4096x2160 full container... why bars?

[C. Pres Alliance]

Hi, all. I'm perplexed by an issue I am having, which I swear I did not have in previous years of using DCP-o-matic to make 4K DCPs, but is popping up every time now: I cannot create a natively 4096x2160 DCP without seeing padding on the top and bottom of the frame.

This doesn't make sense to me. The native spec for 4K DCP = 4096x2160, and my ProRes file is also 4096x2160. Yet, the default when creating a DCP is to "DCI Flat", which reduces the image to 3996x2107 and gives me bars on top and bottom (a window-box effect). And if I select "Full Frame" as my DCP container, it appears correct in preview, with no padding... but I get a warning when I go to render it out saying that Full Frame is "non-standard"... and sure enough, when I view the complete DCP, it appears padded.

I've tried resizing the source as "custom" to match the frame, but that applies a vertical stretch to the image, which is not acceptable. Doesn't seem like that would ever be the desirable solution for anyone.

Why is this happening, and how can I create a DCP which is a 1:1 representation of my 4096x2160 master? I swear I used to be able to. And on the same note, if the 4K standard is 4096x2160, why is that ratio container "non-standard"??

- Peter C.

[Carsten]

The DCP standard is neither full frame, nor 4096*2160 or 2048*1080. Full Containers are only to be used for test content like framing guides.
Only native Laser-IMAX masters use 4096*2160, because IMAX has full control of their screen layout.

That's why the only default choices for containers in DCP-o-matic are FLAT or SCOPE in either 2k or 4k resolution.

[carl]

Why is this happening, and how can I create a DCP which is a 1:1 representation of my 4096x2160 master? I swear I used to be able to. And on the same note, if the 4K standard is 4096x2160, why is that ratio container "non-standard"??

Unless something has gone wrong, you should be able to create such a DCP. The player does not handle full-frame content without letter/pillarboxing. But the DCP should be as you want it.

[C. Pres Alliance]

OK, but to clarify: the industry spec for a 4K master I receive from the lab is 4096x2160.

So what is the correct way to place it within the Flat container so that it shows up without padding/windowboxing? This is the essential issue. I do not wish to stretch-to-fit, which is not a correct representation of the image.

[carl]

Can you share the relevant part of the spec you received?

Whichever way you slice it the image in the DCP is going to have padding/windowboxing. If you make a SMPTE DCP DCP-o-matic will write the <MainPictureActiveArea> tags which say how big the picture is within the frame, but I've no idea if any presentation software looks at these.

I guess the question here is what do you mean by "shows up"? Who is going to use the DCP that you make, and what will they use it for?

[Carsten]

It is all about aspect ratios. If your master doesn't fit into the established ones, you need to crop or pad or scale, there's no way around it.

If there is a 4096*2160 spec somewhere, it is not for cinema. Except, as I said, for iMAX Laser, but they usually master all their DCPs in their own licensed labs.


- Carsten

[RAY-NUE]

I too remember back when doing DCP without any bars. Regardless of the size of the frame

[Carsten]

No bars or cropping only if your master has the same (or close to) aspect ratio as the allowed container types. DCP-o-matic, as every DCP mastering tool, has to comply with RDD52 now:

https://ieeexplore.ieee.org/stamp/stamp ... er=9161348

Section 7


- Carsten

[C. Pres Alliance]

It is all about aspect ratios. If your master doesn't fit into the established ones, you need to crop or pad or scale, there's no way around it.

If there is a 4096*2160 spec somewhere, it is not for cinema. Except, as I said, for iMAX Laser, but they usually master all their DCPs in their own licensed labs.


- Carsten

OK, well, if the insisted upon theatrical 4K spec is now 3996x2160, then that would have to be the new standard applied to every lab and scanning facility that delivers my masters and is used to the 4096x2160 container. Which seems crazy, but...

In any case: back to the essential issue. If my 4096x2160 masters have to be downscaled (horizontally), I need to know how to "zoom" the image to fit the container without stretching or cropping the image. No preservationist worth his or her salt is going to render a DCP – or any exhibition or archival master – with the image being distorted/stretched or cropped. And in my constant experimenting with DCP-o-matic, I cannot find a setting or adjustment that is doing this properly to my eye. All I accomplish is a slight vertical stretch to eliminate the padding – and that's not a suitable solution. So I hope someone can point me to the correct way to accomplish this without destroying the integrity of the image.

[carl]

OK, well, if the insisted upon theatrical 4K spec is now 3996x2160, then that would have to be the new standard applied to every lab and scanning facility that delivers my masters and is used to the 4096x2160 container. Which seems crazy, but...

That is one of the theatrical 4K specs - the one for 1.85:1 ("flat"). If the lab you are sending to wants 4096x2160, that's (personally) what I would give them!

In any case: back to the essential issue. If my 4096x2160 masters have to be downscaled (horizontally), I need to know how to "zoom" the image to fit the container without stretching or cropping the image. No preservationist worth his or her salt is going to render a DCP – or any exhibition or archival master – with the image being distorted/stretched or cropped. And in my constant experimenting with DCP-o-matic, I cannot find a setting or adjustment that is doing this properly to my eye. All I accomplish is a slight vertical stretch to eliminate the padding – and that's not a suitable solution. So I hope someone can point me to the correct way to accomplish this without destroying the integrity of the image.

I'm still a bit confused by these questions, I'm afraid. You're saying you have a 4096x2160 image, with no padding at all? In that case, it's at a ratio of 1.897:1, isn't it? And you want to make this fit in a 1.85:1 frame without any padding, stretching or cropping? I think this is impossible. What am I missing?