Video

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Video

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Section Objectives

After completing this section you will be able to: Describe the components of the video subsystem Differentiate among monitor types including laptop displays Define basic monitor theory and terminology Describe issues regarding video memory Install a video adapter and associated software

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Video Overview

Video should be considered a subsystem that consists of:– the monitor– the electronic circuits which send the monitor

instructions– the connecting cable

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Video Overview

Video – Figure 10.1

Video subsystem

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Types of Monitors

Different ways of classifying monitors:– Color or Non-color– Analog or Digital– Type of video adapter used

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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

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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.

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Types of Monitors

Video – Table 10.1

Video adapters/monitor types

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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.

– 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.

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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.

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Shadow mask

– A metal plate with holes that keeps the electron beam directed (or focused) at the proper dot.

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.

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Video theory of operation

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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.

– The lower the monitor’s dot pitch, the smaller the distance between the dot triads. The lower the number, the better the picture quality.

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Dot pitch

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Aperture grill

– Used in monitors and televisions 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.

– Minimum acceptable dot pitch for the aperture grill is .25mm.

– Some dot pitch descriptions include:

Grill pitch, horizontal mask pitch, and mask pitch.

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Aperture grille

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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

– 480 = # of pixels that fit vertically

– Depends on the combination of the monitor and adapter.

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Refresh Rate

– The maximum number of times a screen is scanned, or redrawn, in one

second, measured in Hz.

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.

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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. 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 all horizontal rows on each vertical refresh.

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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.

– Not as bright as active matrix displays.

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Active matrix (more expensive)

– Have a transistor for each pixel.

– Number of transistors determine maximum resolution.

– Also known as TFT(Thin Film Transistor), which use three transistors per pixel, one for each color.

– Brighter than passive matrix. Flat panel

– Monitors for desktop computers that use LCD technology.

– Viewing area the same as the LCD measurements.

– Take up less desktop space, and use less power than CRTs.

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Flat panel versus regular-sized monitor

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Video Ports

DVI ( Digital Video/Visual Interface)– Interface used on an AGP PCI-E adapter with the better flat panel

monitors.– DVI port is a 24-pin connector.

Single link connection – Allows video resolution up to 1920x1080.

Dual link connection – The use of more pins sends more single allowing for higher resolution.

DVI-D – Type of DVI used for digital connectivity only. DVI-I – Type of DVI used for both digital and analog monitors. HDMI (High-Definition Multimedia Interface) - An upgrade

to DVI which carries both video and audio over the same cable.

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Video Ports


Video Adapter with S-video (TV Out), DVI and VGA Ports

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Projectors

Projector – Projects what is being displayed on the computer onto a larger screen.

The connections for a projector are similar to those of a video card.

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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.

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Monitor Energy Efficiency

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, XP, and Vista.

– Expands control to power modes for CD/DVD drives, network cards, printers, and other attached devices.

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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.

– LCDs do not need the use of screen savers as they use a different technology than CRTs.

– Provide a form of entertainment for the computer user.

– Provide password protection for users.

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Video Adapters

Video adapter

– Controls most of the monitor’s output.

– Use the PCI, AGP, or PCI-E 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.

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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.

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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.

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Video Memory


Bits required for colors

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Video Memory


Video memory requirement examples

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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.

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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 tips can be found on page 368 in the book.

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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.

Documents

Video