1080p LCD to PC, cabling: VGA / SVGA / UXGA
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Posted by Dennis on August 28, 2008, 9:13 am
Please log in for more thread options I recently switched to using a 47" LCD as my monitor. It's 1080p so my resolution is 1920x1080 I'm currently using a normal PC cable, the same one I used for my old 1024x768 monitor. Things look okay to me. But I note that there are different kinds of PC cables (HD15 / Sub D) . There are some called VGA, then there is SVGA and UXGA. Each is supposedly intended for a different resolution, I think I read that the VGA one is intended for 600x480, the SVGA is intended for 800x600, UXGA is 1600x1200, something like that.... etc etc ie: http://www.infinitecables.com/vga.html The questions: am I losing any video quality by using a normal PC cable and not an UXGA one, or better still, a DVI to HDMI cable? Can any VGA cable handle high resolutions? Any links or specific facts would be greatly appreciated. | |||||||||||||
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Posted by Calab on August 28, 2008, 9:52 am
Please log in for more thread options VGA is VGA. Unless you are going LOOOONG distances, you won't see a difference. You would probably see a difference if you switched to DVI/HDMI though, since this is a digital signal. | |||||||||||||
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Posted by Dennis on August 28, 2008, 1:53 pm
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>
> > > > > > >I recently switched to using a 47" LCD as my monitor. It's 1080p so my
> > resolution is 1920x1080 >
> > I'm currently using a normal PC cable, the same one I used for my old
> > 1024x768 monitor. Things look okay to me. But I note that there are > > different kinds of PC cables (HD15 / Sub D) . There are some called > > VGA, then there is SVGA and UXGA. Each is supposedly intended for a > > different resolution, I think I read that the VGA one is intended for > > 600x480, the SVGA is intended for 800x600, UXGA is 1600x1200, > > something like that.... etc etc >
> > ie: =A0http://www.infinitecables.com/vga.html
>
> > The questions: am I losing any video quality by using a normal PC
> > cable and not an UXGA one, or better still, a DVI to HDMI cable? =A0Can > > any VGA cable handle high resolutions? >
> VGA is VGA. Unless you are going LOOOONG distances, you won't see a > difference. > > You would probably see a difference if you switched to DVI/HDMI though, > since this is a digital signal.- Hide quoted text - > > - Show quoted text - Can anyone confirm: (1) It makes no difference which kind of VGA cable you use (2) But using DVI/HDMI cable you would notice a difference vs VGA Agree? | |||||||||||||
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Posted by Benjamin Gawert on August 28, 2008, 2:45 pm
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* Dennis: > (1) It makes no difference which kind of VGA cable you use
No, it doesn't make any difference if your monitor is just shit or if you have an eyesight like Stevie Wonder. For all other situations the quality of the VGA cable does make a difference, and a even bigger one at high resolutions (over 1280x1024). Analog signals like VGA are quite sensible to signal attenuation, xtalk and other funny effects that RF signals usually suffer from. A crap cable will very likely lead to a blurry picture missing sharpness, a good one won't. But as with all analog signals, it also comes down on how good the signal that comes from your gfx card is. Most newer gfx cards have an average to awful analog signal quality because the manufacturers save a few bucks on the analog output filters on the card. > (2) But using DVI/HDMI cable you would notice a difference vs VGA
> > Agree? Yes. But besides the cabling issue you should also check that your LCD TV supports disabling of overscan as this leads to a blurry picture as well. And no matter what the manuals say the HDMI inputs are capable of, use the *native* resolution of your LCD panel. If your TV is "HD ready" and uses a 1366x768 panel then use this resolution and not 1920x1080 as the latter one will be downscaled which also looks blurry on desktop applications. Benjamin | |||||||||||||
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Posted by Paul on August 28, 2008, 3:53 pm
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Dennis wrote: >>
>> >>> I recently switched to using a 47" LCD as my monitor. It's 1080p so my
>>> resolution is 1920x1080 >>> I'm currently using a normal PC cable, the same one I used for my old >>> 1024x768 monitor. Things look okay to me. But I note that there are >>> different kinds of PC cables (HD15 / Sub D) . There are some called >>> VGA, then there is SVGA and UXGA. Each is supposedly intended for a >>> different resolution, I think I read that the VGA one is intended for >>> 600x480, the SVGA is intended for 800x600, UXGA is 1600x1200, >>> something like that.... etc etc >>> ie: http://www.infinitecables.com/vga.html >>> The questions: am I losing any video quality by using a normal PC >>> cable and not an UXGA one, or better still, a DVI to HDMI cable? Can >>> any VGA cable handle high resolutions? >> VGA is VGA. Unless you are going LOOOONG distances, you won't see a
>> difference. >> >> You would probably see a difference if you switched to DVI/HDMI though, >> since this is a digital signal.- Hide quoted text - >> >> - Show quoted text - >
> > Can anyone confirm: > > (1) It makes no difference which kind of VGA cable you use > (2) But using DVI/HDMI cable you would notice a difference vs VGA > > Agree? 1) The old scheme for PC monitors, used status pins on the interface, to help the monitor signal a particular resolution to the PC. Apple used a similar scheme, on their video interfaces. http://www.monitorworld.com/faq_pages/q17_page.html 2) Modern display devices use a DDC interface. That is a serial digital interface, with signal names like SCL and SDA. One signal is a clock and the other signal carries data. http://martin.hinner.info/vga/pinout.html 3) If there are working SCL and SDA pins and wires on the cable, then a utility like this one, can display what the monitor is sending to the computer (the info is used by the video driver). http://www.entechtaiwan.com/util/moninfo.shtm If you go to the store today, and buy a VGA cable, at a minimum it should have RGBHV to handle the analog video signals and sync signals. It should have the two wires for SCL and SDA. Those support the basics. There are cables, where there is no room for SCL and SDA. For example, my old CRT monitor, uses one of these cables. It was a beautiful monitor in its time, a Sony Trinitron, supported multisync, but since it used this cable, there was no plug and play with this. Your situation is unlikely to be using a cable like this. Cabling schemes like this, may continue to be used on projection TV devices. http://www.monitorworld.com/m_images/Page_graphics/bnctovgaphoto.jpg Modern VGA, DVI, and HDMI all have DDC serial interfaces on them, and that means that the cable design can be generic. There shouldn't be several different flavors of VGA cable needed now. HDMI - SCL and SDA pins are listed. http://en.wikipedia.org/wiki/Hdmi DVI - In the picture here, the signals are called DDC Clock and DDC Data http://en.wikipedia.org/wiki/Digital_Visual_Interface VGA - In this article, there is no mention of the older "sense" definitions of the pins. Just the SCL and SDA. http://en.wikipedia.org/wiki/VGA_connector As for signal quality, the failings of the cables happen different ways. On VGA (analog), the signal environment is 75 ohm coax for the RGB. If there are reflections, problems detecting the sync signals cleanly, there can be visual artifacts, like ghosting, or a blurry picture. And, as the cable becomes longer, then only the lower monitor resolutions are sharply rendered. So if I run a 100 foot VGA cable, I might only get a sharp picture at 1024x768. If the cable is 6 feet long, perhaps I can run 1600x1200 and expect it to be nice and sharp. DVI and HDMI use the same method of transmission (the interface standards have a lot in common). The interface is digital and is differential (uses two wires D+ and D-, to carry one information stream). Now, as you make the cable longer on that one, at first there is no visual artifact at all. Digital doesn't degrade if the signal path is working in good conditions. So at least small increases in cable length have no effect on resolution choices or anything else for that matter. But as the cable gets longer, the digital signal is attenuated by the run of cable. Eventually the signal is too small to be detected well. What appears on the screen is "colored snow". Each miscolored dot on the screen represents a digital transmission error, due to poor signal quality. The display will be "sparkly", because the position of each errored dot is rather random. Sometimes the snow happens even with a short cable. Some people have bought new equipment, and the cheap bastards include an inferior HDMI cable with it. Changing the cable to a higher quality one, may fix the snow problem (of course, the price you pay for the replacement cable, may make your jaw drop). The Wikipedia HDMI article suggests what range of cable lengths can be reasonably expected to work. With HDMI and DVI, the resolution and refresh rate, affect the data rate sent digitally across the cable. So in fact, when "snow" happens, it is possible that the resolution and refresh rate will affect the snow. To give you some idea just how fast those signals are, when someone says the "clock" on the cable is 165MHz, the differential data is actually going across the cable at 1650Mbit/sec (ten bits are sent per "clock cycle"). Effectively about as fast as SATA I, only involving longer cables. Paul | |||||||||||||
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> resolution is 1920x1080
>
> I'm currently using a normal PC cable, the same one I used for my old
> 1024x768 monitor. Things look okay to me. But I note that there are
> different kinds of PC cables (HD15 / Sub D) . There are some called
> VGA, then there is SVGA and UXGA. Each is supposedly intended for a
> different resolution, I think I read that the VGA one is intended for
> 600x480, the SVGA is intended for 800x600, UXGA is 1600x1200,
> something like that.... etc etc
>
> ie: http://www.infinitecables.com/vga.html
>
> The questions: am I losing any video quality by using a normal PC
> cable and not an UXGA one, or better still, a DVI to HDMI cable? Can
> any VGA cable handle high resolutions?