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Working with a film at 2.75:1

Posted: Thu Nov 07, 2019 5:19 pm
by MisterSSutcliffe
Hi, I'm very new to this software, so forgive me if this question has a simple answer. I'm converting my .mp4 short film file into DCP file, and I'm having scaling issues. My film's aspect ratio is 2.75:1, and that doesn't seem to be an option in DCP-o-matic. Is there a solution to this? As of now, I've only set "scale to" to 2:39 (Scope), and "Container" to DCI Scope.

Re: Working with a film at 2.75:1

Posted: Thu Nov 07, 2019 5:44 pm
by IoannisSyrogiannis
Instead of using a preset "scale to X", try "no stretch".
Yet, with Scope, that is the widest aspect ratio on Digital Cinema, you can't avoid letterboxing for 2.75.

Re: Working with a film at 2.75:1

Posted: Thu Nov 07, 2019 5:52 pm
by MisterSSutcliffe
Tried "no stretch". It compressed the left and right sides of the film like so:
Image

Re: Working with a film at 2.75:1

Posted: Thu Nov 07, 2019 8:16 pm
by Carsten
Your confusion is much appreciated ;-)

This is not an easy one, as the source, in addition to the display aspect ratio of 2.75:1 also has a pixel aspect ratio of 2:1 - so, non-square Pixels.

Please, enable 'outline content' under preview and post a new screenshot.

If you want to have fun, read this first:

viewtopic.php?f=2&t=1426

As a starter, and repeating most of what Ioannis already said - you need to put your content into a DCI scope container with an aspect ratio of 2.39:1. As your source is 2.75:1, this is 'wider' than DCI scope, so you will see letterbox bars above and below the image. This is 'normal' and has been done for big budget releases as well (e.g. The Hateful 8, La La Land).

Another option would be to fill the scope container vertically - but you would have to crop image off both sides or distort the aspect ratio (vertical stretch). It's your decision, but, my personal choice clearly would be to show the full image letterboxed.

Your choice for a 4k DCI scope container is the right one based on the source resolution.

Would it be possible for you to upload a short snippet of this footage somewhere? One second with image borders visible on all sides would be enough. A screenshot is not sufficient (as it will lose the non-square pixel aspect).

Which version of DCP-o-matic are you using? In this case, and following the thread I linked to above, you may actually need to use DCP-o-matic 2.15.29 to do it properly. I did do 2.76 in 2.39 a couple of times before - but these were with square pixels, not anamorphic.

This is where the current stable version is doing wrong:
Bildschirmfoto 2019-11-07 um 23.08.33.png
Bildschirmfoto 2019-11-07 um 23.08.33.png (21.68 KiB) Viewed 371 times
When doing 'no stretch' it should scale up and keep the display aspect ratio of 2.75:1, not the source container aspect ratio of 1.37:1. That's the reason your content stays compressed, and is not expanded. You're lucky we just had that thread I quoted, Carl has only just uploaded a test version that should fix this behaviour. It should scale the 2450/1782 to 4096/1490 and pad 113 pixels on top and bottom with black in order to fill the 4096/1716 4k scope container.

- Carsten

Re: Working with a film at 2.75:1

Posted: Fri Nov 08, 2019 12:04 am
by MisterSSutcliffe
So I updated my software, and got the screenshot you asked for:
Image

Also, here's a screenshot with "scale to" set to 2.39 (Scope):
Image

As for footage, hopefully the trailer for the film will help:
https://vimeo.com/365127788/bb4ed0c8a4

I would prefer to use letterbox bars to preserve the aspect ratio (as you said, lots of films do). I'll take another look at the thread you posted, and see if I can figure this out. Thanks for your help!

Re: Working with a film at 2.75:1

Posted: Fri Nov 08, 2019 1:04 pm
by Carsten
Unfortunately, the trailers are 2.75:1, but using square pixel aspect ratio. So, they do not have that specific problem with no-stretch scaling.

- Carsten

Re: Working with a film at 2.75:1

Posted: Fri Nov 08, 2019 2:30 pm
by Carsten
So, unfortunately after some testing, it appears that no-stretch is still not working with non-square pixels in DCP-o-matic 2.15.29. I think I misread a line in the changelog dealing with no-stretch - but it was about cropping.

Three options:

- wait for Carl to fix it, hopefully in short time
- try to get a sqare pixel version of the master file, that is, 4900*1782 pixels - someone has done that for the 'UHD2/8k' and 'Original' trailer files on Vimeo
Bildschirmfoto 2019-11-08 um 20.20.29.png
Bildschirmfoto 2019-11-08 um 20.20.29.png (25.75 KiB) Viewed 291 times
.
- use one of the trailers on VIMEO to create the DCP. They are square pixel and don't have that issue (That is, if you are working on the DCP trailer, not the full feature of course...)

See here - this is how it SHOULD look if DCP-o-matic would handle non-square pixel with no-stretch properly (actually, some photoshopping to get the 'Content video is...' line correct, as currently, it is not possible to achieve that scaling pipeline in reality):
.
Bildschirmfoto 2019-11-08 um 16.04.16.png
Bildschirmfoto 2019-11-08 um 16.04.16.png (517.83 KiB) Viewed 317 times
.
You may be wondering, if no-stretch doesn't work - why isn't there a 'Scale-to: 2.75:1'? Well, someone would also need a 2.76:1, a 2.55:1, and so on. Also, the no-stretch option is for footage that has gotten arbitrary aspect ratios, as you sometimes see them on DVDs, where 'some' aspect ratio has been cropped from an original aspect ratio, and put on a 16:9 DVD. No-Stretch should cover all of these.

I forwarded email to Carl, maybe he has time for a quick fix. He was working on it already, maybe he can do it quickly. Hey, it's weekend, isn't it...

- Carsten

Re: Working with a film at 2.75:1

Posted: Fri Nov 08, 2019 4:28 pm
by carl
A fix should hopefully be forthcoming within the next six hours or so, if you are happy to run a version from the "test" set. I'll post when it's uploaded.

Re: Working with a film at 2.75:1

Posted: Fri Nov 08, 2019 4:38 pm
by Carsten
Sorry for spoiling your weekend entry, Carl. :oops:
I'll keep my mouth shut now. Until Monday, maybe ;-)

- Carsten

Re: Working with a film at 2.75:1

Posted: Fri Nov 08, 2019 10:23 pm
by carl
Weekend?! Somebody told me about those once ;) 2.15.30 is up now. Hopefully it will fix it, but it needs to be tested quite carefully, I think.

Also I built these with a different-than-usual macOS environment so if that breaks, don't be too surprised...