video and audio systems chapter 8 ch 81. video systems and display aspects video systems consists of...

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Video and Audio Systems

Chapter 8

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Video Systems and Display Aspects

• Video systems consists of the display (monitor) and the Adaptor (video or graphics card)

• All displayed colors are based on red, blue, and Green the number of bits used to represent each color determines the number of possible displayed colors

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Video Systems and Display Aspects

• Color Display values:

• Create custom colors in MS Paint

Color Display Values Number of Colors

8 - bit 256

16 – bit (true color) 64,536

24 – bit (true color) 167,777,216

32 – bit (true color) 4,294,967,296

48 – bit (deep color) 281,474,976,710,656

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Video Systems and Display AspectsDisplay Resolution• Resolution is the amount of detail that a monitor is

capable of displaying– Also used to describe printers, cameras, and graphic

devices• Pixel is the smallest unit of color a screen display– VGA screen has 640 x 480 pixels or 307,200 pixels

• Monochrome displays only one color usually green or amber (first computer display)– Screen resolution is 720 x 350 – Very sharp and clear for text only displays

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Video Systems and Display Aspects• Color/graphics adapter (CGA - 1981)

– 4 colors in 320x200 resolution – 2 colors in 640x200 resolution– Color palette of 16 colors

• Enhanced graphics adapter (EGA - 1987)– 16 colors in 640x200 resolution– Color palette of 64 colors

• Video Graphics Array (VGA - 1987)– 16 colors in 640x480– Color palette of 256 colors

• Super VGA (SVGA 1988)– Number of displayed colors based on amount of memory– Resolutions up to 1600x1200– Color palette of 16 million colors

• Extended Graphics Array (XGA -1990)– 65,536 colors @ 640 x 480 or 256 colors @ 1024x768– Also supports older graphic standards

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Video Systems and Display Aspects• Common Resolutions:

• When in safe mode Windows uses VGA standard

Resolution Acronym Designated

640 x 480 VGA Video graphics array

800 x 600 SVGA Super video graphics array

1024 x 768 XGA Extended graphics array

1280 x 1024 UVGA Ultra video graphics array

1400 x 1050 SXGA Super extended graphics array

1600 x 1200 UXGA Ultra extended graphics array

1920 x 1200 WUXGA Wide ultra extended graphics array

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Types of Video Displays

Two most common types of displays:• Cathode Ray Tube (CRT)• Liquid Crystal Display (LCD)Television technology and monitor technology are merging• Gas Plasma Display

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Types of Video Displays• Cathode Ray Tubes (CRT) is a glass tube which electrons

are used to produce a picture– Glass tube is a vacuum with a phosphorous coating at one end– Three electron guns at back of tube shoot electrons at screen– Magnets (deflection yoke) aim electrons at specific parts of

screen– Beams pass through a metal mesh (shadow mask) with hole

that limit area of screen hit with electrons – Electron his colorized phosphorous coating and glows for a

short time after the beam moves on (persistence)– By mixing intensities of three colors a complete spectrum of

colors can be produced

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Types of Video Displays• CRT build up magnetic residue that distort

electron beams and thus the picture will be distorted.

• Degaussing removes magnetic build up– Many monitor have a degasser built in just push button– Can manually degauss a monitor using a magnet

• Monitor size is determined by measuring diagonally across the screen (actual viewing area is about 10% less)

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Types of Video Displays• Dot Pitch : the distance measured in millimeters between two color

dots of the same color on a screen– Smaller dot pitch higher quality– Acceptable standard is .28mm to .25mm

• Refresh Rate: the rate the beam sweeps vertically across the screen– Screen flicker can be eliminated by speeding up the refresh rate– Higher refresh rate take time away from CPU

• Raster rate: how fast electron beam sweeps from left to right across the screen– A complete screen sweep is called a field– Field are completed about 60 time a second– Interlaced scan do every other line (i.e. odds first the goes back an does

evens) 1080i– Progressive scan does line by line 1080p

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• Liquid Crystal Display (LCD) are based off of polarized light and the effect of electricity on a crystal– Polarized light is light energy composed of light

beams with matching wage angles– When electricity is applied to crystals they “twist”

the more electricity the more the twist

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• How LCD work:1. A backlight generates light 2. Light passes trough polarizing filter3. Light passes though crystals4. Light passes through color filter5. Light passes though second polarizing filter6. Creating light on screen7. If crystal is twisted by electrical charge less or no light

will get through second filter creating dimmer or dark spot on screen

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Types of Video DisplaysLCD require backlighting, light is created by CCFL or LED• CCFL is cold cathode fluorescent lamp tiny version of the fluorescent lights

seen in everyday life– One CCFL at top and one at bottom of display– Requires high voltage AC (up to 1200 Vac) – If used on battery operated device then a inverter must be incorporated into the

device• Inverters convert DC to AC

• LED or light emitting diode an electronic device that emits light when dc voltage is applied– More compact (no inverter)/less fragile (no glass tubes)– Edge lit or matrix backlit

• OLED Organic Light Emitting Diode– Carbon based rather than crystal based– Thinnest possible display– Flexible display

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• Passive-Matrix Display: Consists of a grid of semitransparent conductors that run to each crystals. voltage is applied briefly and relies on screen persistence and a fast refresh rate

• Active-Matrix Display: each pixel in the grid has its own transistor and has a constant supply of voltage– Much better picture than passive display

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Types of Video Displays• Contrast Ratio: the ratio that describes contract

between the darkest and lightest pixel in the image the higher the ratio the better color will be represented the picture

• Brightness: measured in candela is the brightness levels of the display 200 cd/ - 500 cd/m

• Viewing Angle: measure of the angle at which a person can adequately view an image on the display without it looking distorted (150 degree min best are 170 or better)

• Pixel Pitch: like CRT dot pitch

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• Native resolution: resolution that matches the pixel design of the display (i.e. if a display has a native resolution of 1280 x 1024 it will display the best image at 1280 x 1024resolution)

• Response Time: the amount of time it takes to display an image after a signal is sent to the transistor controlling that pixel

• Monitor Size: measure diagonally like CRT but no 10% loss of viewing

• Aspect ratio: ratio of display areas width & Height– TV 4:3– HDTV 16:10

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Advantages of LCD over CRT:– LCD are smaller, lighter, thinner– LCD are more economical to use (less

power)– LCD produce less heat– LCD produce more detailed images– LCD Produce less electromagnetic

interference

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Trouble Shooting Video Displays

NEVER OPEN A MONITOR CASE EXTREAMLY HIGH VOLTAGE IS PRESSENT EVEN IF UNPLUGED (CAN ACT AS A CAPACITOR)!!!• Dark displays or area on LCD is indication of

backlight failure - replace monitor• Persistent black or white spot is indicator of failed

transistor – replace monitor• Most display failure require monitor replacement as

there are no serviceable parts inside a CRT or LCD

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Trouble Shooting Video Displays

Before replacing monitor Check the following:1. Check monitor is turned on2. Check power cord connections3. Check wall outlet voltage4. Check video cable5. Check video card6. If motherboard doesn’t use a video card try

installing one (may not work )

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Cleaning Video Displays

• Never clean while energized (unplug)• Use dry lint free cloth (to remove dust)• Use damp lint free cloth (to remove smudges)• Avoid detergents will leave film• Avoid paper towels on LCD (can scratch display screen)

• NEVER use acetone, ethyl alcohol, ammonia, chloride or chlorine

• Avoid placing display in direct sun (heat build up)• Avoid spraying liquid onto screen (spray on rag)

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Video Adapter Cards

• Monitor attach to video adaptor card or directly to motherboard

• Heart of video controller is the digital to analog converter (DAC)– Can be one chip that controls all three colors– Can be three chips on for each color (better)– Video performance also depends on amount of

available memory that can be used to process images

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Video Adapter Cards Types

• Accelerated Graphics Port (AGP) a slot strictly for AGP cards designed with graphics as a priority (Obsolete) looks like PCI slot only in reverse.

• PCI-X (PCI Extended): normally not used with video cards (older systems)

• PCIe: Newest preferred video card technology– Allows multiple video cards

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Video Adapter Cards Types• Multiple Video Cards using two or more cards for graphical

intensive applications– Split frame rendering

• 2 cards each card renders half the image• 4 cards each card renders a fourth of the image

– Alternating-frame rendering • Each card is responsible for every other frame

• SLI (Scalable link interface)– Used to require matching cards– Now performance is limited to slowest card

• ATI Crossfire owned by AMD– cards don’t have to match – One in the master card the others are slave cards– 170-180% rate (Not doubled)

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1. Back up files2. Power off computer /unplug3. Read installation procedures4. Take antistatic precautions (wrist strap)5. Check for debris in slot 6. Insert card7. Connect monitor /turn on PC8. If windows can’t find driver load drivers9. Follow screen prompts while loading drivers10. If installation fails

1. Reread instructions2. Check for bent pins3. Check manufactures web sites (card’s and motherboard’s)

11. If all well close case and restartNOTE: some high end video cards require their own power tap from the power supply you may have to upgrade the power supply before video upgrade!

Installing Video Adapter Card

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Graphics Coding• Bitmap (BMP): also called a raster image is a

graphic standard for uncompressed encoding of images the number of bits used to encode the exact location and color of the pixels in the image (used in programs like Paint)

• Vector Graphics: based on a series of mathematical formulas that can be converted into geographical shapes can be resized without losing quality (used in draw programs)

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Graphics Coding• Graphic Compression: Graphic applications require

a lot of memory. Note that many pixels and colors are repeated in images.

• Run Length Encoding (RLE): replaces a series of repeated pixels with a single pixel and the length of the series (run)

• Some compression techniques can achieve a compression ratio as high as 12:1

• JPEG or JPG is the most common photo compression format

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Audio

Sound is comprised of vibrations that are put in motion through a medium such as air.• Sampling is measuring an analog signals at a

regular interval – High frequency sampling (frequent samples taken)

results in better quality sound– 8 bit sound cards are limited to 256 levels– 16 bit sound cards 65,536 levels-100 per second– 24 bit cards uses 16,777,216 levels- 99,000 per

second

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Audio• Musical Instrument Digital Interface (MIDI)

Files: a file standard developed for music synthesizers. Music is electronically simulated on a chipset rather than recorded–Advantage MIDI is universal file format–Disadvantage is music may sound artificial to

the ear

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Audio Devices

• Microphone is a simple electronic device used to convert sound waves into analog signals that are converted into digital signals when it reaches the sound card.

• Speakers use analog signal from the sound card to create sound – Sound cards only put out 2 watts of power– Passive speaker use that power to generate sound– Active speakers have amplifiers to increase power

used to generate sound

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Installing a Sound Card1. Back up files2. Power off computer /unplug3. Read installation procedures4. Take antistatic precautions (wrist strap)5. Check for debris in slot 6. Insert card7. Check if there are any cables that might interfere with the sound

card8. Connect the speakers to the PC / turn on speakers 9. Check for latest drivers at sound card manufactures website10. Power on PC /check sound

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Multimedia• Multimedia is a format that combines audio with video• Codecs (contraction of compression and decompression)

– any hardware or software or combination that compress and decompress software

– MPEG, Quicktime, AVC, and MP3• Moving Picture Experts Group(MPEG)

– MPEG1 Video tape quality– MPEG2 High compression PC CD video– MPEG3 (MP3) music– MPEG4 current video standard DVD /Blu-Ray

• Buffering: Technique for downloading and playing a file without skips or quiet spots- constantly searching alternate download paths.

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Building a Custom ComputerWhen building a Custom Computer ask the following important questions:1. What will the computer be used for?2. How much are your willing to spend?• Item to consider when building a computer

– Motherboard– Power supply– Video card– Display– Sound card– TV tuner card– Mass Storage– Number of ports required– Special application software

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Video Performance Info and Tools• Type “windows Experience” in search box and look

for the result check windows experience index– Rates five major components on a scale of 1.0 – 7.9– Processor, RAM, Graphics, gaming and graphics, and

primary hard disk– 2.0 to 2.9 general computing– 3.0 to 3.9 can play digital TV– 4.0 to 5.9 multiple software applications– 6.0 to 7.9 intense graphics, 3D graphics, HD TV

• DirectX Diagnostic Tool: Makes simple checks of computer audio and video systems

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End of Chapter 8

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