Component Video vs. VGA
Dear Gary: I really enjoyed the article on Digital Video Interfaces in Issue 47. Since SDIs for DVD-Video players and high-def decoder boxes seem to be a far-off thought for us consumers (so long as the corporations and their copyright holders have their way) getting the best analog connection is in our best interest. In the article, Mr. Alan Koebel states that component video is “the highest quality connection method available for analog video signals.” Not to question Mr. Koebel’s credibility or research, but I have to wonder how component video connections compare to VGA connections for DVD-Video, since he doesn’t state so directly? I bring this up for I am ready to complement my current interlaced DVD/LD player with a progressive scan DVD player. The player I have in mind (along with some others I’ve found) not only has a progressive component video output but also a progressive VGA output. Knowing that and the fact that some high-definition monitors have VGA inputs, when I decide to upgrade to a high-definition monitor, would it be worth my money to invest in one with a VGA input? Is the difference in quality between a VGA and component connection worth it at all?
Dustin Blaine Javier, Marlton, New Jersey
Contributing Editor Alen Koebel Comments:
A VGA connection IS, technically, a type of component video interface. It carries three separate components—the red, green, and blue video signals that together form the picture—as well as two additional signals for synchronization. But in North America we don’t typically call RGB “component,” reserving that word for YPbPr. YPbPr has a number of advantages over RGB for connecting a video source such as a DVD player —whether interlaced or progressive scan— to a display. For one thing, it usually allows color saturation to be adjusted, so you can compensate for insufficient (or excessive) color in less-than-perfect video transfers. Second, comparing YPbPr to VGA in particular, the cables available for YPbPr are typically better than those available for VGA. An ideal analog video cable, which includes the wires and the connectors at each end, has an impedance of 75 ohms. Most VGA cables don’t quite meet this requirement, which can result in smearing of detail and ringing on sharp edges. You won’t usually see this on a computer monitor because the length of the cable is very short. Increase the length to that typically used in a home theatre and these problems can become serious enough to see. Separate coaxial cables for each signal, preferably using BNCs rather than RCA connectors, is a better way to connect analog video signals, be they RGB or YPbPr. That said, a VGA interface can still give excellent results with sufficient care, but it won’t perform any better than a YPbPr connection, unless the YPbPr-to-RGB converter in the display is unusually poor. What a VGA interface on a high-definition monitor really buys you is extra flexibility for connecting different kinds of sources (a computer being the obvious one!). Regarding your first point, recently a very small number of higher-end consumer DVD players, upconverters and displays have appeared with SDI and/or HD-SDI interfaces. The companies producing these products are too small to draw the wrath of the Hollywood studios. So, if you really want you CAN go digital today and watch upconverted DVDs in pure digital form before Hollywood lowers the boom and forces encrypted digital connections (assuming this worst-case scenario comes true). But whether it will someday be possible to watch high-definition DVDs in the same way is anyone’s guess.
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