In some cases, you may need to scale down the frame in a DCP to have the original image floating in middle of screen with a black box all around.

An example is where end credits have text dangerously close to edge of frame, and you want to reduce the size of the credits, so they have black margin on all sides.

DOM 2.15.x has a "custom scale" option where you can set size desired exactly in pixels.

So in this case:

• Source is a scope 4K DCP (4096x1716)
• Set scale on the content as "custom"
• Select "Set size"
• Enter scale to size 3686 x 1544 (4096 x 90% / 1716 * 90%)

In the preview, this does exactly as intended - image appears floating in centre of screen with black on all sides.

However, when the new DCP is made, the the scale setting has been ignored and the image fills whole screen, as in original.

Variants:

• Setting "Re-encode JPEG2000 data from input" -> same problem
• Changing one of the scale-to dimensions so resulting aspect is other than 2.39 (the original aspect) -> fixes problem
• Cropping 1 pixel off left -> fixes problem

Therefore, I suspect what is going on is that DOM is assessing if each frame needs to be re-encoded or not. If aspect is not changing, it incorrectly thinks "I don't need to do any scaling here" and passes the frame through unchanged.