Centering of DOM output

[fredjonze]

We have a small film festival that we are automating by converting original source to DCP. In the course of doing this we're converting all of the original source to a Full Frame container. That way, we don't need to have lens changes between aspect ratio changes of the source movies.

All seems to be going well as the content resizes to either the horizontal or vertical boundaries of the Full container. We created a new macro profile on the projector to manage this container.

My only big remaining problem seems to be that the resized content is not accurately centered in the frame. It appears to be offset from 25px to 35px to the right. Any thoughts as to what might be causing this and if it can be solved?

The projector has a pan function to move the image right/left, but even with it all the way to the left the image is still not centered.

Thx in advance!

Jim

[Carsten]

Is this in 2.10.5, or a test version? I guess we need to try to replicate that behaviour ourselves. Does this happen for all content you try? Do you see this on screen, through the cinema projector? I suggest you load one of these DCP's MXF files into VLC and create a screenshot (VLC screenshot, not system screenshot). Load the screenshot into an image editor and count the black pixels from both sides. That should show wether it's caused by DOM, or by a misconfigured projector preset.

- Carsten

[fredjonze]

Carsten

Version: 2.10.5

The problem doesn't seem to arise if I encoded a flat to a flat container, scope to scope, etc. It only seems to happen when I go Flat to Full, Scope to Full, or custom aspect ratio to Full.

The image appears to be centered in the DOM play screen. The centering issue only seems to be present when playing on the DCP Cinema projector. It originally happened with the standard presets for commercial projections. So, to eliminate potential issues we created a brand new preset for a Full container. So, the centering issue seems to be related to a source aspect ratio that is scaled to fit a Full container.

I attempted to play the .mxf files in VLC, but the image is just black as it plays...any thoughts?

Thx,

Jim

[Carsten]

Yes - the VLC live image is black, just cue to an arbitrary position and perform a vlc snapshot from the VLC 'Video' menu - the resulting image will show content at dcp resolution. Hopefully your content isn't all black at that capture position...

I just tried it with 2.10.5 Mac - I created a full white flat image (1998*1080). Add it to a DOM project, scaling is set to 'flat'. I choose 'DCI full container' under the DCP tab, create the DCP. Load it into VLC, create a snap shot.

The source is a full white png at 1998*1080 pixels. The snapshot is a 2048*1080, with black left/right pillar boxes, precisely centered (25pix black on both sides). See attachments. Maybe you can perform the same procedure and project it on your projector. Yes, of course in theory, DCP-o-matic could handle stills different from video, but at least we would have a starting point.

Also, there is an XDC adjustment DCP, in the flat version in the form of a full container with a flat inset and pixel rulers. Playing that should show you wether your projection system does it right. I would assume there is some shift or cropping hidden in the projector macro. Send me your email address privately, then I'll make it available to you.


- Carsten

[IoannisSyrogiannis]

I don't know if there is any point in adding my comment now, since this subject might already be an e-mail correspondence. Yet, I get the feeling (from another thread, regarding ingesting content, started from fredjonze) that the projector in question is a Sony, whereas, the lack of lens shifting while changing between macros (or functions, if you will), might call for small compromises. Even more so, when a full container is in use. In fact, the Sony picture "canvas" gives you a bit more pixels to handle in favor of such cases, but one can imagine, taking into consideration factors like inclined projection (projector not being perpendicular to the center of the screen) etc., that along with an already used electronic shift, margins might be tight for utilizing the full frame (C) format.
If the projector is indeed a Sony one, I would go for using the change of lens/presets setting between feature movies (or shorts), instead of compromising the center balance of the content. If there is a masking that slows things down, I would deactivate it, letting the screen free for both(/all) formats.

In any case, my two cents is that it seems like the issue in hand is not a DCPoM, but a system configuration one.

[Carsten]

If they are able to center a scope image properly, there can't be a problem to center a full container, be it a Sony or a DLP.

So, I would show a proper framing chart through the available presets and check where the problem occurs, and then verify the presets for deviations in shift, masking, etc.

- Carsten

[IoannisSyrogiannis]

You are absolutely right.
And I would too.
What I am writing, though, is that this is a job for the one who sets the projector, not for the one who creates the content.
Implementations of "1 preset to rule them all" is easier told than made in real world, where the screening medium is not a monitor and compromises may have already being made.