HDTV-DVI Protocol Interpretation?

ignipotentis asks: "I have recently been looking into getting a Sony 50" Grand Wega. However, the one thing that deters me is the lack of obvious PC support. I would like to use the TV as a monitor for a living room PC as well as a TV. So I set off to do some investigation. I came across the ATI Component Adapters and then came across the reviews stating their overscan problems. Next I decided to check out the details on DVI (DVI & HDCP) and I've become rather confused. From what I gather, HDTV-DVI is nothing but DVI-D + HDCP. Now, being DVI-D, it can accept a signal from any DVI-I video card as long as a DVI-D male to male cable is used. Where I become confused is in the HDCP protocol. The way I read it, the Host (my computer) in this case, initiates the authenticity check whenever it wants. If it doesn't receive a valid reply, it can stop the stream. However, nothing is stated (that I can see) as to what would happen if no check was ever performed. If the Client (the TV) just continues to display what it receives, then all is good. If it does not, then I guess I'm back to the drawing board looking for other TVs. My question to Slashdot regards that of the protocol. I've emailed [e-mail] only to getan automated response as a reply and I'm hoping that someone a bit more technically savvy than myself can interpret the HDCP protocol better than I have been able to."

The TV doesn't reject

[dschuetz]

From what I understand, you're right -- an HDCP-compliant TV will not reject a non-HDCP signal. At least that's what I've been told. I recently purchased a Sony HDTV (46" rear proj.) with DVI-HDCP, and I've been told (on a mailing list) that it *is* compatible with computer outputs, provided you get your computer to send the right kind of signal. Because this is tricky, the "official" word from Sony is that the set doesn't support computers.

I haven't tried looking for the right kind of cable -- I know there are different kinds of DVI connectors, and the TV's connector is likely different from what's on my video card. One of these days, I'll probably give it a shot.

BTW, I was surprised when I dug into the DVI spec -- it's nothing more than a digitized raster signal. I'd expected something a bit more structured, somehow, like (x,y,r,g,b) data. (though I didn't see anything about how HDCP worked).

It seems the real advantage of DVI over, say, an RGB/VGA connection, is that the pixel levels are exact-digital (as opposed to a varying voltage level) and the digital format (with error correction) is less prone to noise. Or am I missing something? Because unless it allows for direct mapping of pixels, I don't see why DVI would be more precise for, say, an LCD panel, than a very clean VGA signal.

david.

Re:The TV doesn't reject

[dfranks]

I suspect the big difference is the presence of a clock signal. LCD controllers have to "guess" at where the pixel borders are in the analog signal. The transitions between pixel values are not nice square wave transitions, everything looks a lot more rubbery in reality. The result is an unintended antialiasing of the pixel data (in a 1:1 resolution situation), or with a crappy analog->lcd controller pixel jitter.

With the clocked digital DVI signal, the intended value for each pixel can be determined exactly.

Re:The TV doesn't reject

[Polo]

Having used crummy VGA cables (without the ferrite cores), I can say that 'a very clean vga signal' isn't always easy to attain/maintain, even for short distances.

Component video out....

[kraulin]

My friend got a 50 inch sony LCD Projection widescreen TV. He and I messed around with timings using power strip for hours and hours using the DVI interface. When we would push it too far the image would disappear. Quite frustrating when you have to reboot the box each time. But when we used the component video out of the video card (ATI AIW 9700) , It worked like a champ! Even if we "over drove" the display... the resoultion went virtual.

You can probably ignore the HDCP

[Rastor]

I doubt any current PC Video cards implement HDCP, however, I doubt any current TVs will REQUIRE it in order to accept a signal. You are much more likely to have problems outputting a resolution that the TV will display than an issue with HDCP.

There are better forums to ask this question, such as The AVS Forum [avsforum.com] and The Home Theater Forum [hometheaterforum.com]

The TV is fine

[Strange Ranger]

Just buy a 64Mb version of the 8500 (fairly cheap and falling fast) and one of these things here. [ati.com] And off you go to HDTV PC viewing.

That's not a bad investment next to a $4000 TV.

ACRONYM tag

[XO]

Could SOMEONE PLEASE use the Acronym tag? I don't mean to flame (and i'm going to turn off my karma bonus, so please don't moderate this into nothingness as troll or flame) but that whole story reads kind of like Robin Williams dialogue in Good Morning Vietnam where he goes on for like 2 minutes saying nothing but acronyms.

Re:ACRONYM tag

[cmehta1]

Try using the registry mod on http://www.acronymfinder.com to give you right-click to review acronyms

Link to the official specification

[JonTurner]

Check this [digital-cp.com] out. It's the home page for Digital Content Protection, LLC -- the folks who administer the HDCP protocol licensing system. At this site you'll find HDCP's specifications, upstream protocol, license agreements, reseller agreements, etc.

Of interest, also, may be Niels Ferguson's paper [macfergus.com]in which he details the cryptographic weaknesses in HDCP. Unfortunately, he won't publish the document due to fears of being prosecuted under the US DMCA.

HDCP

[14ghz]

HDCP, which for those who asked, is Copy Protection for High Definition TV. It will prevent HD content from being shown on non HDCP compliant monitors, or at least down-res it to 480 lines. It has not been implimented YET, but the TV networks want it and soon. A HDCP-compliant monitor will not reject a non HDCP signal, such as the one from a PC. Using powerstrip and a card like the ATI 8500 you will be able to run DVI from your PC. Using a input card such as the Holo3Dgraph you can turn your PC into a high-end video scaler and deinterlace all your video sources like a DVD player (it takes component in) or a cable tuner. Having the HDCP compliant DVI port is a good idea, especially if the networks get their way.

bob

Was in this same situation

[A_Wandering_Nomad]

Turning the way back clock about a year or so back...

I had my nice little ~2k tax return (I claim 2) burning a hole in my pocket, and decided on doing the same thing, Picked up a Wega, ATI's component video adapter, and an 8500 LE.

Of course, soon discovered that the component video adapter is not worth a cent(you can never see your entire desktop), and it often just doesn't plain work..

Looking into this furthur, I discovered something strange. The component video adapter was 2x the shipping and handling as some of ATI's larger videoCard bundle packages.. Mind you that the adapter is a small thing and came in a "letter" type box. It costs twice as much to ship and handle something twice as small? (when I tried to return it, they mentioned I would pay the shipping, and a small 'handling' fee. They also mentioned that yes the current drivers would not support most TV's, and that a future driver version would enable this) Of course that's also when they told me that with ATI, after 30 days, you pay for customer support. Bad driver/Hardware problem with your card, or anything else? $2.99 a minute(of course you wait the obligatory 10 minutes before you speak to someone).

I honestly felt a little extorted.....really felt like there was a little bit of a bad conspiracy..The component did not do what they said, and raised shipping and handling charges, so that if people did return it, they still came out in the black... (also the 30 day thing is atrocious, (This is a real quote)
ME:"You say that it probably won't work without the newer drivers, and the newer drivers ETA >30 days, so I'll have to pay you to help me get it working the first time?"
ATI Support Rep: "Unforunately, Yes".

I'll admit Iwandered right into a rant, but ATI has a history of bad drivers....Before Buying something from them, do a LOT of research.

YMMV, but I say stay away...