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Topic: Digital show starts without one color...

Mark Lensenmayer
Phenomenal Film Handler

Posts: 1605
From: Upper Arlington, OH
Registered: Sep 1999

posted 08-29-2008 01:39 PM

The digital screening I saw this morning started with only red and green images. Needless to say, the trailers looked very weird. I went to the lobby to tell them, and it was corrected when I got back to the room.

This was a 3-D show but it happened during the 2-D trailers. It was the first show of the day. Theatre was an AMC.

Can someone explain what happened?

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Thomas Pitt
Master Film Handler

Posts: 266
From: Leeds, West Yorkshire, UK
Registered: May 2007

posted 08-30-2008 01:30 AM

Either the blue signal to the projector (the colors are sent through separate wires) wasn't connected properly - loose wire or similar - or the actual DLP chip for the blue channel wasn't responding. Since they were able to fix it so quickly, I'd say it wasn't anything complex, like the DLP mirrors getting jammed.

Sometimes a projector can go wrong and start up without one of the color chips responding. Usually a power-cycle will sort that out, as it'll re-initialize everything.

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Pete Naples
Phenomenal Film Handler

Posts: 1565
From: Dunfermline, Scotland
Registered: Feb 2001

posted 08-30-2008 03:08 AM

quote: Thomas Pitt
(the colors are sent through separate wires)

If this was a D Cinema show, that statement is not true. The signal to a D Cinema projector from the server is carried by dual link SDI.

The point about the projector needing rebooted is valid, I have seen this once or twice.

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Josh Kirkhart
Expert Film Handler

Posts: 165
From: Austin/Houston, TX, USA
Registered: Nov 2001

posted 08-30-2008 05:22 AM

No restart was needed or it would not have been onscreen when he returned to the theatre.
The projector was simply in the wrong Format.
Various formats are preset or customized with defined color/crop/aspect ratio/frame rate/ etc.
They were more than likely using two different format 2d/3d buttons and manually changed it.
Why it did not start in correct format is a whole different question(bad showlist build/operator error/automation cues not reset before show etc.).
Showlist could be built so that the 2D content plays at 48fps in the 3D format so all content conforms to the 3D masking crop, so no Format, lens or zoom changes are needed depending on the house setup(anamorphic/single lens/zoom lens/flat/scope feature etc.)

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Stephen Furley
Film God

Posts: 3059
From: Coulsdon, Croydon, England
Registered: May 2002

posted 08-30-2008 07:36 AM

quote: Pete Naples
If this was a D Cinema show, that statement is not true. The signal to a D Cinema projector from the server is carried by dual link SDI.

It would be possible if the trailers were run form some sort of alternative content system, via a DVI link, though it's not likely since all of the signals are carried on one connector. If it was a broken wire in a cable it seems unlikely that it would have been diagnosed and fixed that quickly. It would be more likely with analogue signals on 3, 4 or 5 separate BNC cables if one of them was incorrectly connected.

A re-boot would be likely to take more than a few seconds, and I can't think of any format/system mis-match which would simply drop the blue. There hadn't been a technician working on the system before the first show that had turned off the blue channel for some reason and forgotten to turn it back on, had there? Even that seems unlikely, since he/she would be likely to check the picture when they finished, and unless they were still there, and realised what had happened it probably wouldn't have been fixed that quickly.

How are the bits shared between the two HDSDI links in a digital cinema system? does each cable carry half the bits for each pixel, or half the pixels for each frame, or do the two cables carry alternate frames, or what? I've never tried disconnecting one cable to see what would happen, but I suspect that you'd lose the entire picture. Does one link carry the clock for both, in the same way that the first AES pair for the audio carries the clock which is used by all four pairs?

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Mark J. Marshall
Film God

Posts: 3188
From: New Castle, DE, USA
Registered: Aug 2002

posted 08-30-2008 09:28 AM

quote: Josh Kirkhart
Why it did not start in correct format is a whole different question(bad showlist build/operator error/automation cues not reset before show etc.).

I'm really confused by this. Does a DLP projector NOT have the ability to look at a movie file, determine its format, and configure itself correctly before playing the file?

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David Zylstra
Master Film Handler

Posts: 432
From: Novi, MI, USA
Registered: Mar 2007

posted 08-30-2008 09:39 AM

quote: Pete Naples
carried by dual link SDI

Which is 2 wires - basically bandwidth is shared across both, one wire is fully used and the other carries the remainder of the information. I've seen it many times where the secondary one comes loose there is picture but it looks like colors are missing, if the primary comes loose there is no picture.

It is also very possible that the playlist was started in the wrong colorspace.

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Chris Slycord
Film God

Posts: 2986
From: 퍼항시, 경상푹도, South Korea
Registered: Mar 2007

posted 08-30-2008 09:45 AM

quote: Mark Lensenmayer
Can someone explain what happened?

Since you said it was with a 3D movie, similar stuff to what you're describing can happen when the server's playlist triggers the projector to switch to a 3D format (either a 3D Flat or 3D Scope) but for whatever reason the projector stayed in the non-3D format.

quote: Mark J. Marshall
I'm really confused by this. Does a DLP projector NOT have the ability to look at a movie file, determine its format, and configure itself correctly before playing the file?

Well, no the DLP doesn't have the ability to look at the file since the file is on the server. And in the end, the problem is an issue of proper communication between DLP and server.

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Mark Gulbrandsen
Resident Trollmaster

Posts: 16657
From: Music City
Registered: Jun 99

posted 08-30-2008 10:00 AM

quote: Mark Lensenmayer
This was a 3-D show but it happened during the 2-D trailers. It was the first show of the day. Theatre was an AMC.

I'm assumming this was not a 4K Sony location but a 2K location.... If this was a Sony System then disregard the below comments since the Sony is a 10 bit system.

Actually it is possible to unplug the B channel HD-SDI cable and see this effect on some projectors. Remember the B channal only carries the extra two bits of data to make this a 12 bit system. Christie SB's will still produce an image with the B channel unplugged and they do look like there is a color missing although I can't recall which one. Now I seriously doubt that anyone was messing with the cables at this theater but ys never know....

Mark

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Joe Elliott
Master Film Handler

Posts: 497
From: Port Orange, Fl USA
Registered: Oct 2006

posted 08-30-2008 11:40 AM

At our location, we have a Doreme server with a Barco, (I know, Marks favorite combination), and if you try to play 2-D content in 3-D mode the colors are off. You have to switch modes in between, or in your server you set the 2-D content to play at 48fps. Then everything plays correctly.

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Mark J. Marshall
Film God

Posts: 3188
From: New Castle, DE, USA
Registered: Aug 2002

posted 08-30-2008 06:30 PM

Maybe I wasn't clear in my question, so let me rephrase...

Does the software which accesses the file on the server and sends the signal to the projector have the ability to read the format of the file and then set the proper configuration on the projector? Or does the user have to tell the projector what it's supposed to be doing? (Which lens to use, 2D or 3D, etc.)

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David Zylstra
Master Film Handler

Posts: 432
From: Novi, MI, USA
Registered: Mar 2007

posted 08-30-2008 08:48 PM

currently not in our case with DoReMi and Christie - our booth staff has to create a playlist with the right format cues that tell the projector what presets to use (and the projector preset chosen determines which lens to use).

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Mike Renlund
Film Handler

Posts: 71
From: San Francisco
Registered: Feb 2008

posted 08-30-2008 11:41 PM

In 2D digital cinema, the video information is carried on both HD-SDI cables.

Cable 1:
Red - 4 bits
Green - 4 bits
Blue - 2 bits

Cable 2:
Blue - 2 bits

When you run 3D, with the increased frame rate, the information is much more intense, and the video data changes:

Cable 1 (Left Eye)
Red - 4 bits
Green - 2 bits
Blue - 2 bits

Cable 2 (Right Eye)
Red - 4 bits
Green - 2 bits
Blue - 2 bits

When your show started, they had it in the 2D format on the projector, and obviously the color info would be read incorrectly.

Hope this helps.

[ 08-31-2008, 09:25 PM: Message edited by: Mike Renlund ]

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Stephen Furley
Film God

Posts: 3059
From: Coulsdon, Croydon, England
Registered: May 2002

posted 08-31-2008 04:33 AM

quote: Mike Renlund
Cable 1 (Left Eye)
Red - 4 bits
Green - 2 bits
Blue - 2 bits

Cable 1 (Right Eye)
Red - 4 bits
Green - 2 bits
Blue - 2 bits

Did you mean 'Cable 2 (Right Eye)', otherwise cable 2 doesn't seem to be doing anything?

Why 4 bits for R and only 2 for G and B? The RGB colour space normally uses the same bandwidth for each channel, unlike the various colour difference systems.

What does this 4 and 2 bits, mean anyway? This obviously isn't enough to transmit the full range of colours, is this 4 bit, 2 bit, 2 bit pattern repeated several times to build up te full pattern of bits for each pixel? If so, then why; why not just transmit all of the red bits, then all of the green, then all of the blue? What is the total bit rate of a HD-SDI interface anyway?

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Tristan Lane
Master Film Handler

Posts: 444
From: Nampa, Idaho
Registered: Feb 2002

posted 08-31-2008 01:11 PM

quote: Mark J. Marshall
Does the software which accesses the file on the server and sends the signal to the projector have the ability to read the format of the file and then set the proper configuration on the projector? Or does the user have to tell the projector what it's supposed to be doing? (Which lens to use, 2D or 3D, etc.)

The settings are not automatic. User specified macros (formats) need to be selected (by use of a cue or automation setting) to tell the projector which macro to use during playback of a specific feature.

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