Making sense of the HDMI DVI ADC DP VGA Video Alphabet Soup

Now that HDMI has entered into the PC video arena alongside DVI, and the old standby VGA, the varied formats with their differing standards and characteristics have created nothing but confusion with computer purchasers who must now determine what video outputs they will need to drive their monitors to optimum performance. When we add to the equation other digital formats such as Apple-ADC and Display Port (DP), as well as older analog formats such as Component Video the situation gets really convoluted.

HDMI, DVI, Apple-ADC, Display Port, VGA, and Component Video are all video standards which support a broad spectrum of resolutions, but which transfer the signal from the main graphics source to the monitor in widely differing methods.

HDMI, Apple-ADC, Display Port, and DVI are digital formats which work in essentially the same way as most of the data being shuffled around in your computer case, it's just a matter of what bits are assigned to do what.

VGA and Component video are two analog formats which does not transmit a stream of bits but as a set of continuously varying voltages which represent the Red, Green and Blue elements of the video signal. To compound the matter further, VGA is a very outdated and narrow standard which only supported 256 colors on a 680 x 480 pixel resolution, and has been superseded by SVGA 800 x 600, XGA 1024 x 768, SXGA 1280 x 1024, UXGA 1600 x 1200, QXGA 2048 x 1536 and a mind boggling variety of + suffixes and W prefixes where the + indicates mid-range steppings of resolution and W for widescreen formats.

Let's suffice to state that if you are buying a new, state of the art, large flatscreen monitor you most definitely want to stick to a digital format. The best thing to do is to do your homework very carefully to determine which interface is best suited to providing optimal performance for the monitor you want to buy before you shell out the big bucks.

Naturally your video card should provide the outputs necessary to provide the correct signals to your monitor. There is no point trying to attach a brand new flatscreen to an old VGA connector. Chances are that your monitor doesn't even have a VGA connector on it and will require a DVI, HDMI or similar. Also note that in order to properly drive a large screen monitor at a high resolution such as 1920 x 1200 (which is pretty well standard for 24 inch widescreens), your video card has to have sufficient processing power and built in memory to be able to keep up.

Another aspect to consider with digital video is that cables are almost never included with video cards or with monitors. Not only can they be a significant additional expense (good cables don't come cheap) but you have to consider that poor quality cables can significantly degrade the video signal. Therefore it is not a good idea to scrimp on your cable budget. Also try to keep the video cable length as short as practicable. A cable length of over 10 to 15 feet could start to manifest unrecoverable bit errors which will show up on your screen as "sparkly" losses of data leading to pixel dropouts. HDMI is even more prone to pixel dropout and sparklies on the monitor, so it's not a good idea to set up your PC in such a way that the monitor is on the other side of the auditorium when using HDMI or any digital video.

Video signal determination to drive your PC's monitor has never an easy task and the newly introduced standards make it even more complex. Read up on the various requirements for the monitors and video cards you prefer very carefully and become an informed video consumer!

 

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Comments 3 comments

Sergey Adamovsky 7 years ago

Hi Hal!

Unlike other your good articles, this one was useless for me.

You write about VGA cable being capable of carrying only 256 colors (ok, you have used the word "format") - still you classify somehow such "cable" or "port" - I mean the 15-pin SUB-D connector.

What I was looking for in such article was the difference between HDMI and DVI. I have heard about DVI<->HDMI adapters without electronics - are these formats compatible? With which limitations?

And about bad quality cables. No doubt, for the analog signal quality of the picture reflects the quality of the cable. But in digital case either the signal is delivered or not: there can not be a "bad quality bit". So "degraded video signal" I would say only in the analog case, in digital it is called "the cable does not work".

And again, thank you for your work and especially for other nice articles.


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ciidoctor 6 years ago

thank you


Jacky 5 years ago

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