VGA monitor bandwidth refers to the second electron gun scans the total pixels, is equal to the horizontal resolution x vertical resolution x-field frequency (screen refresh times). Compared with the line frequency, bandwidth, more comprehensive it is even more direct response display performance. But the horizontal bandwidth calculated by the above formula is only a theoretical value, in practical applications, in order to avoid the edges of the image signal is attenuated, maintained around the image is clear, the scanning capability of the electron gun is larger than the resolution size is required, the horizontal direction is usually 25% larger, vertical direction to 8%, so the actual video bandwidth is calculated as horizontal resolution x125% x vertical resolution x108, that "line frame x135%. still above standard, for example: 1024x768x85Hz image mode, the actual bandwidth approximately "1024x768x85x135% = 90.2MHz".
Ordinary video (AV)
Generally, we think that ordinary video signal baseband transmission bandwidth 6M. The analysis from the technical point of view of the monitor, the general CRT 1MHZ video bandwidth corresponding to 52 lines of horizontal resolution, color monitor to display the video bandwidth is 300/52 = 5.76MHZ.
The amount of information carried by the video bandwidth on behalf of the video signal in the unit time, VGA video signal 1024x768/85Hz and the normal video signal carrying the ratio of the amount of information about 15:1.
Conclusion
Two signal bandwidth, the amount of information carried by AV-VGA AV video signal to carry the amount of information that can not meet the needs of VGA video display the amount of information, showing the picture is not clear, not be able to display text and picture detail .
Above comparison can be seen in the video signal of the two technical indicators: clarity and signal bandwidth above ordinary video to be far behind the VGA video, so the video requirements increasing variety of display systems engineering VGA video inside The show has become a consensus.
