Film-Tech Forum ARCHIVE: DCP Creation -1.78

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Posted by Eugene Lehnert (Member # 7066) on 08-21-2014, 11:10 AM:

Is it best to place a 1.78 film into a 1998x1080 container or a 2048x1080 container?

Thanks!

Posted by Scott Norwood (Member # 30) on 08-21-2014, 12:03 PM:

Wouldn't the result be the same (a 1920x1080 image)?

Posted by Eugene Lehnert (Member # 7066) on 08-21-2014, 12:19 PM:

Yeah. I guess I'm trying to figure out if one resolution or the other can affect the size of the image during playback? Is a projector zoomed into the screen differently for the different resolutions? Would a 1.78 in a 1998x1080 look larger on the screen than a 1.78 in a 2048x1080 container?

Posted by Manny Knowles (Member # 1171) on 08-21-2014, 03:20 PM:

Both aspect ratios (1.85 and 1.78) use the maximum height of the full (2K) container -- 1080 pixels. So, they are the same, in terms of height.

Since 1.78 is not as wide as 1.85, it will appear smaller in that dimension, which is to be expected.

Posted by Stefan Vogels (Member # 5573) on 08-21-2014, 03:29 PM:

It would look the same, however not every cinema probably will have the 2048x1080 preset configured. They do have 1998x1080 as Flat ratio.

Posted by Eugene Lehnert (Member # 7066) on 08-21-2014, 03:35 PM:

Right. But when you have a projector set to 1998x1080 do you through a larger image onto the screen if you fill the screen horizontally? If you were to fill the screen horizontally with a 2048x1080 the vertical length would be shorter?

So a 1.78 in a 2048x0180 container would have to be enlarged where a 1.78 in the 1998x1080 container would not need as much enlarging?

I haven't worked as a projectionist so I was guessing that theaters are set with a standard setting for 1.85 and 2.39. I'm just worried how this 1.78 will be interpreted on the big screen by projectionists.

Posted by Manny Knowles (Member # 1171) on 08-21-2014, 03:45 PM:

According to DCI spec, you're supposed to fill either height, width, or both.

Full width is not an option for this aspect ratio. For 1.78, you need to use the full height dimension. There's no real difference between packing it within 1.85 versus full container. You will end up with the same resolution, and the same amount of unused container on either side.

I think you're worrying needlessly.

Posted by Marcel Birgelen (Member # 6801) on 08-21-2014, 04:25 PM:

According to DCI specs you're quite right, you shouldn't have to worry...

The problem is the reality out there. Many locations don't have any presets for "full container", just scope and flat... If you deliver them content in another container they might start to do stupid things.

So, if you're not going to be present at the screening(s) yourself, I think it's best to put it in a 1998x1080 container, to avoid the locations with "limited skill-sets" messing up.

Posted by Steve Guttag (Member # 268) on 08-21-2014, 04:34 PM:

Marcel is right on the money. It is absolutely safest to list it as "F" or you will get unpredictable results in the cinemas. Current naming conventions would have you put in an "F-178" into its name. While the actual ratio is an "optional" piece, it would go a distance to ensure that when the image didn't fill the width of the 1.85 masking setting, the reason would be known.

Posted by Scott Norwood (Member # 30) on 08-21-2014, 04:35 PM:

quote: Marcel Birgelen
So, if you're not going to be present at the screening(s) yourself, I think it's best to put it in a 1998x1080 container, to avoid the locations with "limited skill-sets" messing up.

What could they do wrong? The picture size would be the same either way.

Posted by Monte L Fullmer (Member # 2797) on 08-21-2014, 09:19 PM:

When using the "DCP-o-Matic" DCP creation program, it give you the option to choose how your file will look in certain containers and will gives you a description, in words and sample image, of how the container is filled.

Thus, a 1.78 formatted file being ready to be placed in a FLAT container will show to the user of the image having slight black bars on the side since it's filling the vertical part, being the 1080p, to top and bottom of the frame.

-Monte

Posted by Steve Guttag (Member # 268) on 08-21-2014, 09:54 PM:

Scott...not knowing what "C" means, they could also use "Scope" and thus would have an 858 x 1920 image cropped in height and not filling the width of the image.

Calling it "F-178" removes all ambiguity including for automated TMS systems.

Posted by Monte L Fullmer (Member # 2797) on 08-21-2014, 11:54 PM:

With the above comment, the program mentioned also puts the lens (_F_, _S_)factor in the content file naming string when all the presets in making the DCP is completed.

Thus, removing any possibility of wrong lens format used with the produced content when used within an assembled SPL.

-Monte

Posted by Manny Knowles (Member # 1171) on 08-22-2014, 01:42 AM:

I'll agree that the uncommon (yet legal) "C" designation could confuse some users. However, for the record, the OP was not asking about how best to name the DCP.

Essentially/technically, placing 1.78 inside 1.85 is the same as placing it inside the full container. Labeling also has no real effect. The result would be the same either way.

As others have pointed out, labeling is an important consideration, in terms of short-circuiting user error. But only in that regard.

I would recommend "F-178" as Steve suggested.

Posted by Steve Guttag (Member # 268) on 08-22-2014, 05:30 AM:

Manny,

Since the OP clarified that a concern was the size/magnification of final result as it would appear in theatres...how an end-user, that may be an automated TMS too, using "C" sets one up to have an unpredictable result. While within the DCP itself, it is the same regardless of F or C.

Now I wish for 65/70mm dupes that they would use C-220 as the format! But that is another discussion.

Posted by Eugene Lehnert (Member # 7066) on 08-22-2014, 01:37 PM:

Ok so it doesn't really matter if I put it in a 1998 container or a 2048 container as long as it's labeled Flat it should get projected correctly?

http://www.knuterikevensen.com/?p=144

Posted by Manny Knowles (Member # 1171) on 08-22-2014, 05:48 PM:

quote: Steve Guttag
Now I wish for 65/70mm dupes that they would use C-220 as the format! But that is another discussion.

Actually, it's been part of several discussions!

70mm DCPs and their formatting (and other classic titles converted to DCP)

2.20 DCPs

Off aspect ratio DCPs

DCI Classic Transfers Good and Bad

Posted by Jim Cassedy (Member # 4115) on 08-22-2014, 06:40 PM:

quote: Eugene Lehnert
as long as it's labeled Flat it should get projected correctly?

Well, with a typical booth staff these days, there's a 50% chance
they'll get it right half the time.

Posted by Monte L Fullmer (Member # 2797) on 08-23-2014, 02:25 PM:

The container has to match the labeling.

It's obviously that a 1.78:1 file would be more appropriate to be assembled within a 1.85:1 (FLAT) container and be satisfied with the slight black bars on each side of the image.

I created the same DCP - a 1.78:1 file was inserted in a 1.85:1 (FLAT) container and it looks great on the screen.

Besides, if you place that file in a Scope container, you lose the HD due to the vertical pixel drops to 858 and the image is heavily cropped to fit that vertical pixel count.

Then, the width of the original image will be zoomed up to fit the 2048 width of the scope container.

Thus, the 1.78:1 image is not zoomed down to fit within the full vertical specs of the container, but zoomed up to match the full width of the container, thus vertical cropping has to take place to make the horizontal fit.

That image will have the "letterbox" look on the screen.

Posted by Carsten Kurz (Member # 5396) on 08-23-2014, 04:51 PM:

quote: Eugene Lehnert
Ok so it doesn't really matter if I put it in a 1998 container or a 2048 container as long as it's labeled Flat it should get projected correctly?

If you put it into a flat container, it has to be labeled F-178. If you put it into a full container, it has to be labeled C-178. Ask your next-door projectionist what to do with a C-178 labeling and you will know the answer: F-178 and 1998*1080 is the only useful choice.

- Carsten

Posted by Marcel Birgelen (Member # 6801) on 08-23-2014, 06:55 PM:

Like Carsten already mentioned, just use a 1998x1080 container and put F-178 into the name. If I would encounter a DCP named F-178 with a resolution of 2048x1080 I would start to scratch my head...

Most people will most probably not notice it and in the end it will work just fine, but why not just do it the way it is supposed to be done? Put it in a 1998x1080 container and put F-178 into the name and it will show as it is intended to be shown, without causing confusion and a minimum of pillar-boxing. And the few locations that actually have a 16:9 preset for their masking, will show it without any pillar-boxing whatsoever.

Posted by Antti Nayha (Member # 4980) on 09-25-2014, 03:28 AM:

What's the exact reasoning behind putting 1920x1080 in a 1998x1080 container? Unless I'm mistaken, you don't need to do that unless your authoring software forces it for some reason.

I have always simply used a 1920x1080 container for 16:9 material, with no added pillarboxing and with F-178 in the CPL. Never had any problems.

The same goes for other less common aspect ratios, so I use a 1440x1080 container for 1.33:1 and so on.

Unless I've missed something, the DCI spec only requires that either the container width is 2048 or the container height is 1080. 2048x858 and 1998x1080 are only mentioned as "example image aspect ratios" (section 3.2.1.8).

dcp_inspect only seems to accept 2048x1080, 2048x858, 1998x1080 and 1920x1080; all other container sizes are reported as an "error". I'm not sure why, since it's not against the spec... wouldn't a "hint" be more appropriate?

Posted by Marcel Birgelen (Member # 6801) on 09-25-2014, 05:54 PM:

Yeah, if you read the actual specs, you're supposed to fill either height or width at 2K or 4K resolution. But then there is the matter of standardized containers.

So, although what you're doing usually works, it unfortunately doesn't imply it's actually according to convention [Wink]

.

Strictly conforming DCP naming conventions, putting an "F" in the name of the DCP implies a resolution of either 1998 x 1080 or 3996 x 2160. You're supposed to pillar- or letterbox any content into that container. If you do it correctly, you provide any odd aspect ratio after the dash.

There are just three standardized containers at this moment as you surely know:
F = Flat
S = Scope
C = Full Container

I'm not entirely sure why dcp_inspect also accepts 1920x1080, as it fits none one of the "known" containers, but probably because the native FullHD resolution is so commonly used, especially for commercials. I'm also not sure wether or not it should throw an error, but it should throw a warning at the least.

So, what you're doing perfectly conforms to most of the DCI specs, but you could never give it a compliant name, as it conflicts with naming conventions [Wink]

.

The guy who wrote the first part of the specs must have gotten all depressed from endless meeting with consortia and endless discussions over irrelevant details. After he hang himself someone equally depressed took over and finished it, but without reading the stuff that was already there.

Posted by Monte L Fullmer (Member # 2797) on 09-29-2014, 01:14 AM:

On a laptop: took me 14 hrs to take a 1G .wma file and convert it to a 35G DCP file.

The .wma had a video ratio of 1.50:1, thus I used the 1.66:1 container.

I set the audio settings to -20dB and this level is just right for our processor volume preset settings.

Glad I wasn't in a hurry - had the weekend.

Posted by Marcel Birgelen (Member # 6801) on 10-02-2014, 04:21 AM:

Yeah, it's not really something to be done on your notebook if you're in a hurry [Wink]

.

It's not really the size of the source file that matters, but the amount of frames in it and the actual resolution of the content. A 1G file in H.264 can contain a lot of frames, even at 720p or even 1080p if you go for some real high compression.