If you've added a still photo to 1SE and when previewing the snippet or the mashed video, it has two black bars on each of its sides; you must know that this is a known issue. We're working on a fix that's coming very soon, but there's a workaround you can try.
Please crop your image to have the following aspect ratio using the Photos app or any other editor:
- Horizontal photos - 16:9
- Vertical photos - 9:16
That's it! Now, re-add the cropped image to the app, and the black bars should be gone.
. . .