a video adapter and associated software.
• Perform basic video troubleshooting techniques.
Video Overview
• Video should be considered a subsystem that consists of:
– the monitor
– the electronic circuits which send the monitor instructions
– the connecting cable
Video Overview
Video Subsystem
Video – Figure # 1
Types of Monitors
• Different ways of classifying monitors:
– Color or Non-color
– Analog or Digital
– Type of video adapter used
Types of Monitors
• Monochrome
– First type to be produced
– Project a single color (white, amber, or green) on black background
– Text-only output, no graphics
• Grayscale
– Display varying shades of black and white
– Used by artists and CAD designers
• Color
– Display up to millions of colors for text and graphics
Types of Monitors
• Digital
– Accept digital signals from the video adapter
– First monochrome and first two types of color monitors
– Limited number of colors
• Analog
– Utilize analog waveforms to generate colors
– Color variations are limitless
Note: Video adapter must match the type of monitor.
Types of Monitors
Video Adapters/Monitor Types
Video – Table # 1
Monitor Terminology and Theory
• Monitor size
– No industry standard, but traditionally defined as the diagonal length
of the picture tube (or CRT)
– Most common sizes are 15-inch, 17-inch, and 21-inch
• CRT (Cathode Ray Tube)
– Main part of the monitor
– Commonly referred to as the picture tube
– Covered by the monitor case which may not allow all of it to be viewed
• VIS (Viewable Image Size)
– Listed by many manufacturers as the viewable area of the CRT to
clarify the monitor size
Monitor Terminology and Theory
• Electron gun
– Directs a beam of electrons at a phosphorous dot on the back of the monitor
tube
• Some monitors have 3, one each for the colors red, green, and blue
• Other monitors utilize only 1 to direct the 3 color beams
– When the beam hits the phosphor, the dot glows on the front of the screen
• All figures, icons, and letters are made up of these glowing dots
• Dot triad (or dot trio)
– 3 phosphorous dots grouped together at each location on the screen
– Consists of 1 dot each for red, green, and blue
– Electron beam hits the dot(s) with varying intensity causing the phosphor to
glow and create different color intensities
Monitor Terminology and Theory
• Shadow mask
– A metal plate with holes that keeps the electron beam directed (or focused) at
the proper dot
– Variations include:
• The Invar shadow mask by Phillips Magnavox (reduces heat problem of
traditional mask)
• A mask used in NEC’s Chromaclear monitors that has elliptical slots
instead of holes
• Pixel (short for picture element)
– One dot on the screen created by the convergence of the phosphorous dot
trio
– Smallest displayable unit on the monitor screen
Monitor Terminology and Theory
Video Theory of Operation
Video – Figure # 2
Monitor Terminology and Theory
• Picture cell
– The single image created by 3 different colored phosphorous dots
• Dot pitch
– The distance between like-colored phosphorous dots on adjacent dot
triads
– Measured in millimeters
– Commonly include .39mm, .35mm, .28mm, .26mm, .25mm
Note: The lower the monitor’s dot pitch, the smaller the distance
between the dot triads. The lower the number, the better the picture
quality. For example, a monitor with a .28mm dot pitch is better than
one with a .35mm dot pitch.
Monitor Terminology and Theory
Dot Pitch
Video – Figure # 3
Monitor Terminology and Theory
• Aperture grill
– Used in Sony Trinitron monitors as an alternative method to the shadow mask
using very fine vertical wires instead of holes
– Allows more electrons to reach the screen, producing deeper color intensities
– Requires horizontal stabilizing wires to keep the fine vertical wires from
vibrating or moving and these can be viewed on bright images
– Dot pitch is relevant to horizontal direction only as the phosphor is coated in
vertical strips rather than dots
– Some high quality CRTs using the aperture grill reach a dot pitch smaller than
.22mm
– Minimum acceptable dot pitch for the aperture grill is .25mm
– Some dot pitch descriptions include:
• Grill pitch, horizontal mask pitch, and mask pitch
Monitor Terminology and Theory
Aperture Grille
Video – Figure # 4
Monitor Terminology and Theory
• Resolution
– The maximum number of pixels of a monitor
– Illustrated by two values separated by an x, meaning by
• Example of a monitor resolution is 640 x 480
– 640 = # of pixels that fit horizontally, or across the screen
– 480 = # of pixels that fit vertically, or up and down, on the screen
– SVGA is often described as 800 x 600, and UVGA as 1024 x 768 (not definite,
but generally accepted by the industry this way)
– Depends on the combination of the monitor and adapter
Note: The higher the monitor’s resolution, the smaller the pixel appears on the
screen. Picking a higher resolution will make Windows icons appear smaller.
This is often misunderstood, with many users setting their resolution too high
relative to their monitor size, making the icons appear too small.
Monitor Terminology and Theory
Recommended Resolutions
Video – Table # 2
Monitor Terminology and Theory
• Refresh Rate
– The maximum number of times a screen is scanned, or redrawn, in one
second, measured in Hz
– Pixels do not stay excited very long and must be refreshed to stay lit
– The electron beam starts from the top left corner and moves horizontally to
the right, at the end of the row, it turns off briefly and moves to the left of the
next row down until the necessary pixels on the whole screen have been
energized again. The video card directs this motion and instructs it on which
pixels need to be lit again
• Horizontal scanning frequency (HRR or Horizontal Refresh Rate)
– The speed which the beam traverses the screen and draws one line
– Measure in kilohertz (kHz) as determined by the video adapter
– Range from 35 to 90 kHz
Monitor Terminology and Theory
• Vertical scan rate (VRR or Vertical Refresh Rate)
– The number of times the electron beam draws from the top-left corner, to the
bottom-right corner, and back again to the top-left, drawing the entire screen
– Determined by the capabilities of the video adapter and the monitor
• Multi-scan monitor (also multi-synch or multiple frequency)
– Can lock onto different vertical and horizontal scanning rates
– More flexible because they can connect to a variety of adapters
• Interlacing
– A monitor that uses interlacing scans first odd numbered pixel rows, then
returns for the even ones on each vertical refresh
– Causes a flickering screen, but is less expensive than non-interlaced, which
scans al horizontal rows on each vertical refresh
LCD (Liquid Crystal Display)
• LCD (Liquid Crystal Display)
– A video technology used with laptops and flat screen monitors
– The two types of LCD are passive matrix and active matrix
• Passive matrix (least expensive)
– Made up of rows and columns of conductors, with the pixels located at
each intersection
– Each pixel has 3 cells in a color monitor, one each for red, green, and
blue
– Also called STN (SuperTwist Nematic) for a technology that twists
light rays to improve the display’s contrast
– Not as bright as active matrix displays
LCD (Liquid Crystal Display)
• Active matrix (more expensive)
– Have a transistor for each pixel
– 3 transistors for each pixel, one each for red, green, and blue
– Number of transistors determine maximum resolution
– Another name is TFT(Thin Film Transistor)
– Brighter than passive matrix
• Flat panel
– Monitors for desktop computers that use LCD technology
– Digital, but some can work off of an analog adapter
LCD (Liquid Crystal Display)
• DVI ( Digital Video/Visual Interface)
– Interface used on an AGP adapter with the better flat panel monitors
– DVI port is a 24-pin connector
Note: Using an analog adapter is not recommended for connecting a flat
panel display because signal must be converted from digital to analog
for the adapter and back to digital by the monitor for the display
output.
LCD (Liquid Crystal Display)
Flat Panel vs. Regular-Sized Monitor
Video – Figure # 5
LCD (Liquid Crystal Display)
Video Adapter with DVI Port
Video – Figure # 6
Monitor Preventive Maintenance
• Cleaning the screen may be performed using anti-static wipes
• Do not get liquid near the edge of the CRT, it may leak into the monitor
• The case may be cleaned with a soft dampened cloth and one of the
following:
– Mild household detergent, glass cleaner, or isopropyl alcohol
– Spray cleaner onto the cloth, not the monitor
Note: Never remove the monitor case unless specifically trained in
monitor repair. Hazardous voltages may be present, even if the
monitor is off and unplugged.
Monitor Energy Efficiency
• DPMS (Display Power Management Signaling)
– Standard produced by VESA
– Defines the signals used to tell the monitor to reduce power
• APM (Advanced Power Management)
– Developed by Microsoft and Intel
– Allows BIOS to control hardware power modes
• ACPI (Advanced Configuration and Power Interface)
– Microsoft introduced on Windows 98, 2000, and XP
– Expands control to power modes for CD-ROMS, network cards,
printers, and other attached devices.
Monitor Energy Efficiency
Power Management Properties Windows
Note: Only use the energy efficiency
CMOS settings, energy efficient
software, or Windows’ energy efficient
settings if the monitor supports them. A
non-green monitor can be damaged if
you enable the settings. Check the
monitors documentation to determine if
it supports energy efficiency modes.
Screen Savers
• Screen Saver
– Changes the image on the monitor constantly to keep any particular
image from burning into the screen.
– With old monitors, they were a necessity to prevent damage
– New monitors’ high refresh rates make screen savers unnecessary
– Provide a form of entertainment for the computer user
– Provide password protection for users
Video Adapters
• Video adapter
– Controls most of the monitor’s output
– Use the ISA, EISA, VL-bus, MCA, PCI, or AGP interface
– Bus connects the video card to the microprocessor
– The bus interface, microprocessor, chipset, and video adapter can affect the
speed of video transfer to the monitor
– Upgrading the chipset, microprocessor, and video adapter can improve video
performance
– Some adapters have a video processor
Note: One way of speeding up a video adapter’s performance is to shadow the
video adapter’s ROM chip through the computer system’s setup program.
This means the software inside the ROM chip is copied to RAM for faster
access to the instructions.
Video Adapters
• Video processor (also called a video coprocessor or video accelerator)
– Assists the video communication between the adapter and the
microprocessor
– Can be up to 64- or 128-bit processors
– Controls many of the video functions otherwise controlled by the
microprocessor for faster performance.
Video Memory
• VRAM (Video RAM) and WRAM (Windows Accelerator Card RAM)
– Dual-ported memory (have separate read/write paths) and can written
to and read from simultaneously
• RDRAM (Rambus DRAM), SGRAM (Synchronous Graphics RAM), and
MDRAM (Multi-bank Dynamic RAM)
– Single-ported memory that cannot be written to or read from
simultaneously
Note: The amount of video adapter memory will determine the number
of colors available at a specific resolution.
Video Memory
Bits Required for Colors
Video – Table # 5
Video Memory
Video Memory Requirement Examples
Video – Table #6
Installing a Video Adapter
• Make sure you have the correct interface type and an available motherboard slot
• Gather required tools
• Download the latest driver for the video adapter including any video BIOS
updates
• Make sure the adapter has the driver required for the operating system you’re
using
• Power off the computer
• Open the computer and install the video adapter in the proper slot
• Connect the monitor to the external video connector
• Power on the computer and install the video driver per the manufacturer’s
instructions and the operating system’s controls
Troubleshooting Video
• Try simple solutions first:
– Check power cables and that monitor is turned on
– Ensure monitor cable is securely connected to the video adapter
– Check settings and controls
– Check to see if any new software or hardware has been installed, or if
an upgrade has occurred
– Replace subsystem components with known good ones
• Raster
– A monitor’s brightness pattern – a bright white screen
– If it appears, most likely the problem is the video adapter
Troubleshooting Video
• Flyback transformer
– Component that boosts the voltage to the high levels the CRT
requires
– Frequently goes bad
– Check prices before replacing, may be more cost-effective to replace
entire monitor
• Degausser (or degaussing coil)
– Can remove CRT magnetization
Windows Video Problems
• Most likely problems are caused by video driver or compatibility issues
with the chipset, video card, and operating system
– Follow a reasonable, patterned approach to ensuring:
• Components are functional
• Drivers are correct and the most up-to-date
• Windows settings are correct