What Is Video Resolution And Refresh Rate?

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What Is Video Resolution And Refresh Rate?

Postby Karlsweldt » Mon Jan 23, 2006 10:45 am

So here is a "composition" on video basics. Google has many quality links, if searched for "Video Bandwidth". Some of them helped in compiling this "presentation". So did the "PC Bible".


Resolution Standards For Graphics Displays:
Type.........Linear Pixels (HxW)....TotalPixels...........Aspect Ratio
CGA............320x200.....................64,200...................1.60
EGA.............640x350...................224,000...................1.83
VGA.............640x480...................307,200...................1.33
WVGA..........854x480....................410,240..................1.78
SVGA...........800x600....................480,000..................1.33
XGA...........1024x768....................786,432..................1.33
XGA+.........1152x864....................995,328..................1.33
WXGA........1280x800.................1,024,000..................1.60
WXGA+......1440x900.................1,296,000..................1.60
SXGA........1280x1024................1,310,720..................1.25
SXGA+.....1400xx1050...............1,470,000..................1.33
WSXGA.....1600x1024................1,638,400..................1.56
WSXGA+...1680x1050................1,764,000..................1.60
UXGA........1600x1200................1,920,000..................1.33
HDTV........1920x1080................ 2,073,600..................1.78
WUXGA.....1920x1200................ 2,304,000..................1.60
QXGA........2048x1536................3,145,728..................1.33
QSXGA......2560x2048................5,242,880..................1.25
QUXGA-W..3824x2400................9,216,000..................1.60

FREQUENCIES USED: (nominal)
Resoultion.....Horizontal......Vertical
640x480........31.5 Khz..........60 Hz
800x600........48 Khz............72 Khz
1024x768......58 Khz............60 Khz
1280x1024 ....64 Khz............60 Khz
1280x1024 ....80 Khz............75 Khz


Aspect Ratios are defined by height x width
Aspect Fields: 1.25=5:4 1.33=4:3 1.56=25:16 1.60=16:10 1.78=16:9 1.83=11:6

A pixel, or dot-pitch, is defined as the triad of color phosphors that comprise the R+G+B colors, measured in mm from one same color to the adjoining same color. The closer, the sharper the image. Dot-pitch of less than .28 mm is considered very sharp.
Interlaced images refer to the odd-trace lines being scanned and then the even-trace lines being scanned consecutively.
Progresssive images refer to the odd and even trace lines being scanned simultaneously per image.
The CGA monitor was a digital-type data stream, as it was only black/white image transition, or basic 8-color.
EGA and VGA/others are analog, in that the data stream is color, with varying intensity of bit strength to brighten/lessen image intensity.
DVI is digital in form, having longer/shorter clock cycles for varying intensity.
Digital signals are of a constant-level square-wave, but the clock signals vary in length, whereas the analog signals are of a sine-wave configuration, varying in intensity (level) and duration (length).
Refresh rates are measured in how many times per second the entire image is refreshed.
Persistency of the CRT pixel activation is what causes our eyes to percieve a constant, moving image from an electronic display. Short duration times cause flicker, and longer duration times cause blurring. The chemical formula for the pixel color determines its persistency, or length of activation. They are "excited" into a glowing state by an electron beam, in a high vacuum environment. Some lab oscilloscopes have up to a 10-second persistency!
With an LCD screen, there are no phosphors to excite from an electron beam.. there are individual transistors which switch on and off per the data stream, activating individual diodes, or LEDs.
Almost all video cards have a default level of 16-color display, up to 256 colors. In full-mode operation, up to 17 million color shades can be displayed.
Older ISA video cards worked with a bus speed of 4.7 Mhz to 8.33 Mhz, a PCI card had a bus speed of 33 Mhz, and AGP slots varied from 33 Mhz to 266 Mhz. 33.34 is the actual base clock speed. 66.67 is the next higher speed, then 133.34, then 266.68. There are no odd multiples of 3,5, or 7x bus speeds. Only 1x, 2x, 4x, or 8x. The ISA bus was either 8-bit or 16-bit bus width. The PCI bus width is 32-bit. AGP bus width is 64-bit. There is a 64-bit PCI slot, but it is used only with servers.

AGP bus speeds are stanardized as:
1x: 32 bit, 66 Mhz, 1 data bit per clock cycle, 266 Mhz effective bandwidth (Mega-Bytes per second).
2x: 32 bit, 66 Mhz, 2 data bits per clock cycle, 533 Mhz effective bandwidth.
4x: 32 bit, 66 Mhz, 4 data bits per clock cycle, 1,066 Mhz effective bandwidth.
8x: 32 bit, 66 Mhz, 8 data bits per clock cycle, 2,133 Mhz effective bandwidth.

Bandwidth basic standards:
NTSC Broadcast and VHS: 4.2 MHz.
Laser Disk: 5.3 MHz.
Regular NTSC DVD: 7 (6.8) MHz.
Progressive Scan NTSC DVD and 480p DTV: 13.5 MHz.
1080i HDTV: 37 MHz; (22 MHz still very good quality).
720p HDTV; 37 MHz.

Signal frequency is determined by the formula SF = [(TP x Vt)/2]3 where SF = Signal frequency and TP = The total number of displayable pixels.
Examples: (Reference Page: http://www.extron.com/technology/archiv ... d=vidband3 )

CGA resolution is 320 x 200,
the horizontal scanning rate is 15.75 kHz
the vertical scanning rate is 60 Hz.
Thus:
TP = (320 x 200) or 64000
Vt = 60 Hz
Therefore:
SF = [(64000 x 60)/2]3
SF = 5.76 MHz

VGA resolution is 640 x 480,
the horizontal scanning rate is 31.5 kHz, and
the vertical scanning rate is 60 Hz.
Thus:
TP = (640 x 480) or 307,200
Vt = 60 Hz
Therefore:
SF = [(307200 x 60)/2]3
SF = 27.6 MHz


PCI-E bus types. They are similar in architecture to the standard PCI slots, with added bus connections. But the data stream is accellerated, similar to the AGP bus. The main difference is that they are multi-port type, unlike AGP, and are somewhat backward-compatible to "standard" PCI devices. Bus frequency is is not dependent on a synchronous bus "clock" but rather on a bandwidth "clock" which can vary depending on the data streams encountered.
The most important feature is the "hot-swap" allowance, where other device types are not. The bus is of a serial type, wheras the older PCI design is a parallel bus setup. Speed of the bus can approach up to 8,000 MB/s, compared to the normal PCI bus speed of 133 MB/s max.
IBM must be given credit for the PCI-E innovation, and bus speeds start at around 2.5 Ghz, and can approach 10 Ghz with future revisions. A PCI-E bus may be able to support up to 32 Gb/s data bit speeds!
Karlsweldt
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