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This topic comprises 2 pages: 1 2
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Topic: Digital Cinema Initiative
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Steve Guttag
We forgot the crackers Gromit!!!
Posts: 12814
From: Annapolis, MD
Registered: Dec 1999
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posted 08-08-2005 06:54 PM
I've made it through just about 1/2 the specification (it is something like 170-180 pages).
The bulk of it is all wrapped up with the Security of the movie. Very little of the DCI standards actually have to do with the standards.
At present, the DCI recognizes 2K (at 24 or 48 fps)and 4K (at 24fps)resolutions (with no mentino of 1.3K resolutions, that I've found yet) so I guess you are left out if you were an early adopter...perhaps a forshadowing of things to come.
At no time can the signal outside of the projector be in a decrypted form (i.e. there will be NO visual monitors). A DCI compliant projection system will perform the final decryption within the projector and also apply forensic marking that can be traced to the projector (btw...the same goes for the audio where the DCI audio decoder is to forensically mark the audio in some way). As I understand it...the current DCinema projectors do have "Link Decryption" within the projectors so concievably they can be used if the 2K/4K files can be downconverted suitably.
The Screen Managment System (SMS) will rat you out on everything...if you run the movie...it will be logged. Your "keys" for decrypting a movie will have a provision for a time limit (engagement) and will delete the files in a non-recoverable manner) when your engagement expires. Which should not be a problem, if everything works properly. At least now...if Technicolor shows up at your door when you still have the film booked they won't be able to take it off your platter...with DCinema...a simple mistake will erase your show.
You sound buffs should take note of the...anyone, anyone? 16-channel sound provision. Thats right...16 wonderful channels that are not entirely defined yet but I agree it is nice that more than the present 5.1 or even 8 can be accommodated. I'm sure 16 came up merely as 8 times 2. There is an example layout that has 7-screen channels (the five usual suspects, left and right upper...sorry IMAX, VOG is left out), the stupid 3-walls of surrounds (I say stupid since the back wall should be descrete left and right rear wall...for current EX films, they would be the same signal) and the long awaited Ceiling surround.
The above is merely a "suggested" layout. 5.1 remains the minimum configuration. However, I have not read yet how one, that has only a 5.1 system, would play a more sophisticated soundtrack or if a 5.1 is always to be made available.
But again, security remains the key to this document.
They should rename this document "There's a new Sherrif in town!"
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Lyle Romer
Phenomenal Film Handler
Posts: 1400
From: Davie, FL, USA
Registered: May 2002
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posted 08-09-2005 06:48 PM
Here are my comments from that other thread but I think they are more relevanat here:
Well, so much for quality. No anamorphic format for 'scope. I guess the way the spec is written, common width screens are the right way to design a theatre.
quote:
3.2.1.2. Image Structure
The DCDM shall provide an image structure container that consists of either a 2K (2048 x 1080) or 4K (4096 x 2160)image file as defined in Table 1. It is expected that the image structure shall use one of the two containers such that either the horizontal or vertical resolution is filled. For example, a 4K image file with a 2.39:1 aspect ratio would require an image structure of 4096 x 1714, therefore filling the horizontal resolution of the 4K container. The pixel orientation, as displayed on the screen, shall be understood to flow from left to right and top to bottom. Also, the horizontal and vertical pixel count shall begin with 0. For example, the top left pixel of the displayed image shall be anotated as (0, 0).
A few good things in the spec......
1) Audio will be uncompressed, 24 bit, 48 or 96 kHz and up to 16 discreet channels are supported
2) Image compression is JPEG 2000. Since JPEG 2000 compresses each frame without regard to preceeding or following frames, there shouldn't be the MPEG type motion artifacts.
3) Data rate will be 8 to 9 times the data rate of HD-DVD or blu-ray.
What I think they should have done is required that the image source and distribution be in 4k and then the playback equipment could be either 2k or 4k.
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Steve Guttag
We forgot the crackers Gromit!!!
Posts: 12814
From: Annapolis, MD
Registered: Dec 1999
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posted 08-09-2005 07:30 PM
Ah...that may be true but the phrase "DCI-Compliant" has already worked its way into manufacturer's descriptions. Furthermore...if the DCI is the body that is trying to have uniform standards that all manufacturers are ensure they meet, then it can't be so wishy washy. How can a manufacturer make a product, spending great volumes of money, only to find out that they are not compliant with some aspect(s)?
The idea, as I understand it, is to have a single set of requirements such that if a manufacturer makes their product to the set specifications, then it will be compatible with the DCinema industry.
To put it in film terms...film projector manufacturers know that they must support 35mm film that is perforated in such and such a way, that it must advance at a rate of 24 frames per second....and so forth. The net result is that we have Century, Simplex, Kinoton, Christie....and the list goes on for quite a while...with everyone's equipment handling the same film without any surprises from the film itself. Some may do it better than others and one would expect that some DCinema systems will perform better than others too.
Note on the 2.39:1 shows...the DCI document does not preclude the use of anamorphic lenses...it does require that the change to a secondary lens be automatic and that the scaling done within the projector not introduce any visual artifacts. However...the spec does say that the master file be a 1:1 ratio file that fills the width of the 2048 (2K) or 4096(4K) imager. Thus, the scope image, that SHOULD fill a larger screen area, will actually start out with less data (fewer pixels).
A superior specification would have had all 1.85 and 2.39 images fill the imagers and that it was the responsibility of the projector to scale the height down for constant width theatres.
All that the current spec allows for is a 1:1 mapping of the pixels, regardless of format, upon projection if you have constant width....sounds like a screening room spec.
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Heath Dutton
Film Handler
Posts: 37
From: Montgomery, Alabama / United States of America
Registered: Jul 2005
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posted 08-10-2005 01:56 PM
I have been a member of DCI for quite some time, so that I could read the beta specifications before the recent release of the first "public spec" sheet. I think all of this work should have been done years ago, but I'm glad someone has finally gotten around to doing it. And yes, I would agree that the specifications mostly concern security of the process, but the original betas up until recently did not even touch the surface of the security issue. Most of the early work was about deciding audio channels, pixel rates for 2K and 4K, not to mention decisions upon file types...
It has a long way to go, the file types and compression methods are very vague, and there are a couple requirements that are nearly impossible with current technology (i.e. a 10gbit connection inside the projector payout) which I do not believe are truly necessary. But of course there will be dozens of revisions over the next year or two I'm sure.
Now you may ask, why would I be interested in all this "digital mumbo jumbo", especially since my theater doesn't even have any DLP projectors? Well, I've seen the price tags on the DLPs and I find them hideously overpriced. I would like to one day build my own 2K projector, and after reading their specs I believe a slightly toned-down (using lcd instead of dlp) version of a 2K could be created for under $3000, including dci-compliant computer hardware with enough storage for 2 films.
The hardest part would be creating the software, and for that I would use a modified windows-media activeX for post-decryption.
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Heath Dutton
Film Handler
Posts: 37
From: Montgomery, Alabama / United States of America
Registered: Jul 2005
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posted 08-11-2005 04:18 PM
I realize windows is not the most reliable OS out there, but linux doesn't offer the broad functionality, at least not yet...
Windows XP can be extremely stable, if it is coupled with the right hardware. I have a 2ghz machine at home that has been running for the past 4 months, asside from occasional power-outages and upgrades. I attribute this mostly to the excellent motherboard, Intel CPU and ECC server grade ram. The machine was simply built for reliability. My other computer I built purely for speed, and although it is twice as fast, it doesn't have error checking ram and those rock solid hardware pieces, and it shows. It will occasionally lock up, or reset due to hardware related issues. But this is not the fault of XP.
If I were using windows for a hardware application such as a projector-to-screen presentation I would use a stripped down home-brewed version. Microsoft has all the tools available to do this yourself, and as long as you aren't marketing the device you don't have to pay licensing fees, etc.
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