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There has been lots of discussion surround HDCP and the huge (negative) impact that this may have on the majority of current owners of HD equipment that have “only†analog HD inputs and outputs. The basic rule seems to be that any analog signal must be image constrained to 900x540 (or there about) if the content is protected. By protected content, this means premium programming and prerecorded material (which, frankly, is about all I care about!), the focus of this discussion.


I was wonder if any has considered the implications of this on two devices discussed below.


1. Line-doublers and scalars. While equipment that line-doubles or scales HD signals is probably pretty esoteric at this point, I expect this to change over time, especially among owners of fixed-panel displays that want to optimize for their device’s native resolution. Another driver will be the demand for progressive scanning and inverse telecine of 1080i film-based material.


As far as I know, all (or nearly all) such devices sport analog outputs. So, even if a scalar with a DVI/DTCP input were to become available, would it be “legal†for such a device to output a scaled analog image?


2. HTPCs. Today, most (if not all) implementations of HDTV on PCs involved an expansion card with a separate output to an HD device. In the not-so-distance future, as PC computational power continues to grow, I expect HDTV on PCs to become like NTSC tuners or composite video grabbers are today – the captured image can be scaled to an arbitrary size and imbedded in the PC user’s desktop. Likewise, HD-DVD (which is a matter of when and not if in my estimation) will enable the display of HD DVD context on the user’s desktop.


Of course, the VGA output of a PC is analog. When HD-DVD content becomes available, will PC users be unable to display this content at full resolution on their PC’s monitor? Furthermore, if a DVI/DTCP input card were to become available, would it be “illegal†to display these images at full resolution


Does anyone have any thoughts on this matter? I looked around for previous discussion on this facet of HDCP, but found none. My apologies if I am rehashing discussion mined to exhaustion.
 

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Quote:
By protected content, this means premium programming and prerecorded material (which, frankly, is about all I care about!)
Do you really not watch any OTA HDTV? If stuff like the Discovery channels and A&E were in HD, would you watch them? None of that would be copy-protected (or at least not "image constrained").
Quote:
Originally posted by ken_atwell:
1. Line-doublers and scalars. While equipment that line-doubles or scales HD signals is probably pretty esoteric at this point, I expect this to change over time, especially among owners of fixed-panel displays that want to optimize for their device’s native resolution. Another driver will be the demand for progressive scanning and inverse telecine of 1080i film-based material.


As far as I know, all (or nearly all) such devices sport analog outputs. So, even if a scalar with a DVI/DTCP input were to become available, would it be “legal†for such a device to output a scaled analog image?
The DTCP Adopter's Agreement contains the following definition:
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2.8 “Constrained Image†shall mean an image having the visual equivalent of no more than 520,000 pixels per frame (e.g., an image with resolution of 960 pixels by 540 pixels for a 16:9 aspect ratio). A Constrained Image may be attained by reducing resolution, for example, by discarding, dithering, or averaging pixels to obtain the specified value. A Constrained Image can be displayed using video processing techniques such as line doubling or sharpening to improve the perceived quality of the image. By way of example, a Constrained Image may be stretched or doubled, and displayed full-screen, on a 1000-line monitor.
So, yes, a device could reduce the real resolution by discarding some real pixels and then use line doubling techniques to improve the visual quality of it. I'm sure the DTLA would want to take a long, hard look at such a converter, but it sounds perfectly legal. Since it would have to perform MPEG decoding, it could even pass non-copy-protected content or "Copy One Generation" content with "Image Constraint Tokens" in full HD resolution over its analog outputs, from sources that don't have HD analog outputs, like Mitsubishi's new HD D-VHS VCR.
Quote:
2. HTPCs. Today, most (if not all) implementations of HDTV on PCs involved an expansion card with a separate output to an HD device. In the not-so-distance future, as PC computational power continues to grow, I expect HDTV on PCs to become like NTSC tuners or composite video grabbers are today – the captured image can be scaled to an arbitrary size and imbedded in the PC user’s desktop. Likewise, HD-DVD (which is a matter of when and not if in my estimation) will enable the display of HD DVD context on the user’s desktop.
I can't forsee HD DVDs being published in an open format that would allow them to be displayed directly by any kind of PC. The code for the protected DTCP protocol and its stored public and private keys must be implemented in physically tamper-proof (as much as possible) purpose-specific devices only, or the whole protocol is useless. Any program running on a PC which can run arbitrary other programs would be easy to compromise. For that reason, I can't imagine the DTLA ever licensing PC programs to perform DTCP or the studios licensing PC programs to decrypt whatever format they end up using for HD DVD (look what happened with CSS--wasn't it a security leak at Xing Technology Corp. that resulted in distribution of the key initially used with DeCSS? Maybe it could have leaked from a CE manufacturer, but it didn't).
Quote:
Of course, the VGA output of a PC is analog. When HD-DVD content becomes available, will PC users be unable to display this content at full resolution on their PC’s monitor? Furthermore, if a DVI/DTCP input card were to become available, would it be “illegal†to display these images at full resolution?
The DTCP Adopter's Agreement has the following extremely cryptic stuff to say about that:
Quote:
4.3 High Definition Analog Output. Licensed Products shall not pass Decrypted DT Data to a High Definition Analog Output, except as set forth in this Section 4.3:

4.3.1 Licensed Products may pass Decrypted DT Data to a High Definition Analog Output as a Constrained Image.

4.3.2 Licensed Products that recognize and respond to the Image Constraint Token in accordance with the Specification may pass Decrypted DT Data to an output in High Definition Analog Form when authorized by the setting of the Image Constraint Token.

4.3.3 Licensed Products incorporated into Computer Products may pass Copy One Generation or No More Copies Decrypted DT Data without image constraint to SVGA (1024x768 and greater), XGA(1024x768), SXGA and UXGA or similar computer video outputs that were widely implemented as of May 1, 2001 (but not to such typical consumer electronics outputs as NTSC, PAL, SECAM, SCART, YUV, S-Video and consumer RGB, whether or not such outputs are found on any Computer Product) in High Definition Analog Form for devices manufactured prior to December 31, 2005, unless otherwise

notified by DTLA.

4.3.4 Licensed Products may pass Decrypted DT Data in High Definition Analog Form to a High Definition Analog Output where such Decrypted DT Data is encoded Copy Freely.
If you can fully understand 4.3.3 (or their motivation for putting it in there--probably some pressure from Microsoft http://www.avsforum.com/ubb/smile.gif ), you're a better man than me, Gunga Din.


-- Mike Scott



[This message has been edited by michaeltscott (edited 10-04-2001).]
 

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Quote:
Originally posted by ken_atwell:


As far as I know, all (or nearly all) such devices sport analog outputs. So, even if a scalar with a DVI/DTCP input were to become available, would it be “legal†for such a device to output a scaled analog image?


..........


Of course, the VGA output of a PC is analog. When HD-DVD content becomes available, will PC users be unable to display this content at full resolution on their PC’s monitor? Furthermore, if a DVI/DTCP input card were to become available, would it be “illegal†to display these images at full resolution
The output of line multiplier/ scaler would have to be encrypted DVI to satisfy the requirements of no analog output.


It would seem foolish to have DVI input to the line multiplier / scaler and throw away all that large amount of MPEG-2 computation to measure motion and interpolation between frames.


Motion and interpolation information would be used to increase the frame rate and interpolate between fields & frames for the best possible image. A good design would probably want a Firewire input with the MPEG-2 data and a DVI output.


I have not seen anything on PC monitors and HDTV. Maybe they will have to use DVI connections to display HDTV. With hopefully a large HDTV market, high resolution HDTV digital monitors may be cheaper than analog computer only monitors which would then go away.
 

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Quote:
Originally posted by jackmay:
The output of line multiplier/ scaler would have to be encrypted DVI to satisfy the requirements of no analog output.
See my post above--there is no "requirement of no analog output". You just have to reduce the real resolution to no more than one quarter of 1080i (980x540)--you are explicitly allowed to apply any post processing to that that you want. The HD analog outputs would be the entire point of such a device--it would be a means to view digitally transported content on a HD monitor with no digital connections.
Quote:
I have not seen anything on PC monitors and HDTV. Maybe they will have to use DVI connections to display HDTV. With hopefully a large HDTV market, high resolution HDTV digital monitors may be cheaper than analog computer only monitors which would then go away.
This is an interesting thought--if you had a high resolution digital monitor with multiple DVI inputs, one of them copy-protected, you could securely display HDTV on a computer monitor. If the monitor was internally capable of scaling, you could even display the HD in a moveable window. The HD, however, would have to originate outside the computer. The possiblity exists of a physically tamper-proof HD-DVDROM drive with a DVI/HDCP output that could play HD-DVDs out of the secure DVI outputs, but not pass any data from a decrypted DVD into a computer through its IDE or SCSI (or whatever) interface, but which could be used to read other forms of discs. Of course, since it'd have to implement an MPEG decoder, it'd be wickedly expensive.


-- Mike Scott
 

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Yes I know about the analog restriction but went down the mental tunnel of thinking about HDTV only output.


There is already at least one MPEG-2, MPEG-4 chip on the market for about $24 which I think handles HDTV. Decoding should be cheap in the future.


A more likely HD-DVD output would be 1394 / 5C. People will want their PC connected to 1394 / 5C to control their system and to display the output of other components. People will also want their HD-DVD output to go to other displays.


Maybe there will be a 1394 card in computers that will have a decoder to output HDTV to the display along with other computer data. That way the decoder would be shared with multiple devices in the computer and elsewhere.
 

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Quote:
Originally posted by jackmay:
A more likely HD-DVD output would be 1394 / 5C. People will want their PC connected to 1394 / 5C to control their system and to display the output of other components. People will also want their HD-DVD output to go to other displays.
What people want and what they get are often very different things. The consumer has no desire for copy-protection at all, yet we're likely to get it.


There's no way that the DTLA can prevent people from connecting the appropriate Firewire connector into a 1394/DTCP device from a computer Firewire interface, but I just don't seem them sanctioning a PC interface that speaks DTCP, unless HD video only travelled in one direction--from the computer, into the interface. The interface itself would have to be some some of physically tamper-proofed box to mount in a drive-bay, with maybe some sort of minimal PCI card connected to it. The computer could pass HAVi commands and HD video through to it, but any protected video emerging from it would have to come out either image constrained or in protected digital form. Even image constrained HD analog stuff is supposed to have analog copy-protection measures applied to it, to prevent it's being recorded off the analog outputs by a W-VHS deck or something. There's no way they'd allow even image constrained digital copy-protected video to be delivered into the computer from such an interface.


Still, there might be some sort of use for the limited functionality such a device could be allowed to deliver in a secure fashion. You could feed it the digital output from your display card to be turned into an MPEG stream and sent downstream for display on a monitor with digital connections.


-- Mike Scott
 

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Hmmm. Looks like I eat my words-- DTCP Tutorial (two years old) and the DTCP Whitepaper (three years old) show that, at a least a few years back, the DTLA thought that the PC was a viable participant in 1394/DTCP networks. The DTCP Adopter's Agreement has some pretty heavy specifications for "robustness" and I don't see how a PC could ever be made to comply with them. (Of course, it was completed a couple of a years after the last document they wrote with PCs in their diagrams). Now, the Adopter's Agreement does repeatedly mention "licensed product incorporated into a Computer Product", though it doesn't specify specifically what it envisions such to be. It does state, however, that decrypted data cannot be put unto a common bus, specifically not PCI or PCMCIA, so if it handled copy-protected video, the computer would have to do all its encryption/decryption in realtime itself. The product is supposed to obfuscate the methods of the protocol and store all keys in a secure fashion--I have no idea how this could be achieved by a PC program. How it could absolutely prevent another program from snooping on decrypted data in its buffers is also beyond me.


-- Mike Scott


[This message has been edited by michaeltscott (edited 10-04-2001).]
 

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The HAVi FAQ says


"A PC can be a HAVi device just like any other. Its use is neither required nor prohibited in a HAVi network. It can control other HAVi devices and it can offer AV related functionality that can be controlled by other HAVi devices."


They may make it extremely difficult to satisfy their requirement to bring in 1394/CJ/HAVi into a PC but it does not appear that they are ruling it out.
 

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Some DVD implementations allow content to be shown via an overlay, but not as decoded MPEG-2, i.e., something you can copy. That's the way Apple does it with CSS DVDs and also why they attempted to prevent the use of a debugger and running their DVD Player application at the same time. The funny part is that you'd have virtually no chance of getting video with a debugger and besides its so much easier to just rip the DVDs using the Mac OS version of DeCSS.


No matter what Hollywood does, these systems will be breakable. Hell, "Star Wars: The Phantom Menace" is available on VideoCD and DVD in Asia because someone stole a film print from a theater. They should just get a life and hope we allow them to remain in business. Computers are an integral part of the production process so making it more expensive to use computers to make movies isn't in their interest.


Michael Eisner is just clueless...


Dennis


------------------

Dennis Whiteman

FastPipe Media, Inc.
 

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Quote:
Originally posted by jackmay:
The HAVi FAQ says


"A PC can be a HAVi device just like any other. Its use is neither required nor prohibited in a HAVi network. It can control other HAVi devices and it can offer AV related functionality that can be controlled by other HAVi devices."


They may make it extremely difficult to satisfy their requirement to bring in 1394/CJ/HAVi into a PC but it does not appear that they are ruling it out.
Sure--like I said before, you can connect a computer into a 1394/DTCP network. You can connect anything with a Firewire connection into it. I'm sure that there is nothing in HAVi to keep a computer from talking HAVi over such a connection. HAVi, however, is not a secure protocol.


The question is whether you could make a computer program designed to participate in a secure DTCP connection secure enough to satisfy the Adopter's Agreement. There are all sorts of measures that you can take to make a CE device secure. But PCs are intended to be physically user serviceable devices. Users can write and run protected mode programs on Windows that can look at any part of memory and there's nothing that a DTCP protocol stack running in the machine could do to keep such a program from looking at the decrypted video data in its buffers.


Personally, I think that it'll be quite a while before we see such a thing, if ever. There's no actual need for it.


-- Mike Scott
 
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