Video, Sound and Multimedia
Video, Sound and Multimedia |
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VIDEO
Two terms, "screen" and "display", are both used to describe the graphic information that your computer is showing on the monitor's face. You plug your monitor into a video card within your computer so that you can view graphics and text. A PC monitor does so by plugging into a console’s standard video port.
What you see on your monitor is largely governed by your video card, keeping in mind
that knobs on the monitor's front (they could be placed on the back) adjust brightness,
contrast, etc. This card determines what to display, where to display it, what colors to
use and how many colors that you can see on your monitor. The number of colors and
resolution depend on your video adapter's abilities. Most of today's displays can show
from 256 on up to 16 million colors, although only a certain number of colors can be
displayed on the screen at any given time.
Literally every desktop computer that is sold today has a video card, although laptops and some lower-end computers have video circuitry directly on the main board. 3D-accelerated video, once optional, is now standard on all new computers.
A graphics card intended for basic office use differs greatly from a board for 3D games and multimedia. Word processing and spreadsheets require only 2 MB SDRAM whereas multimedia and gaming necessitates 8 MB SGRAM, RDRAM or WRAM and photo editing benefits from 8 MB or 16 MB WRAM or VRAM.
For those wishing to purchase a personal computer with state-of-the-art graphics
capabilities (in February 2003), www.sharkyextreme.com
recommends a $4000 system with a 3 GHz Pentium 4 CPU, 1 gigabyte RAM, ATI Radeon 9700 Pro
graphics card, SoundBlaster Audigy2 Platinum sound card, and twin 120 gigabyte 7200 RPM
hard drives. By the time this document is distributed at ASNR 2003, the ultimate
commercially available video card, the NVIDIA GeForce MX, will have been released.
According to a preview at http://www.sharkyextreme.com/hardware/videocards/article.php/1502451
The basic premise behind the GeForce FX technology is one of bridging the gap between film and real-time rendering capabilities. If you've seen any of the computer-animated flicks like Monsters Inc., Final Fantasy or Ice Age, then it's pretty easy to visualize what we're referring to. When transitioning this type of visual detail to a graphics processor, it requires a great deal more horsepower and features.
Keep in mind that your computer relies on system RAM to access graphics more quickly and to run more applications at one time (even 32 MB and 64 MB graphics cards still rely extensively on main memory). Thus, the more system memory you have the smoother DVDs and other multimedia programs will run. Insufficient RAM causes your PC to constantly retrieve information directly from your hard drive – and keep in mind that your hard drive is nowhere near as fast as memory. There has never been a better time for adding RAM since prices for high quality memory have dropped considerably.
When evaluating a graphics card find out the operating system for which it is tuned. These various types of RAM are considered further in this article, under Memory below.
You can install more than one card and monitor using a modern operating system such as Windows XP. Attaching several video cards and monitors into your computer can enable your operating system to also show television (if you have a TV tuner card) or, you can spread your single desktop over a bank of monitors.
Standards for PC video display
VGA (Video Graphics Array, not Video Graphics Adapter) is the minimum standard for PC video display. IBM introduced the VGA standard with its PS/2 models in 1987. VGA offered superior colors, high-resolution graphics nice, readable text and supported earlier CGA and EGA modes. VGA was initially 640 x 480 pixels with 16 colors, but non-IBM vendors quickly boosted resolution and colors to so-called “Super VGA,” which was later standardized by the Video Electronics Standards Association (VESA). All VGA display adapters today start at 256 colors. Super VGA monitors can display up to 16 million colors at resolutions ranging from 640 x 480 up to 1,280 x 1,024 pixels, as defined by VESA. Nearly all PCs today support Super VGA.
Many SuperVGA display adapters are on the market offering a wide range of features and prices. Accelerated video adapters that work faster are typically SuperVGA in nature. A monitor that can handle the output of a SuperVGA adapter is required. Although some claim that SuperVGA works with any monitor (which may be true), the best results are possible only with monitors built to handle SuperVGA. The monitor must be capable of accepting the bandwidth of the graphics adapter. The higher the bandwidth value (measured in megahertz or MHz), the more speedily information is sent from the computer's graphics adapter to the monitor.
Some high-end graphics adapters expand upon SuperVGA but such is needed only if the
software you use specifically requires it.
This section deals with changing Display settings in Windows XP. The Settings panel in the Display Properties dialog box is where you adjust your monitor’s color, resolution, etc. To quickly bring up the Display Properties dialog you can right click over a bare area of your monitor screen. From the Display Properties dialog select the "Settings" tab and proceed as per the instructions below (be sure to read all paragraphs in this section for critical instructions).
Each version of Windows comes with display driver tables that can identify the maximum internal clock speed of each type of adapter card and display. If you go to Start - Control Panel – Appearance and Themes (if you’re using the “Category View” to display the contents of your control panel, instead of “Classic View”) - Display - Settings, Windows gives the current settings for resolution, color depth, and refresh rate. The model of display monitor establishes limits. If you increase the value of the resolution, the system may reduce the refresh rate to keep the chip speed within tolerance.
You can also reach the Display Properties dialog in the conventional way by opening the
Control Panel. From the Start menu, choose Control Panel. This displays the Control
Panel's main window. If your Control Panel is in “Classic Mode”, double-click on
the Display icon. Otherwise, if you’re in “Category View”, double-click
“Appearance and Themes”, then the Display icon. The Display Properties dialog
box appears. You can change the desktop's background, add a screen saver, and change the
system colors or screen resolution using the Settings dialog box. The sections that follow
outline how this is done. When you're done, close the Settings dialog box by clicking the
"OK" button to keep your changes, or by clicking "Cancel" to go back
to the way things were. NOTE: When make changes click "OK", but do not select
"Apply" until you have tested your new settings (this will allow your original
settings to be restored if the change causes Windows to appear incorrectly).
Settings – when on top this tab has, side-by-side, two areas for making color and screen adjustments and one box labeled "Advanced":
The monitor and display adapter you choose makes a big difference in your computer viewing. Important factors include monitor size and resolution (and LCD versus CRT), number of colors, refresh rate and graphics and video acceleration
Actual monitor size, referring to the cathode ray tube (CRT) inside the monitor, is larger than the viewable image size because the plastic rim holding the monitor together masks a small portion of the CRT.
The term "viewable image size" refers to the diagonal measurement of the portion of the monitor screen that you can actually see (from one corner to the other). Monitors generally range in size from 15 to 21 inches. A 17-inch monitor is now the standard. Prices have come down and these are no longer much more costly than 15-inch monitors. I use the latter though, partly because of desk space limitations. Yet I function quite well without the added viewing area. However, no one will argue about the capacity of a large monitor to display a great deal of information on the screen at once and its ability to use many colors.
Your need for monitor size and resolution depend on the applications you run. The standard resolutions are 640 x 480 (VGA), 800 x 600 (SGVA), 1024 x 768, 1280 x 1024 and 1600 x 1200 and above. For example, 640 x 480 means that there are 640 columns and 480 rows of pixels on screen. The higher the resolution, the more viewable material can be displayed on screen at one time. You can adjust most of your software to display text larger on the screen. The popular notion is that for standard Windows applications, 1024 x 768 is the desired resolution with at least a 17" monitor. A 19" or 20" monitor can offer even better. For teleradiology, desktop publishing and graphics work, 1280 x 1024 on a 20" monitor may be preferable.
Resolution refers to the number of dots, or pixels, on the screen, expressed as a pair of numbers that give the number of dots across (horizontal) and down (vertical) a display monitor. More pixels give a higher resolution and a finer image. The higher the resolution the more information (pixels) can be displayed on screen at one time. Commonly used resolutions include 640 x 480, 800 x 600, and 1,024 x 768. The higher the resolution, the more pixels there are on the screen and the more information can be displayed at one time. There is a trade-off between resolution and color, but this applies only if you have insufficient VRAM. The Video Electronics Standards Association (VESA) maintains industry standards for resolution, and for the number of colors that can display at given resolutions. VGA and Super VGA are examples of common resolution standards.
Dot pitch refers to the distance between each dot, pixel, on the screen (measured from the center of each pixel in millimeters on a computer monitor). This is the distance between a red (or green or blue) dot and the closest red (or green or blue) dot on a color monitor (typically from .28 to .51 mm; large presentation monitors may go up to 1.0 mm). The closer the dot pitch, and the smaller the pixels, the crisper and clearer the image. A dot pitch of 0.28 mm (millimeters) is considered very good, with smaller values being even better. A .28 dot pitch means dots are 28/100ths of a millimeter apart. A dot pitch of .31 or less provides a sharp image, especially on text.
A computer display is essentially similar to a high-resolution TV set. It generates colors by combining amounts of Red, Green, and Blue (an "RGB" connection). In current use, three wires in the display cable control these colors. Each has a variable amount of voltage represented by a number from 0 to 255. This produces a theoretical 16 million possible colors. Complete control of color ("Truecolor") may be needed for displaying photographs, but ordinary applications get along with far fewer.
The standard number of colors that are displayed are: 16, 256, 65K and 16M. The jumps are large, from 256 to 65 thousand to 16 million. The number of colors is known as the color depth, or bit depth. The number of bits assigned to hold color value determines the color depth. The display adapter stores a value (4 to 32-bits) in memory for every dot on the screen. The amount of storage needed is determined by multiplying the number of dots (resolution) by the memory required for each dot. The combination of 16 colors and 4-bit color depth are commonly considered as Standard VGA. The combination of 256 colors and 8-bit color depth are commonly considered as Super VGA. The combination of 32K colors and 8-bit color depth or 65K colors and 16-bit color depth are commonly considered as High Color. The combination of 16M colors and 24-bit color depth imply "True Color". Windows XP has two standard settings for color quality: Standard (16-bit) and Highest (32-bit).
To display multimedia applications, you need at least 65K colors, or 32K colors if your adapter supports it. The most realistic photographs and full-motion video will be achieved with 16M colors, but 65K is generally adequate. For standard business applications, such as word processing and spreadsheets, even 256 colors will suffice. These constraints are more for historical interest, since one would be hard pressed to find a new desktop computer that was not capable of displaying 1600 x 1200 resolution at 32-bit color depth.
The refresh (or scan) rate is the number of times per second the dots on an image are painted onto the screen by a monitor's electron gun. Refresh is necessary, because the phosphors hold their glow for just a fraction of a second. The higher the refresh rate, the more clear and solid (without flicker) the image appears on the screen. It is measured in kilohertz (kHz), and the higher the value, the better. The higher the resolution, the larger the number of dots that have to be written in every refresh cycle. The greater the color depth, the more work that has to be done per point. Increase any of these values and the system has to speed up the clock to support it. The original VGA displays ran at 60 Hz, but some people complained that this produced a flicker. It is desirable to have a refresh rate of at least 70 Hz at your desired resolution - at a lower rate the image flickers. Thus, international standards now require a rate of 70 Hz. A "multisync" monitor can adapter to refresh rates in a range, typically 60-75 Hz.
Non-interlaced monitors redraw every single line each time the screen is refreshed. The resulting images are clearer and have fewer flickers than the images produced by interlaced monitors. Interlaced monitors only redraw every other line with each refresh. This takes twice as long to do and causes the flicker. Interlacing is a contrived method for trying to get a monitor to display a picture that is better than it should be able to display.
The Cathode ray tube (CRT) is the vacuum tube that makes up most of a monitor's bulk. The image is projected from the back of the tube onto the inside of the glass display screen, which is what we see. CRTs are generally about as deep as the diagonal measurement of the screen and they get larger as the monitor size increases.
Many desktop monitors now employ Liquid Crystal Displays (LCD), the same technology that is used for displays on portable systems. Light is filtered through microscopic liquid crystals sealed in between very thin layers of glass in order to create an image on the screen. Active matrix or Thin Film Transistor (TFT) active matrix is the most vivid and clear liquid crystal display (LCD) screen technology since every pixel is redrawn with each screen refresh. These cost considerably more than CRTs - the price of an active matrix monitor is four times that of a regular CRT monitor. However, the clear image and wide viewing angle are desirable for many graphic-intensive applications.
LCD flat panel displays for desktop use have several advantages over CRTs. They take up less room on the desk, emit less radiation, use less current, and they are not affected by glare. When at their very best they provide a very crisp and pleasing display. In addition, since they do not flicker, they are less prone to cause eye fatigue. A major disadvantage is their higher cost.
Be careful when reading the ads. A flat screen monitor may mean a CRT, not a thin panel LCD screen. A "flat screen" is not a "flat panel LCD screen." Monitors with flat-screen displays have virtually no curve to the viewing surface resulting in less image distortion. The screens on CRTs have become flatter over the years, providing more uniform sharpness at the edges of the screen.
As of February 2003, 15” LCD TFT monitors cost below $270. At the high end, the 23” LCD TFT Apple HD Cinema Display has just been reduced from $3500 to $2000. If you are considering making an investment of this magnitude in a monitor, be sure to understand the manufacturer’s return policy for monitors that have “bad” pixels (permanently “off” or “on”). Some manufacturers consider a few bad pixels to be an unavoidable part of the manufacturing process, and will not repair or exchange new monitors with a few bad pixels. It may be necessary to test the monitor in a local retail outlet prior to purchase, or get the written return policy from the retailer prior to purchase.
A monitor and graphics adapter must be compatible for the display system to work. When earlier standards that created digital signals were being used more extensively, it was important to be sure that a VGA adapter was connected to an analog-type monitor (as opposed to a digital monitor). For example, the RGB (acronym for Red, Green, and Blue) monitor was a basic digital monitor that was preferred with the old CGA standard. Some monitors are switchable and can handle both analog and digital signals. A laptop's display circuitry is digital from end to end and is built into the motherboard.
A mismatch in signal frequency represents one of the gravest dangers to your PC's hardware. When your graphics board sends more than your monitor can handle, known as overdriving the monitor, this can overheat the internal components and damage or even ruin the display. Overdriving can even pose a fire hazard. Overkill on three settings can cause your card to overdrive the monitor. These are - refresh rates, the resolution setting and the color depth setting
A video card is an expansion board that plugs into a desktop computer. In a PC, the display adapter is known by many names, including graphics adapter, graphics board, graphics card, graphics controller, video display adapter, video display board, video display card, video display controller, video adapter, video board, video controller, display board, display card, display controller, VGA adapter, VGA board, VGA card and VGA controller. In contrast a video graphics board is a video capture board that accepts analog NTSC video from a videotape player (VCR) or camera. Increasingly, NTSC video is being integrated with computers, so the terminology might become even more confusing.
Graphics cards are to some extent like a miniature PC inside your PC and contain memory, called a frame buffer, and an internal bus for moving bits from memory to the processor and back. The card’s memory is used to build the images before they are displayed; the card converts the images created in the computer to the electronic signals required by the monitor. Thus, the display adapter converts the characters or graphic patterns (bitmaps) within the computer's memory into signals used to refresh the display screen. It determines the maximum resolution, maximum refresh rate, and the number of colors that can be sent to the monitor. Resolution and number of colors are determined by the amount of video memory, and refresh rate is determined by the quality of the components. The monitor must be equally capable of handling its highest resolution and refresh.
If you add on a new graphics board, you should notice additional resolution and color depth options that were not available before the upgrade. Just right-click the desktop, select Properties, and choose the Settings tab. Check the Color palette and Desktop Area controls to see what it shows with your new configuration.
In earlier PCs, the display adapters (CGA, EGA, etc.) generated digital signals for the monitor, which converted them into analog for the screen. Current display adapters (VGA, Mac, etc.) create the analog signals that are sent to the monitor. Increasingly, display adapters offer digital outputs for flat panel monitors. On a laptop, the equivalent display circuitry, which is digital from end to end, is built into the motherboard.
With more colors, resolution and refresh, a display adapter has to work harder and the more expensive it will be. In addition, at higher settings, the slower the adapter operates, and the slower your screen redraws. Whenever there is a faster adapter that runs 16 million colors at yet a higher resolution, it is always a breakthrough. Placing drawing functions into the circuits of the display adapter speeds up displaying images on screen. After Windows became popular, vendors added graphics acceleration to their cards, which put various screen drawing functions into the hardware. Today, any worthwhile display adapter has built-in graphics acceleration. The latest trend in hardware-supported features is video acceleration, which puts several full-motion video functions into the chips. Having these features will be advantageous if you plan to run many multimedia movies.
What goes into a graphics board? The following systems help determine a board's features, performance, and cost:
Graphics coprocessor - This chip is the heart of any graphics board, as such, determines exactly what the board can, and cannot do - it contains crucial features for accelerating 2D and 3D graphics and video playback.
Bus - PC display adapter cards can process commands as quickly as the CPU can send them. The most common factor that limits performance is the I/O bus. The most recent development has been the 8X AGP (Accelerated Graphics Port) port on Pentium 4 systems.
The first display adapter cards plugged into the old 8 MHz ISA bus – and they did poorly. However, as the PCI bus became a standard feature of all systems, the display adapters also switched over to PCI. PCI proved a valuable performance boost to PCs, being capable of pushing 132 MBps of data. Its predecessor, the ISA bus, could move only 5 MBps.
The fast Accelerated Graphics Port (AGP) bus is used to pipe textures stored in system memory directly to the graphics chip. The fine timings of AGP limit PCs to a single AGP slot, which is dedicated to graphics. The arrival of the Pentium II processor and Intel's 440LX chipset introduced the new graphics-only AGP bus. This bus, which is essentially a fancier PCI bus, can push up to 526 MBps of data over a 32-bit, 66 MHz connection. If a system has an AGP bus, it should definitely have an AGP card because it will open the path to better performance. Going with AGP will also help open PCI slots for other devices. The bus inside your PC determines what type of card you can buy and the potential extent of your selection. It also affects performance. Whenever possible, purchasing an AGP graphics card, which provides key advantages in 3D graphics, games and titles, is recommended. Most PC’s that are currently being sold contain 4X AGP graphics ports. High-end 8X ports are also available.
Memory - how much you have, and what type it is, are important. The amount of memory determines the maximum resolution and color depth that your PC can support in displaying more colors and pixels on your monitor. It takes more memory on the display adapter to achieve higher resolutions and higher colors at the same time. Type of memory can also make a big difference in graphics performance. 3D graphics and image and photo editing are examples of applications that require 4 MB or more of graphics memory. 8 MB of RAM enables greater texture detail. EDO DRAM, SDRAM, and SGRAM are single-ported memory architectures (using a single door to move data in and out of the frame buffer). However, since the same port must be used to both accept incoming data from the controller and send data to the monitor, a bottleneck exists, restricting and slowing performance at higher resolutions, color depths, and refresh rates. These single-ported memory architectures are manufactured inexpensively.
The more expensive dual-ported memory enables boards to break through the refresh-rate bottleneck. VRAM (Video RAM) and WRAM architectures use two doors - one going in, the other going out - to improve the flow of data through the frame buffer. They can simultaneously refresh the screen while text and images are drawn in memory. They are faster than the common dynamic RAM (DRAM) used as main memory in the computer.
Single ported memories can keep pace with applications graphics demands running at 800 x 600 resolution and below 24-bit color. However, consider VRAM or WRAM memory when running at 1024 x 768 and 24-bit color. At these higher settings the additional data ports can make a difference - particularly with a monitor running at high refresh rates of 75 Hz or more. Consider the size of your PC's monitor when you buy a new graphics board. It probably isn't worthwhile spending extra money on a card that has 16 MB of RAM and can display 1600 x l200 pixels or better when all you have is a 14-inch monitor.
RAMDAC (Random Access Memory Digital to Analog Converter): This is the card's controller chip that acts as the digital-to-analog converter and also color manager (it stores the color palette). The speed of the RAMDAC determines how frequently (number of times per second) the graphics card can refresh the image on the monitor (maximum refresh rate). The faster the RAMDAC, the more quickly the board can update things, and the more stable the images that appear onscreen. Each of three component values (red, green, and blue) from the color palette is fed to a separate DAC, whose analog output goes to the monitor, and ultimately to one of its three electron guns. Most affordable graphics boards don't have separate. Instead, this component is built directly into the graphics chip, enabling board vendors to cut costs.
Although not a part of the card itself, there is another important part of the equation:
Software drivers - driver software enables the operating system and programs to communicate with your graphics hardware, keeping everything working together. Drivers aren't actually part of the board per se, but in many ways this software plays the most critical role of all. In general, drivers are the complicated codes that enable peripherals (such as graphics cards) to talk to and take orders from the operating system and its applications. Hardware vendors write drivers for their products, and this is where you should look first for updates. The board maker has a stake in adding value and performance to its products and is usually responsible for providing service and support for the card. Periodically check for updated driver software - these drivers will help you get more performance out of your existing hardware. The best way to get new graphics drivers is from your board vendor's Web site - typically, there are several drivers for each board, serving different operating systems such as Windows and Mac OS. Always look for driver version numbers that are higher and driver dates that are newer than those of your current driver. When downloading the latest drivers from the Internet you can simply have Windows install this driver from an existing location. The best thing to do is to download the driver code and expand the compressed files into a temporary directory dedicated to the new driver. When you are navigating Windows' Add New Hardware wizard, click the "Have Disk" button to install the drivers from a specific directory. If you are contemplating an operating system upgrade to Windows XP, be sure to check the compatibility of the drivers with XP. Most Windows 2000 drivers will also work with XP, but this is not guaranteed. The Microsoft web site contains a hardware compatibility database.
Hard Drive – an often-neglected component of the digital video PC is the hard drive. Digital video creates prodigious amounts of data that need to be quickly read from and written to hard disk. Drives that spin at a higher rate not only read and write data faster, but they also have a lower "seek time", or the dead time before the needed sector reaches the drive head to begin reading or writing. Any system used for digital video production should have at least a 7200-RPM hard drive, preferably 80 gigabytes minimum. If cost is no object, opt for a 10,000-RPM drive. Many low-cost PC’s use 5400 RPM drives. Don’t use them for digital video production.
Copyright © 2003 American Society of Neuroradiology, www.asnr.org