Film-Tech Forum ARCHIVE: 3D Content Distribution

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Posted by Demetris Thoupis (Member # 833) on 05-23-2009, 03:31 AM:

Hi folks. I am really curious to see how the 3D content is being distributed to the theater chains. For example, is there a different film for a Dolby 3D playback and a different for a Master Image 3D playback? Do you need to get the distributors to know which 3D system a theater is using?
Demetris

Posted by Julio Roberto (Member # 4976) on 05-23-2009, 06:12 AM:

There is no technical reason to have separate masters for Dolby and other systems. Dolby-compatible DCI players (not all of them at this time) do the necessary color correction on-the-fly during playback from regular 3D content (2K, 48fps, alternate frames for each eye).

None of the other systems REQUIRE a special package either. Thus, Master Image could play the exact same 2K 48fps master you use for Dolby, i.e.

Your DCI player probably have settings to indicate what 3D playback system you are using so it may adjust minor changes (i.e. change the projector mode to 144hz with blanking intervals, etc). If it doesn't have settings for a particular system, it may work with other settings just fine (i.e. you can choose RealD in your DCI player when using a Master Image system, as they are totally compatible).

But so far, because RealD system is not up to par in the ghosting performance (double image), it is highly desirable for the film to suffer a selective contrast reduction prior to hitting the screen. Again, very few servers can currently perform this contrast reduction on-the-fly during playback of a normal DCI 3D package, so it has been the norm until now that studios supplied in the same hard drive two packages of the 3D movie: one "pre-ghostbusted" at the studio and another one "normal" (non-ghostbusted).

You can playback either one with either system. All systems would show even reduced ghosting if you chose to use the ghostbusted version, but also some added artifacts and reduced localized contrast. If you don't use the ghostbusted version and playback the normal 3D version instead, you will get more ghosting, specially on "bad" systems like RealD (less on dual-projectiong/Imax, Sony, Master Image, XpanD and specially on Dolby, which suffers from very little ghosting to begin with).

Eventually a large enough number of DCI players may start supporting real-time, on-the-fly ghostbusting of 3D movies during playback. At that moment, studios would stop supplying two different versions of the 3D film and just send a single one.

Also, hopefully, eventually more and more servers will start supporting real time, on-the-fly infitec color correction during playback and thus, be able to work with Dolby fitted projectors.

Sony takes a regular package (or a ghostbusted, your choice depending on how much ghosting is bothering your audiences) and adapts it for playback on their own system as well.

The goal for the studios is to send a single package for all 3D eventually, even if right now they must send two to aid RealD's relatively poor performance.

Posted by Mike Moreno (Member # 4887) on 05-28-2009, 09:35 AM:

the distridutor send us a paper (excel) here they ask what kind of 3D technology we have, serial numbers from the equipment, sometimes they ask about the sound of the auditorium.
i think they ask in order to see if they have to send the movie non gostb or viveversa

Posted by Stu Jamieson (Member # 4626) on 05-30-2009, 08:57 AM:

@Julio: Could you clarify the term "ghostbusted" please mate? From what I've gathered in your post it has something to do with reduced contrast levels in the source, is that right?

Posted by Julio Roberto (Member # 4976) on 05-30-2009, 10:12 AM:

Yeah.

In a nutshell, it goes like this: in 3D, you have two similar pictures on the screen at once, one for the right eye and another one for the left. When objects on the screen "stick out of the screen" a lot in "3D space" or when they go really "far out behind the screen", the image meant for the right eye and the image meant for the left eye appear further appart from each other on the screen (i.e. an obvious double image when you don't wear the glasses).

In a scene like someone with a flash light sticking out of the screen (bright object) in a cave (dark background), the bright part of the "right eye" image could easily ovelap a dark part of the image meant for the other eye on the 2D screen.

Since the filters used in 3D, specially polarized, don't filter out 100% of the light meant for the "wrong eye", only something like 97%-99% at best, you could see the right eyes' part of the "bright torch light" meant for the right eye when it ovelaps the "black background" part meant for the left eye.

Then you see a "double" or ghost image even with the glasses on, as you see a (bright) torchlight with both, the "right" eye and, because of the strong contrast against the black background in that part of the image, you also see it with the "wrong" eye, as with the ~98% efficiency of the filters, "2% of a flashlight" overpowers the "zero light from a black background".

With ghostbusting you scan the right and left eye images, figure out what parts overlap the physical 2D screen whereas it's really bright on one eye but happens to be really dark for the other eye on that spot. And once you find areas like this, you turn the brightness of the object way down (or increase the brightness of the background). In another words, you reduce the contrast so that it doesn't "stand out" so much and, thus, you won't see such a "bright" double image, but a much dimmer one that perhaps you won't notice (so much).

Of course that leaves you with funky potential artifacts where a "bright torch light" on dark background may end up looking brighter to one eye than the other, pictures with weird dark(er) "random" spots etc.

But this, as I said, only occurs on parts of the image that have a lot of "stereo disparity" (are away from the screen plane, either in front or behind) and happen to have large contrast in the illuminated part of the 2D screen where they overlap.

In short: ghostbusting is a selective contrast reduction technique that only affects "random" parts of the screen at "random" times according to how objects move in 3D space and how bright they are in one eye compared to how dark the background is supposed to be to the other eye at the point in the 2D screen where they cross paths.

You could apply this "selective contrast reduction" (ghostbusting) on your master and send out a "pre-ghostbusted print" or have a computer (server) do it "on the fly" while the movie is playing out of a regular (non-ghostbusted) "print".