Aspect Ratio Confusion

[am14k]

I am working on a DCP that the goal is “4K, flat, 16:9”
File that was sent over for me to work with appears to not fit the flat container. I cropped it, but the person sending the file mentioned that it should not need to be cropped and that something must be wrong. I’ve been trying to go through container ratios and various sizes and still cannot figure out where the problem is.

As it’s running right now, it reads “cropped 3840x2076, scaled 3996x2160”
Attaching a picture of what it looked like after adding the file to the project.

https://www.flickr.com/photos/199128327 ... ed-public/

[carl]

Perhaps you can show us what the main DCP-o-matic window says when you load the file.

[Carsten]

We need to see the left side of DCP-o-matic window under Content->video where it says: Content video is xxxx. Also, please create another screenshot with 'Outline content' checked. If your source is 16:9, it is normal that is does not fit the flat container. In that case, the image will probably have to be padded with black slightly on sides or top/bottom. You don't need to be concerned about that. 16:9 is simply not one of the established cinema format standards. So a bit of tweaking may be necessary.

[am14k]

Sorry for the delay, I had to restart the project on another computer to grab the information and keep the other one running.

screen 915-2

Also, does the fact that is being cropped slow down the encoding time or could that just be running it as 4k vs 2k?

Sorry for all the questions

[carl]

It looks like the actual image of the film is more or less "scope" i.e. 2.39:1 (or 2.35:1 depending on who you ask) and it has been put into a 16:9 frame by padding top and bottom with black (the black parts you see inside the red rectangle).

If you have to work with this file you have some options:

• Set the DCP container to "Scope" and then set top and bottom crop on the source file until the black bits inside the red rectangle are all gone. This is the most "correct" answer from a cinema/DCP point of view. You will get a scope DCP that will be projected by a cinema just like any other scope DCP.
• Leave the DCP container on "Flat" and crop enough from top and bottom so that the image fits width-ways without any gap. When projected however this will give you big spaces at the top and bottom of the screen, which is almost certainly not what you want.
• Leave it exactly as you have it. This will give you black spaces all around the image on projection, but maybe that's what the client wants when they say 'flat, 16:9'

The ideal thing would be to get the file again from the client but in the original ratio without any padding. Then you could just make a scope DCP.

As a general rule it's better if the source file to DCP-o-matic has no padding. It's not necessary (as DCP-o-matic can add it if required) and it often makes things worse.

[Kewl]

Visible image ratio is 2.46:1. I would make a Scope DCP and crop top and bottom until image width is flush with the Scope container.

But, if they insist on Flat, it's the same, your crop top and bottom until image width is flush with the Flat container.

Edit: Carl answered while I was writing.

[am14k]

Thank you both!
The person wants an original version with the capability to make version files in the future with subtitles, hoping to have the captions play in the included padding on the bottom.
The file was already very large to download and he’s on a tight schedule so for now I’ll crop it like you mentioned to have it run as flat.
In the future if someone wants subtitles, do they not need to include the letterboxing when sending a file?

[Carsten]

Hmm. This is a weird application. I understand some film makers do not want subtitles over their precious image. However, when then version files are to be used, it is mandatory that the OV also includes visible black bars at least on the bottom - for no good reason. I think the film maker needs to rethink this.

2.46:1 is a 'bad' aspect ratio for cinema. Although it is close enough to 2.39:1.

The proper way to do this is to crop the black bars from top and bottom and ceate a scope DCP. Choose a 4k scope container, and crop roughly 300 pixels symetrically from top and bottom. This will cut away the baked in black bars and will let the image extend to the sides.The remaining lean black bars on top and bottom (due to the 2.46:1 AR not perfectly fitting a 2.39:1 container) will, practically, not be visible in cinemas.

Bildschirmfoto 2023-09-16 um 02.17.40.png

The subtitled version should then use this OV DCP, and the subtitles should be placed within the lower image area.

If the subtitles absolutely have to be shown in black bars on the bottom, a NEW OV with different crop and additional subtitles should be created, not a version file. In that case, one should probably only crop away the top black bars, leave the bottom black bars, and create a flat container. This will make sure that the subtitles will be visible on the lower part of the screen. But again, I would advise against this method.

Cropping/padding does not add to encoding times. 4k vs 2k will (considerably, roughly a factor of 4)

A DCP is a format strictly for cinema presentation. It doesn't make sense to apply home video or computer video viewing experience to a DCP. One needs to think about an actual cinema screen layout when creating the DCP.