I have played a bit with the file, and in both FCPX (10.7.1) and Resolve Studio (18.6.6) I see the same problem with your file. And depending on settings in motion, I can "control" the outcome on my 4444 with Alpha render (se example later in text).
My 4444 with Alpha original file has specifically been produced with these settings in motion:
- Transparent background
- Transparent 2024-05-06 kl. 09.17.16.png (41.41 KiB) Viewed 2029 times
I have different options, where a background color is defined as "solid" in:
- Solid background
- Solid 2024-05-06 kl. 09.49.58.png (50.79 KiB) Viewed 2029 times
And when I combine “kuddibras” (transparent alpha channel), your 4444 (solid alpha channel???) and my “kuddibras” (solid Alpha channel) I get this result:
- Example reproducing the behaviour
- transparent-solid-solid 2024-05-06 kl. 09.30.28.png (927.87 KiB) Viewed 2029 times
Each “overlay is placed into ⅓ of the total frame (1280 pixel) by cropping the first example (transparent Alpha) 0 left and 2560 right, your example 1280 left and 1280 right, and my solid background color 2560 left and 0 right.
I’m not going to say, what is right or wrong or how things should be, but it is clear, that if the background is rendered as transparent, there is no Alpha problem, whereas if the background is rendered as solid, there is an Alpha problem. Whether it is a case of “strict interpretation” (previous behaviour “only” convention) or “wrong interpretation” (previous behaviour correct) in Sonoma may require the study of the actual technical reference on ProRES 4444 including all comments and amendments over the years.
Not my task to be referee or even judge here. I can only say, that I can reproduce the problem, and I can render identical media with different Alpha behavior, depending on background being defined as solid or transparent.
When working in Resolve, I can remove the BLUE background in Delta-keyer, but since I have NO original render (some image, with the 4444 with Alpha overlay), that demonstrates the intended outcome, I’m guessing here, and cannot know, if I get the actual and intended outcome in Sonoma.
Could probably also be done in FCPX - just haven't tried.
Regards