For the umpteenth time : HDCP and Analog (CRT) Displays (1 Viewer)

[alan halvorson]

I have a question and HDCP encryption and CRT rear-projections displays.

Here's what I understand about HDCP:

HDCP is the encryption scheme used for HD sources. To be HDCP compliant from source to display means that the signal must be maintained in its encrypted digital form all the way from the source to the display and (assuming we want to keep the signal in HD) never, ever be allowed to be converted to analog, this to prevent the analog signal from being pirated. Thus, when a dvd player detects an HDCP-flagged disc, it encrypts the bitstream, passes it through the digital outputs and disables the analog outputs. The display decodes the HDCP encrypted bitstream and, being digital in operation already, maps the signal.

All this, I thought, left out analog (CRT) displays.

I'm certain you can see my next question coming. How can CRT rear-projection sets have an HDMI input, which is by definition HDCP compliant, since at some point the digital signal must be converted to analog? Cannot a pirate-minded thief simply extract the analog signal? Are CRT RP's allowed to display HDCP encrypted sources in high-def? And if it is ok for CRT to accept HDCP encrypted signals, couldn't CRT front projectors and other non-HDCP compliant displays be modified to do it the same way?

I know that to be HDCP compliant, there must be a certain level of "robustness", but this would seem to leave out all analog displays. I must be missing something.

 

[alan halvorson]

I can't believe no one on this forum has an answer to this. Where are the experts?!

 

[Michael TLV]

Greetings

Anything can be done if one wants to put the time and effort and resources into it. You want to do it?

Encryption can be defeated ...

But this is not the site to talk about such things. It is taboo.

Regards

 

[alan halvorson]

You misunderstand. I am not asking specifics on how to defeat HDCP encryption. I am asking how CRT RP sets with HDMI inputs being sold at Best Buy, Circuit City, etc. right now, can be analog and not in violation of any law, rule or agreement. How have manufacturers designed the circuitry to prevent pirates from tapping the analog signal? I don't need the dirty details, just an overview.

 

[Jeff Gatie]

Easy, the digital to analog conversion is confined to the TV electronics only, which make pirating the signal diffcult to impossible. There are no video outputs on the set that would allow you to "copy" the analog signal, you would have to tap into the signal that is sent to the CRT's, which is not an easy task.

 

[alan halvorson]

I cannot believe it is impossible, Jeff. At some point the digital signal is converted to analog and then that analog signal must connect to the CRT. It may be difficult to do (sure would be for me), but someone knowledgeable enough in electronics will be able to find that analog signal and extract it. There's a big fuss going on over on the AVS Forum because the implementation of HDCP has made all those nice, big, heavy CRT front projectors obsolete, at least as far as displaying the coming high-def sources. I don't believe CRT RP's get a bye while CRT FP's don't.

Perhaps you're correct, but I'd like to know why.

 

[Michael TLV]

Greetings

IT may not be impossibe, but what makes it easier than just breaking the encryption?

And exactly what will they be recording this HD signal with? A Hard drive ... ? A WVHS vcr that costs $5000 and uses $60 tapes?

YOu have to take that signal and convert it into something like RGB or component and make an interface to take it into a computer ...?

I'd just go the break the encryption route ... and no more or less difficult than tapping the signal stream.

Of course much of this is a short term issue anyway since you won't be able to buy CRT's soon anyway.

regards

 

[Jeff Gatie]

There are also ways for those knowledgable enough to go down to Radio Shack and buy $100 worth of parts to build their own digital to analog converter and hook that up. It's just not easy (or legal).

 

[alan halvorson]

Yes, of course you are correct - I believe both of you are correct. Clever people can do clever things. But figuring out how to de-encrypt HDCP is not what I'm inquiring about.

Maybe I can explain my inquiry another way. There are now several HDCP compliant scalers that you can buy. One of the rules of HDCP compliance is that when an HDCP encrypted signal is input to the scaler, the scaler cannot pass that signal in high-def through its analog (component, RGB or whatever) output. Why? To prevent that high-def analog signal from being captured and digitized (and no longer HDCP flagged). Yes, there will be a quality loss but it won't be much. Now, how that high-def signal is captured, whether to hard disc, tape, or stone tablets is of no consequence to my inquiry. It does matter that the paranoid powers-in-charge have decreed that it shall not be done.

Ok - HDCP compliant scalers cannot pass along an HDCP encrypted input in its high-def form through its analog outputs. But - an HDCP compliant CRT RP must if it is to perform as advertised. All a RP is is a FP in a box with a mirror and an integral screen. HD capable RP's normally include deinterlacing and some kind of scaling. Am I off base here? I've never owned a RP set. The output of that scaler is analog. The input to the CRT is analog. If the RP is HDCP compliant, there must be an extra step that prevents the analog signal from being externally captured. All I am asking is, what is that step? Can it be applied to existing non-HDCP compliant displays? Is anyone certain that that step is actually there? Maybe it's not.

I would guess that you, Michael, being an ISF Calibrationist, would be most likely to know, but perhaps your duties as a calibrationist don't require you delve that deep.

I think this is an interesting and maybe an important thing to know, and I'm still looking for the answer.

 

[Jeff Gatie]

You have your answer right at the end of this statement - "the scaler cannot pass that signal in high-def through its analog (component, RGB or whatever) output". What analog (component, RGB or whatever) output does a CRT RPTV have? None, so it is not analogous to the scaler that you refer to. Can someone hook up to the analog inputs to the crt's and somehow capture the signal, yes. But it is quite different from having the analog output exit the TV from standard component outputs that can easily be diverted to a computer, HD-VCR or other capture device.

 

[alan halvorson]

Jeff: I quite realize that there are no high-def analog outputs. Your average run-of-the-mill copyist is stopped by this fact. But he's not the only problem. If I am determined to make money by pirating software, I just might get me one of these RP's, take it apart, find that analog signal, capture it and I'm on my way. This is worlds easier than developing a box to decrypt HDCP (I do know that such boxes are available right now, so it's probably more likely that a pirate will pursue this route). Studios want to defeat both the casual recorder and the pros. I'm certain that they've thought of this potential loophole. Has something been done about it? I have never come across a discussion of this question, so that's why I'm asking.

 

[Jeff Gatie]

Why would anyone be concerned about this when you yourself state "I do know that such boxes are available right now, so it's probably more likely that a pirate will pursue this route". It's like worrying that someone will tunnel under the streets and into a bank vault when the vault door is already unguarded and open.

I guess I do not understand why you are concerned about this question. Do you think CRT's should be banned from sale? I see you think that something may have been done to eliminate this "loophole". This has been answered a few times. They simply do not allow the analog to be transmitted outside of the TV. Your question is akin to asking "if someone can defeat macrovision by methods x, y and z (I'm not stating the methods, it's against the rules; but it is certainly easier than tapping into the CRT feeds on an RPTV), why do they allow a company to sell VCR's?" It's a question that has no reason, similar to saying "If a professional car thief can easily defeat a car alarm, why do they sell alarms (or the car itself, for that matter)?"

 

[Michael TLV]

Greetings

Same reason why you cannot stop one man and a gun if he is determined to give up his life to achieve something.

You can't plan and budget for infinite possibilities and we won't punish 1 billion because 1 person might break the rules.

Ditto why we should not sell guns ... or cars ... or toothpicks because someone might use them for nefarious purposes ...

Regards

 

[alan halvorson]

My inquiry has been answered no times. I have pointed out a potential loophole. What, if anything, has been done to close it? I am not concerned about it - I am simply interested in the answer. I want to know why an internal scaler is permitted to do something an external scaler isn't. I don't believe anything should be banned.

Mike, I understand what you're saying but you're being waaaaay too philisophical. I thought I had asked a technical question which I had hoped would garner a technical answer.

Thank you gentlemen for your responses, but I guess I'll have to search elsewhere.

 

[John S]

Shhhhhh... The studios may come across this thread and say yeah he is right. Lets ban CRT/Analog technology all together!!! That would be a shame, it is still the best in my opinion.


I still think somebody will make an external scaler that will do this eventually. If there is a buck to be made, ya know.

I'd even bet eventually you can take HDMI input, and output it over Component Analog Video. But if not, I am not going to sweat being limited to 480p on bit.

 

[Jeff Gatie]

Look for Bigfoot, the Yeti and Noah's Ark while you are out there.:rolleyes

 

[alan halvorson]

Jeff: Tell me exactly how the HD output of an RP's internal scaler gets to the analog inputs of the CRT itself and what has been done to prevent capture of the HD analog signal? If nothing has been done, fine, if you know, in fact, that that's the answer. It's obvious you don't. Have you opened up a CRT RP set to find out? Have you looked at the schematics? Have you read a paper, or know somebody that is familar with the innards? I was hoping to come across someone with real knowledge on this matter.

I thought it was an interesting question and that some would be interested in the answer. I'm still interested, and still looking, but I'll bet that I'll find Bigfoot, the Yeti and Noah's Ark before I get the true answer out of you. No smilies for me.

 

[Jeff Gatie]

Yes I do know in fact, no it is not obvious because I do know, Yes (I ignored the sticker), Yes, No, Yes (in that order).

I have told you a few times now that there is not special circuitry to prevent your scenario from coming true. There is no way you can have a closed digital->analog conversion without being able to tap into the analog somewhere along the circuit. That said, it is highly improbable that a pirate is going to tap this difficult a route to analog HD when there are so many other weak points in the chain (gee where have I heard that before).

 

[John S]

Alan, I guess the short logical answer is.....

"There are simpler ways around it" There would be no reason for somebody to do it like that.


I'd bank with my, what I would lable as limited general level electronic and digital circuit knowledge, I could by the cheapest HDCP compliant device and come up with some analog output from it. Not to sure what such a mod would cost though. Probably a lot cheaper than buying a CRT based HDCP compliant display though.

I mean even on a digital display, by the time it gets to the actual display panel connections, HDCP is long gone, so you would design the interface right there.

I guess I'm still not sure, what answer your looking for here.

 

[Jeff Gatie]

Not to mention that every digital display has "analog" at the very end of it. No matter how much of the circuitry relies on a digital pathway, it is still an "analog" connection to the individual pixels at the end of the path. Deriving a (decoded) digital HD signal from a series of those would probably be no more difficult than deriving an analog one from the individual analog signals to 3 CRT's (and about as practical).