DCP has wrong gamma

[Carsten]

Okay, I DO see that washed out image when using OpenGL mode in the player. Practically, OpenGL is mandatory for a 'decent' playout performance on highres Macs, so I assume you have that enabled. For a test, switch it to simple/safe mode, restart the player.


You may also load the MXF video file from the created DCP into VLC. While VLC usually can not play DCP mxf files without serious frame skipping, the VLC color rendering of DCPs is very dependable. You may at a specific point in the video create a VLC video snapshot (video menu), and have a look at that image for a pixel-peep.


Now, assuming that the DCP is correct (I still advise to install 2.16.18) - you may see a washed out image in a cinema. Unfortunately, some cinemas use under-performing DLP projectors with a very bad black level. And I think this becomes even more obvious with black&white footage.
So, even with these two things having nothing to do with each other, they may cause a similiar visual impression. Do you have a chance to check your DCP at another cinema?

[dhl]

I wouldn't expect something like that between 2.16.5 and 2.16.18, but, wild guess - try the latest version.


The difference you see with the JPEG2000 export from Premiere is easy to explain - with JPEG2000 content, DCP-o-matic disables any color processing and just passes through the images, as it assumes the content has been compressed for digital cinema in another application. So, DCP-o-matic assumes it is, essentially, JPEG2000 in X'Y'Z', gamma 2.6. But that is a digital cinema specific JPEG2000 'dialect', the Premiere (or Davinci) 'plain' JPEG2000 export is not targeted at DCI/DCP compliance. So it would be RGB, gamma 2.2 or so, and would give a completely wrong DCP.


Be careful to assume JPEG2000 is always DCI/DCP compliant. If not constrained to proper DCI/DCP parameters, such DCPs will usually cause problems like frame skipping, false colors, playout server crashing, etc. The Kakadu DCP export in Davinci uses a different JPEG2000 encoder than Davincis JPEG2000 image export, and the Wraptor DCP encoder in Premiere Pro uses a different JPEG2000 encoder than Adobes JPEG2000 image encoder.

I happen to have 2.16.5 stored on my machine, will see if I can replicate the issue.

Very interesting. I'll download the latest version of DCP-o-matic and see if anything changes. Another variable – I'm on macOS Catalina 10.15.7. I've been working on this feature the past couple years and didn't want to upgrade macOS and risk breaking anything.

Thanks for the JPEG2000 info. Good to know.

[dhl]

Okay, I DO see that washed out image when using OpenGL mode in the player. Practically, OpenGL is mandatory for a 'decent' playout performance on highres Macs, so I assume you have that enabled. For a test, switch it to simple/safe mode, restart the player.

Now, assuming that the DCP is correct (I still advise to install 2.16.18) - you may see a washed out image in a cinema. Unfortunately, some cinemas use under-performing DLP projectors with a very bad black level. And I think this becomes even more obvious with black&white footage.
So, even with these two things having nothing to do with each other, they may cause a similiar visual impression. Do you have a chance to check your DCP at another cinema?

Okay, I installed 2.16.18 for both DCP-o-matic and the player. I made a new DCP and I can confirm that with OpenGL enabled in the player it looks washed out but with OpenGL off, it seems to look correct. It also looks correct in VLC. Here's a screengrab:

Screen Shot 2022-08-10 at 7.44.36 PM.png

VLC is upper left, ProRes source is upper right, and DCP-o-matic Player with OpenGL turned OFF is at bottom. Can we assume from this screengrab the DCP is correct?

Yes we can get access to a cinema to confirm. I suppose that's the next step.

[Carsten]

I checked this OpenGL behaviour with a well lit color clip. Same behaviour, just that it appears 'less wrong' with color.

You should be safe.

[dhl]

I checked this OpenGL behaviour with a well lit color clip. Same behaviour, just that it appears 'less wrong' with color.

You should be safe.

If the gamma problem is OpenGL in Player and our DCP is valid, what does that mean that if we're still seeing a washed out image when the DCP is projected in the cinema?

When we look at the DCP projected, it still looks washed out lacking black blacks, contrast and pop. Our goal is for it to look as good on screen as it does on our monitors. How do we achieve this? Do we need to go to a cinema grading suite and do a final grade with a projector? Any advice much appreciated.

[Carsten]

How is this DCP projected currently? In a cinema on a DCI projector?

[dhl]

How is this DCP projected currently? In a cinema on a DCI projector?

I've seen the DCP projected at the Rafael Film Center cinema in San Rafael and it recently screened at a festival in Chicago where I'm told it had the same gamma problem. I don't know if the projectors in either of these theaters are DCI. I could ask about the Rafael.

[dhl]

How is this DCP projected currently? In a cinema on a DCI projector?

I've seen the DCP projected at the Rafael Film Center cinema in San Rafael and it recently screened at a festival in Chicago where I'm told it had the same gamma problem. I don't know if the projectors in either of these theaters are DCI. I could ask about the Rafael.

Here are the specs of the cinema where we did our test screening:

https://rafaelfilm.cafilm.org/theater-specs/

All rooms are DCI compliant and THX certified. If our DCP looks washed out in a room like this, what do we need to do to make our DCP image look as close to our ProRes source as possible?

[carl]

I think you may have found a slightly unbelievable bug in DoM (in the sense that it's hard to believe it hasn't been spotted before) in which it handles "limited" (video-range) sources wrongly. I have a potential fix here; I'll make a test mac build overnight and send you a link with a new version to try as soon as I can.

[Carsten]

They probably use calibrated DCI projectors, but, some DLP projectors show unbelievably bad black levels. I'll convert your master and check it on our system. That issue probably is completely separate from the safe/simple vs. OpenGL rendering difference.

@Carl - can you be more specific towards what is happening there? Most content will use video/limited range, and a gross level/gamma misinterpretation as the one shown here should have been noticed by users a long time ago.