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The State of Video Connections
mikemuch writes "Joel Durham provides a nice rundown on what's happening in video interfaces as we leave VGA behind and move through the DVI flavors, visit HDMI along the way, and look forward to UDI and DisplayPort."
Spare your eyeballs with the ad free, one page print version.
Most of my monitors are 19-inch CRT monsters. They do what I need them to do, they deliver a pretty image, but they're old. I still have a ViewSonic Optiquest V95 in service that dates back to around 1999. It's a VGA monitor, as are all of my displays. I shudder at the idea of updating them, not because of some sentimental attachment, but because connecting displays to computers has become so darned complicated.
The analog VGA was the standard for such a long time, some of us just got used to it. Today, I don't remember the last time I got a performance-grade graphics card with a VGA port on the back of it; I have a small cadre of DVI-to-VGA adapters that I use to plug in my monitors.
DVI as a standard features a number of sub-standards, some analog, some digital. Now DVI is already seeing the writing on the wall due to its limited bandwidth, just as the world grows accustomed to it. HDMI is crossing from the TV set to the computer, UDI is creeping into the market, and DisplayPort is riding over the horizon and hoping to take over the world.
What if you just want to play Supreme Commander or do your taxes? Can't you just poke a monitor cable plug into a display adapter and be done with it? Sure you can, if you know what to expect when you face the next generation of graphics-to-display connections.
VGA
Sure it's old, but it still works. Video Graphics Array (VGA) has been around since 1987, a few years after which it became the standard connection between the PC and its monitor and stayed that way for more than a decade. If you happen to purchase an analog CRT monitor, even one made today, it's likely to require a VGA connection to a computer.
The term VGA has come to mean a number of things. In one sense, it's used to refer to the actual port found on a graphics card or the corresponding plug (a 15-pin mini D-sub male) on a monitor cable. VGA is also sometimes used to describe the outdated and rarely used screen resolution of 640x480 pixels, which was once considered sharp and sexy.
VGA Connector
click on image for full view
VGA graphics cards date back to the days of ISA expansion ports. Such cards were typically capable of addressing only 256K of local memory and displaying 256 colors at 640x480 at a 70Hz refresh rate. As demand grew for higher resolutions and more robust graphics support, the original VGA spec became outmoded but the connection port was preserved.
VGA is analog. Graphics cards with VGA compatibility employ RAMDAC (random access memory digital to analog converter) chips to pipe digital graphics signals through the analog display cable. Of course, with digital displays like flat-panel monitors being all the rage, it would be even cooler to have a direct digital-to-digital connection from PC to display, wouldn't it? That's where DVI came to the rescue.
DVI
DVI stands for Digital Visual Interface. As digital flat-panel monitors started to become the rage at the tail end of the last century, the analog VGA connector quickly became inadequate for the needs of such displays. The DVI port is quite different from that of VGA: It's made up of up to 24 pins (most of which are for TMDS) and an additional five pins for analog compatibility. TMDS stands for Transition Minimized Differential Signaling; it's a high-speed serial interface used by the DVI and HDMI display standards.
DVI comes in three flavors:
* DVI-A, in which the A stands for analog. This type of DVI connection only transmits analog signals and is intended for use with CRT monitors. You almost never see DVI-A.
* DVI-D, the D meaning digital. This is purely digital, without any analog compatibility at all.
* DVI-I, with the I standing for integrated. This connection carries both analog and digital signals and can be used with either analog or digital displays. This is the most common DVI connector found on graphics cards.
To further complicate matters, DVI-D and D
No mention of Wireless HDMI?
Wizard Needs Food, Badly
Perhaps this is because even a modest resolution (by today's standards) needs nearly 2Gbps of bandwidth?
Do the math your self: 1280 x 1024 x 24 x 60 = 1.887Gbps
This doesn't even begin to take into account any protocol overhead, sync signals, or other useful data such as audio.
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HDMI video quality is identical to DVI.
Never mistake "can" for "should".
Because that's where the big electronics stores make their profit. Ask a BestBuy employee how much that $100 monster cable costs him under the employee discount program. It'll be significantly closer to the $0 side of the range than the sticker price...
That said, there are some good companies out there that will sell perfectly good HDMI (and other) cables at reasonable prices. http://www.monoprice.com/ is one I've ordered from multiple times and had great results with. My last purchase was 10' of HDMI - I think I paid $10 shipped.
I actually was surprised to see that Target had 6' of HDMI for $15. A lot better than the $60/6' that was the best I found when I was looking for a quick cable at BestBuy...
Just do what I do. I have a media server that uses samba to share media files. I use my XBox to stream the video from my server over the LAN and display it to my TV with XBMC (XBox Media Center http://www.xboxmediacenter.com/). Although the original XBox does not do HD, the XBox 360 does. Wait a few year(s) for XBMC 360 to come out (after they figure out how to hack the damn thing to run unsigned software) and the only thing you'll have to run from your basement is an ethernet cable to the XBox 360, which then interfaces with your HD display via a short cable. I'm sure 100 meters is long enough for you to work with ;).
I had no idea what this post was about, then I actually looked at the left hand navigation frame. I had never noticed this Opinion Center, with the highlighted 'Intel' under it. How long has it been there? Guess I have been ready Slashdot so long now* that I don't bother looking at those things. At home my RSS feed means I never even see the front page. Now to get back top ignoring those links. *early 2000, though I didn't register until recently.
Boolean logic: True, False, and File not found.
There's no reason analog RGB won't carry 2560 x 1600 resolution - it's just that Apple doesn't support it.
DisplayPort: 15m with 2 wires at 1080p. Demonstrated with 2 crappy wires in one of the earliest demonstrations.
For longer distances you'll have to rely on extenders.
The fight for the next-generation connector is now between HDMI and DisplayPort.
DisplayPort was in good part started as a reaction against HDMI's control by Intel & Silicon Image, and the associated licensing fees. Intel tried to counter it with UDI, basically HDMI without the licensing issues, but failed. DisplayPort had issues with the proposed DRM, proposed by Philips for a non-trivial amount of money. Much stronger than HDCP, but also more costly in silicon real estate.
Intel killed the UDI effort and pushed for HDCP to be used instead in DisplayPort. The Philips DRM remain an option, but I doubt it will ever be used since it is way more expensive and not required to comply with Hollywood's requirements. Thankfully HDCP is seen as "good enough" by the MPAA. That's nice, given how weak it really is.
Reference on UDI being dead
HDMI is trying to spin its current wins to prepare the battle against DisplayPort
Personally I am rooting for DisplayPort to kill DVI and hopefully make enough headway on TVs to also (very long term) kill HDMI. I am looking forward to DisplayPort 2.0 (expected in 2008), this should enable high-resolution displays with a single (thin) cable. Think 4K / 2160p at greater than 60Hz and greater than 24bits/pixel.
How about we stop pretending it doesn't? Especially, as in your case, when there is no basis for such an assertion. I have full HD over component. My system looks beautiful. Ergo, analog doesn't give you a poor image, there's nothing inherent in it that prevents a good picture.
Please. My cables hang slack in the basement, hooked over projecting screws, run about 30 feet, and they are fine. Why? Because it doesn't take much (as in, proper termination, decent coax, low-loss connectors) to run high bandwidth analog just about any distance you like. Claims to the contrary are nonsense. Can you screw up such a run? Sure. Just try it using audio cables. But for that matter, try running a multi GB/s digital signal through an audio cable and watch what happens. I mean, aside from hosing every RF receiver in your home. Yes, we're in a zone where the cables need to be right. This is no different from a digital copper run. Optical is something else entirely. But of course, you can run analog optically as well. :)
Oh, please. Such marketing-inspired tripe. You picked the wrong person to try and push over what you thought was a hypothetical.
I have a 17 foot (204 inch) display driven exclusively by component from the receiver, though I also feed it analog from a Mac via a VGA input - that's the media librarian using Delicious Library. It looks absolutely fabulous either way. You can see every glorious pixel in HD, up close. The projector has about 30 feet of cable on it, not counting the various lengths of cable the component HD input sources (XBox360, HDDVD, Blueray, PS3, Satellite) feed to the receiver and the switches; there are no problems with ringing or artifacts whatsoever. The cables go down through the floor, along for quite a distance, and back up at, and through, the projector's pedestal. Of course I don't use radio shack RCA cables to do this, I use a triple run of coax and I have it properly terminated, but this is no big deal and the technology can be built into any simple cable without adding significant cost as compared to, for instance, a many-pinned multi-pin connector.
The manufacturers have been feeding you bullshit so long you think it is true. Well, it's not, and I can prove it.
Are there advantages or unique uses to/for digital transport? Certainly. But is digital transport in any way required to view for instance, full HD at 1080x1920 at 60fps in high quality? No. Absolutely, resoundingly, factually, no.
No, shitty equipment and/or shitty standards and/or shitty service is why your cable looks like shit. Cable can look butter smooth. The fact that yours doesn't isn't a reflection on technology, it is a reflection on what consumers will put up with because they're badly misinformed about what is reasonable and possible.
Listen to yourself. "Try using a crappy..." Why would I do that? Really, why? When I need one, I use one that is adequate to my needs. Nothing screws up at all. I switch between linux servers using a KVM and the results are pixel-perfect. It's 100% analog. Using crappy equipment will certainly get you crappy results, but why would you think this has any bearing whatsoever upon the inherent capabilities or limitations of the underlying technology? Talk about backwards reasoning!
I've fallen off your lawn, and I can't get up.
I think it's downright shameful that an article like that completely ignores the best video interface in the world SDI: http://en.wikipedia.org/wiki/Serial_Digital_Interf ace
DVI (and thus HDMI) is limited to very short cables, SDI does several hundred meters.
There is no DRM on SDI.
The cable for SDI is simple coax cable, it doesn't get much cheaper or robust than this.
The connectors are BNC, also robust and cheap.
The transmitters and receivers are also relatively simple and reliable.
SDI is what is currently used for digital transmission of video in professional environments, so it's not like it's completely unknown.
I'm pretty sure SDI is what we would be using if the MPAA didn't get to write standards.
-- To dream a dream is grand, but to live it is divine. -- Leto ][
That's why VESA came with it's BIOS extension, exposing much more function via the int 0x10, either as a TSR driver, or as part of the video BIOS later.
1.0 gave additional video modes, a standard mechanism for bank-switching, and other similar facilities (including saving the screen and mouse state).
2.0 gave linear frame buffers : no more paging required for 32-bits applications
3.0 gave support for hardware blitters.
also this whole extension made much more simpler modes that uses beyond 64Kb, because otherwise, the only portable way across all SVGA card and the original from IBM one was a crazy "unchained" mode which used a bizarre planar addressing mode (also called ModeX or Tweaked Mode... used to program those in assembly when i was a kid).
"Sufficiently advanced satire is indistinguishable from reality." - [Tips: 1DrYakQDKCQ6y52z6QbnkxHXAocMZJE61o ]
It proves the point; such systems are workable. That's all it is there for, to solidly discredit the ridiculous claims that are appearing in this thread about noise, resolution and so forth at HD. However, presuming mine is the only such system is really kind of dim. I bought everything off the shelf. You can reasonably assume I am not the only consumer to have done so. Or do you think I'm really the only guy with a high end component system?
We're talking about HD media here, not computers per se. And I really don't care if the content came from a renderer or a camera, or if it went digital or stayed analog. The POINT is it HAS to be analog at the last stage, and so analog to the monitor is a perfectly reasonable way to go. It puts the D/a at the signal origin, instead of in the display device, that's all.
No, for the Nth time, they do not. I wish you would have the courtesy to read the thread instead of forcing me to repeat myself over and over. LCDs take ANALOG drive at the LCD cell level. ANALOG. All systems take analog at the final leg. Plasma, CRT, point emission systems. All ANALOG. There is no 24-bit input to individual triplets inside an LCD, or 8-bit to individual cells, or any other common panel display. There are ANALOG lines that set the crystal to the state it needs to be in until its next refresh. ANALOG.
All LCD panels that take a digital input have to convert that signal to analog, because analog is what they use. That is a "GOOD REASON." Finally, with 24-bit RGB (8-bit per channel) you don't have to worry about degradation at all. Truly. It isn't a problem. And I don't want to get into the number of bits you actually need to see a quality image with someone who doesn't even know how LCD's work.
I've fallen off your lawn, and I can't get up.
It's actually worse than that. A lot worse. For reasons that I don't really understand, DVI and HDMI use timings that are derived from the analog standards, which have to leave significant pauses at the end of the line and frame to allow the electron beam to be blanked and to return to the left (or top) of the screen to begin painting the next line. 1280x1024 at 60 Hz adds 432 pixels horizontally and 36 lines, making the overall "picture" 1712x1060. That's just above 2.6 Gbps. HDMI actually uses the blanking interval to transmit audio and control data