Video

1. Video Chapter 11

2. Overview • In this chapter, you will learn to • Identify variations of CD media technology • Identify variants in DVD media technology • Install CD and DVD media drives • Troubleshoot CD and DVD media drives

3. Warning Opening up a monitor can be deadly! Even when the power is disconnected, certain components inside a monitor retain a substantial voltage for an extended period of time. If you accidentally short one of the components, it could actually kill you!

4. CRT and LCD Displays

5. Video • Video consists of two devices - the video card (or display adapter) and the monitor • The video card consists of two distinct components – one to take commands from the computer and update its own onboard RAM, and the other to scan the RAM and send data to the monitor

6. Video Monitor Types • Cathode ray tube (CRT) • Liquid crystal display (LCD)

7. CRT • All CRT monitors have a cathode ray tube (CRT), which is a vacuum tube • One end of this tube is a slender cylinder that consists of three electron guns • The wide end of the CRT is the display screen

8. CRT • When power is applied to one or more of the electron guns, a stream of electrons is generated • This stream is subjected to a magnetic field generated by a ring of electromagnets called a yoke • The phosphor coating, when struck by the electron beam, releases energy as visible light • The phospors continue to glow momentarily after being struck – called persistence.

9. Horizontal Refresh Rate (HRR) The speed at which the electron beam moves across the screen Vertical Refresh Rate (VRR) The amount of time taken by the monitor to draw the entire screen and get the electron beam back to the start CRT Refresh Rates Videodata is displayed on the monitor as the electron gun sweeps the display horizontally, energizing appropriate areas on the phosphor coating.

10. CRT Refresh Rates

11. CRT Refresh Rates • Video cards push the monitor at a given VRR, and then the monitor determines the HRR • If the VRR is set too low, you’ll see flicker • If it is set too high, you’ll have a distorted screen image and may damage the monitor • Multisync (multiple-frequency monitor) monitors support multiple VRRs

12. Phosphors • Phosphors and shadow mask: • Phosphors are dots inside the CRT monitor that glow red, green, or blue when an electron gun sweeps over them • Phosphors are evenly distributed across the front of the monitor One group of red, green, and blue phosphors is called a triad.

13. Shadow Mask • Shadow mask is a screen that enables the proper electron gun to light the proper phosphor • Electron guns sweep across the phosphors as a group • The area of phosphors lit at one time by a group of guns is called a pictureelement, orpixel

14. Resolution • Monitor resolution is always shown as the number of horizontal pixels times the number of vertical pixels • Some common resolutions are 640X480, 800X600, 1024X768, 1280X1024, and 1600X1200 • These resolutions match a 4:3 ratio called the aspect ratio

15. Dot Pitch • Dot pitch defines the diagonal distance between phosphorous dots of the same color. • The dot pitch can range from as high as .39 mm to as low as .18 mm • The lower the dot pitch, the more dots across the screen which produces a sharper, more defined image

16. Interlacing • Interlacing is the process in which the monitor sweeps or refreshes alternate lines of pixels on the display • It enables a low-end monitor to support faster refresh rates by giving it twice as much time to make a screen • Can create eyestrain and headaches

17. Bandwidth • Bandwidth defines the maximum number of times an electron gun can be turned on or off per second • Bandwidth is measured in megahertz (MHz) • How fast the monitor can put an image on the screen Maximum VRR = bandwidth  pixels per page For example, a 17-inch monitor with a 100MHz bandwidth and a resolution of 1024x768 can support a maximum VRR of 127 Hz: 100,000,000  (1024x768) = 127 Hz

18. LCDs • Liquid Crystal Displays • Thinner and lighter • Much less power • Flicker free • Don’t emit radiation • Called Flat Panels or Flat Panel Displays

19. Light • Travels in waves • Wavelength determines the color • If light came at us in one wavelength we would see just one color • We usually see many different wavelengths which looks white

20. How LCDs Work • Liquid crystals take advantage of the property of polarization • These crystals are composed of specially formulated liquid, full of long, thin crystals that always orient themselves in the same direction • The crystals act exactly like a liquid polarized filter

21. Liquid Crystal Molecules • LCD monitors use liquid crystal molecules that tend to line up together • These molecules take advantage of polarization • Fine grooves in a piece of glass will cause the molecules to line up along the grooves

22. Twisting Molecules • Use two pieces of glass with fine grooves oriented at a 90° angle • Molecules in the middle will try to line up to both sides – creating a nice twist

23. Add Polarizing Filters • Now add polarizing filters to both sides • The liquid crystal will twist the light and enable it to pass through • Adding an electrical potential will cause the crystals to try to align to the electrical field • To darken an area, apply a charge

24. LCD Matrix • Calculators use static charging to darken areas • LCD screens use a matrix of wires to provide a charge with greater precision

25. Passive Matrix • Use three matrices to produce color • Above the intersections of the wires add tiny red, green, and blue dots • The amount of voltage will allow different levels of red, green, and blue

26. Dual-Scan Passive Matrix • Passive matrix is slow and tends to create an overlap between pixels • Dual-scan passive matrix is faster by refreshing two lines at a time • Still used on some lower-end LCD panels

27. Thin Film Transistor (TFT) • Thin Film Transistor (TFT) is also known as the active matrix • It uses one or more tiny transistors to control each color dot • TFTs are brighter, with better contrast, can handle a variety of colors, and have a much wider viewing area

28. LCD Resolution • LCD panels come with a fixed number of pixels, which is always equivalent to a common resolution • LCD panels cannot display more than their pixel limitation • Lower resolutions are faked by estimating the pixels

29. Backlighting • Backlighting is needed to improve visibility • LCD uses a type of cold fluorescent light with prisms to spread light evenly across the screen • The measurement unit nits (candela/meter2) is used to quantify the brightness of the backlighting

30. Contrast Ratios • The contrast ratio is the difference between the darkest and lightest spots a monitor can display • CRT monitors can display 450:1 • LCD monitors display 250:1

31. Monitor Size • The size of CRT monitors is measured in inches • All monitors provide two numbers - the monitor size and the actual size • Viewable Image Size (VIS) is the measurement of the actual screen from one edge of the screen to the opposite diagonal side • LCD monitors just use the VIS value

32. CRT Connections • CRT monitors use a 15-pin, 3 row, DB type connector, and a power plug

33. RAMDAC • The Random Access Memory Digital-to-Analog Converter (RAMDAC) chip converts digital signals into analog signals for analog CRTs • LCD monitors use digital signals and need a circuitry for converting analog signals to digital (analog LCD monitor)

34. RAMDAC

35. LCD Connections • We now see LCD monitors that use digital video cards (no RAMDAC) and a totally different Digital Video Interface (DVI) connector • DVI-A (analog) • DVI-D (digital) • DVI-A/D or DVI-I (interchangeable) accepts either

36. Adjustments • The on/off button, the brightness and contrast button, and the onboard menu system on the monitor allow you to make a number of adjustments. • The physical screen adjustments and color adjustments are the two main functions provided by all monitor manufacturers

37. Power Conservation • Monitors that meet the VESA (Video Electronics Standards Association) specification for display power-management signaling (DPMS) can reduce power consumption by roughly 75 percent • Turning off the monitor with the power switch is the most basic form of power management. It is better to leave the monitor on if you have power management! • DPMS works with Windows Advanced Power Management (APM) or Advanced Configuration and Power Interface (ACPI) power management software

38. The Video Card

39. Video RAM stores the video image Video processor circuitry takes the information from the video RAM and displays it on the monitor The Video Card A video card, also known as the display adapter, processes information from the CPU and sends it out to the monitor.

40. Video RAM • Text video cards display only the 256 ASCII characters • For a screen with 80 characters per row and 24 rows, you would need 80 characters x 24 rows x 8 bits per character or 1,920 bytes of RAM • Graphics video cards could turn any pixel on or off • A resolution of 320 x 200 pixels would require 64,000 bits (1 bit per pixel = on or off) or 8,000 bytes of RAM • To add color you would need multiple bits to define the color • To display 256 colors it takes 8 bits. For true color (16.7 million colors) you would need 24 bits per pixel. Color depth is usually represented as how many bits (color depth of 24 bits) and not the number of colors.

41. Color Depth

42. Modes • Monochrome text, color text, monochrome graphics, and color graphics are the four different types of video cards that exist. Each of these is called a video mode • Modern video cards enable switching between modes • IBM and then VESA defined specific, uniform video modes for video cards

43. Video Cards and Standards • Monochrome display adapter (MDA) card • First text-only video card • Color graphics adapter (CGA) card • First-generation color display adapter that supported colors • Four-color screen offered 320x200 resolution

44. Video Cards and Standards • Enhanced graphic adapter (EGA) card • Resolutions of up to 640X360 with 16 colors in text mode, or 640X200 and two colors in graphics mode. Late 1984 • Professional graphic adapters (PGA) card • This standard offered 640X480 resolution, 3-D rotation, and 60-frames/second animation • Cost over $4,000 and used 3 ISA slots • Aimed at engineering community

45. Video Cards and Standards • Video graphics array (VGA) standard • 16 colors at a resolution of 640X480 pixels (1987) • Often referred to as the minimum display requirements on software packages • Extended graphics array (XGA) standard • 16-bit color at a resolution of 1024X768 • Super VGA (SVGA) standard • Extensible standard - meaning that VESA adds to the list as higher resolutions and deeper color depths develop

46. Memory Requirements • Different video modes require different amounts of RAM on the video card • The amount of video memory required at a given resolution and color depth is determined by multiplying the resolution by the number of bytes of color depth • 24-bit color uses 24/8=3 bytes per pixel • Example: 800x600 with a 24-bit color depth requires 800x600x3 =1,440,000 bytes of memory. If your display adapter does not have that much memory, then this mode would not be supported

47. Accelerated Graphics Port • AGP is a single special port, similar to a PCI slot, which is dedicated to video • Derived from the 66 MHz, 32-bit PCI 2.1 specification • Uses its own personal data bus (PCI is limited to 32-bit transfers at 33 MHz or bandwidth of 132 Mbps – it cannot handle some of the video demands), and supports pipelining (the steps required to process a command)

48. Graphics Processor • The most important decision in buying a video card is the graphics processor • Most video processors are made by • NVIDIA • ATI • Matrox • Third-party video card manufacturers use one of these video processors on their cards

49. Video Memory • The video RAM constantly updates to reflect every change that takes place on the screen • Low cost video cards ($50-$100) use standard DRAM for video data storage • DRAM needs to be refreshed 18.5 times per second. Also, the access/response time of DRAM is 50 nanoseconds or longer. These bottlenecks are overcome by: • Increasing the width of the bus between video RAM and the video processor • Using specialized RAM • Most of the graphics rendering and processing is handled on the card by the video processor rather than the CPU

50. Video Memory • The three styles of RAM specifically designed for video are: • Video RAM (VRAM) • Dual-port memory that can send and receive at the same time. • DRAM can only send or receive at a given time • Windows RAM (WRAM) • Dual-port memory that is slightly faster than VRAM • Synchronous graphics RAM (SGRAM) • Synchronized to the system clock • Extremely fast • Newer, generalized RAM types such as Double Data Rate SDRAM, are often used instead of the specialized video memory above