Lecture - 5

1. Lecture - 5 • Video Hardware : Video display technologies,

2. display device • A display device is an output device for presentation of information for visual.

3. A monitor or display (sometimes called a visual display unit) is an electronic visual display for computers. • The monitor comprises the display device, circuitry, and an enclosure. • The display device in modern monitors is typically a thin filter transistor liquid crystal display (TFT-LCD) thin panel, • while older monitors use a cathode ray tube.

4. Along with the mouse and keyboard, the video display is a vital part of the user interface of any computer. • Actually, it is a latecomer to computing; before CRT monitors came into general use, the teletypewriter was the standard computer interface—a large, loud device that printed the input and output characters on a roll of paper.

7. The first CRT displays used on computers were primitive by today's standards; they displayed only text in a single color (usually green), but to users at the time they were a great improvement, allowing real-time display of input and output data.

8. Over time, color displays were introduced, screen sizes increased, and LCD technologies moved from the portable computer to the desktop.

9. Today, PC video displays are much more sophisticated, but you must be careful when selecting video hardware for your computer. • A slow video adapter can slow down even the fastest and most-powerful PC. • Incorrect monitor and video adapter combinations can also cause eyestrain or be unsuitable for the tasks you want to accomplish. • The video subsystem of a PC consists of two main components: • Monitor (or video display). The monitor can be either a CRT or an LCD panel. • Video adapter (also called the video card or graphics adapter). On many recent low-cost systems, video might be built into the motherboard or included as part of this motherboard's chipset.

10. How CRT Display Technology Works • A monitor can use one of several display technologies. • The original display technology, and still the most popular, is cathode ray tube (CRT) technology—the same technology used in television sets. • CRTs consist of a vacuum tube enclosed in glass. • One end of the tube contains an electron gun assembly that projects three electron beams, one each for the red, green, and blue phosphors used to create the colors you see onscreen; • the other end contains a screen with a phosphorous coating.

11. When heated, the electron gun emits a stream of high-speed electrons that are attracted to the other end of the tube. • Along the way, a focus control and deflection coil steer(turn/push) the beam to a specific point on the phosphorous screen. • When struck by the beam, the phosphor glows. • This light is what you see when you watch TV or look at your computer screen. • Three layers of phosphors are used: red, green, and blue. • A metal plate called a shadow mask is used to align the electron beams; it has slots or holes that divide the red, green, and blue phosphors into groups of three (one of each color). • Various types of shadow masks affect picture quality, and the distance between each group of three (the dot pitch) affects picture sharpness.

13. A typical CRT monitor is a large vacuum tube. It contains three electron guns (red, green, and blue) that project the picture toward the front glass of the monitor. High voltage is used to produce the magnetism that controls the electron beams that create the picture displayed on the front of the CRT.

14. The phosphor chemical has a quality called persistence, which indicates how long this glow remains onscreen. Persistence is what causes a faint image to remain on your TV screen for a few seconds after you turn the set off.

15. Resolution : it is the amount of detail a monitor can have. • It is expressed as the number of horizontal and vertical picture elements that are present in the screen. • The more the number of pixels the more detailed is the image.

16. A triad in simplest terms is defined as a "group of three". • Dot Pitch: it is defined as the distance between the phosphor triads, • Measured from the centre of a phosphor dot in a given triad to the same colour phosphor dot in the next triad in relation to colour monitors.

17. Lecture - 6 • DVI • Digital signals for CRT Monitor.

18. The latest trend in CRT monitor design is the use of digital input signals using the same Digital Video Interface (DVI) standard used for LCD flat-panel displays. • Although several major monitor vendors announced support for DVI-I interfaces for their CRT monitors in 1999, most CRT monitors (except for a few 19'' or larger high-end monitors) continue to use the conventional 15-pin analog VGA connector. • CRT monitors that use the DVI-I connector—unlike the TTL digital displays of the 1980s that supported only a few colors—support the same unlimited color spectrum as analog CRTs. • Users benefit from digital displays because these displays can feature better picture quality, better signal reception, and precise auto setup. • Because most low-end and mid-range video cards still feature only analog (DB-15) VGA connectors, many of these monitors feature both analog and 20-pin DVI interfaces. • However, as all-digital LCD display panels that also use the DVI interface increase in popularity, analog VGA eventually might be replaced by DVI-based CRT and LCD displays.

19. The Digital Visual Interface (DVI) is a video interface standard designed to provide very high visual quality on digital display devices such as flat panel LCD computer displays and digital projectors.

21. DVI-D (single link) connector

22. DVI-I socket from the front

25. C1 Analog red   • C2 Analog green   • C3 Analog blue   • C4 Analog horizontal sync   • C5 Analog ground

26. DVI connector pins

27. The new form in the CRT monitor is the use of digital input signals using the same Digital Video Interface (DVI) standard used for LCD flat – panel displays and high end video graphics cards.

28. There are three types of DVI formats. They are: • A) DVI – D (Digital) • B) DVI – A (Analog) • C) DVI – I (Integrated Digital / Analog)

29. DVI – D format: • This is used for direct digital connections between the video cards and digital LCD monitors. • This provides a faster, higher quality image than analog. • Initially a digital video signal is produced by all video cards. • This digital video signal is converted to analog at the VGA output. • The analog signal travels in the monitor.

30. DVI – A format: • This format is used to carry a DVI signal to an analog display. • Example : CRT monitor.

31. DVI – I format: • The DVI – I format is an integrated cable, that is capable of transmitting either a digital – digital signal or an analog – analog signal.

32. The DVI formats are available in single or dual link connectors. • Single link cables use one 165 MHz transmitter • Whereas dual link cables use two 165 MHz transmitters. • A single link cable uses 2 separate 9 pin sets • A dual link cable uses a 24 pin set

33. In the single-link mode, it uses 3 different source synchronous data channels and a different clock channel. • In the dual-link mode it has 6 data channels and 1 clock channel. Moreover, it multiplexes 10 bits of data on each channel during one clock period. • The DVI standard is designed to carry up to 1.65 Gbps of video data per channel. • Thus a Single-Link DVI connection has total bandwidth of 4.95 Gbps.  • The dual link cable doubles the transmission power. • It provides an increase in signal quality and speed.

35. Lecture - 7 • LCD Panels, Video adapter types. Integrated Video/Motherboard chipset,

36. LCD Panels • Borrowing technology from laptop manufacturers, most major monitor makers sell monitors with liquid crystal displays (LCDs). • LCDs have low-glare, completely flat screens and low power requirements (5 watts versus nearly 100 watts for an ordinary monitor). • The color quality of an active-matrix LCD panel actually exceeds that of most CRT displays. • At this point, however, LCD screens usually are more limited in resolution than typical CRTs.

37. For example, a typical 15'' LCD panel (which offers about the same viewable area as a 17'' CRT display) has a maximum resolution of 1024x768, whereas a typical 17'' CRT might offer a maximum resolution of 1280x1024 or 1600x1200. • 17'' and 18'' LCD panels (comparable in viewing area to 19'' CRTs) have also become popular. • However, these larger LCD panels offer a maximum resolution of 1280x1024, whereas a typical 19'' CRT has a maximum resolution of 1600x1200.

38. A typical example of a 15'' LCD display panel.

39. How LCDs Work • In an LCD, a polarizing filter creates two separate light waves. • The polarizing filter allows light waves that are aligned only with the filter to pass through. • After passing through the polarizing filter, the remaining light waves are all aligned in the same direction. • By aligning a second polarizing filter at a right angle to the first, all those waves are blocked. • By changing the angle of the second polarizing filter, the amount of light allowed to pass can be changed. • It is the role of the liquid crystal cell to change the angle of polarization and control the amount of light that passes.

41. The liquid crystals are rod-shaped molecules that flow like a liquid. • They enable light to pass straight through, but an electrical charge alters their orientations and the orientation(direction) of light passing through them. • Although monochrome LCDs do not have color filters, they can have multiple cells per pixel for controlling shades of gray. • In a color LCD, an additional filter has three cells for each pixel—one each for displaying red, green, and blue—with a corresponding transistor for each cell. • The red, green, and blue cells, which make up a pixel, are sometimes referred to as subpixels.

42. The main principle behind liquid crystal molecules is that when an electric current is applied to them, they tend to untwist. • This causes a change in the light angle passing through them. • This causes a change in the angle of the top polarizing filter with respect to it. • So little light is allowed to pass through that particular area of LCD. • Thus that area becomes darker comparing to others.

44. Lecture - 8 • Video RAM, Video driver, Multiple Monitor, Graphic accelerators.

45. video card • A video card, video adapter, graphics accelerator card, display adapter, or graphics card is an expansion card whose function is to generate output images to a display. • A modern video card consists of a printed circuit board on which the components are mounted

46. Video display adapter’s components: • Video BIOS • Video Processor • Video RAM (Video Memory) • Digital to Analog Converter • Video Bus Width • Video Driver

48. Video BIOS: VA include a BIOS. • The video BIOS contains the basic program, which is usually hidden, that governs the video card's operations and provides the instructions that allow the computer and software to interact with the card • This BIOS is entirely different from the main system BIOS. • The VA BIOS takes the form of a ROM chip. • It contains the instructions that provide an interface between the VA Hardware and the Software running on the system. • The software can be an OS. • Programming the video BIOS chip enables the system to display information on the monitor during the system POST and boot sequences, before any software drivers are loaded from the disk.

49. The video BIOS can be upgraded by two methods: • It uses a rewrittable chip called an EEPROM. • The chip can be replaced by a new chip in case of older video cards. • The video BIOS can be upgraded by flash BIOS software. • This method is commonly used for upgrades in the recent systems.

50. The Video Processor: • A GPU is a dedicated processor optimized for accelerating graphics. • GPU is Graphics processing unit. • The VP is the heart of a VA it defines the cards functions and performance levels.