video terms and definitions. chapter objectives after completing this chapter you will: describe the...

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 – Figure # 1

Video Subsystem

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 – Table # 1

Video Adapters/Monitor Types

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


• 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


• 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



Video Theory of Operation


• 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.



Dot Pitch


• 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



Aperture Grille


• 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.


Video – Table # 2

Recommended Resolutions


• 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


• 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


• 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


• 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.



Flat Panel vs. Regular-Sized Monitor



Video Adapter with DVI Port

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

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.

Power Management Properties Windows

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

Video – Table # 5

Bits Required for Colors

Video Memory

Video – Table #6

Video Memory Requirement Examples

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

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