Yes, of course, but it's a lossy copy since you're de-compressing and then re-compressing the content. (At 4k is that as important? I dunno, I'm not a movie fanatic.)
I would not say a brute force copy must be necessarily lossy by default.
In theory, if the picture is revealed on a display, upon which the full pixel raster can be distinguished for every frame (in real time or slower), an optical capture may be performed, which preserves the original fidelity of the image, and one need not recompress as lossy for peers who have the capacity to receive the full duplicate.
All images are eventually revealed optically somehow. Such images may be captured directly, and corrected and restored according to original quality, if you have good video equipment.
Only one good copy needs to make it into the open, and then the cat's out of the bag.
In theory, if the picture is revealed on a display, upon which the full pixel raster can be distinguished for every frame (in real time or slower), an optical capture may be performed, which preserves the original fidelity of the image, and one need not recompress as lossy for peers who have the capacity to receive the full duplicate.
All images are eventually revealed optically somehow. Such images may be captured directly, and corrected and restored according to original quality, if you have good video equipment.
Only one good copy needs to make it into the open, and then the cat's out of the bag.