Alternative input to a Christie cp2220 projector

[Tony Smith]

Having problems at times with what looks like a colour space mismatch when taking in satellite feeds for cinema of opera house's etc.
We go in via the DVI-D socket, using a HDMI to DVI-D convertor socket.
The problem shows itself as wrong colour, almost like a purple cast over the picture.

I think this is maybe due to my input colour space sampling as 4.2.0, where as the projector expects 4.4.4 (SMPTE 295M now archived)
As it looks as if it can cope with 1080 interlaced 25 Hz frame rate 50 Hz field rate. Sometimes it will go to correct colour by switching inputs
from DVI-D A to B and back, maybe more than once.

Anybody know any more as to this problem

Tony Smith UK

[Phil Ranucci]

The DVI input has to be to REC709 colorspace. I think it's in channel setup.

[Robert Hardage]

When we have seen this issue, the Target Color is usually wrong (should be Rec709 for an Alternative Content channel). See section 6-13 of the Christie CP2220 Manual . Your solution (switch sources then switch back) is what we try first, and it usually seems to work.

[Carsten Kurz]

You may also want to have a look at the HDMI/output settings of the satellite receiver. Sometimes you can set them to a fixed colorspace, sometimes they want to negotiate with the projector. Always try to set these image parameters to some fixed value instead of 'Auto'.

- Carsten

[Tony Smith]

Hi Folks
Thank you for your helpful posts, looking at our Christie CP 2220 , it's not that clear how to be sure in our DVI-D A or B channel set up has called up CP709, unless we have an out of date CP manual.
We have 020.100420.08 as number on the front of our CP2220 manual. looking at section 6-13 and Appendix A .Spec

REC 709 was brought out to help HD colour tv interchange by ITU/EBU near the start of the 1990's , but gives no ref to the sample rate of A to D (4x subcarrier for Y, R, B, 4xY 2xR 0xB)
But it is called up as 8 bit so should help.

Christie does call up all it's sample rates are 4x4x4, so we may be stuck with it.

We have looked at our HDMI settings menu of the satellite receivers ( Technomate 5402 M3) not much help there.

Maybe REC709 can be modified by switching backwards and forwards on DVI-D inputs and we are stuck with this.

Tony Smith

[Steve Guttag]

You have two things at play here. You have the target color, which, for HDMI/HD sources (particularly HDMI 1.4 and earlier) which will be REC 709. But you also have to set if the color is being represented in an RGB or Component (aka YCrCb). DVI native color is transported as RGB. HDMI's native color is YCrCb.

Anything coming in on a digital cinema projector's DVI ports will be 8-bit so you need not worry about the higher stuff (it is possible to go to 10 and 12-bit if you were to do "twin-link" DVI as I don't think any dual link DVI ever made it to digital cinema's DVI ports.

If you look on your "Config 2" page on the Christie...you can set both the Target Color (REC 709) and the Color Space. You'll have a range of RGB and YCrCb choices based on content. If they are greyed out, then on Config 1, you are using a PCF (Projector Configuration File) and it should be a REC709 one. Within that PCF will be the color space and the target color.

So, keep in mind, the projector presents itself as a DVI port (in the EDID table) so it's prefered color format will be RGB...but your source, if it is an HDMI device will have a preferred format of YCrCb and this is often where the conflict arises. Normally, one can do the colorspace conversion at either end (the projector or the source. Which makes the most sense will depend on the installation. I agree with Carsten, do not leave things in "Auto" because that requires each device to guess at what the other is. Pick a format at stick with it. Computers normally output RGB so if you are going to plug computers in, and they can be less accommodating, but have gotten better because they can use HDMI now...traditionally, they were DVI devices), then RGB might be your preferred format and tell the Blu-ray or source to output RGB. If you are just worried about HDMI native devices like your Satellite or Blu-ray, then let YCrCb be your standard and set the Christie to that and, push come to shove, create additional channels that will allow for alternate color space selection. But Auto, that leaves too much to chance.

[Tony Smith]

Hi Steve
This is very useful information, need to check our config 1 and 2 out see if we are already called up a PCF.
As you informed the HDMI 1.4 is YCbCr, but 8 bit is aiways 4.4.4 need to get 12 bit for 4.2.2 but not sure how
this will affect our problem if at all, using single input.
Do we know if the RGB has colour space defined (sRGB) or left open?

It may well be that REC 709 which was brought out for Television is a silver bullet as TV is YCbCr.

Yes we will normally only use the DVI-D inputs for our Alternative inputs thats satellite or Blu Ray.

Thanks

Tony Smith

[Sam Chavez]

I did an early Barco installation and used dual-link DVI to get the last 2 bits from what I can no longer recall. Being 30 feet away, nothing but the best and most expensive DVI cables would work reliably.

[Carsten Kurz]

We have looked at our HDMI settings menu of the satellite receivers ( Technomate 5402 M3) not much help there.

Hmm. That receiver does not look like a particular good choice in a cinema environment. I browsed the manual, and what the receiver software offers is indeed not very helpful.

I could think of some options like HDMI splitters, EDIDmanagers, etc, that could be helpful, but it involves quite a bit of testing, and it seems your options/know how with this stuff is limited.

[Tony Smith]

Hi Folks
Thank you for all your comments, which have been very helpful to me. I think this forum is one of the very few with very well informed members on a multitude of subjects connected with cinema aspects
Thank you again

Tony Smith