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All About Video: An Introduction
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I've spent the past two days in frustration at the lack of product and technical knowledge exhibited by suppliers. All I wanted is a PCI-E video card with component out! To date the only video card to advertise itself as having component out is the Abit RX600 Pro-HDTV, unfortunately Sydneys biggest supplier of Abit hardware has neglected to order more than a handfull of these cards are is now out of stock (I bought most of them). However on closer inspection it seems there are a multitude of video cards with Component out, its just that the manufacturers have descided to use non standard naming conventions when describing this feaute.
This lack of product knowledge has prompted me to ask a question, If the manufacturers and Suppliers don't have a clue how are you guys supposed to know what is the right thing to get and why?
I'm writing this series of posts in an effort to take some of the voodoo and mysticism out of buying the right video card for MCE 2005.
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All About Video:* DVI
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Before listing the types of DVI standards out there, it would be nice to know the typical types of configurations you will see using this standard. There are so many possibilities when thinking about using DVI. Whether you want to use your existing set up and add DVI to it or you want to build a new set up using DVI, there are many ways you could go.
DVI output to DVI input (Digital to Digital):
Always the best situation to have, there are no adapters to mess with and no headaches in the set up. Basically, this is a DVI connection off the video card to a DVI connection on an LCD monitor (Fig. 3). CRT's will rarely have a DVI connection since they are inherently analog devices. Usually there is no loss in image quality here.
Analog output to Analog input LCD:
This is the worst situation. Your PC creates its digital signal, the video card turns it into an analog signal and then the signal goes back to digital at the LCD via an integrated graphics converter in the LCD. There is image quality loss here due to the fact that the signal is changed to analog and then back again to digital. Any time there is a conversion to analog, you'll notice a quality loss.
Analog output to Analog input CRT:
This is the typical set up for most people who have CRT monitors. With this setup there is a minor loss of quality but it's better then analog to analog input LCD. The quality loss will be completely dependent on the image quality of the Video card, and the CRT.
* * * Note: Many video cards these days have 1 DVI port and one standard VGA port. With an adapter you can often make the DVI port function as a second VGA port for dual display use. With this setup (DVI-> VGA CRT via adapter) there may be a very slight quality loss vs VGA -> VGA but it's unlikely to be noticeable with a good adapter.
Analog output to DVI input LCD:
This is a bit better as far as image quality, but there is still a loss because the signal is converted to analog once again. This works virtually the same as the connection above, except the LCD is the one who has a DVI connection instead of the PC. An adapter cable is attached to the VGA (analog) output on the video card; it carries the analog signal to the LCD where it's turned into digital at the DVI connection. Again, you'll see a nice quality loss in the image, especially at higher resolutions.
Understanding the spectrum of configurations with DVI connections and monitor choices can be confusing, what can be even more confusing is the abundance in different types of DVI cables. Which one do you buy? Which type of DVI does my video card have? How do I make use of my DVI connection even if I have a standard VGA connection? All will be explained here, plus a little more.
There are three basic rules of thumb when thinking about DVI and what you want to do with it:
Above all DVI to DVI is always best. Here you will lose virtually no image quality because video signals are not even converted to analog, so a 0 or 1 will look just as is to a monitor. As far as monitors, DVI will only be found in your upper price range LCD's. A few rare CRT's are coming out with digital, but DVI?, I'm not for sure. Some rare CRTs will use the DVI-A standard (Analog DVI). The main point, if at all possible, just make sure to buy a video card that supports DVI as well as a DVI monitor. Your best shot at flawless image quality lies here.
Check your connectors. It's important to know what you have before you know what you can do. Check your video card and monitor to see if they even support DVI and what kind of DVI standard they use. Remember adapters too. If you need one, know what kind of connection from one end to the other is needed. This is important when thinking about buying a monitor or video card to add DVI support to your set up.
Know what you want and your limitations. Knowing the connections you have is the first step, but knowing what you want and what you want to do is the next. DVI standards will be explained later, but if you have one type of standard as your video connection and you want an LCD monitor with DVI, make sure the standards match. You can't mix standards. And if you have a DVI monitor but a video card that doesn't support it, you're better off getting a new video card with DVI support. Just know what you're dealing with before you go shopping. This article should help you with that
DVI Cabling Standards
There are three types of standards you will see in DVI cables as well as many types of cross over adapter cables. I will explain several here. You should get to know what each type looks like before you go out and buy your equipment to upgrade to DVI. It's important to know how each works and which ones are needed for what you want.
DVI-D is a direct digital connection between your video card and your monitor. This type of connection provides a fast transfer rate, high quality image and no quality loss due to the fact that all signals from PC's are purely digital; no digital-analog-digital conversion is needed. Unfortunately, due to the lack in conformity by the monitor and video card industry, this standard is not usually seen in either piece of hardware. (Of the two it's slightly more common on monitors)
This format is used to carry a DVI signal to an analog display, and we all know what that is ?CRT. This format is also used to carry a DVI signal to some HDTV's. Some image quality is lost of course due to the conversion process, but the format transmits a picture of higher quality than standard VGA formats. Also, this format is virtually obsolete. I have seen cables for this standard, but no equipment that actually supports it.
DVI-I is the most common format. Any video card out there that does support DVI will more often than not have a DVI-I connection on it. It supports both analog signals and digital signals in one cable. This means that the cable can transmit either a digital-to-digital signal or an analog-to-analog one, but it will not transmit crossovers of either one (digital-to-analog or analog-to-digital). It also means that if you have a DVI-I port on your video card your fine hooking up most DVI-D or DVI-A devices without needing a seperate adapter.
* * * Note: None of these cables can be interchanged with other cables. A DVI-D cable cannot be placed on an analog system nor can a DVI-A cable be placed on a digital system. The standards can not be mixed. A DVI-I port however can accept another DVI-I, DVI-D or DVI-A cable.
These adapter cables or plugs are DVI at one end and VGA at the other. These are typically used to transmit a DVI signal from the video card to VGA at the monitor or vice versa. Each standard (DVI-D, A and I) has a respective adapter cable to accommodate the type of standard your system uses.
Another note to add in this section, all cables and adapter plugs have male and female ends depending on what you need. Know which ones you need to attach your PC to your monitor. Usually, the video card has the female end of the DVI and VGA connectors, so the adapter cable should be a male end for the PC and a male end for the monitor. If you need an adapter plug to change the DVI or VGA port to the opposite standard, the plug will usually be male to female so the cable can attach to the plug properly.
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All About Video: Component
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If you are just getting into home theater you will no doubt be confused by a lot of the jargon. And since the term component video is sure to befuddle just about everyone, here's a little primer on the subject. It might sound a little technical at first, but if you've got a DVD player, read on for some important information.
Starting at the beginning: RGB
Believe it or not, your eyes can see only three colors—red, green, and blue. All of the other colors and shades of the spectrum you perceive are the result of your brain interpreting the mix of red, green, and blue signals coming from your eyes. Pigments of your imagination, you might call them. (Sorry.)
Therefore, since your eyes only see red, green, and blue, a video system needs to capture and reproduce only red, green, and blue, or RGB as it's called. The camera must capture RGB on the front end. That information must be delivered accurately to your television or projector which must display RGB. By varying the intensity of red, green, and blue, every color of the spectrum can be reproduced. Voila. Perfectly natural color on your screen.
A Problem: Bandwidth
So how do you transport an image from the camera to your TV or projector? You could transmit it in the RGB format in which the camera first captured it. However, RGB is a bandwidth hog and bandwidth is expensive. So the first thing that happens is RGB is converted into a more compact format. This format is component video.
Component video consists of three signals. The first is the luminance signal, which indicates brightness or black & white information that is contained in the original RGB signal. It is referred to as the "Y" component. The second and third signals are called "color difference" signals which indicate how much blue and red there is relative to luminance. The blue component is "B-Y" and the red component is "R-Y". The color difference signals are mathematical derivatives of the RGB signal.
Green doesn't need to be transmitted as a separate signal since it can be inferred from the "Y, B-Y, R-Y" combination. The display device knows how bright the image is from the Y component, and since it knows how much is blue and red, it figures the rest must be green so it fills it in.
Once we've got our video information packaged up in component video format we've reduced bandwidth requirements by a factor of 3 to 2. But more compression was required for broadcast purposes. So back in 1953 when color television was born, a technique was developed to compress all of the component video information into one signal for broadcast. That one signal defined by the National Television Standards Committee (NTSC) is known as composite video.
Composite video shows up everywhere these days. It is (except for HDTV) what comes over the air to your TV's antenna, or through the coaxial cable from your cable TV provider. The yellow "video" jacks on the back of your VCR, laserdisc player or DVD player all output composite video.
The good news is that it only takes one wire to carry a composite video signal. The bad news is that the display system, whether it's a television or projector, needs to un-compress the composite signal, restore it to its original three-signal component video format, and then derive from that the RGB information for final display.
The problem is that picture information is lost when component video is compressed into composite format. Furthermore, once you pack luminance (Y) and chrominance (C) information into one signal, it cannot ever be separated cleanly again. So when the television or projector tries to convert the composite signal back to component video, it can't recover the entire original signal. The result is that the final video image on the screen is diminished—the picture is not as crisp and clean, and the colors aren't as accurate and rich as they would have been had the composite video compression been avoided.
So what does all this mean to you?
If you want good picture quality, there's some amazingly good news here. The news is this:
DVDs and HDTV signal (SD and HD) are encoded in component video!. This is a big step forward since VHS tapes and laserdiscs are encoded in composite video. So the signal information in those media is already diminished and compromised. But DVD and Digital TV signals are different animals—not only is it more compact and easy to use, but a much higher quality format is on the DVD itself. All you need to do is take advantage of it.
To do that, you need a Video card with component video output, and a television or projector with component video input. You can connect the two with a three-wire component video cable. When you do this, you transfer the high quality signal from the Video card straight into your display system without it ever being converted to composite video. The result—better detail, a cleaner picture, and more accurate and richer color.
But wait, there's more. Let's say you are one of the vast majority of consumers out there whose Video card doesn't have component video outputs or your television or projector doesn't take component video input. What you then have is two connection options.
First, you can do what most people do--use the simple yellow (RCA) video jacks. Actually this cable is often bound together with the audio connectors to make it even easier—yellow for video and red and white for audio. Couldn't be easier, right? Big mistake.
The second connection option (the better option) is that you can use the clumsy 4-pin S-video jacks. This often requires a trip to the electronics store to get a more expensive cable. Most people don't want to bother. So they use the yellow RCA jacks because they are labeled VIDEO, and because that's the cable that came with the video card. Once they hook it up and turn it on, they find that the picture looks better than their VCR. So they are happy and forget about S-video. This is of course the wrong thing to do.
Why? Because by using the yellow RCA video jacks, you are forcing your Video card to down-convert all that great component video information on the DVD or Digital TV signal to lowly composite video in order to transmit it to your television or projector. You lose much of the picture quality that the DVD or Digital TV signal can deliver by doing this. OK, it looks better than your VCR. But you aren't getting the best picture you can get.
So the alternative, S-video, is a MUCH better solution. An S-video cable actually carries two separate signals, one for luminance (Y) and one for chrominance or color (C). The Y signal is the same as in the native component video format. And the C is simply a combination of the B-Y and R-Y color difference signals. (Sometimes you will see S-video referred to as Y/C.) By keeping luminance and chrominance information separate on two wires it prevents most of the signal degradation that is inherent in the conversion to single-wire composite video.
So. If you've got a Video card and want to give yourself an instant video system upgrade, replace the composite video RCA cable (the one with the yellow plugs) with an S-video cable (round connector with four little pins). It's simple and inexpensive, and you will get a much better picture.
Use component video if you have it
If you have component video output on your Video card and your TV or projector can take that signal, use it. Video cardes with this output usually have three RCA jacks which are color-coded green, blue, and red. They are labeled either Y, B-Y, R-Y, or alternatively Y, Pb,
Pr, or Y, Cb, Cr. For practical purposes they are all the same thing. If your television or projector also has the same three RCA jacks, just connect them with a three-wire component video cable making sure the colors match up on both ends (or you can use three standard composite video cables to do the same thing).
Conclusion
The way to get the best DVD picture is to use component video connections (if you have them) between your DVD player and your TV or projector. Component-progressive is preferred when you have both progressive and interlaced options.
For the vast majority of DVD users who don't have component capability in either their players or their display systems, the next best thing is S-video. If you are one of the large majority of DVD enthusiasts who are running composite video out of your DVD player and inadvertently degrading the picture as a result, give yourself a quality upgrade--get an S-video cable as soon as possible.
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All About Video: Displays
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High Definition TV comes in two formats and only two. You can't get HD via SVideo or Composite signal as the bandwidth capabilities are inadequate. SD looks ordinary via composite or svideo inputs on all display technology.
Read here for more info on why:
these are:
1080i, 720p.
How these numbers correspond to resolutions is as follows:
1080i
1920 pixels x 1080 lines in interlaced mode
720p
1280 pixels x 720 lines in progressive scan mode
Plasma Screens and LCDs
Currently the best plasma screen resolution is arguably the NEC PX-61XR3W with a native resolution of 1365 pixels x 768 lines. This is good for displaying 720p HD natively but has to do weird and wonderfull compression to display 1080i HD. There is currently NO plasma screen that can do 1080i nativiely in a single pannel. This is why 720p looks better on plasma screen than 1080i. Picture quality looks best when component inputs are used even when compared to DVI.
CRT TV's
These buggers compress every SD or HD signal presented on any input type. The technology has been around for a very long time and the compression methods are very mature and look good. Picture quality looks best when component inputs are used. DVI non existant on CRT TV's.
Projectors
There are projectors that can do 1080i natively but you will not find one for under $100,000 AU period. Having said that and scared off everyone from projectors. I have found that projectors seem to have the very best compression technology when it comes to managing HD signals. Probably the minimum resolution I'd look for in a projector is 1280 X 768 native widescreen (commonly called WXGA) which will at least do 720p natively. When connecting up one of these buggers use component cable as most projectors have predefined compression techniques specifiacally suited to HD signals. Picture quality is best when component inputs are used even compared to DVI.
When using VGA or DVI to component adaptors instead of deriving a real component signal from a video card, you can sometimes get bizare screen over or under stretched images when you set the dip switches to one type of resolution while you monitor is set to another. Why does this happen? There is actually supposed to be two way communication when you plug a display into a PC one is the obvious video signal but there is also the display plug'n'play ID which the Display sends back to the PC. Windows uses to ID to set the display parameters like refresh rate and sync rates. If your display does not send the ID, Windows has no way of knowing what refresh or sync rate to use and fally back to a default set. Properly generated Component signal usually have sync-on-green or sync-on-red timings embedded in the signal (this is why a DVD player component out always uses the full screen area of the display device) The problem is caused by the adaptors/windows being a little too dumb to select the correct sync rates.
Re: All About Video: DVI, Component & Displays
