Other Peripherals Cahpter 9

Video Overview video as a subsystem that consists of the monitor, the electronic circuits that send the monitor instructions, and the cable that connects them. The electronic video circuits are on a separate video adapter or built into the motherboard. Figure 9.1 illustrates a computer’s video subsystem.

Types of Video Output Devices Monitors can be classified several ways—color or non-color, analog or digital signals used to produce colors, and the type of video adapter used. The easiest way to classify video output is by the way in which the output is created—the technology. Table 9.1 lists some of the most popular display output technologies.

Video Terminology and Theory A monitor’s resolution is the maximum number of pixels on the monitor. Two numbers separated by an x (meaning by) describe a monitor’s resolution, such as 640×480 (640 “by” 480). ▫The first number, 640, is the number of pixels that fit horizontally across the screen. ▫The second number, 480, describes the number of pixels that fit vertically on the screen. Table 9.2 shows terms used with resolution and the different modes that can be chosen for the display output. Table 9.3 lists important video features with which we need to be familiar.

LCD (Liquid Crystal Display) LCD is a video technology used with laptops and flat screen monitors that are powered by a low voltage DC power source. They are more reliable and have a longer life span than CRT monitors. There are two basic types of LCD: passive matrix and active matrix. The difference between the two lies in how the screen image is created.

Passive matrix, is made up of rows and columns of conductors. Each pixel is located at the intersection of a row and a column. (This is a similar concept to a cell in a spreadsheet.) Current on the grid determines whether a pixel is turned on or off. Each pixel has three cells in a color monitor: one for red, one for green, and one for blue. Active matrix displays have a transistor for each pixel. The number of transistors depends on the maximum resolution. A 1280×800 resolution requires 1,024,000 transistors (1280 times 800 and more are added for color). This technology provides a brighter display (more luminance). Active matrix monitors take more power than passive matrix, but both of them require less power than CRT-based displays.

Laptops use LCDs and have a video cable that connects the LCD to the motherboard. A backlight bulb is used on many models so images on the screen can be seen. The bulb connects to an inverter. The inverter converts low DC voltage to high AC voltage for the backlight bulb. Figure 9.6 demonstrates this concept.

Video Ports Flat panel monitors are digital, but some can work off an analog adapter (like the one most likely installed in your computer now). With the better flat panel monitors, you need an AGP or PCIe adapter that has a DVI (Digital Video/Visual Interface). Figure 9.7 shows an adapter with VGA, DVI, and TV out ports. The DVI port is a 24-pin connector.

There are several types of DVI connectors and the one used depends on the type of monitor being connected. Two terms used with the connectors are dual link and single link. ▫A single link connection allows video resolutions up to 1920×1080. ▫With a dual link connection, more pins are available to send more signals, thus allowing higher resolutions for a monitor designed for it. The two major types of DVI are DVI-D and DVI-I. ▫DVI-D is used for digital connectivity only. ▫DVI-I is used for both digital and analog monitors and is the most common. ▫A less common type is DVI-A, which is used for only analog output. Figure 9.8 shows the different DVI pinouts.

An upgrade to DVI is HDMI (High-Definition Multimedia Interface), which is a digital interface that can carry audio and video over the same cable. Figure 9.9 shows a video adapter from XFX that has an S-video connector on the far left, an RCA jack, the HDMI connector, and a dual link DVI-I connector.

To have two monitors connected to a single computer, you have several options. ▫Use the two video ports on the motherboard (not common). ▫Use the integrated motherboard port and buy a video card with one video port. (This is the cheapest solution, but the motherboard might disable the integrated video port automatically, and that setting has to be changed through BIOS.) ▫Buy a video card that has two video ports (best option). ▫Buy two video cards. (Usually the motherboard has one expansion slot for a video card, and that means using an older and slower technology expansion slot for the second video card.)

A specialized use of video is with TV tuner cards and video capture cards. A TV tuner card allows TV signals to be brought into the computer and output to the monitor. Some TV tuner cards have the ability to record video. Figure 9.10 shows a photo of a TV tuner card. A video capture card usually has specialized software that allows video to be captured from a camera, tape, DVD, recorder, or live audio and video and manipulated into a presentation, an archived file, or a saved document or streamed onto the Internet. Not all video capture cards support audio. Video surveillance systems sometimes use video capture cards.

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