Video
What it is
• Collection of parts and software designed
to put a picture on a screen
• Monitor shows you what is going on with
software (and OS)
• Primary output device for PC
• Video card, or Display Adapter handles
communication between CPU and monitor
CRT Monitors
• A LOT of high voltage, resist the urge to
take it apart!
Electron
Beam Electron Guns
(3)
Shadow Mask Yoke
Phosphor Coating on
inside of tube
How it works
• Electron gun fires a beam of electrons
• Path of electrons is shaped by the yoke
(bent)
• Electrons strike the phosphors and make
them glow
• Phosphors have persistence so they
continue to glow after electron beam stops
Refresh
• Electron beams sweep from upper left to
right – across then down to next line
Raster Line
Horizontal
Refresh Rate
Vertical Refresh Rate
Adjustments
• Try not to do it; the manufacturer knows
better than you do.
• The video card “pushes” the monitor –
that’s where changes are made
Resolution
• Number of horizontal pixels by the number
of vertical pixels
640x480
800x600
Aspect Ratio
• Ratio of horizontal to vertical pixels
• 4:3 for CRT and many LCD monitors
• 16:9 for wide-screen monitors (same as
theaters use)
Dot Pitch
• One significant measure of value of
monitor: more expensive = lower number
Dot Pitch
In millimeters
Dot pitch of .28 or less gives a nice, sharp image.
At .35 it seems like you can see the dots (TV image)
LCD (Passive) Monitors
• Light travels in waves (one definition)
• Liquid crystals tend to align with grooved
surface or magnetic field.
• Aligned crystals will allow light to pass
through (no electrical potential)
• Apply electrical potential and no light
passes through
• This is digital, rather than analog of CRTs
LCD Pixels
Passive Matrix
• Wires in “Y” and “X” directions
• Voltage on wires allowed light to pass
• Slow response: “smeared” image
• Laptops for early years
Thin Film Transistor (TFT)
• Also called Active Matrix
• Vast improvement over Passive Matrix
• One, or more, transistors control each
color dot
• Brighter, better contrast, faster, more
colors and wider viewing angle
Resolution
• LCDs have a native resolution – looks best
there
• Mine is 1280x1024 @ 60 Hz (19”)
• Can run lower resolution, but picture
sharpness suffers – even with anti-aliasing
• Object size does not “grow” quite as
quickly as monitor size
Other Measures
• Contrast Ratio: Bright to dark 700:1
• Brightness: 400cd/m2
• Response time: 4 ms
Projectors
• Lumens = brightness of projected image
• Throw = size of image at a certain
distance from screen
• Lamps get hot quickly, need fan to cool
them and are expensive to replace
Common Features
• Size does NOT belong here. CRT’s are
smaller (for same size) than LCDs
Viewable
image size
15.5”
CRT
LCD
Monitor size 15” screen
17” size
Connections
• CRTs only use analog, 15-pin connector
• LCDs can use either analog or digital
connector
• Video cards use RAMDAC to convert
digital to analog for display
Graphics
Processing
Unit
Power Conservation
• Turn off the CRT to reduce power
consumption or when you walk away
• Burn-in of image is a long lost art. Used to
happen on older monitors.
• Typical CRT = 120-200 watts
Adjustments
• On/Off switch
• Brightness and contrast buttons (CRT)
• Menu activate/select button for on-board
menu system
Video Cards
• Three parts: Video RAM, video processor
circuitry and RAMDAC
• Early cards just shuffled BIOS bit-maps to
the screen (put a dot here, and one there)
• Used small amounts of RAM
• 80 characters by 24 rows
Color Depth
• 16 colors = 4 bits
• 256 colors = 8 bits
• 64k colors = 16 bits
• 16.7 million colors = 24 bits
• VGA mode is 640x480 @ 16 colors
• Please don’t memorize table 17-1!
AGP
• Accelerated Graphics Port
• Single slot, never two
• 66 MHz, 32-bits wide
• Uses strobing for 2x, 4x and 8x transfers
on each clock cycle
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On its own bus
Video RAM
• VRAM – Video RAM – allowed read/write
at same time
• WRAM – Windows RAM – optimized for
moving windows around – died quickly
• Replaced with DDR, DDR2, GDDR3 and
GDDR4 SDRAM
Graphics Processor
• Can be done by CPU (for on-board
graphics) but not efficient
• ATI and NVIDIA make most GPUs
• New GPUs come out often; a challenge to
keep up with models
• More dollars = newer GPU
PCIe x16
• Serial communication
• 16 “lanes” or channels
• Replacement for PCI bus as cards
become available (x1 and x4 variants)
• SLI – its either Scan Line Interleave or
Scalable Link Interface – two video cards
(matched set)
Installation
• Read the install manual first, not later!
• Remove old drivers first. Reset system to
VGA mode on existing card
• Install new drivers
• Install new card
• Finish driver installation
• Try to keep other cards away from video
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Display Applet
11
Drivers
• Windows can crash and require a re-install of
OS simply by installing a new video card and not
uninstalling the old video drivers first.
• Go to Add/Remove Programs to uninstall video
driver. (Step 1)
• Insert CD for new card and start driver
installation. (Step 2)
• Stop system where directed and install card.
(Step 3)
• Finish driver installation.
If the Card went bad
• Can’t get to Add/Remove programs.
• Have to install card to get working display.
• Start up in Safe Mode; you can delete
drivers in this mode.
• Load drivers for new card. I lucked out as
Windows recognized card and had drivers.
Color Correction
• Also called color temperature
• Device that fits on monitor and looks at the
display
• Graphic artists use these so they can set
colors exactly.
3-D Games
• Started with sprites – still images of an
object; multiple images used to create
depth
• True 3-D uses vertices to define points on
an object which are then “edged” with flat
polygons
• Last step is to cover the edges with
texture(s)
• Takes a lot of computing horsepower
6
3-D Video Cards
• Graphical Processing Units (GPU) to do
the 3-D rendering tasks
• Lots of RAM to store textures
• We need standardized command sets to
allow communication between game and
video card:
– OpenGL for UNIX, then PC’s
– DirectX API (Application Programming
Interface) from Microsoft
DirectX
• Supports Video, Sound, Network
connections and Input devices
• Provides common interface for games –
don’t have to write to specific video card
• Vista wants DirectX 10, not 9.0c which
most of us have
4
Troubleshooting Cards
• Video cards seldom fail, but might
• Often a driver issue – Windows cares about
video card, but not monitor
• You can go to Add/Remove Programs to delete
video driver
• Try Safe Mode to see if problem “goes away” –
then you know it is driver (or setting)
• Try another monitor – often a hassle, but well
worth the time
• Check the settings for resolution, refresh & color
2
Troubleshooting CRTs
• Try another monitor, then get another
monitor – don’t try to fix them, the dollars
don’t work out
• Check the signal cable connections –
loose cable will color the screen or miss
colors
• Client with no video turned out to be failure
to start up
And then…
• Plasma Display Panels
– Large screen sizes
– Miniature florescent lights – three per pixel
– Uses as much power as CRT
– First ones had bad habit of burning out
• Digital Light Processing (DLP)
– One mirror for each pixel
– Don’t know how they move, but they do